High-volume spinal anaesthesia. A dose-response study of bupivacaine 0.125%

The clinical effects of high-volume spinal anaesthesia with bupivacaine 0.125% were studied in 30 patients presenting for postpartum sterilisation. Group A, B and C patients received 6, 8 and 10 ml of bupivacaine 0.125% respectively. Onset, duration and regression of sensory block and motor blockade, haemodynamic parameters and postoperative complications were studied. A sensory level of T10 was reliably obtained in Group B and C but not in Group A. Similarly motor blockade was unreliable in Group A compared with Group B (P < 0.05) and Group C (P < 0.05). Two segment regression times were similar in all three groups. L1 regression times were 47.9, 94.3 and 99.0 minutes in Groups A, B and C respectively. The corresponding times for complete recovery of motor power were 120, 212.3 and 182.7 minutes respectively (P < 0.01 when Group A compared to B and C). A significant incidence of high spinal anaesthesia occurred when 10 ml bupivacaine 0.125% was administered (P < 0.05 when compared with Group A). No patient experienced respiratory discomfort in spite of sensory levels of up to T1. Hypotension responded readily to intravenous fluids and small doses of ephedrine (three patients). Only one patient (Group A) developed a postdural puncture headache. In this study, high-volume spinal anaesthesia with bupivacaine 0.125% was found to be satisfactory for postpartum tubal ligation. The optimal volume of bupivacaine 0.125% was 8 ml.