Abstract

Variables of ventilation were obtained preoperatively and during the first two postoperative days in 28 patients after thoracic surgery. All patients received 0.5% bupivacaine with epinephrine, 5 μg·ml⁻¹ (5-10 ml), through an epidural catheter at the thoracic level supplemented by light general anesthesia. One hour after the initial dose of bupivacaine, patients were randomly allocated to one of two groups: an epidural (EP) sufentanil and an intravenous (IV) sufentanil group. Both groups received 0.125% bupivacaine via continuous epidural infusion postoperatively for three days. In addition, the EP group received 0.83 μg · ml⁻¹ sufentanil added to the epidural infusion of 5-10 ml · hour⁻¹, while the IV group received an identical dose of sufentanil via continuous intravenous infusion of 5-10 ml · hour⁻¹. The ventilatory response to 5% CO₂ was analyzed preoperatively and on postoperative Days 1 and 2. No significant depression in ventilatory response to CO₂ could be detected by measurement of minute ventilation and mouth occlusion pressure at 100 milliseconds (P_0.1). Pain measurement was assessed by blinded observers using the Inverse Visual Analog Scale, where 0 signifies most pain and 10 signifies least pain. The mean scores were above 7 in both groups and were attained at similar analgesic requirements. The incidence of side effects was not different. Only the initial mean sufentanil plasma levels in patients of the IV group were higher than those of the EP group. This study shows that the variables of ventilation were not affected by sufentanil administered via the epidural or the intravenous route, and that both techniques provided excellent pain relief when employed to supplement low-dose 0.125% bupivacaine epidurally.