Extradural pressure following the injection of two volumes of bupivacaine

Abstract

We investigated the influence of the pressure generated by low lumbar extradural injection of bupivacaine on the development of block in a randomized double-blind study. Thirty patients (aged 17-66 yr) received one of two volumes of 0.75% bupivacaine. Group I (n=15) received 10 ml (75 mg) and group II (n=15) 15 ml (112.5 mg). Injection of the larger volume resulted in a greater pressure at the end of injection, but within 1 min this decayed to the same plateau pressure that was produced by the smaller volume. Mean maximum cephalad spread of block was the same in each group (group I, T9.5; group II, T8.4) and there was no correlation between individual level of block and maximum or plateau extradural pressure, or with patient characteristics. © 1989 British Journal of Anaesthesia.