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Scoping review of quality of anesthetic induction and recovery scales used for dogs

      Abstract

      Objective

      To compare, describe and assess the level of validation of all instruments measuring quality of induction and recovery from anesthesia in dogs.

      Databases used

      A search was performed using the electronic database PubMed to find articles containing an induction quality scale, a recovery quality scale or both in dogs. Articles not directly accessible through PubMed were obtained through the Auburn University Library website and Google Scholar. The phrases ‘induction scoring systems dogs’, ‘recovery scoring systems dogs’, ‘anesthetic induction score dogs’, and ‘anesthetic recovery score dogs’ were used for searches using the ‘best match search’ function. The time frame searched was from 1980 to May 2020. The search was conducted from March 2020 to May 2020.

      Conclusions

      A thoroughly tested and validated scale for measuring the quality of induction and recovery does not exist in the current veterinary literature. A large disagreement exists between studies on the use of induction and recovery scales, and many have reported inconsistent results with current instruments. It is recommended that an induction and recovery scale intended for wide-scale use be constructed and tested extensively for psychometric validation and reliability.

      Keywords

      Introduction

      To ensure that a scale is measuring what it is intended to measure, a psychometric validation process is vital (
      • DeVellis R.F.
      Scale Development: Theory and Applications.
      ;
      • Boateng G.O.
      • Neilands T.B.
      • Frongillo E.A.
      • et al.
      Best practices for developing and validating scales for health, social, and behavioral research: a primer.
      ). The construction of a validated scoring instrument is a lengthy, elaborate process that many researchers do not pursue. Without validation, the results yielded from an instrument are of questionable value, given that the results may not reflect objective reality (
      • Boateng G.O.
      • Neilands T.B.
      • Frongillo E.A.
      • et al.
      Best practices for developing and validating scales for health, social, and behavioral research: a primer.
      ). Commonly used induction and recovery quality scales include simple descriptive scales (SDSs), numerical rating scales (NRSs) and visual analog scales (VASs), which researchers often construct or borrow without validation or analysis. SDS can be numeric, rating a variable from 0 to 4 with associated descriptors, or nonnumeric, rating a variable from best to worst. NRS often consists of a range from 0 to 10 in which each value represents increasing degrees of severity. VAS rates a variable based on a continuum with end values commonly at 0 and 100 mm. These scales, while easy to build and use, are unidimensional and may not provide a complete assessment of the variable being measured (
      • Holton L.
      • Reid J.
      • Scott E.M.
      • et al.
      Development of a behaviour-based scale to measure acute pain in dogs.
      ). One study found that standardization and validation of these scales is needed due to the large variability of scale length, descriptors and instructions for use (
      • Hjermstad M.J.
      • Fayers P.M.
      • Haugen D.F.
      • et al.
      Studies comparing Numerical Rating Scales, Verbal Rating Scales, and Visual Analogue Scales for assessment of pain intensity in adults: a systematic literature review.
      ). In addition, if the criteria for selecting the contents of an SDS or NRS have not been subjected to validity testing, the results from the scale may be unreliable (
      • Streiner D.L.N.
      • Norman G.R.
      • Cairney J.
      Health Measurement Scales: a practical guide to their development and use.
      ). Validated unidimensional scales may be adequate to measure things such as pain and induction quality in a clinical setting, but in research, a multidimensional scale is often better suited to collect more accurate data (
      • Hjermstad M.J.
      • Fayers P.M.
      • Haugen D.F.
      • et al.
      Studies comparing Numerical Rating Scales, Verbal Rating Scales, and Visual Analogue Scales for assessment of pain intensity in adults: a systematic literature review.
      ). Both unidimensional scales and multidimensional scales should be tested for psychometric validity and reliability before use in a study. Induction and recovery scales within studies are frequently limited by a lack of reliability, unclear descriptors, lack of testing, subjectivity of the scale, lack of agreement between researchers and disagreement with other studies as a result of differences in scoring instrument (
      • Laing S.
      • Paul V.
      • Murison P.J.
      The effects of nitrous oxide on recovery from isoflurane anaesthesia in dogs.
      ;
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      ;
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      ;
      • O'Hagan B.
      • Pasloske K.
      • McKinnon C.
      • et al.
      Clinical evaluation of alfaxalone as an anaesthetic induction agent in dogs less than 12 weeks of age.
      ;
      • Hunt J.R.
      • Slingsby L.S.
      • Murrell J.C.
      The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.
      ;
      • Pinelas R.
      • Alibhai H.I.
      • Mathis A.
      • et al.
      Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone-a clinical trial.
      ;
      • Ferreira J.P.
      • Dzikiti T.B.
      • Zeiler G.E.
      • et al.
      Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs.
      ;
      • Conde Ruiz C.
      • Del Carro A.P.
      • Rosset E.
      • et al.
      Alfaxalone for total intravenous anaesthesia in bitches undergoing elective caesarean section and its effects on puppies: a randomized clinical trial.
      ;
      • Copeland J.E.
      • Hofmeister E.H.
      • Brainard B.M.
      • Quandt J.E.
      Reliability of video recordings to evaluate quality of anesthesia recovery in dogs.
      ;
      • White K.L.
      • Yates D.
      Clinical comparison of alfaxalone, ketamine and propofol following medetomidine and methadone in dogs.
      ;
      • Miller C.
      • Hughes E.
      • Gurney M.
      Co-induction of anaesthesia with alfaxalone and midazolam in dogs: a randomized, blinded clinical trial.
      ;
      • Reed R.A.
      • Quandt J.E.
      • Brainard B.M.
      • et al.
      The effect of induction with propofol or ketamine and diazepam on quality of anaesthetic recovery in dogs.
      ). Subjectivity is unavoidable in research, especially when measuring variables such as quality of induction, but can be minimized by using clear descriptors. Additionally, excluding descriptors that are less focused on the measurement can be achieved through psychometric validity testing (
      • Spector P.E.
      • Fox S.
      Reducing subjectivity in the assessment of the job environment: development of the Factual Autonomy Scale (FAS).
      ). There are validated scales that measure pain in dogs, the Glasgow composite pain scale being one of the most widely recognized (
      • Holton L.
      • Reid J.
      • Scott E.M.
      • et al.
      Development of a behaviour-based scale to measure acute pain in dogs.
      ). The same rigorous validation and testing used in the development of these scales is lacking in quality of induction and recovery scales, yet these scales are frequently used as the primary outcome variable in anesthesia research studies.
      Induction and recovery quality scoring instruments are included in studies as an indicator of the smoothness of an induction and recovery from anesthesia. These instruments are often used to help measure the effectiveness of a particular anesthetic protocol, to compare protocols or anesthetics, or to determine the efficacy of a premedication, mixture of premedications or an induction agent (
      • Pottie R.G.
      • Dart C.M.
      • Perkins N.R.
      Speed of induction of anaesthesia in dogs administered halothane, isoflurane, sevoflurane or propofol in a clinical setting.
      ;
      • Psatha E.
      • Alibhai H.I.K.
      • Jimenez-Lozano A.
      • et al.
      Clinical efficacy and cardiorespiratory effects of alfaxalone, or diazepam/fentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk.
      ;
      • Ferreira J.P.
      • Dzikiti T.B.
      • Zeiler G.E.
      • et al.
      Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs.
      ;
      • Liao P.
      • Sinclair M.
      • Valverde A.
      • et al.
      Induction dose and recovery quality of propofol and alfaxalone with or without midazolam coinduction followed by total intravenous anesthesia in dogs.
      ;
      • Kropi J.
      • Hughes J.L.
      Effect of midazolam on the quality and duration of anaesthetic recovery in healthy dogs undergoing elective ovariohysterectomy or castration.
      ). The instruments attempt to quantify induction and recovery quality by analyzing the behaviors of a dog through numerical ratings or descriptors. While a large number of these scales exist, there is wide disparity in size and construction, and researchers often use them interchangeably between studies. The included descriptors in the scales vary by scale, study and researcher, with frequent overlaps in descriptor usage between scales (e.g., emergence delirium used as a descriptor for a score of ‘4’ in one scale and for a score of ‘6’ in another scale) (
      • Dehuisser V.
      • Bosmans T.
      • Devreese M.
      • et al.
      Alfaxalone total intravenous anaesthesia in dogs: pharmacokinetics, cardiovascular data and recovery characteristics.
      ;
      • Lehnus K.S.
      • Brearley J.
      Evaluation of two different radiotherapy anaesthetic protocols for dogs: a randomized clinical crossover trial.
      ). No attempt has been made to describe and compile the expressions from these scales to examine the extent of issues such as these. Furthermore, these studies contain instruments that are not validated. The subjectivity of induction and recovery scales is also a recognized issue in veterinary research and has been reported as a limitation in multiple studies (
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      ;
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      ;
      • Caines D.
      • Sinclair M.
      • Valverde A.
      • et al.
      Comparison of isoflurane and propofol for maintenance of anesthesia in dogs with intracranial disease undergoing magnetic resonance imaging.
      ;
      • Hunt J.R.
      • Slingsby L.S.
      • Murrell J.C.
      The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.
      ;
      • Pinelas R.
      • Alibhai H.I.
      • Mathis A.
      • et al.
      Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone-a clinical trial.
      ;
      • Conde Ruiz C.
      • Del Carro A.P.
      • Rosset E.
      • et al.
      Alfaxalone for total intravenous anaesthesia in bitches undergoing elective caesarean section and its effects on puppies: a randomized clinical trial.
      ;
      • Warrit K.
      • Griffenhagen G.
      • Goh C.
      • Boscan P.
      Comparison of ultrasound-guided lumbar plexus and sciatic nerve blocks with ropivacaine and sham blocks with saline on perianesthetic analgesia and recovery in dogs undergoing tibial plateau leveling osteotomy surgery.
      ). Researchers are aware of the lack of homogeneity in recovery and induction scales and realize the shortcomings of the scales they are using, but no attempt has been made to examine the need for validated scales (
      • O'Hagan B.
      • Pasloske K.
      • McKinnon C.
      • et al.
      Clinical evaluation of alfaxalone as an anaesthetic induction agent in dogs less than 12 weeks of age.
      ;
      • Hunt J.R.
      • Slingsby L.S.
      • Murrell J.C.
      The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.
      ;
      • White K.L.
      • Yates D.
      Clinical comparison of alfaxalone, ketamine and propofol following medetomidine and methadone in dogs.
      ).
      The objective of this scoping review is to describe and compare the induction and recovery scales in dogs published in the veterinary literature. A scoping review aims to provide an overview of a topic to identify gaps and areas for improvement in research.

      Materials and methods

      This scoping review was performed by one investigator and utilized one database. The methodology was based on the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines (
      • Moher D.
      • Liberati A.
      • Tetzlaff J.
      • et al.
      Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement.
      ). This review also follows the extension checklist for scoping reviews (PRISMA-ScR) (
      • Tricco A.C.
      • Lillie E.
      • Zarin W.
      • et al.
      PRISMA Extension for scoping reviews (PRISMA-ScR): checklist and explanation.
      ).

       Search strategy

      A search was performed using the electronic database PubMed to find articles containing an induction quality scale, a recovery quality scale or both in dogs. Articles not directly accessible through PubMed were obtained through the Auburn University, AL, USA, Library website and Google Scholar. The phrases ‘induction scoring systems dogs’, ‘recovery scoring systems dogs’, ‘anesthetic induction score dogs’, and ‘anesthetic recovery score dogs’ were used for searches using the ‘best match search’ function. The time frame searched was from 1980 to May 2020. The search was conducted from March 2020 to May 2020. One investigator performed all searches, reviewed results, and selected papers for the study. The citations of the selected studies were reviewed and were also included in some cases.

       Inclusion and exclusion criteria

      Initially, all studies that referenced scoring quality of induction or recovery in the abstract were included. Studies were not excluded based on breed, sample size or surgery type. The studies were then carefully reviewed in their entirety. Studies were included if they contained a clearly defined system of measurement of induction quality, recovery quality or both. Studies were excluded if they were not in English or contained only behavior scales, sedation scales, or scales evaluating a single aspect of recovery or induction (e.g., quality of intubation scales). Behavior scales were assessed by the investigator and included if the scale directly measured induction or recovery behavior. Studies measuring neurological damage as it relates to recovery quality in dogs were excluded.

       Data collection

      Data extraction was performed by the same investigator that performed the search and review of the papers. All data were extracted manually and placed into a spreadsheet by the investigator. The data extracted from the studies included the induction or recovery scales as a description or a table, methods of validation described and citations associated with the instrument. The date of publication, study design and sample sizes were also extracted. Additional notes made in the study regarding the scale, such as effectiveness and lack of validity, were made as the articles were reviewed. If a validation technique was not described in the paper, it was assumed that the instrument was unvalidated. The main focus for this review was previous validation of the scale, not reliability testing or analysis done within the study in which it was found. The scales from each study were evaluated and compared for individuality. Scales that included a reference from another study, as well as scales that were identical to a scale in another study without reference, were deemed to be not unique. The number of unique induction and recovery scales was determined.

       Quality assessment

      Each study was evaluated for quality using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system (
      • Ryan R.
      • Hill S.
      How to GRADE the quality of the evidence.
      ). The studies were scored as high quality, moderate quality, low quality or very low quality based on aspects of the study (Table 1). Randomized trials were assigned an initial score of high quality and nonrandomized trials were assigned an initial score of low quality. The score was upgraded based on magnitude of effect or downgraded based on limitations to evidence or risk of bias, including sample size and level of blinding.
      Table 1Summary and GRADE rating of included studies
      PaperStudy designSample sizeInduction or recoveryMethods of reliability or validation testingGRADE Quality ratingType of scale(s)
      • Ambros B.
      • Duke-Novakovski T.
      • Pasloske K.S.
      Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-beta-cyclodextrin and propofol in dogs.
      Crossover study with 6 day washout period between treatments6 young adult medium-sized healthy cross-bred dogsBothSingle assessor for all cases. No validation was described.ModerateSDS
      • Amengual M.
      • Flaherty D.
      • Auckburally A.
      • et al.
      An evaluation of anaesthetic induction in healthy dogs using rapid intravenous injection of propofol or alfaxalone.
      Prospective, randomized, blinded clinical study60 healthy dogs (ASA I-II) anesthetized for elective surgery or diagnostic proceduresInductionNone describedHighSDS
      • Becker W.M.
      • Mama K.R.
      • Rao S.
      • et al.
      Prevalence of dysphoria after fentanyl in dogs undergoing stifle surgery.
      Prospective, nonblinded, randomized clinical trial92 dogs that underwent tibial plateau leveling osteotomy or tibial tuberosity advancementRecoveryStudent anesthetist assigned all recovery scores. Investigators developed the scale from descriptions in previous studies. No validation was described.ModerateSDS
      • Buback J.L.
      • Boothe H.W.
      • Carroll G.L.
      • Green R.W.
      Comparison of three methods for relief of pain after ear canal ablation in dogs.
      Randomized, observer-blinded clinical trial31 dogs presenting for ear canal ablationRecoverySingle blinded assessor for all cases. No validation was described.HighSDS
      • Caines D.
      • Sinclair M.
      • Valverde A.
      • et al.
      Comparison of isoflurane and propofol for maintenance of anesthesia in dogs with intracranial disease undergoing magnetic resonance imaging.
      Prospective, randomized, clinical trial25 client-owned dogs with intracranial pathology, 13 females and 12 males, aged from 11 months to 13 years, weighing 3.0–48.0 kgRecoveryObservers not blinded for evaluations. Scores not assessed for repeatability. No validation was described.ModerateSDS
      • Canfrán S.
      • Bustamante R.
      • González P.
      • et al.
      Comparison of sedation scores and propofol induction doses in dogs after intramuscular administration of dexmedetomidine alone or in combination with methadone, midazolam, or methadone plus midazolam.
      Blinded crossover7 adult healthy Beagles, 6 male, 1 femaleRecoveryUsed a standardized scale from
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      . Single blinded observer performed all assessments. No validation was described.
      LowSDS
      • Le Chevallier D.
      • Slingsby L.
      • Murrell J.
      Use of midazolam in combination with medetomidine for premedication in healthy dogs.
      Prospective, randomized, blinded clinical study40 adult healthy client-owned dogs weighing 18 ± 7 kgInductionSingle assessor for all cases. No validation was described.HighSDS
      • Conde Ruiz C.
      • Del Carro A.P.
      • Rosset E.
      • et al.
      Alfaxalone for total intravenous anaesthesia in bitches undergoing elective caesarean section and its effects on puppies: a randomized clinical trial.
      Prospective, randomized, ‘blinded’ clinical trial22 client-owned bitches and 94 puppiesBothPreviously described scales were used for induction and recovery. No validation was described.ModerateVAS & NRS
      • Copeland J.E.
      • Hofmeister E.H.
      • Brainard B.M.
      • Quandt J.E.
      Reliability of video recordings to evaluate quality of anesthesia recovery in dogs.
      Prospective, study30 dogs undergoing surgeryRecoveryUndergraduate student scored recoveries in real time and video recordings were also taken. Videos were distributed to 3 board-certified anesthesiologists and the original rater and scored. The same videos were scored again by the same raters after 4 months. Previously published SDS was used. No validation was described.Very lowSDS, VAS and NRS
      • Covey-Crump G.L.
      • Murison P.J.
      Fentanyl or midazolam for co-induction of anaesthesia with propofol in dogs.
      Randomized, controlled, blinded clinical study66 client-owned dogs, 35 male, 31 female, ASA I-II, aged 6–120 months, 4.7–48.0 kgInductionA single blinded anesthetist assigned scores. No validation was described.HighSDS
      • Dehuisser V.
      • Bosmans T.
      • Kitshoff A.
      • et al.
      Cardiovascular effects, induction and recovery characteristics and alfaxalone dose assessment in alfaxalone versus alfaxalone-fentanyl total intravenous anaesthesia in dogs.
      Prospective, blinded, randomized, experimental study12 intact female dogsBothPreviously described scales were used for induction and recovery. No validation was described.HighSDS
      • Dehuisser V.
      • Bosmans T.
      • Devreese M.
      • et al.
      Alfaxalone total intravenous anaesthesia in dogs: pharmacokinetics, cardiovascular data and recovery characteristics.
      Experimental, prospective, randomized, crossover study6 intact female BeaglesBothPreviously described scales were used for induction and recovery. No validation was described.ModerateSDS
      • Dehuisser V.
      • Bosmans T.
      • Kitshoff A.
      • et al.
      Effect of premedication on dose requirement, cardiovascular effects and recovery quality of alfaxalone total intravenous anaesthesia in dogs.
      Prospective, blinded, randomized, experimental study12 female BeaglesBothPreviously described scales were used for induction and recovery. No validation was described.HighSDS
      • Diao H.X.
      • Jiang S.
      • Gao P.Y.
      • et al.
      Comparison of the effects of propofol and emulsified isoflurane alone or combined with dexmedetomidine on induction of anesthesia in dogs.
      Prospective, randomized, blinded experimental trial36 adult mixed breedBothPreviously standardized scale by
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      was used. No validation was described.
      HighSDS
      • Faggella A.M.
      • Aronsohn M.G.
      Evaluation of anesthetic protocols for neutering 6- to 14-week-old pups.
      Randomized clinical trial99 puppies, 49 males, 50 females, aged 6–14 weeks, weighing 1.5–11 kgBothNone described.ModerateSDS
      • Ferreira J.P.
      • Dzikiti T.B.
      • Zeiler G.E.
      • et al.
      Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs.
      Randomized36 healthy male small-breed dogs weighing 5.5 ± 2.3 kg of mean age 26 ± 13 monthsBothPrimary investigator scored all inductions. Primary and co-investigator scored recovery and blinded observer (anesthetist) scored recovery with video. Scales not validated. Validity of recovery SDS previously questioned by
      • Ferchichi S.
      • Troncy E.
      • Guillot M.
      • et al.
      Excitement in dogs recovering from alfaxalone anaesthesia: is the absent drug blamed in error?.
      .
      ModerateSDS
      • Hampton C.E.
      • Riebold T.W.
      • Mandsager R.E.
      Recovery characteristics of dogs following anesthesia induced with tiletamine-zolazepam, alfaxalone, ketamine-diazepam, or propofol and maintained with isoflurane.
      Prospective, randomized, blinded crossover study6 healthy adult houndsRecoveryVideo recordings were taken of each recovery and viewed by 3 blinded raters twice, 6 months after the procedure, 30 days apart. Videos were randomized each time. Interrater and intrarater reliability of scoring was assessed by intraclass correlation coefficient calculator. Previously published scales were adapted. No validation was described.ModerateComposite NRS
      • Herbert G.L.
      • Bowlt K.L.
      • Ford-Fennah V.
      • et al.
      Alfaxalone for total intravenous anaesthesia in dogs undergoing ovariohysterectomy: a comparison of premedication with acepromazine or dexmedetomidine.
      Prospective, randomized, clinical study38 healthy female dogsBoth1 of 2 anesthetists assessed all inductions and recoveries and use of scales was discussed thoroughly to minimize interobserver variability. Previously published scales (NRS) were used. No validation was described.ModerateSDS
      • Hopkins A.
      • Giuffrida M.
      • Larenza M.P.
      Midazolam, as a co-induction agent, has propofol sparing effects but also decreases systolic blood pressure in healthy dogs.
      Prospective, randomized, controlled and blinded clinical study, with owner consent17 healthy, client-owned dogs, weighing 28 ± 18 kg and aged 4.9 ± 3.9 yearsInductionPreviously published scale was used. Single investigator assigned all scores. No validation was described.HighSDS
      • Hunt J.R.
      • Attenburrow P.M.
      • Slingsby L.S.
      • Murrell J.C.
      Comparison of premedication with buprenorphine or methadone with meloxicam for postoperative analgesia in dogs undergoing orthopaedic surgery.
      Observer-blinded, randomized, prospective clinical study38 client-owned dogs aged > 6 months presented for orthopedic surgeryRecovery1 blinded assessor for all cases. No validation was described.HighSDS
      • Hunt J.R.
      • Slingsby L.S.
      • Murrell J.C.
      The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.
      Observer-blinded, randomized, placebo-controlled clinical study44 healthy dogs, weighing 1.8–19.95 kg, aged > 12 weeks, presented for soft tissue or orthopedic surgery that caused mild to moderate painRecoveryScale similar to one used in several other studies was used. No validation was described.ModerateSDS
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      Prospective, randomized clinical trial42 client-owned dogs, 21 females and 21 males, weighing 5.7–55 kgRecovery3 assessors: 1 aware of induction agent, 2 unaware. No validation was described. Validity questioned by
      • Ferchichi S.
      • Troncy E.
      • Guillot M.
      • et al.
      Excitement in dogs recovering from alfaxalone anaesthesia: is the absent drug blamed in error?.
      .
      ModerateSDS and VAS
      • Johnson R.A.
      • Striler E.
      • Sawyer D.C.
      • Brunson D.B.
      Comparison of isoflurane with sevoflurane for anesthesia induction and recovery in adult dogs.
      Randomized crossover study16 clinically normal, young adult BeaglesBothNone describedModerateSDS
      • Kennedy M.J.
      • Smith L.J.
      A comparison of cardiopulmonary function, recovery quality, and total dosages required for induction and total intravenous anesthesia with propofol versus a propofol-ketamine combination in healthy Beagle dogs.
      Randomized, blinded crossover study10 female Beagles weighing 9.4 ± 1.8 kgRecoveryBlinded anesthetist scored all recoveries. No validation was described.HighSDS
      • Ko J.C.
      • Nicklin C.F.
      • Melendaz M.
      • et al.
      Effects of a microdose of medetomidine on diazepam-ketamine induced anesthesia in dogs.
      Randomized crossover study6 healthy female dogs aged 2 yearsBothNone described.ModerateSDS
      • Ko J.C.
      • Golder F.J.
      • Mandsager R.E.
      • et al.
      Anesthetic and cardiorespiratory effects of a 1:1 mixture of propofol and thiopental sodium in dogs.
      Randomized crossover study10 healthy Walker HoundsBothNone described.ModerateSDS
      • Ko J.C.
      • Fox S.M.
      • Mandsager R.E.
      Sedative and cardiorespiratory effects of medetomidine, medetomidine-butorphanol, and medetomidine-ketamine in dogs.
      Randomized, blinded, crossover study6 healthy adult dogsEase of intubation and recoveryBlinded investigators scored. No validation was described.HighSDS
      • Ko J.C.
      • Payton M.E.
      • White A.G.
      • et al.
      Effects of intravenous diazepam or microdose medetomidine on propofol-induced sedation in dogs.
      Randomized, blinded crossover study8 female mixed-breed hound-type dogs, aged 1 year and weighing 18–23 kgBothSingle blinded investigator scored all inductions and recoveries. No validation was described.HighSDS
      • Kropi J.
      • Hughes J.L.
      Effect of midazolam on the quality and duration of anaesthetic recovery in healthy dogs undergoing elective ovariohysterectomy or castration.
      Prospective, randomized, placebo-controlled, masked clinical trial74 client-owned dogs undergoing neuteringRecoveryBlinded main investigator scored all recoveries. Previously published scale was used. No validation was described.HighSDS
      • Laing S.
      • Paul V.
      • Murison P.J.
      The effects of nitrous oxide on recovery from isoflurane anaesthesia in dogs.
      Randomized, blinded clinical trial54 dogs, excluding Boxers, presented for neutering, aged 6 months to 6 years and weighing less than 32 kgRecoveryPreviously published scale was used as well as an NRS with no previous validation. 1 of 2 blinded observers (blinding was not possible in all cases) scored all cases. No validation was described.HighComposite NRS and VAS
      • Lehnus K.S.
      • Brearley J.
      Evaluation of two different radiotherapy anaesthetic protocols for dogs: a randomized clinical crossover trial.
      Prospective, masked, randomized clinical crossover trial40 client-owned dogs anesthetized from October 2017 to June 2018RecoveryPreviously published scale was used. 2 blinded observers scored recoveries from video recordings. No validation was described.ModerateSDS
      • Liao P.
      • Sinclair M.
      • Valverde A.
      • et al.
      Induction dose and recovery quality of propofol and alfaxalone with or without midazolam coinduction followed by total intravenous anesthesia in dogs.
      Prospective, blinded, randomized, incomplete, Latin square study10 dogs weighing 24.5 ± 3.1 kgBothSingle blinded observer scored, 3 ACVAA diplomates also gave scores for extubation and recovery from video clips. No validation was described..HighSDS
      • Liu C.
      • Lin T.
      • Zhou Z.
      Dexmedetomidine combined with etomidate or emulsified isoflurane for induction reduced cardiopulmonary response in dogs.
      Nonrandomized, observer blinded5 mixed-breed dogs weighing 9.2 ± 0.6 kg aged 12–36 monthsBothSingle blinded observer scored induction and recovery. Previously published scales was used. No validation was described.LowSDS
      • Lopez L.A.
      • Hofmeister E.H.
      • Pavez J.C.
      • Brainard B.M.
      Comparison of recovery from anesthesia with isoflurane, sevoflurane, or desflurane in healthy dogs.
      Randomized, blinded, Williams crossover study11 healthy, random-source dogsBothSingle blinded observer scored all inductions and recoveries. Previously described scale was used. No validation was described.HighSDS
      • Love E.J.
      • Holt P.E.
      • Murison P.J.
      Recovery characteristics following maintenance of anaesthesia with sevoflurane or isoflurane in dogs premedicated with acepromazine.
      Randomized, blinded clinical trial with owner consent40 dogs presenting for investigation of urinary incontinenceBothInduction: no validation described. Recovery: used a VAS system based on success when used in human studies, due to higher sensitivity and familiarity than other scale systems. No validation was described.HighSDS and VAS
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      Prospective, randomized clinical trial38 dogs weighing 23.7 ± 12.6 kgRecoveryAn anesthetist scored all recoveries directly, then 2 others who were unaware of the treatment scored from a recording. VAS and SDS were used. No validation was described.ModerateSDS and VAS
      • Maddern K.
      • Adams V.J.
      • Hill N.A.T.
      • Leece E.A.
      Alfaxalone induction dose following administration of medetomidine and butorphanol in the dog.
      Prospective, randomized, blinded clinical trial85 client-owned dogs (ASA I-II)InductionSingle blinded observer scored all cases. No validation was described.HighSDS
      • Maney J.K.
      • Shepard M.K.
      • Braun C.
      • et al.
      A comparison of cardiopulmonary and anesthetic effects of an induction dose of alfaxalone or propofol in dogs.
      Prospective, randomized, blinded crossover8 random-source adult female mixed-breed dogs weighing 18.7 ± 4.7 kgBothSingle blinded observer scored induction and recovery. Used a standardized scale from
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      . No validation was described.
      HighSDS
      • Martinez-Taboada F.
      • Leece E.A.
      Comparison of propofol with ketofol, a propofol-ketamine admixture, for induction of anaesthesia in healthy dogs.
      Prospective, randomized, controlled, ‘blinded’ study70 healthy dogs, 33 male and 37 female aged 6–157 months and weighing 4–48 kginductionPreviously published scale was used. No validation was described.HighSDS
      • Metcalfe S.
      • Hulands-Nave A.
      • Bell M.
      • et al.
      Multicentre, randomised clinical trial evaluating the efficacy and safety of alfaxalone administered to bitches for induction of anaesthesia prior to caesarean section.
      Multicenter, randomized, positive-controlled clinical study74 bitchesBothSDS with no described validation was used in conjunction with a scoring system used in a previously published study. No validation was described.ModerateSDS
      • Miller C.
      • Hughes E.
      • Gurney M.
      Co-induction of anaesthesia with alfaxalone and midazolam in dogs: a randomized, blinded clinical trial.
      Randomized, blinded clinical trial29 client-owned dogs undergoing elective orthopedic or soft tissue surgeryInductionPrimary investigator was blind to group allocation and scored all inductions. Previously published scale was used. No validation was described.HighSDS
      • Montefiori F.
      • Pawson P.
      • Auckburally A.
      • et al.
      An evaluation of a target-controlled infusion of propofol or propofol-alfentanil admixture for sedation in dogs.
      Randomized, blinded clinical trial60 client-owned dogs undergoing diagnostic imaging, aged 8 months to 8 years and weighing 8–50 kgRecoverySingle blinded observer scored all cases. No validation was described.HighSDS
      • Muir W.
      • Lerche P.
      • Wiese A.
      • et al.
      Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.
      Blinded four-way crossover randomized by dose8 healthy adult purpose-bred mixed-breed dogs (4 males, 4 females) weighing 12–28 kgBothNone described.HighSDS
      • Niggemann J.R.
      • Tichy A.
      • Eberspächer-Schweda M.C.
      • Eberspächer-Schweda E.
      Preoperative calming effect of melatonin and its influence on propofol dose for anesthesia induction in healthy dogs.
      Prospective, randomized, blinded, placebo-controlled clinical study50 healthy, adult, client-owned dogs scheduled for elective surgeryInduction3 blinded observers (veterinarians) scored based on video recordings. Previously published scale was used. No validation was described.HighSDS
      • O'Hagan B.
      • Pasloske K.
      • McKinnon C.
      • et al.
      Clinical evaluation of alfaxalone as an anaesthetic induction agent in dogs less than 12 weeks of age.
      Clinical study25 juvenile dogs aged < 12 weeks presented for surgical desexingBothPreviously described scoring system was modified for this study. No validation was described.LowSDS
      • Pinelas R.
      • Alibhai H.I.
      • Mathis A.
      • et al.
      Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone-a clinical trial.
      Randomized, blinded, controlled clinical trial61 client-owned dogs, status ASA I-IIBothUsed previously published scales for induction and recovery. A single anesthetist performed and scored all inductions. No validation was described.ModerateSDS
      • Pottie R.G.
      • Dart C.M.
      • Perkins N.R.
      Speed of induction of anaesthesia in dogs administered halothane, isoflurane, sevoflurane or propofol in a clinical setting.
      Randomized, nonblinded clinical study71 dogs, 68 data collected from, 3 excluded from part of the data, various breeds weighing 14.2 ± 11.2 kgInduction1 veterinarian performed and scored all inductions. No validation was described.HighSDS
      • Psatha E.
      • Alibhai H.I.K.
      • Jimenez-Lozano A.
      • et al.
      Clinical efficacy and cardiorespiratory effects of alfaxalone, or diazepam/fentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk.
      Randomized prospective clinical study40 dogs of physical status ASA III-V referred for various surgical purposesBothSingle blinded observer scored from video recording. No validation was described.HighSDS & VAS
      • Quirós Carmona S.
      • Navarrete-Calvo R.
      • Granados M.M.
      • et al.
      Cardiorespiratory and anaesthetic effects of two continuous rate infusions of dexmedetomidine in alfaxalone anaesthetized dogs.
      Prospective, blinded, randomized crossover experimental study6 healthy purpose-bred Beagles, 3 males and 3 females aged 2.3 ± 0.4 years and weighing 15.3 ± 2.3 kgRecoverySingle blinded observer scored all recoveries. Previously described scale was used. No validation was described.HighSDS
      • Quirós-Carmona S.
      • Navarrete R.
      • Domínguez J.M.
      • et al.
      A comparison of cardiopulmonary effects and anaesthetic requirements of two dexmedetomidine continuous rate infusions in alfaxalone-anaesthetized Greyhounds.
      Prospective, randomized and blinded clinical study24 female GreyhoundsBothPreviously published scales used. Single blinded experienced anesthetist assessed all inductions and recoveries. No validation was described.HighSDS
      • Radlinsky M.G.
      • Mason D.E.
      • Roush J.K.
      • Pineda R.
      Use of a continuous, local infusion of bupivacaine for postoperative analgesia in dogs undergoing total ear canal ablation.
      Randomized controlled trial16 dogs undergoing ear canal ablationRecoverySingle blinded observer scored all recoveries. Previously described scale used in a study on cats was used. No further validation described. Validation from
      • Carroll G.L.
      • Howe L.B.
      • Slater M.R.
      • et al.
      Evaluation of analgesia provided by postoperative administration of butorphanol to cats undergoing onychectomy.
      : Used a scoring system similar to the one used in
      • Buback J.L.
      • Boothe H.W.
      • Carroll G.L.
      • Green R.W.
      Comparison of three methods for relief of pain after ear canal ablation in dogs.
      , also developed by observing several cats recover.
      HighSDS
      • Raillard M.
      • Love E.J.
      • Murison P.J.
      Effect of predosing versus slow administration of propofol on the dose required for anaesthetic induction and on physiologic variables in healthy dogs.
      Randomized, investigator-blinded clinical study32 healthy dogs 6–144 months and weighing 3.5–47.2 kgInductionPrimary investigator scored cases. Previously published scales used. No validation was described.HighSDS
      • Reed R.A.
      • Quandt J.E.
      • Brainard B.M.
      • et al.
      The effect of induction with propofol or ketamine and diazepam on quality of anaesthetic recovery in dogs.
      Randomized clinical trial60 client-owned dogs undergoing single-limb elective orthopedic proceduresRecoveryPilot study was conducted with 3 systems to determine sample size needed. Video recordings were viewed by 3 blinded ACVAA board-certified anesthesiologist raters over 4 weeks; no instructions were given on scoring and each rater gave 1 score for each video per scoring system. No validation was described.HighSDS, VAS & NRS
      • Rodríguez J.M.
      • Muñoz-Rascón P.
      • Navarrete-Calvo R.
      • et al.
      Comparison of the cardiopulmonary parameters after induction of anaesthesia with alphaxalone or etomidate in dogs.
      Randomized ‘blinded’ crossover study, 24 hours between phases8 healthy adult Beagles, 4 males, 4 femalesBothPreviously published scale was used. Single blinded researcher scored all cases. No validation was described.ModerateSDS
      • Romano M.
      • Portela D.A.
      • Breghi G.
      • Otero P.E.
      Stress-related biomarkers in dogs administered regional anaesthesia or fentanyl for analgesia during stifle surgery.
      Prospective, randomized, blinded clinical study45 dogs anesthetized for orthopedic procedures, 15 healthy dogs undergoing noninvasive orthopedic diagnostic proceduresRecoveryPreviously published scale used. Partially nonblinded observer scored recovery. No validation was described.ModerateSDS
      • Romano M.
      • Portela D.A.
      • Verdier N.
      • Otero P.E.
      Changes in serum cortisol and blood glucose concentrations in anesthetized, pain-free dogs administered fentanyl.
      Experimental, blinded, randomized crossover6 adult research dogsRecoveryPreviously published scale used. All scorers were blinded. No validation was described.ModerateSDS
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      Randomized, blinded trial18 purpose-bred adult BeaglesBothSingle blinded observer scored. No validation was described..HighSDS
      • Sánchez A.
      • Belda E.
      • Escobar M.
      • et al.
      Effects of altering the sequence of midazolam and propofol during co-induction of anaesthesia.
      Randomized, controlled, clinical study33 client-owned dogs (ASA I-III, 0.5–10 years, 5–30 kg)InductionModified version of a previously published scale used. No validation was described.ModerateSDS
      • Seo J.I.
      • Han S.H.
      • Choi R.
      • et al.
      Cardiopulmonary and anesthetic effects of the combination of butorphanol, midazolam and alfaxalone in Beagle dogs.
      Non-randomized clinical trial10 healthy adult Beagle dogs weighing 8.3 ± 3.1 kgBothStandardized scale from
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      was used. No validation was described.
      LowSDS
      • Skelding A.
      • Valverde A.
      • Aguilera R.
      • et al.
      Comparison of 3 blind brachial plexus block techniques during maintenance of anesthesia and postoperative pain scores in dogs undergoing surgical procedures of the thoracic limb.
      Nonrandomized, nonblinded, clinical study with client consent24 client-owned dogs of various breeds presenting for thoracic limb surgeryRecoveryModified version of a previously published scale was used. Novalidation was described.LowSDS
      • Suarez M.A.
      • Dzikiti B.T.
      • Stegmann F.G.
      • Hartman M.
      Comparison of alfaxalone and propofol administered as total intravenous anaesthesia for ovariohysterectomy in dogs.
      Prospective nonblinded randomized clinical study14 healthy female crossbred bitches, aged 0.5–5 years and weighing 16–42 kgBothPreviously published scale was used. No validation was described.HighSDS
      • Tamura J.
      • Ishizuka T.
      • Fukui S.
      • et al.
      The pharmacological effects of the anesthetic alfaxalone after intramuscular administration to dogs.
      Nonrandomized6 intact, adult Beagle dogs, 3 males and 3 females aged 3–5 years and weighing 9–11.5 kgBothWell-trained veterinarian scored all cases. Previously published scale was used. No validation was described.Very lowSDS
      • Tamura J.
      • Hatakeyama N.
      • Ishizuka T.
      • et al.
      The pharmacological effects of intramuscular administration of alfaxalone combined with medetomidine and butorphanol in dogs.
      Clinical study6 intact, adult Beagle dogs, 3 males and 3 females aged 1–5 years weighing 8.6–16.8 kgBothPreviously published scales was used. Single observer assigned all scores. No validation was described.ModerateSDS
      • Tsai Y.C.
      • Wang L.Y.
      • Yeh L.S.
      Clinical comparison of recovery from total intravenous anesthesia with propofol and inhalation anesthesia with isoflurane in dogs.
      Randomized, systematic comparative study149 client-owned dogs presented for various surgical or diagnostic proceduresRecoveryNone described.ModerateSDS
      • Uilenreef J.J.
      • Murrell J.C.
      • McKusick B.C.
      • Hellebrekers L.J.
      Dexmedetomidine continuous rate infusion during isoflurane anaesthesia in canine surgical patients.
      Prospective, randomized, blinded clinical study31 client-owned dogs presented for soft tissue or orthopedic surgeryRecoveryNone described.HighSDS
      • Warrit K.
      • Griffenhagen G.
      • Goh C.
      • Boscan P.
      Comparison of ultrasound-guided lumbar plexus and sciatic nerve blocks with ropivacaine and sham blocks with saline on perianesthetic analgesia and recovery in dogs undergoing tibial plateau leveling osteotomy surgery.
      Prospective, randomized, blinded, clinical trial20 dogsRecoverySingle blinded investigator scored all recoveries. Previously described scale used. No validation was described.ModerateSDS
      • White K.L.
      • Yates D.
      Clinical comparison of alfaxalone, ketamine and propofol following medetomidine and methadone in dogs.
      Prospective, ‘blinded’ and randomized clinical study75 male dogs presented for neuteringBothSDS used in pilot study to determine sample size. Previously published scales used in a cat study were modified for this study. Single blinded observer scored all cases. No further validation was described. Validation from
      • Mathis A.
      • Pinelas R.
      • Brodbelt D.C.
      • Alibhai H.I.K.
      Comparison of quality of recovery from anaesthesia in cats induced with propofol or alfaxalone.
      : induction: none described; recovery: scored once with a nonblinded anesthetist and once with a blinded anesthetist watching recording.
      HighSDS
      • White K.L.
      • Shelton K.
      • Taylor P.M.
      Comparison of diazepam-ketamine and thiopentone for induction of anaesthesia in healthy dogs.
      Randomized clinical trial20 healthy dogs of various breeds weighing 3.8–42.6 kg undergoing major orthopedic or soft tissue surgeryBothNone described.ModerateSDS
      • Wolfe T.M.
      • Bateman S.W.
      • Cole L.K.
      • Smeak D.D.
      Evaluation of a local anesthetic delivery system for the postoperative analgesic management of canine total ear canal ablation-a randomized, controlled, double-blinded study.
      Randomized, blinded clinical trial20 client-owned dogs undergoing total ear canal ablationRecoverySingle observer, the primary investigator, scored all cases. Previously published scale used. No validation was described.HighSDS
      • Zapata A.
      • Laredo F.G.
      • Escobar M.
      • et al.
      Effects of midazolam before or after alfaxalone for co-induction of anaesthesia in healthy dogs.
      Prospective, randomized, controlled, clinical trial33 client-owned dogs undergoing elective proceduresInductionSingle nonblinded investigator scored all cases. Previously published scale was modified for this study. No validation was described.ModerateSDS
      ACVAA, American College of Veterinary Anesthesia and Analgesia; ASA, American Society of Anesthesiologists; NRS, numerical rating scale; SDS, simple descriptive scale; VAS, visual analog scale.

       Scale analysis

      To describe and compare the expressions used in the scales, the induction and recovery scales extracted from the studies were examined and separated based on scale type (SDS, NRS and VAS) for the purpose of creating a comprehensive induction and recovery scale (Table 2, Table 3). The SDSs and NRSs were compared, and duplicate scales were removed. The VASs were not used. The methods of scoring in the remaining SDSs and NRSs (e.g., 0–3, 1–4, 1–5) were analyzed and the most commonly used method of scoring was used as the template for the comprehensive scale. In this study, a scale ranging 0–3 (0 being a smooth induction/recovery and 3 being the worst) was constructed for both induction and recovery. A 0–3 scale was chosen because a four-level scale was the most common type of scale in the included studies. In order to transfer the descriptors from the individual scales to the comprehensive scale, larger scales were condensed to fit and smaller scales were spread out. The descriptors from scales ranging 0–3, as well as scales ranging 1–4, were transferred directly to the comprehensive scale (e.g., descriptors of a score of 1 from a scale ranging 1–4 would correspond with a score of 0 in the comprehensive scale, descriptors of a score of 2 would correspond with a score of 1, etc.). For scales with two levels of descriptors (e.g., 0–1, 1–2), the descriptors were placed with a score of 0 or 3 accordingly in the comprehensive scales (e.g., for a 0–1 scale, descriptors for a score of 0 would correspond with a score of 0 in the comprehensive scale and the descriptors for a score of 1 would correspond with a score of 3). For scales with three levels of descriptors (e.g., 0–2, 1–3), the bottom and top level of descriptors were placed with a score of 0 or 3, respectively, and the middle level of descriptors was placed with a score of 1 or 2 according to where it fit best. In scales with five levels of descriptors (e.g., 0–4 and 1–5), the first level of descriptors was put with a score of 0, and the second and third levels of descriptors were placed with a score of 1. The fourth level of descriptors was placed with a score of 2 and the top level was put with a score of 3 in the comprehensive scale (e.g., in a scale ranging 0–4, the descriptors for a score of 0 would correspond with a score of 0 in the comprehensive scale, the descriptors for a score of 1 and 2 would both correspond with a score of 1, the descriptors for a score of 3 would correspond with a score of 2, and the descriptors for a score of 4 would correspond with a score of 3). Finally, for scales with six levels of descriptors (e.g., 0–5, 1–6), the first level of descriptors would correspond with a score of 0 in the comprehensive scale, and the second and third levels of descriptors would correspond with a score of 1. The fourth and fifth would correspond with a score of 2, and the last level would correspond with a score of 3 (e.g., in a 1–6 scale, the descriptors for a score of 2 and 3 would both correspond with a score of 1 in the comprehensive scale, and the descriptors for a score of 4 and 5 would both correspond with a score of 2). The comprehensive scales were reviewed, and duplicate expressions removed.
      Table 2Compilation of descriptors used in quality of inductions scales
      ScoreDescription
      0Smooth with no resistance: dog relaxes within 30 seconds, no jaw tone, no lateral palpebral reflex, no tongue tone, no response to laryngoscope placement, dog easily intubated with initial bolus dose within 45 seconds; perfect, smooth uncomplicated induction; smooth transition with no paddling; no swallowing, intubation at first attempt, no coughing, no struggling, no vocalization, calm transition; without excitement; very smooth with gradual patient relaxation; excellent: smooth and rapid transition from conscious to anesthetized with minimal resistance in terms of movement, minimal restraint required—1 nurse sufficient; uneventful induction; quiet, calm induction of anesthesia; no outward sign of excitement, rapidly assumes lateral recumbency, good muscular relaxation, easily intubated within 60 seconds of finishing dosing; bitch readily intubated after administration of no more than the calculated induction dose; minimal gagging during endotracheal intubation; good; acceptable; calm transition into anesthesia within 15 minutes after injection
      1Slight resistance but smooth: dog relaxes within 30 seconds, no jaw tone, no lateral palpebral reflex, no tongue tone, no response to laryngoscope placement, dog coughs on intubation and/or swallows once intubated, requires 1 or 2 subsequent boluses of induction drug, dog intubated within 45 seconds; good, induction uncomplicated; occasional slow paddling movements; quite smooth, some swallowing, intubation after 2–3 attempts, no coughing, some physical movement, no vocalization; fair, slight excitement/muscle twitching/limb movement; some swallowing, coughing, tongue or jaw movement; transition from conscious to anesthetized associated with some movements requiring restraint by a single assistant, movements do not interfere with process of endotracheal intubation; presence of some myoclonus; quiet and calm but slight muscle twitching; good (tracheal intubation easy but minimal reflex response or mildly persistent jaw tone); satisfactory, mild signs of excitement, no gagging during endotracheal intubation, tight jaw tone; fair, several attempts before successful intubation; intermediate; 1 but not more than 2 episodes of struggling, vocalization, excitement
      2Mild-moderate resistance: dog relaxes within 30 seconds, no jaw tone, no lateral palpebral reflex, dog responds to laryngoscope placement with tongue curl, requires 1 or 2 additional subsequent boluses of the drug to proceed, cough and swallow may also be noted, dog is intubated within 60 seconds, unacceptable quality, dog does not relax within 30 seconds, resistance to intubation attempt within 45 seconds, dog relaxes after intubation without further movement but is at a light plane, dog is intubated within 60 seconds; ok, induction difficult; moderate sustained paddling movements; moderately smooth, swallowing a lot, more than 3 attempts to intubate, coughing, vocalization and/or physical movement for more than half the induction time, some distress and excitement; poor, marked excitement/muscle twitching/limb movement; rather uneasy, bumpy, uneven; poor; fair: moderate excitation present during transition from conscious to anesthetized in terms of gross movement, vocalization, urination or defecation, firm restraint required—an additional person required for larger dogs—poor to medium muscle relaxation, making opening mouth for endotracheal intubation more difficult; marked excitation, firm restraint required but still difficult to retain dog in position, poor muscle relaxation making opening mouth difficult; myoclonus; mild signs of excitement, some struggling, may or may not be intubated within 60 seconds of finishing dosing; difficult to intubate and/or large amount of jaw tone; poor, difficult to intubate; multiple episodes of struggling
      3Excitement: paddling, hyperkinesis, vocalizing, defecation, urination, unable to intubate without significant number of subsequent doses of the induction drug, intubation > 60 seconds; rough; poor, vocalization and physical movement during entire induction period, major distress aggression or excitement, additional induction agent needed for intubation; very poor; rather agitated; unacceptable: marked excitation and struggling, and/or aggression, unable to maintain dog in position despite firm restraint; inhalant induction protocols—abandon, move to intravenous induction, intravenous induction protocols—abandon, reassess suitability of dog for anesthesia at this time; excitement evident with additional restraint required; intubation not possible even with additional induction agent; did not become recumbent or did so only briefly, little or no muscle relaxation; severe excitement; induction time > 15 minutes after injection; requiring physical restraint to prevent injury to the dog or the investigators
      Table 3Compilation of descriptors used in quality of recovery scales
      ScoreDescription
      0No sedation, dog attempts to leave the cage, whining, barking, animal is alert and responsive, resembling behavior observed before anesthesia, including ambulatory; perfect, walking without ataxia, smooth uncomplicated recovery; extubated, easy transition to alertness, coordinated movement; no excitement no paddling, vocalizing, trembling, or vomiting, no convulsions; quiet, nonvocal; excellent, whimpering free recovery, assumes sternal recumbency with little or no difficulty; raises head calmly, does not appear agitated; dog is relaxed during recovery; stood and walked without assistance or struggle, once standing did not return to sternal recumbency; no thrashing; requiring little or no physical restraint to prevent self-injury to the patient; dog achieved sternal recumbency and stood in 1 attempt; good, transition to an awake state free from hyperactivity, aggression, hyperventilation, prolonged recovery time, or gastric dilatation
      1Mild sedation, mild to moderate resistance to manual restraint in lateral recumbency in cage, moderately interactive, whining but responds to voice and caregivers, attempts to assume sternal recumbency and/or standing position but able to maintain balance; good, walking with minimal ataxia, recovery uncomplicated; fairly easy transition, holds head up, no body movement attempted; some incoordination, does not startle, generally quiet; quite smooth, a little excitement, possibly some shivering but no paddling, vocalizing, trembling or vomiting, no convulsions; unremarkable transition, routine extubation; no uncoordinated movement; smooth, some excitement or paddling or vocalization on recovery; with slight short < 30 seconds excitement; may have slight whimpering < 1 minute, somewhat prolonged recumbency (>40 minutes following atipamezole); some struggling, requires assistance to sternal recumbency or standing, responsive to external stimuli; dog transiently pants or whines and/or appears to gently paddle with front feet immediately upon extubation, but then settles; fair transition to alertness, short period of disorientation; with 1 of these conditions—struggling, vocalization, or excitement and requiring physical restraint to prevent self-injury to the patient; at least 1 but not more than 2 episodes of struggling, vocalization, excitement or unsuccessful attempts to gain sternal recumbency or stand in recovery; muscle twitching or movement of limbs
      2Moderate sedation, no excitement, animal remains in lateral recumbency in cage with minimal to no restraint, mild response to voice or touch, no attempts to sternal or standing; not smooth, moderate excitement, persistent paddling, vocalization and trembling, vomiting may be observed; ok, walking with moderate ataxia, recovery difficult; limited muscle control, startles; uncoordinated whole body movements; moderately smooth, no convulsions, struggling during transition; unremarkable transition, routine extubation, startles, difficult extubation with chewing and coughing elicited; easily calmed; poor; with mild excitement; may have some excitation < 2 minutes, whimpering < 5 minutes, attention to wound area suspected, consider rescue analgesia; dog is panting/whining or whimpering, wondering if they are ‘present’, behavior continues and may worsen over time; fair, thrashing when moving; substantial period of disorientation, does not startle, generally quiet; disoriented with some emergence delirium, limited muscle control; moving around rapidly unaware of surroundings, growling, but responds to gentle handling by calming down; restlessness but no need for restraint; repeated attempts to move from lateral to sternal recumbency, premature standing with hind-limb weakness, once standing, returned to sternal recumbency; 2 of these conditions – struggling, vocalization, or excitement and requiring physical restraint to prevent self-injury to the patient; multiple episodes of struggling, vocalization, ataxia, excitement, or unsuccessful attempts when reaching sternal recumbency or standing
      3Profound sedation, dull, depressed, no restraint required to keep animal in lateral recumbency in cage, does not respond to voice or touch, no attempts to sternal recumbency and/or nonambulatory; rough, walking with significant ataxia/crawling; emergence delirium, thrashing, cannot easily restrain; poor, extreme excitement observed, aggression, vocalizing, violent movements or convulsions, rescue sedation or anticonvulsant drugs necessary; violent transition., restraint required for extubation; uncoordinated movement; very poor, paddling, with risk of injury; vomiting may be observed, convulsions noted; poor, excitation/whimpering > 10 minutes, no persistent licking/biting at wound, persistent biting/scratching at wound; prolonged struggling, unable to assume sternal recumbency or difficulty in maintaining sternal or standing position, becomes hyperkinetic when assisted; dog is agitated, does not seem to be ‘present’; rough recovery, opisthotonos and/or clonic-tonic seizures; startles; moving around rapidly unaware of surroundings, growling, which does not respond to gentle handling; premature standing with splayed and weak hind limbs, once standing, repeatedly returned to sternal recumbency; urinating, defecating; 2 or more of these conditions—struggling, vocalization, or excitement and requiring physical restraint to prevent self-injury to the patient; excessively long recovery times or hyperactivity, hyperventilation, or gastric dilatation; muscle twitching, head movements

      Results

      The search yielded 267 studies and, from these, 80 studies were chosen based on abstract content (Fig. 1 & Table 1). The articles were reviewed and duplicates and nonapplicable studies were removed. The citations of the 80 articles were reviewed as well, and additional studies were chosen and reviewed. A total of 70 articles were included in the study, and of those, 18 articles were chosen for inclusion after reviewing citations. Of the studies that were cited within the selected studies as relevant to building the induction or recovery scales, 12 were not deemed applicable to this study and were not included. These studies were cited as the reference study for a scale but were not included because of failure to meet the inclusion criteria, such as studies including cats or studies not measuring quality of induction or recovery directly (
      • Carroll G.L.
      • Howe L.B.
      • Slater M.R.
      • et al.
      Evaluation of analgesia provided by postoperative administration of butorphanol to cats undergoing onychectomy.
      ;
      • Murison P.J.
      Effect of propofol at two injection rates or thiopentone on post-intubation apnoea in the dog.
      ;
      • Mathis A.
      • Pinelas R.
      • Brodbelt D.C.
      • Alibhai H.I.K.
      Comparison of quality of recovery from anaesthesia in cats induced with propofol or alfaxalone.
      ). The publication year range was 1994–2019, and sample size ranged from five to 149 dogs of various breeds undergoing a variety of procedures. There were 45 total induction scales, 16 of which were unique SDSs and one was a unique VAS. Of the 44 total SDSs for induction, scales with four levels were the most common. One had two levels, 11 had three levels, 30 had four levels and two had five levels. There were 68 total recovery scales, of which there were 18 unique SDSs, four unique VASs and one unique 0–10 NRS. Additionally, there were two composite NRSs that scored multiple characteristics of recovery individually. Of the 56 total SDSs for recovery, scales with four levels were the most common; one had two levels, six had three levels, 32 had four levels, 11 had five levels and six had six levels.
      Figure 1
      Figure 1Study flow diagram. Adapted from
      • Page M.J.
      • Moher D.
      • Bossuyt P.M.
      • et al.
      PRISMA 2020 explanation and elaboration: updated guidance and exemplars for reporting systematic reviews.
      .
      For the induction scales, a 2008 study studying fentanyl or midazolam for co-induction with propofol in dogs was the most frequently referenced (n = 10) (
      • Covey-Crump G.L.
      • Murison P.J.
      Fentanyl or midazolam for co-induction of anaesthesia with propofol in dogs.
      ). The most frequently referenced recovery scale (n = 6) was adapted from a study on the effect of propofol and etomidate on induction and cardiopulmonary variables in dogs; several studies (n = 5) also used the induction scale (
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      ). There was no evidence of psychometric validity for any of the scales in any of the studies (Table 1). The study by
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      using a simple descriptive induction and recovery scale was described as a ‘standardized scale’ by four other studies (
      • Maney J.K.
      • Shepard M.K.
      • Braun C.
      • et al.
      A comparison of cardiopulmonary and anesthetic effects of an induction dose of alfaxalone or propofol in dogs.
      ;
      • Seo J.I.
      • Han S.H.
      • Choi R.
      • et al.
      Cardiopulmonary and anesthetic effects of the combination of butorphanol, midazolam and alfaxalone in Beagle dogs.
      ;
      • Canfrán S.
      • Bustamante R.
      • González P.
      • et al.
      Comparison of sedation scores and propofol induction doses in dogs after intramuscular administration of dexmedetomidine alone or in combination with methadone, midazolam, or methadone plus midazolam.
      ;
      • Diao H.X.
      • Jiang S.
      • Gao P.Y.
      • et al.
      Comparison of the effects of propofol and emulsified isoflurane alone or combined with dexmedetomidine on induction of anesthesia in dogs.
      ). However,
      • Sams L.
      • Braun C.
      • Allman D.
      • Hofmeister E.
      A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs.
      did not describe any standardization or validation methods, or mention the word standardized.
      The most commonly reported issue among these scales was subjectivity. Multiple studies described poor results attributed to the nature of their scoring instruments and/or unclear phrases and instructions for using the scale (
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      ;
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      ;
      • Pinelas R.
      • Alibhai H.I.
      • Mathis A.
      • et al.
      Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone-a clinical trial.
      ;
      • Copeland J.E.
      • Hofmeister E.H.
      • Brainard B.M.
      • Quandt J.E.
      Reliability of video recordings to evaluate quality of anesthesia recovery in dogs.
      ;
      • Warrit K.
      • Griffenhagen G.
      • Goh C.
      • Boscan P.
      Comparison of ultrasound-guided lumbar plexus and sciatic nerve blocks with ropivacaine and sham blocks with saline on perianesthetic analgesia and recovery in dogs undergoing tibial plateau leveling osteotomy surgery.
      ). Another issue, reported in two studies, was the inability to compare studies because of variations in scoring instruments (
      • O'Hagan B.
      • Pasloske K.
      • McKinnon C.
      • et al.
      Clinical evaluation of alfaxalone as an anaesthetic induction agent in dogs less than 12 weeks of age.
      ;
      • White K.L.
      • Yates D.
      Clinical comparison of alfaxalone, ketamine and propofol following medetomidine and methadone in dogs.
      ). One study reported using the same unvalidated scale they had used in previous research for consistency (
      • Tamura J.
      • Hatakeyama N.
      • Ishizuka T.
      • et al.
      The pharmacological effects of intramuscular administration of alfaxalone combined with medetomidine and butorphanol in dogs.
      ). The VAS did not show more consistent results than the SDS in several studies. Two studies containing a VAS contained unclear descriptors (
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      ,
      • Reed R.A.
      • Quandt J.E.
      • Brainard B.M.
      • et al.
      The effect of induction with propofol or ketamine and diazepam on quality of anaesthetic recovery in dogs.
      ), another study was affected by longer recovery time (
      • Conde Ruiz C.
      • Del Carro A.P.
      • Rosset E.
      • et al.
      Alfaxalone for total intravenous anaesthesia in bitches undergoing elective caesarean section and its effects on puppies: a randomized clinical trial.
      ), and one had only moderate agreement between scorers (
      • Copeland J.E.
      • Hofmeister E.H.
      • Brainard B.M.
      • Quandt J.E.
      Reliability of video recordings to evaluate quality of anesthesia recovery in dogs.
      ). Finally, only 43 of the 70 studies listed a reference study for the scale that was used. The remaining 27 studies did not provide any evidence of construction technique for any of the scales.
      To assess the content of the induction and recovery scales, the descriptors from each scale were compiled into a four-level SDS ranging 0–3, with 0 being the smoothest induction/recovery and 3 being the worst (Table 2, Table 3). From this, an induction scored as 0 would be a smooth induction with easy intubation and no struggling or reflexes (calm, easily intubated, good muscular relaxation; Table 2). Score of 1 would be a quick relaxation but with some reflexes or slight difficulty intubating (slight resistance, some movements, slight muscle twitching; Table 2). Score of 2 would involve moderate struggling and coughing or other reflexes with additional boluses of drug required (moderate excitation, resistance to intubation, poor muscle relaxation; Table 2). Score of 3 would be unacceptable, with vocalization, struggling and inability to intubate (paddling, vocalization, aggression, additional restraint required; Table 2). A recovery scored as 0 would be a quick transition from sedation to alertness, with no disorientation or struggling (no sedation, coordinated movement, raises head calmly; Table 3). Score of 1 would have a slightly longer transition to alertness and very few instances of struggling or excitement (moderately interactive, some shivering but no paddling; Table 3). Score of 2 would involve some episodes of struggling (paddling, coughing, inability to stand on first attempt) and a prolonged time to consciousness (thrashing when moving, vomiting may be observed, limited muscle control; Table 3). Score of 3 would be a poor recovery with an excessively prolonged time to consciousness, vocalization, dysphoria, poor muscle control and inability to stand (does not respond to voice or touch, emergence delirium, unaware of surroundings; Table 3).

      Discussion

      A validated and accepted scale for measuring the quality of induction and recovery in dogs does not currently exist. The results of this scoping review show large inconsistencies among researchers in their methods of selecting, using and validating scales for quality of induction and recovery in dogs. No literature was found that investigated the validation of a quality of induction or recovery scale in dogs. All studies chosen included an evaluation of induction and recovery within an investigation of various anesthetic protocols, comparison of analgesics or other related research. The results of the scale analysis show that there are common expressions being used in the developments of induction and recovery scales across studies. It is also evident that there are many similar expressions that are on different levels of quality (e.g. ‘whining’ appears on recovery scores with a value of 0 or 1 and ‘vocalization’ appears on recovery scales with a value of 1, 2 or 3). This shows that researchers are producing similar scales, but there are discrepancies created by the differing allocations of these expressions to level of quality.
      This problem was further evidenced through review of the literature. The inability to compare the results between two similar studies because of differences in scoring systems was commonly found among scales (
      • O'Hagan B.
      • Pasloske K.
      • McKinnon C.
      • et al.
      Clinical evaluation of alfaxalone as an anaesthetic induction agent in dogs less than 12 weeks of age.
      ;
      • White K.L.
      • Yates D.
      Clinical comparison of alfaxalone, ketamine and propofol following medetomidine and methadone in dogs.
      ). The data obtained from a study cannot be fully analyzed if it cannot be compared with other research. The large variability between scoring systems has created a disconnect between studies that are very similar in nature. The resulting effect is that there is a large section of literature examining the same thing but held to the standard of their own unique scoring instrument instead of a tested, valid and reliable instrument, yielding incompatible results.
      Little research has been done on quality of induction and recovery specifically, but the inability to compare studies renders the possibility of retrospective studies for this purpose almost impossible. In some instances, scales were used in multiple studies, but did not measure the same variable. For example, a scale used to measure recovery quality in one study (
      • Caines D.
      • Sinclair M.
      • Valverde A.
      • et al.
      Comparison of isoflurane and propofol for maintenance of anesthesia in dogs with intracranial disease undergoing magnetic resonance imaging.
      ) was used to measure extubation quality in another study (
      • Liao P.
      • Sinclair M.
      • Valverde A.
      • et al.
      Induction dose and recovery quality of propofol and alfaxalone with or without midazolam coinduction followed by total intravenous anesthesia in dogs.
      ). This case emphasizes the ambiguity of the definitions of induction and recovery quality, despite being commonly measured variables.
      In one study (
      • Ferreira J.P.
      • Dzikiti T.B.
      • Zeiler G.E.
      • et al.
      Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs.
      ), the recovery scale that was used was adapted from another study (
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      ); however, the scale was previously questioned for its validity and usefulness (
      • Ferchichi S.
      • Troncy E.
      • Guillot M.
      • et al.
      Excitement in dogs recovering from alfaxalone anaesthesia: is the absent drug blamed in error?.
      ). According to
      • Ferchichi S.
      • Troncy E.
      • Guillot M.
      • et al.
      Excitement in dogs recovering from alfaxalone anaesthesia: is the absent drug blamed in error?.
      , the recovery scale used in the original study was not sufficient to measure what was intended, and further statistical measurements were needed to test for accuracy and responsiveness to change. Without confidence in the integrity of the original scale, any subsequent studies using the same scale cannot produce confident results.
      It was found that while there were only 16 unique induction SDSs and 18 unique recovery scales from the 70 studies, only a fraction of them actually listed a reference study or described the construction of the scale. One study (
      • Reed R.A.
      • Quandt J.E.
      • Brainard B.M.
      • et al.
      The effect of induction with propofol or ketamine and diazepam on quality of anaesthetic recovery in dogs.
      ) included no information about the recovery scale used but was found to be nearly identical to a scale used in three other studies (
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      ;
      • Pinelas R.
      • Alibhai H.I.
      • Mathis A.
      • et al.
      Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone-a clinical trial.
      ;
      • Copeland J.E.
      • Hofmeister E.H.
      • Brainard B.M.
      • Quandt J.E.
      Reliability of video recordings to evaluate quality of anesthesia recovery in dogs.
      ). This complicates the ability to trace scales back to their original study, furthering the problem of validity confirmation. There is evident uncertainty in the origin of the current scales in use for research, made clear by the appearance of scales throughout the literature that give varying levels of credit to the study it was adapted from. When a study does cite a previously published scale, the studies referenced are not necessarily the study that created the instrument. For example, the scale used by
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      was adapted and referenced by four other studies (
      • Ferreira J.P.
      • Dzikiti T.B.
      • Zeiler G.E.
      • et al.
      Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs.
      ;
      • Hampton C.E.
      • Riebold T.W.
      • Mandsager R.E.
      Recovery characteristics of dogs following anesthesia induced with tiletamine-zolazepam, alfaxalone, ketamine-diazepam, or propofol and maintained with isoflurane.
      ;
      • Kropi J.
      • Hughes J.L.
      Effect of midazolam on the quality and duration of anaesthetic recovery in healthy dogs undergoing elective ovariohysterectomy or castration.
      ;
      • Lehnus K.S.
      • Brearley J.
      Evaluation of two different radiotherapy anaesthetic protocols for dogs: a randomized clinical crossover trial.
      ), but this scale is also similar to the scale used in
      • Kennedy M.J.
      • Smith L.J.
      A comparison of cardiopulmonary function, recovery quality, and total dosages required for induction and total intravenous anesthesia with propofol versus a propofol-ketamine combination in healthy Beagle dogs.
      . The study by
      • Kennedy M.J.
      • Smith L.J.
      A comparison of cardiopulmonary function, recovery quality, and total dosages required for induction and total intravenous anesthesia with propofol versus a propofol-ketamine combination in healthy Beagle dogs.
      does not indicate that it adapted the scale from
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      . Two older studies used a scale that was similar to the one used in
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      and
      • Kennedy M.J.
      • Smith L.J.
      A comparison of cardiopulmonary function, recovery quality, and total dosages required for induction and total intravenous anesthesia with propofol versus a propofol-ketamine combination in healthy Beagle dogs.
      but neither
      • Jiménez C.P.
      • Mathis A.
      • Mora S.S.
      • et al.
      Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging.
      nor
      • Kennedy M.J.
      • Smith L.J.
      A comparison of cardiopulmonary function, recovery quality, and total dosages required for induction and total intravenous anesthesia with propofol versus a propofol-ketamine combination in healthy Beagle dogs.
      referenced these previous studies (
      • Buback J.L.
      • Boothe H.W.
      • Carroll G.L.
      • Green R.W.
      Comparison of three methods for relief of pain after ear canal ablation in dogs.
      ;
      • Wolfe T.M.
      • Bateman S.W.
      • Cole L.K.
      • Smeak D.D.
      Evaluation of a local anesthetic delivery system for the postoperative analgesic management of canine total ear canal ablation-a randomized, controlled, double-blinded study.
      ). The connections between instruments become too numerous to summarize, but situations like these present many challenges to a researcher attempting to find a reputable scale.
      Furthermore, researchers have varying reasons for choosing a particular scale, and some researchers have chosen a VAS over an SDS because of the potential unreliability of existing SDSs for induction and recovery (
      • Love E.J.
      • Holt P.E.
      • Murison P.J.
      Recovery characteristics following maintenance of anaesthesia with sevoflurane or isoflurane in dogs premedicated with acepromazine.
      ;
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      ;
      • Hunt J.R.
      • Slingsby L.S.
      • Murrell J.C.
      The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.
      ). It was noted by three studies that the VAS in general was more reliable because of known testing of the scale for similar variables (
      • Love E.J.
      • Holt P.E.
      • Murison P.J.
      Recovery characteristics following maintenance of anaesthesia with sevoflurane or isoflurane in dogs premedicated with acepromazine.
      ;
      • Lopez L.A.
      • Hofmeister E.H.
      • Pavez J.C.
      • Brainard B.M.
      Comparison of recovery from anesthesia with isoflurane, sevoflurane, or desflurane in healthy dogs.
      ;
      • Hunt J.R.
      • Slingsby L.S.
      • Murrell J.C.
      The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.
      ). One study specifically pointed out the lack of a widely accepted scoring instrument for recovery and chose the VAS for higher sensitivity (
      • Hunt J.R.
      • Slingsby L.S.
      • Murrell J.C.
      The effects of an intravenous bolus of dexmedetomidine following extubation in a mixed population of dogs undergoing general anaesthesia and surgery.
      ). However, several studies using the VAS still had inconsistent results for various reasons (
      • Lozano A.J.
      • Brodbelt D.C.
      • Borer K.E.
      • et al.
      A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging.
      ;
      • Conde Ruiz C.
      • Del Carro A.P.
      • Rosset E.
      • et al.
      Alfaxalone for total intravenous anaesthesia in bitches undergoing elective caesarean section and its effects on puppies: a randomized clinical trial.
      ;
      • Copeland J.E.
      • Hofmeister E.H.
      • Brainard B.M.
      • Quandt J.E.
      Reliability of video recordings to evaluate quality of anesthesia recovery in dogs.
      ;
      • Reed R.A.
      • Quandt J.E.
      • Brainard B.M.
      • et al.
      The effect of induction with propofol or ketamine and diazepam on quality of anaesthetic recovery in dogs.
      ). This implies that the usage of alternate scoring instruments to escape the subjectivity and insensitivity of SDSs for recovery and induction quality is potentially still altering the data, even without taking into account that these scoring systems have not been tested to measure induction/recovery quality specifically (
      • Love E.J.
      • Holt P.E.
      • Murison P.J.
      Recovery characteristics following maintenance of anaesthesia with sevoflurane or isoflurane in dogs premedicated with acepromazine.
      ).
      Regarding subjectivity, inconsistent results resulting from misinterpretation by the scorers or lack of sufficient training to use the scale are easily fixable, but researchers have no preexisting validated induction or recovery scoring systems to draw from to minimize these inconsistencies. The risk of subjectivity when using a scale is unavoidable, but it can be reduced considerably with validation and proper instructions for usage (
      • Elasy T.A.
      • Gaddy G.
      Measuring subjective outcomes: rethinking reliability and validity.
      ).
      Whereas creation and psychometric testing of a common scale, or validation of a smaller number of scales, to measure quality of induction and recovery would be ideal, it must be acknowledged that this is a difficult task to realize. There are many variables that affect induction and recovery, such as neurological symptoms, pain, types of premedication and behavior, which may also affect the quality and subsequent score of an induction or recovery when using an instrument. The induction and recovery processes also do not have clearly defined end points. This may lead researchers to create their own scales for convenience, their own ease of use and to fit the specific needs of their study. Furthermore, the validation process takes a long time, especially when the instrument is to be used on such a wide range of subjects (dogs undergoing different types of surgery, different levels of pain, drugs used, etc.). In light of this, it is important to note that the goal of this study is to collect information on current scales, and a deficiency has been found. It is not a gap that will be easily bridged, but the evidence provided in this paper serves to present the problem and urge researchers to strive toward continual improvement.
      There is a potential limitation in that during the search, articles that were applicable to this study were overlooked because the abstract did not mention the use of an induction or recovery scale. The usage of one database to conduct the scoping review also limits the breadth of the search. It is possible that the use of the ‘best match’ search function on PubMed over the general search sorted by ‘most recent’ may have excluded relevant studies. Only four phrases were used to perform the search and condensing these phrases or adding additional searches may have yielded more results. In addition, studies containing behavioral scales for induction and recovery were included or excluded at the discretion of the investigator, which may have impacted results. The literature search, study selection and data analysis were performed by one investigator, which introduces the potential for bias. Several studies did not give a reference with their scale or describe a construction or validity process, so it was not always possible to discover the source of a scale.

      Conclusion

      A thoroughly tested and validated scale for measuring the quality of induction and recovery in dogs does not exist in the current literature. A large disagreement exists between studies on the use of induction and recovery scales, and many have reported inconsistent results with current instruments. Consequently, the results of this study suggest that researchers should examine a scale closely before including it in their work to ensure that it measures the appropriate variable, as well as investigate the construction of the scale to ensure the most reliability. These results should prompt researchers to psychometrically validate, and/or assess for reliability, instruments currently used with further testing. Furthermore, it is recommended that an induction and recovery scale intended for wide-scale use be constructed and tested extensively for validation and reliability using psychometric principles.

      Authors’ contributions

      KLW: study design, conducting the search, data collection, data analysis, preparation of manuscript. EHH: study design, preparation of manuscript. Both authors read and approved the final version of the manuscript.

      Conflict of interest statement

      Authors declare no conflict of interest. A disclosure is noted that EHH is a deputy editor of this journal but had no access to the review process.

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