[Effects of total spinal block on the circulatory system and myocardial oxygen demand and supply balance].

Total spinal block with 1.5% lidocaine was performed in adult mongrel dogs, and its effects on circulatory system and myocardial oxygen demand and supply balance were investigated. The study demonstrates that the circulatory system is depressed under induced total spinal block, as manifested by a marked decrease in HR, MAP, CI, and LV dp/dt max. A decrease in SvO2 suggests that total spinal block places the animals in lack of oxygen supply. On the other hand, coronary arterial blood flow was significantly reduced by total spinal block. With reduction in myocardial oxygen consumption, however, coronary venous oxygen saturation (ScvO2) and myocardial oxygen extraction rate remained unaffected, and myocardial lactate uptake was also affected little. The results suggest that sufficient coronary arterial blood flow is maintained during total spinal block to respond to the myocardial oxygen demand. There is a possibility that myocardial oxygen demand and supply are well balanced under total spinal block.