Abstract

In a prospective study, 40 patients who had undergone thoracotomy for lung resection were investigated. During operation, all patients received intravenous anesthesics, halothane and an initial dose of bupivacaine 0.5% with epinephrine 5 μg-ml⁻¹ (5 to 10 ml) by thoracic epidural catheter. One hour after the initial dose of bupivacaine 0.5% with epinephrine, patients were divided in two groups for analgesia, the sufentanil group (50 μg sufentanil in 60 ml bupivacaine 0.125%) or the nicomorphine group (3 mg nicomorphine in 60 ml bupivacaine 0.125%) by a continuous epidural infusion (5 to 10 ml·h⁻¹) for three days. Cardiovascular differences between the sufentanil group and the nicomorphine group were not statistically significant per- or postoperatively. The minimum respiratory frequency on either Day 1, 2, or 3 was 12 breaths·min⁻¹ in the sufentanil group, corresponding to a PaCO₂ of 32 mmHg, and 11 breaths·min⁻¹, corresponding to a PaCO₂ of 41 mmHg in the nicomorphine group. On Day 1, the PaCO₂ in the sufentanil group was significantly lower ( p < 0.01), but in both groups the PaCO₂ on Day 1 was significantly higher than the preoperative value. An inverse visual analogue pain scale (0 to 10 IVAS) showed mean scores above 7.5 for all patients during the three days. Scoring pain relief during exercise showed a significant difference in favor of the sufentanil group on Days 1, 2, and 3 ( p < 0.0008). The mean plasma bupivacaine level doubled every day, 138 ng·ml⁻¹ on Day 1, 290 ng·ml⁻¹ on Day 2, and 596 ng·ml⁻¹ on Day 3. The mean plasma sufentanil levels on Days 1, 2, and 3 were 0.031 ng·ml⁻¹, 0.0881 ng·ml⁻¹, and 0.1252 ng·ml⁻¹. No plasma levels of nicomorphine and its metabolites, 6-nicotinoylmorphine, 3-nicotinoylmorphine, and morphine, could be detected. This study shows that the continuous infusion of low dose bupivacaine 0.125% with either sufentanil or nicomorphine provides excellent pain relief at rest, with no need of systemic opioids and minimal respiratory depression. In spite of the cumulation of bupivacaine and sufentanil in the plasma, no serious adverse effects of either drug could be observed.