Prothrombin and the one-stage prothrombin time

Fresh frozen plasma: the most commonly prescribed hemostatic agent

Although fresh frozen plasma (FFP) is one of the most commonly prescribed therapies in clinical practice throughout the world today, there is little medical evidence available supporting its use. Recent guidelines have called for limiting FFP transfusions. Despite this, FFP use does not seem to be decreasing. The reasons for this are likely to be multifactorial, and may be based on ideas regarding medical practices dating back to Galen and Hippocrates. A review of the history of the development of FFP may shed some light on current clinical practice and guide the direction of future investigations and therapies.

Non-specific therapy of a hemorrhagic diathesis after a bite by a young Bothrops asper (barba amarilla): a case report

Hemorrhagic diathesis developed 4 hr after a bite by one fang of a two-month-old specimen of Bothrops asper. Severe allergy to horse serum contraindicated the use of horse antivenom, and a substitution therapy was started 20 hr after the bite. During the following 4 days the patient was treated with infusions of 8 g human fibrinogen, 2500 U of cryoprecipitate, 1000 ml of human plasma and vitamin K in several portions. By means of plasmapheresis 1800 ml of plasma was exchanged. Until plasmapheresis on the third day the treatment resulted in short remission and diminution of the spontaneous bleeding, which ceased on the 5th day. Coagulation tests relevant to disseminated intravascular coagulation and consumption coagulopathy were performed for 12 days. Fibrinogen levels started to rise on the 8th day and normalized 12 days after the bite. Analysis of the venoms from juvenile and adult Bothrops asper snakes revealed that the former has a strong prothrombin-converting activity, the latter contained mainly a thrombin-like, fibrinogen-converting enzyme.

The pathogenesis of hemophilia; an experimental analysis of the anticephalin hypothesis in hemophilic dogs

It has been possible to duplicate in the hemophilic dog four of the major experiments which have suggested in humans an "anticephalin" hypothesis for the pathogenesis of hemophilia. The experiments in the dog have been considerably extended, as compared with the human experiments, by a variety of techniques. I. Asbestos was placed in contact with hemophilic dog plasma, and the clotting time became shorter. When transfused, this plasma had no effect on the defective prothrombin utilization of hemophilic dogs, in contrast to untreated normal plasma. II. The ionic strength of native dog plasma and dog plasma citrated (38 per cent sodium citrate) then recalcified (0.2 M CaCl(2)) were calculated. The ionic strength of the native plasma was approximately 0.15 while that of the citrated plasma was approximately 0.21. Conductivity and freezing point determinations on the plasmas described above were consistent with the idea that the ionic strength of the citrated plasma was significantly higher. The biphasic dilution curve, to which much significance has been attached in arriving at the "anticephalin" hypothesis, can be produced readily in the dog. Diluting dog plasma with "iso-ionic" or "hyper-ionic" NaCl solution abolished the biphasic phenomenon. Dilution with distilled water exaggerated the biphasic curve. These experiments suggest that the biphasic curve is an artifact of uncontrolled ionic strength. III. The prothrombin utilization rates of undiluted whole hemophilic dog blood and hemophilic dog blood diluted 1:2 with 0.85 per cent NaCl were found to be the same. IV. Ether extraction of both normal and hemophilic dog plasma removed fibrinogen and reduced somewhat the concentration of prothrombin. In treated normal plasma AHF was reduced to the level of untreated hemophilic plasma, thus producing a quasi-hemophilic plasma. Defibrination and ether extraction of both normal and hemophilic dog plasma "generated" clotting activity which shortened the clotting time of hemophilic plasma and was active in the thromboplastin generation test. The activity "generated" by defibrination and ether extraction of dog plasma was adsorbed by a BaSO(4) suspension and shown, therefore, not to be the anti-hemophilic factor (AHF). Transfusion of ether-extracted normal or hemophilic dog plasma into hemophilic dogs had no effect on the prothrombin utilization rate, unlike untreated normal plasma which had a marked effect. Thus, four of the main lines of evidence supporting the "anticephalin" hypothesis were duplicated in the dog. However, by extending the experiments it was found that all were explainable on bases other than the presence of "anticephalin." Such an hypothesis is not necessary, therefore, to explain the pathogenesis of canine hemophilia. The apparent identity of hemophilia in the two species suggests that the hypothesis is also not applicable to humans.