Control of the Postirradiation Hemorrhagic State by Platelet Transfusions

Suspensions of concentrated, homologous blood platelets when introduced intravenously into lymph-cannulated dogs and rats (nine to twelve days after exposure to an LD₅₀ or greater dose of x-rays) have been shown to eliminate the large scale diversion of erythrocytes into the lymph during the hemorrhagic phase of radiation injury. By means of injection of platelets preinjection levels of below 50,000 were raised to an average of 107,000 in 6 dogs, and to an average of 310,000 in five rats at 15 to 30 minutes after injection. All platelet-injected animals showed clearing of the bloody lymph within the first hour after injection, and within 5 to 6 hours the average erythrocyte count in the dogs dropped from an average of 270,000 to an average of 12,000 and in the rats from an average of 900,000 to an average of 30,000. No depression of lymph erythrocyte counts was found in control rats receiving plasma only. Lymph erythrocyte counts in the platelet recipients remained low for 24 to 36 hours after injection; bleeding into the lymph space reappeared in both rats and dogs when the platelet level dropped below approximately 50,000. Blood platelet and lymph erythrocyte levels are excellent indices to quantitate the severity of the hemorrhagic phase of radiation injury and to gauge the results of therapeutic procedures.

While the mechanism of platelet action remains to be demonstrated, the present studies support the thesis of earlier workers that platelets are essential to maintain vascular integrity and that a platelet deficiency is the main cause of the postirradiation hemorrhagic state.