A comparison of xylazine and medetomidine in an anesthetic combination in New Zealand White Rabbits.

A comparison was made of two anesthetic protocols for cardiothoracic surgery in rabbits. Eight male New Zealand White rabbits (2.8 to 3.2 kg) were used in a double crossover study. Each rabbit received intramuscular ketamine (35 mg/kg), xylazine (5 mg/kg), and buprenorphine (0.03 mg/kg) or ketamine (35 mg/kg), medetomidine (0.5 mg/kg), and buprenorphine (0.03 mg/kg) on alternate weeks. After intramuscular injection, each rabbit was intubated and placed on 0.75% isoflurane in 1 L O2/min. Palpebral, pedal, and righting reflexes and cardiopulmonary parameters were measured every minute for the first 10 min and every 5 min thereafter. Rabbits were monitored for 20 min of spontaneous ventilation followed by 60 min of intermittent positive pressure ventilation. Intermittent positive pressure ventilation and isoflurane then were discontinued and recovery monitored. Systolic, mean, and diastolic blood pressures were higher in the medetomidine-treated rabbits. Return of the palpebral, pedal, and righting reflexes was prolonged in the medetomidine-treated rabbits. There were no differences in heart rate, respiratory rate, return to spontaneous breathing, and time to extubation between the two groups. These results indicate medetomidine can be safely used in rabbit anesthesia, provides acceptable cardiovascular parameters, and induces a longer anesthetic period than that of xylazine.