Blood Platelet Economy during Moderate and Intensive Heparin Therapy

A study was made of the effects of heparin on platelet survival. The same subjects were studied during control periods and during heparin treatment at two levels of dosage. In most subjects, platelet survival was considerably prolonged and platelet turnover correspondingly diminished when 8000 units of heparin were given 8-hourly, but not with smaller dosage. The evidence in no way implies that such a dosage is optimal—several patients showed little or no response to it. Comparable results were obtained with various in vitro measures of blood coagulability. There was some evidence suggesting that platelet adhesiveness was paradoxically increased when the effect of heparin was wearing off.

These findings raise questions of clinical importance. Moreover, they provide yet further evidence that the survival of the blood platelet is considerably influenced by factors in its external environment.