Post- operative analgesic effect of epidural bupivacaine alone and bupivacaine with tramadol for ovariohysterectomy in bitches
Pre-emptive analgesia refers to the application of analgesic before the patient exposal to noxious stimuli. The study was conducted from December, 2013 to May, 2014 on 12 healthy bitches presented to the University of Gondar Teaching Veterinary Clinic for ovariohysterectomy to compare the epidural analgesic efficacy of bupivacaine alone and bupivacaine with tramadol to relieve postoperative pain and asses changes on physiological and heamatological parameters. The bitches were randomly assigned to experimental group I and II. Premedication was done with atropine sulphate and xylazine hydrochloride at 0.04 mg/kg subcutaneously and 1mg/kg intramuscular, respectively. Induction was employed by diazepam at0.25 mg/kg intravenous, immediately followed with ketamine hydrochloride at 5mg/kg intravenously for effect and maintenance, incremental injections of ketamine hydrochloride was administered. Bupivacaine at 1 mg/ kg was administered epidurally in group I bitches while 1 mg/kg of bupivacaine combined with 2 mg/kg tramadol were administered epidurally in group II bitches. Physiological and haematological parameters were assessed at different stages of analgesia, in addition to pain scoring using visual analogue scale (VAS) and categorized numerical rating scale (CNRS). After epidural administration, mean temperature and heart rate between treatment groups showed statistically (p<0.01) high significant reduction while respiratory rate reduction was significant (p<0.05) in group-II bitches compared to group-I due to the inclusion of opioid analgesic tramadol. Haemoglobin, Packed cell volume, total erythrocyte and leukocyte counts showed a significant (p<0.05) decrease in 1 hour after surgery in both groups. There was a significant (p<0.05) difference in both visual analogue scale (VAS) and categorized numerical rating Scale (CNRS) score postoperatively in 2 and 6 hours between group I and II bitches. In fact, the visual analogue scale score of group II bitches at 6 hour after surgery was statistically (p<0.01) highly reduced compared to group I bitches. In conclusion, postoperative pain assessment revealed better reduction in pain at all intervals in group-II bitches compared to group-I due to the inclusion of opioid analgesic tramadol. However, further studies are needed to compare the efficacy and doses of this combination as epidural analgesic for various surgeries.
Keywords: Bitches, Bupivacaine, Epidural, Ovariohysterectomy, Postoperative pain, Tramadol