To describe the anesthetic and adverse effects of an injectable anesthetic protocol
in dogs as part of a high-volume sterilization program under field conditions in Belize.
Prospective, observational, field study.
A total of 23 female and eight male dogs (14.2 ± 7.7 kg; age ≥ 8 weeks).
Using a volume per kg-based dose chart, dogs were administered ketamine (4.5 mg kg−1), medetomidine (0.04 mg kg−1) and hydromorphone (0.09 mg kg−1) intramuscularly. After induction of anesthesia, an endotracheal tube was inserted
and dogs were allowed spontaneous breathing in room air. Monitoring included peripheral
oxygen saturation (SpO2), mean arterial pressure (MAP), heart rate (HR), respiratory rate, rectal temperature
and end-tidal carbon dioxide (Pe′CO2). Meloxicam (0.2 mg kg−1) was administered subcutaneously after surgery. Data were analyzed with linear models
and chi-square tests (p < 0.05).
Onset of lateral recumbency (3.4 ± 2 minutes) was rapid. Desaturation (SpO2 < 90%) was observed at least once in 64.5% of dogs and was more frequent in large
dogs (p = 0.019). Hypercapnia (Pe′CO2 ≥ 50 mmHg; 6.7 kPa) was observed in 48.4% of dogs. MAP was 111 ± 19 mmHg, mean ±
standard deviation. Hypertension (MAP ≥ 120 mmHg), bradycardia (HR ≤ 60 beats minute−1) and tachycardia (HR ≥ 140 beats minute−1) were observed in 45.2%, 16.1% and 3.3% of dogs, respectively. Hypotension and hypothermia
were not observed. Sex was not significantly associated with any complication. Return
of swallowing reflex and time to standing were 71 ± 23 and 152 ± 50 minutes after
injection, respectively. Return of swallowing was significantly longer in large dogs.
Conclusions and clinical relevance
At the doses used, ketamine–medetomidine–hydromorphone was effective in dogs for high-volume
sterilization. In this field setting, adverse effects included hypoventilation, hypoxemia
and prolonged recovery.