The Effect of Heparin and ε‐Aminocaproic Acid on the Coagulation in Hypothermic Dogs

Coagulation studies were performed in 15 dogs subjected to cooling to 20° C under various conditions. Thrombocytopenia invariably occurred during the cooling process. Hypothermia alone was followed by decrease of fibrinogen and prothrombin and factor VII and by an increased fibrinolytic activity and antithrombin activity. Hyperactive factor V levels were recorded during hypothermia and the plasma also showed thromboplastic activity. Administration of e‐ACA to the dogs before and during the hypothermia prevented the development of fibrinolytic activity but it did not prevent the decrease of fibrinogen and prothrombin and factor VII. Hyperactive factor V levels were recorded during the cooling as well as a marked thromboplastic activity in the plasma. Administration of heparin to the dogs before and during the hypothermia prevented the decrease of fibrinogen. The fibrinolytic activity was not prevented. No hyperactive factor V levels occurred. Simultaneous administration of heparin and e‐ACA to the hypothermic dogs prevented both the decrease of fibrinogen and the fibrinolytic activity. It is concluded that the coagulation defects induced by hypothermia are due mainly to intravascular coagulation. The decrease of fibrinogen which takes place in connection with hypothermia is due to its consumption in the coagulation process and not caused by the fibrinolytic process. It appears unwise to use ε‐ACA alone during hypothermia.