The Prothrombin Response to the Parenteral Administration of Large Doses

There are a multiplicity of tests for liver functions, each depending upon a particular function of the liver. There has been growing recognition that the response in prothrombin time to the administration of vitamin K is of aid in the evaluation of hepatic function. The procedures heretofore employed to estimate the prothrombin response have lacked uniformity and, as a consequence, conflicting opinions of its significance and reliability have been expressed. Need exists for further study in both normal and abnormal subjects, and comparison with other liver function tests to establish its status as an index of at least 1 particular function of the liver. The present study deals with a standardized, sensitive method for the estimation of the prothrombin response to the administration of vitamin K. Our results show that the ability to maintain a normal prothrombin level is a function of the liver apt to be affected before others are sufficiently disturbed to permit clinical detection. For this reason, the response of the liver in prothrombin production to the parenteral administration of large doses of synthetic vitamin K is a sensitive indicator of hepatic function. The use of plasma prothrombin levels as an indicator of the ability of the liver to elaborate prothrombin was originally studied by Stewart and Rourke (1) and pursued subsequently by numerous investigators, (2 to 5), all of whom employed whole plasma for prothrombin assay. Warner, Brinkhous and Smith (6) in dogs and Pohle and Stewart (3) in man, introduced the response of depressed production levels to orally administered