Urinary function during epidural analgesia with methadone and morphine in post-cesarean section patients.

Urinary function was assessed in 120 women after cesarean section under epidural anesthesia. Postoperative analgesia was obtained by means of epidurally administered methadone (40 patients) or morphine (40 patients). In the remaining 40 women, no narcotic drugs were given and postoperative pain was treated with intramuscular or oral non-opiate analgesics and sedatives. Both methadone and morphine provided potent postoperative pain relief. Following epidural methadone, mean urine volumes of the first two postoperative voidings were increased (543 +/- 38 ml and 571 +/- 31 ml) as compared with those after epidural morphine (219 +/- 25 ml and 218 +/- 18 ml) and with those of patients receiving non-opiate analgesics (319 +/- 28 ml and 414 +/- 30 ml). The mean time interval between the end of surgery and first voiding following methadone analgesia was shorter (336 +/- 27 min) than after morphine (582 +/- 18 min) or after non-opiate (448 +/- 28 min) analgesic drugs. Difficulty in micturition and the need for bladder catheterization were also decreased in the group with epidural methadone (2.5%) in comparison with the groups receiving morphine (57.5%) or non-opiate analgesic medicaments (12.5%). The use of epidural methadone for postoperative pain relief is advocated, both in view of its analgesic potency and of the low incidence of urinary disturbances.