The effect of phenoxybenzamine on postoperative urinary complications during extradural morphine analgesia.

One hundred and fifty patients, post-Caesarean section, were investigated to evaluate the effect of epidural morphine analgesia and that of phenoxybenzamine on the frequency and extent of urinary complications. Forty patients (group A) underwent Caesarian section under general anaesthesia, while 110 patients received epidural anaesthesia. Of the latter patients, 40 received postoperative mild analgesics (group B) whilst in another 40, postoperative continuous epidural morphine was administered (group C). Thirty patients who received postoperative epidural morphine, also received oral phenoxybenzamine 10 mg, 24 and 1 hr prior to, and 8 and 16 hr following surgery (group D). The volume of urine of the first two postoperative voidings, the time delay to first micturition, difficulty in micturition and urinary retention necessitating bladder catheterization were studied. The mean volumes of the first two postoperative voidings were markedly reduced in group C (219 and 218 ml, respectively) as compared with group A (383 and 453 ml) and with group B (319 and 414 ml, respectively). In group D, these mean volumes were significantly larger at 478 ml (p less than 0.01) and 417 ml (p less than 0.01) as compared with those of group C. The mean time to the first postoperative voiding was 582 min in group C, which was significantly longer than that in group A (339 min) or in group B (448 min). In the patients treated with phenoxybenzamine, the time to the first postoperative voiding was significantly less at 322 min (p less than 0.01). The need for bladder catheterization was also increased in group B compared with group A, while in group C this increase was marked compared with both groups A and B. It was significantly less frequent in those receiving phenoxybenzamine. Phenoxybenzamine is recommended in the prevention of postoperative urinary complications associated with epidural anaesthesia and epidural morphine analgesia.