[Measurements of skin resistance in detecting activity of the sympathetic nervous system in spinal anesthesia]

Abstract

The skin resistance and temperature of the surface of the skin were measured in more than 20 patients by means of mobile measuring equipment. The phasic skin-resistance activities of anesthetized parts were compared with unanesthetized regions at the extremities. Considerable phasic skin-resistance activity was shown in both anesthetized and unanesthetized regions. The two measured signals were partly identical in time and amplitude behavior. Temperature signals served as additional indicators of the activity of the sympathetic nervous system. To explain the results, an interpretation is proposed: the phasic components of the sympathetic activity can still exist and be measured below a nerve block - even if the tonic component of the sympathetic activity below this block is strongly reduced or vanishes, which is indicated by an increase in the surface temperature of the skin, as observed. This theory also holds regarding measurements of a patient who underwent a sympathectomy. Total lack of tonic and phasic components of sympathetic activity can be observed only under a high spinal analgesia (T3) or intubation anesthesia.