Effect of lateral versus supine wedged position on development of spinal blockade and hypotension

Aortocaval compression may not be completely prevented by the supine wedged ol tilted positions. It is commonly believed, however, that the unmodified full lateral position after induction of spinal anaesthesia might allow ex cessive spread of the block. We therefore compared baseline arterial pressu res in the supine wedged, sitting, tilted and full lateral positions in 40 women who were about to undergo elective caesarean section. They were then given spinal anaesthesia in the left lateral position and randomised to be turned to the right lateral or the supine wedged position, after which spee d of onset and spread of blockade to cold sensation were measured every 2 m in for 10 min and mean arterial pressure and ephedrine requirement were rec orded every minute for 20 min. Baseline mean arterial pressure was 9 mmHg ( 95% CI 3 to 14) lower in the left lateral (measured in the upper arm) than in the sitting position; those in the supine wedged and tilted positions we re intermediate. Following spinal anaesthesia, hypotension (defined as a re ading less than or equal to 80% of the baseline value in the same position) lasted 2.4 min longer (CI +0.6 to +4.1) in the supine wedged group, but th ere was no significant difference between the groups in maximum fall or eph edrine requirement. The upper level of block rose more rapidly in the supin e wedged than in the lateral group and showed less variability. There is th erefore no reason to fear the unmodified lateral group position, which may offer better protection against hypotension. (C) 2001 Harcourt Publishers L td.