Effects of the lithotomy position on arterial blood flow in the lower extremities

The lithotomy position is known to decrease venous blood flow and predispose to lower extremity venous thrombosis. However, arterial thrombosis secondary to surgical positioning has rarely been discussed. One hundred patients underwent measurements of their ankle-arm index, the ratio of their ankle systolic pressure compared to their brachial blood pressure, preoperatively (AAI); immediately after being placed in the lithotomy position (AAII); and immediately prior to returning to the supine position (AAIII). Comparison of all the ankle-arm indexes revealed significant drops between preoperatively and immediately after being placed in the lithotomy position, and between preoperatively (p less than .01) and immediately prior to the supine position (p less than .05). When only preoperative ankle-arm indexes of 0.99 were examined, a very significant drop of p less than .005 was obtained. No significant drop was seen in the group with preoperative ankle-arm indexes less than 0.99. In view of this pressure drop, standard lithotomy stirrups, such as those usually utilized for OB procedures, should be used with caution for procedures requiring prolonged lithotomy position.