Effect of morphine on lower urinary tract discomfort after transurethral resection of prostate under general anesthesia: a randomised clinical study.

Background: Lower urinary tract (LUT) discomfort is a common complaint after transurethral resection of the prostate (TURP), and it may lead to agitation and restlessnes. We have evaluated the efficacy of morphine for preventing TURP-related LUT discomfort symptoms.

Methods: This was a prospective randomised study including 60 patients (American Society of Anesthesiologists class I and II) who were scheduled to undergo TURP. The patients were divided into two equally sized groups (group M: morphine, group C: control). A standartized anesthesia method was used. Group M patients received morphine 0.04 mg/kg intravenous (iv) in 100 ml of normal saline followed by an infusion of morphine for 24 h (0.01 mg/kg/h); group C patients received 100 ml normal saline 20 min before the expected extubation time, followed by a normal saline infusion which looked identical to that of the morphine infusion. The incidences and severity of LUT discomfort, postoperative pain, sedation level, postoperative nausea and vomiting (PONV) and respiratory depression were recorded at 0, 1, 2, 6, 12 and 24 h postoperatively.

Results: The incidence of LUT discomfort was lower in group M patients at all time points during the study (p < 0.05) except for 2 h postoperatively, and the severity of LUT discomfort was also lower this group at 0, 12 and 24 h postoperatively (p = 0.001, p = 0.04 and p = 0.02, respectively). Pain (numeric rating scale) scores were lower in group M patients at 0 (p = 0.003) and 6 h (p < 0.001). The need for rescue analgesic was lower in group M patients (19 patients in group C, 10 patients in group M; p = 0.04). The incidence of PONV was higher in group M patients (p = 0.03). The incidence of pruritus, respiratory depression and over-sedation were similar among the groups.

Conclusion: Based on these results, we conclude that morphine effectively reduces LUT discomfort after TURP at a cost of postoperative nausea and vomiting.