Platelet function in fulminant hepatic failure and effect of charcoal haemoperfusion.

In 34 patients with fulminant hepatic failure, platelets, in addition to being reduced in numbers, were smaller than those of healthy controls. In keeping with this, capillary bleeding times were significantly longer than could be accounted for by reduction in numbers alone. In a small group of these patients use of charcoal haemoperfusion for temporary liver support produced a doubling of the capillary bleeding time despite only a small drop in arterial platelet counts. This disproportionate prolongation of bleeding time was almost certainly caused by the loss of larger platelets in the charcoal columns during perfusion, as the mean median volume also fell during perfusion. Rises in screen filtration pressure of blood leaving the columns were found during some perfusions and thought to be indicative of platelet aggregates. Release of vasoactive substances from platelets could account for the hypotension often found at this time.