In vivo attempt to consume antithrombin III by i.v. injection of a thrombin-heparin mixture.

15 rabbits and 6 dogs were injected with a mixture of thrombin and heparin. Increasing amounts of thrombin, and various ratio of thrombin in relation to heparin, were used. It was found that huge amounts of thrombin could be perfused, under the protection of heparin, without untoward effects. But the high amount of thrombin needed to obtain a 50% reduction of the circulating AT III required a corresponding high amount of protective heparin. Since the secondary injection of protamin sulphate (after the end of the perfusion with the thrombin-heparin mixture) was precipitating the DIC syndrome, such attempts to decrease AT III in man are not feasible.