Abstract

Eight patients undergoing abdominal surgery received a combination of spinal anesthesia (catheter at L2-3 level) and epidural anesthesia (catheter at T10-11 level). Sensory thresholds to electrical stimulation were measured at the S1, L1, T10, and T5 levels before injection, after spinal anesthesia, and after the addition of epidural anesthesia. Subarachnoid injections with 5% lidocaine (without dextrose) were given until a T4 sensory level to pinprick was obtained (mean dose, 175 mg lidocaine). The mean sensory thresholds were increased from 2.2 ± 0.3, 2.4 ± 0.4, 2.9 ± 0.4, and 3.8 ± 0.4 mA to 21.3 ± 4.3, 13.3 ± 4.9, 10 ± 4.4, and 10.6 ± 4.3 mA, respectively ( p < 0.05 at all levels). The addition of 5 ml 0.5% epidural bupivacaine further increased the mean sensory thresholds to 26.9 ± 3.1, 21.7 ± 4.1, 21.3 ± 4.1, and 17.5 ± 4.7 mA, respectively ( p < 0.05 at all levels). Combined subarachnoid and epidural local anesthetics provide an enhanced afferent block not obtainable by either technique alone.