[Clinical evaluations of tourniquet shock, with special references to the circulation and biochemistry of the blood].

The air tourniquet is routinely used in the surgery of the lower limbs. Circulatory and biochemical changes in the blood were investigated during the use of the tourniquet and after its removal. The blood flow was stopped by tourniquet for 60•`120 minutes under general anesthesia with intra-tracheal intubation. The results obtained were as follows. Blood pressure and CVP were sharply reduced after the blood flow was restored and the reduction was the largest one minute after the release of the tourniquet. Blood pressure was normalized 15 minutes after the release of the tourniquet and CVP was significantly lower even 60 minutes after the release of the tourniquet as compared with the control values. It was assumed that there changes were caused by the decrease in the relative circulating blood volume and the reactive hyperemia. The heart rate was slightly elevated one minute after the release of the tourniquet. The reduction of the cardiac output began 10 minutes after the release of the tourniquet and continued for 30 minutes. The amount of the reduction was statistically significant. This may have been partly due to the influence of accumulated lactic acid. PaCO2 was slightly elevated 1 minute after the release of the tourniquet and the levels of lactate and excess lactate were also elevated, which concided with the tendency of pH and base excess. Metabolic acidosis prevailed for 30 minutes after the release of the tourniquet. There were no variations in PaO2 following the tourniquet release, nor were there any significant changes in the level of Na, K or Cl. The above findings indicate that the changes in circulation and biochemistry of the blood existed for 30 minutes after the release of the tourniquet. Consequently, it may be concluded that at least 30 minutes should be allowed before the resumption of the tourniquet.