Dosage of epidural morphine analgesia after lower abdominal cancer surgery: a randomized clinical trial among the older adults

BACKGROUND: Epidural morphine is considered one of the most potent drugs used for postoperative analgesia; however, its side effects are dose-related and exaggerated in elderly people. In this study, we aimed to determine which of three doses within that range (1.5 mg, 3 mg, or 4.5 mg) can provide adequate pain relief. METHODS: A total of 102 patients were assessed for allocation into one of four groups to receive either placebo (group Morphine 0, N = 22), 1.5 mg of epidural morphine (Morphine 1.5, N = 22), 3 mg of epidural morphine (Morphine 3, N = 22), or 4.5 mg of epidural morphine (Morphine 4.5, N = 22) before skin incision, 24 h after surgery and 48 h after surgery. Cumulative intravenous IV-PCA morphine consumption, VAS pain scores, modified Ramsay Sedation Scores, nausea, vomiting, and pruritus were evaluated. RESULTS: The VAS pain scores at activity of patients who received epidural morphine at doses of 3 mg and 4.5 mg were significantly lower than the placebo and 1.5 mg groups, VAS Score at 72 h was (2 ± 0.8) and (1.7 ± 1) vs (4.3 ± 1.1) and (4 ± 1) respectively, p value = 0.000. The mean total IV-PCA morphine consumption (mg) was significantly higher in patients who received received epidural 0.9% sodium chloride alone compared to 1.5 mg, 3 mg and 4.5 mg epidural morphine groups (38.1 ± 4.8 mg vs 27.2 ± 5.6 mg, 9.2 ± 3.5 mg, and 6.3 ± 3.3 mg respectively), p value = 0.000). However, the difference between the 3 mg and the 4.5 mg groups was not statistically significant in both of VAS scores and IV-PCA morphine consumption (P value > 0.05 for 3 mg vs. 4.5 mg). Patients who received 4.5 mg of epidural morphine experienced a significant increase in the level of sedation, measured by the Ramsay sedation scale, in comparison with 1.5 mg, 3 mg and placebo epidural morphine groups in the first 24 h, the Scale for this group was (2.5 ± 0.5) vs (2.1 ± 0.2, 2.1 ± 0.2, and 2.2 ± 0.5 respectively); p value = 0.000. No relationship between postoperative nausea and the dosage of epidural morphine was found. CONCLUSION: Epidural morphine 3 mg as a bolus every 24 h with add on IV patient control analgesia (PCA) morphine, set to deliver 1.5 mg boluses on demand without background infusion with a lockout period of 45 min, could achieve effective and adequate analgesia lasting up to 72 h postoperatively without increasing in the level of sedation or other side effects in older adults after a lower abdominal cancer surgery.