In this study, the analgesic potency of constant rate infusion of tramadol hydrochloride and as adjunct to ketoprofen on laparotomy-induced pain was evaluated. Dogs were randomly assigned to 4 groups (n=5). Groups 1, 2 and 3 received 0.5mg/kg/hr, 1.0mg/kg/hr and 2.0mg/kg/hr IV; CRI of tramadol hydrochloride respectively while group 4 which served as control received normal saline. Infusions were administered from 30 minutes before surgery and lasted for 105 minutes. All dogs underwent ventral midline laparotomy. Ketoprofen 50 mg/ml at the dose of 5mg/kg, SC was given at 1 hour post-surgery (hps) after pain assessment and on days 2 and 3 post-surgery (dps) to dogs in all the groups. Parameters determined were heart and respiratory rates, blood glucose level, pain score and body weight. Results showed that mean heart rate, respiratory rate and body weight were not differed significantly (p > 0.05) within and among the groups. Mean blood glucose level of group 4 was significantly higher (p < 0.05) than the other groups intra- and post-surgery. Mean blood glucose level of group 3 was significantly lower (p < 0.05) than that of group 1 at 1 hps. Group 4 dogs also had significantly higher mean blood glucose intra-surgery and at 1 hps than their baseline value. Group 4 dogs had significantly higher (p < 0.05) mean rank pain score than other dog groups on 0-3 dps while mean rank pain scores of groups 1 and 2 were significantly (p < 0.05) higher than that of group 3 on 0 dps. It was concluded that tramadol HCL at constant rate infusion doses of 0.5mg/kg, 1.0mg/kg/hr and 2.0mg/kg/hr were effective at managing laparotomy-induced pain up to one hour post-surgery. As an adjunct to ketoprofen, 2.0mg/kg/hr of tramadol hydrochloride offered better analgesia than the other doses studied during the post-surgical days.
Key words: Analgesia, Constant rate infusion, Ketoprofen, Laparotomy, Pain, Tramadol
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