The effect of interpleural analgesia on postoperative hospital course was analyzed ina prospective randomized study of patients undergoing cholecystectomy. Control patients were treated in the standard manner with systemic narcotics alone; catheter patients had an interpleural catheter placed at the end of surgery and, in addition, could receive systemic narcotics if necessary. The catheter group received interpleural 0.5% bupivacaine with epinephrine every six hours for a total of four injections. Thirteen patients were in each group. Pain score, pulmonary function and narcotic requirement were measured over the first postoperative day. Catheter patients had a lower average pain score (visual analog scale (VAS), 3.6 versus 5.2), decreased narcotic requirement in the recovery room and improved oxygen saturation (96% versus 93%). However, there was no statistical difference in amount of morphine (catheter, 25 +/- 14 mg; control, 31 +/- 15 mg), number of narcotic injections (catheter, 3.8 +/- 1.5; control, 3.5 +/- 1.5), forced vital capacity (catheter, 44% preoperative control, 41% preoperative), recovery room time (catheter, 129 +/- 54 minutes, control, 117 +/- 39 minutes) or total hospital stay (catheter, 4.1 +/- 0.9 days; control, 3.7 +/- 0.8 days). Analysis of hourly VAS scores following a bolus indicated that the analgesia disappeared within approximately four hours. The mean time to a request for narcotic following a bolus was 4.2 hours (excluding 17 of a potential total of 52 instances when narcotic was not requested at all). Therefore, the duration of pain relief for subcostal incisions using interpleural 0.5% bupivacaine is approximately four hours.(ABSTRACT TRUNCATED AT 250 WORDS)