Background: Subcutaneous opioid is one way of managing postoperative pain in patients undergoing anticoagulant therapy. We have evaluated the safety and the efficacy of postoperative pain management using subcutaneous fentanyl and ketamine after abdominal gynecologic surgery.
Methods: Written informed consent was obtained from 50 ASA physical status 1 or 2 female patients aged between 20 and 65. Patients were randomized to one of 5 groups. Group 1, 2 and 3 received 25, 35 and 50 microg x h(-1) subcutaneous fentanyl infusion, respectively. Group 4 received 25 microg x h(-1) fentanyl and 2 mg x h(-1) ketamine subcutaneously; group 5 received 25 microg x h(-1) fentanyl and 4 mg x h(-1) ketamine subcutaneously. General anesthesia was administered to all patients. Two hours after induction, subcutaneous infusion of fentanyl and ketamine was started in the patients and discontinued 24 hours after the operation. All patients were assessed twice, at 4 hours and at 24 hours after operation. Blood gas analysis was performed. Number of analgesic administration required during the 24 hours after operation was recorded. Groups 1, 2, 3 and groups 1, 4, 5 were evaluated as one group, respectively. Group differences were analyzed by variance analysis. Differences of analgesic administration were analyzed with Kruskal-Wallis test.
Results: As to anesthetic requirement during the 24 hours after operation, there were no significant differences among treatment groups. With respect to blood gas analysis, only individuals receiving subcutaneous 25 microg x h(-1) fentanyl and 4 mg x h(-1) ketamine maintained high PaO2 4 hours after the operation (P<0.05).
Conclusions: We recommend administration of 25 microg x h(-1) fentanyl and 4 mg x h(-1) ketamine subcutaneously, which maintains high Pao2 and requires less analgesic.