948 OCT. 15, 1955 PROTHROMBIN CONCENTRATIONS BDJu MEDICAL JOURNL so well to expectation would also correspond so closely to a natural rhythm, or would show so wide a range of variation.On average the ethyl biscoumacetate group showed a wider variation of prothrombin over the 24 hours than the phenindione group, four patients treated with ethyl biscoumacetate having a range of variation greater than 20%, whilst the greatest range among patients on phenindione was 19%. The variability of the two groups is compared in Fig. 2, where the standard deviation of the readings obtained at each interval of two hours is plotted against time. As in Fig. 1
ConclusionsAn experiment of this kind is laborious and involves considerable inconvenience to the patient. The number of observations has therefore been limited, but the following conclusions may be drawn.1. Anticoagulants of the ethyl biscoumacetate and phenindione type are effective when given in a single daily dose as soon as the patient is considered to be stabilized.2. The prothrombin concentration remains at a relatively high level for 8 to 10 hours after administration of the anticoagulant, and falls progressively to its lowest level after about 18 hours.3. Blood for prothrombin estimations should be withdrawn from any individual patient at approximately the sam.e time of day.4. Although our investigation has shown a difference in response to the two anticoagulants, our observations are not sufficient to allow an appraisal of their relative merits.