Clinical response to three different doses of epidural morphine analgesia in frail older adults undergoing lower abdominal cancer surgery: a randomized clinical trial

Abstract Background: Epidural morphine is considered one of the potent drugs that used for post operative analgesia; however, side effects of its usage are dose-related and exaggerated in the elderly. Methods: 88 elderly patients undergoing lower abdominal cancer surgery were divided into four equal groups received either, placebo (group Morphine 0, N = 22), or 1.5 mg epidural morphine (Morphine 1.5, N = 22), or 3 mg epidural morphine (Morphine 3, N = 22), or 4.5 mg epidural morphine (Morphine 4.5, N = 22) immediately preoperatively, 24 hours and 48 hours postoperatively. Cumulative intravenous PCA morphine consumption, VAS pain scores, modified Ramsay Sedation Score, nausea, vomiting, and pruritis were evaluated. Results: The mean cumulative IV PCA morphine consumption (mg) in the first postoperative 72 hours was significantly decreased in all interventional groups, Morphine 1.5 mg, Morphine 3 mg and morphine 4.5 mg, compared to Morphine 0, P < 0.001 (Bonferroni corrected). However, non-significant reduction was observed between 3 mg epidural morphine group Vs. 4.5 mg group as P value = 0.191 (Bonferroni corrected). 0 mg Vs. 1.5 mg; 38.136 (4.8037) Vs. 27.182 (5.6115), 0 mg Vs. 3 mg; 38.136 (4.8037) Vs. 9.182 (3.5273), 0 mg Vs. 4.5 mg; 38.136 (4.8037) Vs. 6.273 (3.3407), 1.5 mg Vs. 3mg; 27.182 (5.6115) Vs. 9.182 (3.5273), 1.5 mg Vs. 4.5 mg; 27.182 (5.6115) Vs. 6.273 (3.3407), 3 mg Vs 4.5 mg; 9.182 (3.5273) Vs. 6.273 (3.3407). The VAS score of pain intensity during cough in the first postoperative 72 hours was significantly decreased in 3 mg and 4.5 mg treatment groups compared to the control group. However, no significant difference was observed between 0 mg group Vs. 1.5 mg group or between 3 mg group Vs. 4.5 mg group. Patients in epidural morphine 4.5 mg group showed an increased level of sedation compared to all other groups. Nausea score was similar across both control and treatment groups. Vomiting and pruritis scores were similar across all the treatment groups but significantly higher than the placebo group. Conclusion: Epidural morphine at a dose of 3 mg, for older adults undergoing lower abdominal cancer surgery, is the balanced optimal dose considering its analgesic efficacy and side effects. Trial registration: clinicaltrials.gov with ID number NCT0431687, Registered 20 March 2020, https://clinicaltrials.gov/ct2/show/NCT04316871