Effects of posture and baricity on spinal anaesthesia with 0.5% bupivacaine 5 ml. A double-blind study

In four groups of 10 patients, 0.5% bupivacaine 5 ml was used in spinal anaesthesia for gynaecological surgery. Group 1 received plain solution in the sitting position, group 2 plain solution in the lateral position, group 3 hyperbaric solution in the sitting position and group 4 hyperbaric solution in the lateral position. All patients were returned to the horizontal supine position, the sitting subjects 2 min after, and the lateral subjects immediately after, spinal injection. In each group the mean height of block was to the mid-thoracic segments, but there was no significant difference between the groups. There was, however, considerable scatter within each group. Posture had some effect on the speed of onset of the analgesia, but no significant effect on the final outcome. The use of 0.5% bupivacaine as a test dose in extradural blockade is discussed.