A comparison of ketamine combined with dexmedetomidine and ketamine combined with xylazine on analgesia in rabbits

Abstract

The effects of ketamine combined with dexmedetomidine and ketamine combined with xylazine on analgesia and cardiopulmonary variables in rabbits were evaluated in eight healthy New Zealand White rabbits. The experiment used a randomized double-crossover design. The rabbits were randomly divided into two groups, Group KD (n=4: 2 males/2 females) receivied 35 mg kg -1of ketamine and 0.5 mg kg -1of dexmedetomidine SC, while Group KX (n=4: 2 males/2 females) receivied 35 mg kg -1of ketamine and 5 mg kg -1of xylazine SC. The physiological parameters included HR, RR, PR, SpO2, SBP and RT were determined every 5 minutes and continuously monitored until the pedal withdrawal reflex returned. Mechanical and electrical stimuli were applied to evaluate the depth of anesthesia. Once the response to the noxious stimuli returned, 1 mg kg -1of atipamezole SC was administered in all rabbits. Rabbit reactions were monitored using videorecording. The blinded evaluator assessed the drug effect on anesthesia induction and the recovery reaction of all rabbits from videos recorded. There was significant difference in the induction time and the duration of anesthesia between KD and KX groups (p<0.05). The mean induction time and the duration of anesthesia were determined as 6.6 and 110.9 min respectively in the KD group and 19.8 and 17.8 min respectively in the KX group. Atipamezole reversal time was not significantly different between KD and KX. Intergroup comparison exhibited significant difference in terms of HR at the 10th min, PR at the 10th min, RT at the 25th min, SBP at 25th and 30th after loss of the righting reflex (p<0.05). As for intragroup comparison, HR and RR in both KD and KX were significantly decreased compared to the baseline (T=0). RT in both KD and KX was significantly decreased while PR, SBP and SpO2 were not, compared to 5th min after loss of the righting reflex (T=5). In conclusion, KD provided better analgesia, longer anesthesia, more rapid induction time, smoother and less complicated induction and recovery than KX. Both treatments demonstrated cardiopulmonary effects of significant decrease respiratory rate and heart rate. Therefore, both combinations should be used with caution in patients with respiratory depression.