Higher postoperative pain and increased morphine consumption follow pre- rather than post-incisional single dose epidural morphine

Background. Neuraxial administration of morphine is an effective way of controlling postoperative pain and reducing analgesic consumption. Some animal models have demonstrated that preemptive administration of neuraxial narcotics reduces pain, while others have revealed the contrary. In addition, there have been no consistent results in clinical settings. This double-blind, randomized study compared the effects of pre- vs. post-incisional administration of neuraxial morphine on postoperative pain perception and analgesic requirements over 48 hours following laparotomy for open colectomy under standardized general anesthesia. Methods. Twenty patients received epidural morphine (3 mg) before the incision and saline after wound closure (MO1 group), and twenty patients received epidural saline before the incision and morphine after wound closure (MO2 group). Postoperatively, all patients received morphine boluses (1.5 mg) via intravenous patient-controlled analgesia (IV-PCA) and rescue doses of intramuscular diclofenac (75 mg) every 6 hours, as needed. Results. MO1 patients used significantly (P<0.05) more morphine than the MO2 group during the first 24 postoperative hours and activated the PCA device more frequently throughout the 48-hour study period. The MO1 group was characterized by significantly (P<0.05) higher self-rated pain scores than the MO2 group throughout the study. The self-rated levels of sedation and satisfaction of the MO2 patients were also consistently better (P<0.05) than those of the MO1 patients, especially during the second postoperative day. Conclusion. Pre-incisional epidural morphine in patients undergoing open colonic surgery under general anesthesia was associated with more postoperative pain, a greater need for analgesics, and poorer patient satisfaction compared to post-incisional morphine administration.