EFFECT OF EPIDURAL-ANESTHESIA ON DORSAL PEDIS ARTERIAL DIAMETER AND BLOOD-FLOW

In nine subjects the influence of low (LE: blockade at or below the um bilicus; Th, 10) and high epidural anaesthesia (HE: block above the um bilicus) on vascular tone was evaluated by high frequency ultrasound ( 20 mHz) determined luminal diameter and a Doppler (8 mHz) assessment o f mean blood flow velocity (V-mean) in the dorsalis pedis artery. The LE was induced by 0.5% bupivacain through a catheter at L(3)-L(4), and HE was established by further infusion. Resting blood pressure and he art rate were not affected by LE or HE. One subject developed selectiv e thoracic anaesthesia, and another was blocked on the contralateral s ide only. In the seven adequately blocked subjects, the luminal diamet er of the dorsalis pedis artery increased from 1.70 (1.25-1.93) to 1.9 0 (1.75-2.23) mm during LE (+12%) and further to 2.08 (1.83-2.96) mm d uring HE (22%; P<0.05). The V-mean was similar during control (7[4-26] cm s(-1)) and LE (12 [4-55] cm s(-1)), but increased during HE to 35 (12-78) cm s(-1) (+500%; P<0.05). Thus, arterial blood now was higher during LE (21[7-98] ml min(-1); +263%) and HE (94 [21-177] ml min(-1); +1175%) than at rest (8[7-36] ml min(-1); P<0.05). This study quantif ied the importance of sympathetic nerve activity for vascular tone and in turn blood flow in an artery of a resting human limb, as the diame ter and V-mean increased with progressive epidural anaesthesia.