Prevention of urinary retention with phenoxybenzamine during epidural morphine.

Since the first reports by Wang and Behar and others the use of epidu-ral and intrathecal opiates for pain relief has become widely accepted. The most common and distressing complication of this mode of anal-gesia is acute urinary retention, which occurs in 3%' to 100%'o2 of patients. We studied the postoperative urinary complications in a group of patients who underwent elective caesarean section under epidural anaesthesia and who received epidural morphine for post-operative pain relief. In addition, the efficacy of the alpha adrenergic blocking agent phenoxybenzamine (Dibenyline) in alleviating post-operative micturition difficulties and urinary retention was investigated. Methods and results After giving informed consent, 60 patients aged 23-42 years were divided at random into two equal groups. All were injected with 20 ml bupivacaine 0 5% via a Tuohy needle inserted epidurally into the Ll-2 or L2-3 interspace. An indwelling catheter was then placed caudally. At the end of surgery a single dose of 4 mg morphine hydrochloride diluted in 10 ml isotonic saline without preservative was injected through the epidural catheter for postoperative analgesia. In addition, the 30 patients in group 2 received four oral doses of 10 mg phenoxybenzamine 24 and two hours before and eight and 16 hours after surgery. Except for the epidural morphine no opiates were given to either group. A non-narcotic drug (1000 mg dipyrone intramuscularly or by mouth), however, was dispensed freely on request. The same amount of postoperative fluid (2-5-3-01 Hartman's solution) was administered to both groups. The patients were closely observed for 48 hours. Medical staff did not know which of the patients had been given phenoxybenzamine. Difficulty in micturition, volumes of the first two voidings after operation, the time intervals between the end of surgery and first micturition, urinary tract infection, and urinary retention were noted. For this investigation we designated "urinary retention" as discomfort and sensation of a full bladder or a palpable distended bladder. In such instances the patient was encouraged to void. If urine was not passed spontaneously after one hour the bladder was catheterised. From the volumes of the two initial urine voidings and the time interval between the end of the operation and first micturition phenoxybenzamine clearly alleviated or prevented difficulties in micturition and urinary retention (table). In group 1, 26 patients complained of difficulty in micturition, whereas in group 2 only two patients did so. The overall rate of urinary retention diminished from 46-60/ …