PLAIN BUPIVACAINE: AN UNPREDICTABLE SPINAL ANAESTHETIC AGENT

Abstract
Plain bupivacaine 0.5% or 0.75% was injected intrathecally in four groups of 10 patients. Group A received 0.75% bupivacaine 2.7 ml at L3/4, group B 0.5% bupivacaine 4 ml at L3/4, group C 0.75% bupivacaine 2.7 ml at L2/3 and group D 0.75% bupivacaine 2ml at L3/4. A very wide range of height of block was found in each group and because of this there were few statistically significant differences between the groups. The mean height of anaesthetic blockade was significantly higher when 20 mg (group C) was injected compared with 15 mg (group D). Decreasing the volume of injection from 4ml (group B) to 2.7 ml (group A) did not decrease this variability. By injecting at L2/3 spinal space (group C) the mean maximum level of anaesthesia (T7) was four segments higher than group A (T11) injected at L3/4, and this was reflected in a greater incidence of arterial hypotension.