HUMORAL FACTORS IN MASSIVE PULMONARY EMBOLISM - AN EXPERIMENTAL STUDY

Alterations in central venous pressure (CVP) were measured in response to embolization with standardized autologous venous thrombi. Platelets were counted before and after embolization and their accretion on the embolus was determined microscopically at autopsy. The rise in CVP could be blocked by heparin but only at sufficient doses to prevent the platelet accretion, or by aging the thrombus prior to embolization. conversely, the postembolic rise in CVP and mortality rates were augmented by an inhibitor of monoamine oxidase whose effect in turn was nullified by a serotonin antagonist. It is concluded that the release of biogenic amines from platelets, triggered by thrombin on the embolus, plays a significant role in the animal's response to thromboemboli. Both in vivo and in vitro evidence is presented demonstrating that the dose requirements of heparin necessary to inhibit these events is greater than that generally used in treating pulmonary embolism. Certain clinical observations relating to these experimental findings are reviewed and the therapeutic implications discussed. © 1968.