The hemodynamic effects of medetomidine continuous rate infusions in the dog



      To characterize the hemodynamic effects of continuous rate infusions (CRI) of medetomidine administered at doses ranging from 0 to 3 μg kg−1 hour−1.

      Study design

      Prospective, blinded, randomized experimental trial.


      Six adult purpose-bred mongrel dogs.


      Anesthesia was induced with sevoflurane for placement of arterial and venous catheters. Dogs recovered from anesthesia after which baseline hemodynamic measurements were obtained via lithium dilution cardiac output (CO) determination, with subsequent measurements via pulse power analysis to provide continuous CO determinations. Medetomidine, 1, 2, or 3 μg kg−1 hour−1 or a volume equivalent placebo, was administered via CRI for 60 minutes. Systolic, mean, and diastolic arterial pressure, heart rate (HR), CO and stroke volume were measured and stroke index (SI), cardiac index (CI), total peripheral resistance (TPR), and total peripheral resistance index (TPRI) were calculated at 3, 7, 10, 20, 30, 45, 60, 90, and 120 minutes from the start of the infusion.


      Increase in dose decreased SI by 25%, 19%, and 30%, HR by 33%, 57%, and 60%, CI by 50%, 65%, 70% and increased TPRI by 109%, 235%, and 222% from baseline to the 60-minute measurement for the 1, 2, and 3 μg kg−1 hour−1 doses, respectively. HR, TPRI, and CI all showed significant differences over the duration of the study from the placebo treatment.


      Medetomidine CRI produces clinically relevant changes in CO, TPR, and HR. The demonstrated decrease in CO is largely because of bradycardia and the degree of cardiovascular depression appears to be dose-dependent. These findings are consistent with previously described hemodynamic changes with single bolus administration of medetomidine.

      Clinical relevance

      Low-dose medetomidine CRIs produce clinically relevant hemodynamic depression at doses as low as 1 μg kg−1 hour−1 and should be used cautiously in dogs.


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        • Ambrisko TD
        • Hikasa Y
        • Sato K
        Influence of medetomidine on stress-related neurohormonal and metabolic effects caused by butorphanol, fentanyl and ketamine administration in dogs.
        Am J Vet Res. 2005; 66: 406-412
        • Bein G
        • Meybohm P
        • Cavus E
        • et al.
        The reliability of pulse contour-derived cardiac output during hemorrhage and after vasopressor administration.
        Anesth Analg. 2007; 105: 107-113
        • Bloor B
        • Frankland M
        • Alper G
        • et al.
        Haemodynamic and sedative effects of dexmedetomidine in dog.
        J Pharmacol Exp Ther. 1992; 263: 690-697
        • Duffy AL
        • Butler AL
        • Radecki SV
        • et al.
        Comparison of continuous arterial pressure waveform analysis with the lithium dilution technique to monitor cardiac output in conscious dogs with systemic inflammatory response syndrome.
        Am J Vet Res. 2009; 70: 1365-1373
        • Ebert TJ
        • Hall JE
        • Barney JA
        • et al.
        The effects of increasing plasma concentrations of dexmedetomidine in humans.
        Anaesthesiology. 2000; 93: 382-394
        • Enouri SS
        • Kerr CL
        • McDonell WN
        • et al.
        Effects of a peripheral alpha-2 adrenergic-receptor antagonist on the hemodynamic changes induced by medetomidine administration in conscious dogs.
        Am J Vet Res. 2008; 69: 728-736
        • Flacke JW
        • Flacke WE
        • Bloor BC
        • et al.
        Hemodynamic effects of dexmedetomidine, an alpha 2-adrenergic agonist, in autonomically denervated dogs.
        J Cardiovasc Pharmacol. 1990; 16: 616-623
        • Flacke W
        • Flacke J
        • Bloor B
        • et al.
        Effects of dexmedetomidine on systemic and coronary haemodynamics in the anesthetized dog.
        J Cardiothorac Vasc Anesth. 1993; 7: 41-49
        • Grimm KA
        • Tranquilli WJ
        • Gross DR
        • et al.
        Cardiopulmonary effects of fentanyl in conscious dogs and dogs sedated with a continuous rate infusion of medetomidine.
        Am J Vet Res. 2005; 66: 1222-1226
        • Honkavaara JM
        • Raekallio MR
        • Kuusela EK
        • et al.
        The effects of L-659,066, a peripheral alpha-2-adrenoceptor antagonist, on dexmedetomidine-induced sedation and bradycardia in dogs.
        Vet Anaesth Analg. 2008; 35: 409-413
        • Housmans P
        Effects of dexmedetomidine on contractility, relaxation and intracellular calcium transients of isolated ventricular myocardium.
        Anesthesiology. 1990; 73: 919-922
        • Ko J
        • Fox S
        • Mandsager R
        Sedative and cardiorespiratory effects of medetomidine, medetomidine-butorphanol, and medetomidine-ketamine in dogs.
        J Vet Med Assoc. 2000; 216: 1578-1583
        • Kuo WC
        • Keegan RD
        Comparative cardiovascular, analgesic, and sedative effects of medetomidine, medetomidine-hydromorphone, and medetomidine-butorphanol in dogs.
        Am J Vet Res. 2004; 65: 931-937
        • Kuusela E
        • Raekallio M
        • Antilla M
        • et al.
        Clinical effects and pharmacokinetics of medetomidine and its enantiomers in dogs.
        J Vet Pharmacol Ther. 2000; 23: 15-20
        • Maze M
        • Tranquilli W
        Alpha-2 adrenoceptor agonists: defining the role in clinical anesthesia.
        Anesthesiology. 1991; 74: 581-605
        • De Morais HS
        • Muir WW
        The effects of medetomidine on cardiac contractility in autonomically blocked dogs.
        Vet Surg. 1995; 24: 356-364
        • Ossipov M
        • Harris S
        • Lloyd P
        • et al.
        Antinociceptive interaction between opioids and medetomidine: systemic additivity and spinal synergy.
        Anesthesiology. 1990; 73: 1227-1235
        • Pascoe PJ
        The cardiovascular effects of dexmedetomidine given by continuous infusion during isoflurane anesthesia in dogs.
        Vet Anaesth Analg. 2005; 32 (abstract).: 9
        • Pascoe PJ
        • Raekallio M
        • Kuusela E
        • et al.
        Changes in the minimum alveolar concentration of isoflurane and some cardiopulmonary measurements during three continuous infusion rates of dexmedetomidine in dogs.
        Vet Anaesth Analg. 2006; 33: 39-103
        • Pittman J
        • Bar-Yosef S
        • Sumping J
        • et al.
        Continuous cardiac output monitoring with pulse contour analysis: a comparison with lithium indicator dilution cardiac output measurement.
        Crit Care Med. 2005; 33: 2015-2021
        • Pypendop B
        • Verstegen J
        Hemodynamic effects of medetomidine in the dog: a dose titration study.
        Vet Surg. 1998; 27: 612-622
        • Rhodes A
        • Sunderland R
        Arterial pulse power analysis: the LiDCO™ plus system.
        in: Pinksy MR Payen D Functional Hemodynamic Monitoring: Update in Intensive Care and Emergency Medicine. Springer-Verlag, Heidelberg, Germany2005: 183-192
        • Savola JM
        Cardiovascular actions of medetomidine and their reversal by atipamezole.
        Acta Vet Scand. 1989; 85: 39-47
        • Schauvliege S
        • Van den Eege A
        • Duchateau L
        • et al.
        Comparison between lithium dilution and pulse contour analysis techniques for cardiac output measurement in isoflurane anaesthetized ponies: influence of different inotropic drugs.
        Vet Anaesth Analg. 2009; 36: 197-208
        • Valtonlina C
        • Robben JH
        • Uilenreef J
        • et al.
        Clinical evaluation of the efficacy and safely of a constant rate infusion of dexmedetomidine for postoperative pain management in dogs.
        Vet Anaesth Analg. 2009; 36: 369-383
        • Virtanen R
        Pharmacologic profiles of medetomidine and its antagonist atipamezole.
        Acta Vet Scand. 1989; 85: 85-88