The effect of lithotomy position on arterial blood pressure after spinal anesthesia.

We compared the effect of the lithotomy position on the systolic blood pressure (SBP) with the horizontal position after spinal block. The lithotomy position was performed 5 min after spinal block. The change in SBP was expressed as percent of depression from the baseline value. The SBP increased by the lithotomy position (n = 14) from a 16% decrease to an 8% decrease. On the contrary, in the horizontal group (n = 14), SBP decreased 16% at 5 min and continued to decrease to 21%. The extent of the cephalad spread of analgesia 20 min after spinal block was same between the two groups (T-5 +/- 2 vs T-5 +/- 2, respectively). From these results we conclude that the lithotomy position after spinal anesthesia attenuates the decrease in arterial blood pressure and does not affect the cephalad spread of analgesia.