Anesthetic effects of ketamine-medetomidine-hydromorphone in dogs during high-quality, high-volume surgical sterilization program under field conditions.

OBJECTIVE: 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. STUDY DESIGN: Prospective, observational, field study. ANIMALS: A total of 23 female and eight male dogs (14.2 ± 7.7 kg; age ≥ 8 weeks). METHODS: 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). RESULTS: 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.