Control of Vitamin K Therapy. Compensatory Mechanisms at Low Prothrombin Levels.

Fibrinogen deficiency as a factor in haemorrhagic disease

“…Ziffren, Owen, Hoffman and Smith (1939) stated that when prothrombin falls below 30 to 50 per cent. a bleeding tendency appears.…”

The estimation of prothrombin in human plasma

“…Another objection to any method which depends on the rate of thrombin formation is that other factors, beside the concentrations of prothrombin and thromboplastin, may affect the results. The differences in the rate of conversion of prothrombin into thrombin in different species have already been mentioned, and there is evidence that in human plasma under different conditions there may be variations in the rate of prothrombin conversion [Ziffren et al 1939;Owen et al 1939]. These authors recommend a modification of Quick's method as a useful practical measure of the tendency to haemorrhage, but do not regard this type of method as giving a true measure of prothrombin titres.…”

Clinical and Experimental Studies on Vitamin K

“…It is now known that the bleeding is due to abnormal lowering of the plasma prothrombin level and that in most cases the bleeding tendency can be relieved by vitamin K therapy. We wish to outline the experimental and clinical work on which this theory is based, and along with this we wish to describe, briefly, a simple method that we 1 have recently devised for the recognition of the vitamin deficiency. With the aid of this test it is now possible to obtain information at the bedside regarding vitamin K requirements.…”