STEAL PHENOMENON AFTER LUMBAR AND THORACIC SYMPATHETIC GANGLION BLOCKADE IN DOGS1 THE INFLUENCE OF INTRAVASCULAR VOLUME

Abstract

The steal phenomenon between the bilateral sides following unilateral sympathetic denervation can be influenced by intravascular blood volume. We studied the changes in skin temperature as an indicator of this phenomenon induced by unilateral lumbar or thoracic sympathetic ganglion blockade in dogs under various hemodynamics. Each of 30 dogs in lumbar and thoracic experiments, which were divided into three groups according to mean right atrial pressure (RAP, mmHg) as hypovolemic (RAP＜3 ; n=10), normovolemic (3≦RAP≦6 ; n=10) and hypervolemic (RAP＞6 ; n=10), underwent'unilat- eral high-frequency thermocoagulation in lumbar (L5-L7) or thoracic (Th7-Th11) sympathetic ganglia. Skin temperature at planta of both hindlimbs or bilateral costal arches was compared among three groups for 60 minutes following･either blockade. Ipsilateral skin temperature rose in all groups (p＜0.05). Contralateral skin temperature fell significantly only in the hypovolemic and the normovolemic groups (p＜0.05), but not in the hypervolemic group. After lumbar sympathetic blockade, the changes is the contralateral skin temperature for 60 minutes, expressed as a percentage of the respective control value, were significantly larger (p＜0.05) in the hypovolemic (-6.4±1.8%) and the normovolemic (-6.0±2.2%) groups than that in the hypervolemic group (+0.1±1.7 %). After thoracic sympathetic blockade, this percentage change was significantly differ- ent (p＜0.05) among the hypovolemic (-1.2±0.7%), the normovolemic (-0.7±0.6%) and the hypervolemic (+0.0±0.4%) groups. We conclude that the steal phenomenon may be influenced by intravascular volume. Therefore, it is necessary to sufficiently understand the patient's systemic hemodynamics or peripheral circulation in performing unilateral sympathetic ganglion blockade. Further- more, a pretreatment such as a preoperative volume loading can be beneficial, especially for the hypovolemic patient who has bilateral vascular disorders.