Guaifenesin-Ketamine-Xylazine Infusions to Provide Anesthesia in Donkeys

The purpose of this study was to determine a satisfactory combination of guaifenesin, ketamine, and xylazine (GKX) that would produce safe and satisfactory total intravenous anesthesia in donkeys for use under field conditions. Donkeys require higher amounts of ketamine in GKX to achieve satisfactory anesthetic levels without producing excessive depression with guaifenesin. Five adult standard donkeys (average weight, 264 kg) were anesthetized with 1.5 mg/mL ketamine, 0.5 mg/mL xylazine, 50 mg/mL guaifenesin (GKX-1); 2.0 mg/mL ketamine, 0.5 mg/mL xylazine, 50 mg/mL guaifenesin (GKX-2); or 2.0 mg/mL ketamine, 0.75 mg/mL xylazine, 50 mg/mL guaifenesin (GKX-3). For the first trial, two donkeys received GKX-1, two received GKX-2, and one received GKX-3. One donkey received GKX-1, one received GKX-2, and three received GKX-3 for the second trial. In the final trial, two received GKX-1, two received GKX-2, and one received GKX-3. Donkeys were sedated with xylazine (1.1 mg/kg body weight) intravenously, and anesthesia was induced using intravenous GKX-1, GKX-2, or GKX-3. Anesthesia was maintained for 45 minutes; temperature, respiration rate, heart rate, hemoglobin saturation, partial pressure of arterial oxygen (PaO2), partial pressure of carbon dioxide in arterial gas (PaCO2), and pH were measured. There was no significant difference between combinations for temperature, respiration rate, heart rate, hemoglobin saturation, PaCO2, or pH. At 30 and 45 minutes, GKX-3 produced significantly (P < .05) lower PaO2 values than GKX-1 and GKX-2. GKX-3 is not recommended for field use in donkeys because of respiratory depression (PaO2= 48.7 [±5.84] and 46.0 ± 3.11 mmHg at 30 and 45 minutes, respectively), whereas more voluntary movement was apparent with GKX-1. GKX-2 produced satisfactory anesthesia without significant respiratory depression in donkeys and should produce safe and effective anesthesia in donkeys under field conditions.