A preliminary communication on the degeneration of thrombin in serum of normal controls and of patients before and after surgery.

The presence of an antithrombin in normal plasma and serum has been known for many years. In 1892 Schmidt postulated its existence when he observed the rapid disappearance of thrombin from blood after coagulation. Tests have been devised enabling the titre of antithrombin to be determined. Most of these tests depend on the inactivation of serial dilutions of thrombin of known concentration by the antithrombin being investigated; after incubation the specimens are added to fibrinogen and the presence or absence of coagulation observed (Astrup and Darling, 1942; Hurn and Mann, 1947; Owen and Bollman, 1948; Levy-Solal and Roost, 1952). Such tests have been used to investigate variations in antithrombin activity of plasma following surgical operations, and attempts have been made to predict the onset of thromboses in these patients. Results have been conflicting, however. Boshamer (1927) demonstrated a fall in the antithrombin titre following operation. Holden, Cole, and Davis (1949) found no change in the uncomplicated postoperative period, but demonstrated a marked fall in titre in those patients undergoing thrombosis. Volkert and Piper (1943) had been unable to show any change during active thrombosis. In a series of patients with thrombosing tendencies investigated by Hurn, Barker, and Mann (1947) low and high antithrombin titres were found in equal numbers, although all the patients who were being treated with dicoumarol showed an increase in serum antithrombin activity. It has been suggested that thrombosis is more likely to occur in the post-operative period when the antithrombin level is low and the prothrombin conversion rate normal (Kay, Hutton, Weiss, and Ochsner, 1950). This paper describes a test of thrombin degeneration in serum, and the results obtained using this test in normal controls and in a small series of patients who have been examined before and after surgical operation. This work forms part of an investigation into the effects of surgical trauma on the coagulation mechanism, the results of which will be presented more fully in a later communication.