Safe per-operative anticoagulation.

Pre-, per-, and post-operative anticoagulation at the therapeutic level is nowadays the most, if not the only, available effective method to prevent post-operative thrombo-embolism. There is no increased tendency to bleeding to be feared during the operation. The real danger of this prophylaxis consists of a treacherous tendency to acute relative overdosage after the operation. This is explained by the combined indirect action of anticoagulants and influences related to the operation. As its development can accurately be followed by laboratory tests, dangerous levels of anticoagulation can be prevented. Experiences in 242 surgical patients are presented to demonstrate the efficacy of the following post-operative routine: Coagulation studies (prothrombin time or thrombotest) at least twice daily during one week; fractionated administration of anticoagulants and, if necessary, small amounts (0·25-1 mg.) of vitamin K. The results suggest that with this policy the risk of thrombo-embolism in surgery can be considerably reduced, if not abolished.