Thrombocytogenesis in surgical patients.

ACARDINAL feature of more recent contributions to our understanding of the physiologic responses to trauma has been a growing realization of the unique importance of platelets in the mechanisms of hemostasis. If, as has been suggested,' * platelet alterations are the major determinant in the pathogenesis of postoperative thrombophilia, information concerning the mediation of the responses which have been observed may provide a rational approach to the prevention of thrombo-embolism. A consistent pattern is discernible in the fluctuations of circulating platelet concentration following major surgery. A fall in concentration of platelets early in the course of a major operation terminates in a thrombocytopenia which is sustained until the third or fourth postoperative day. The ensuing upward trend usually returns the platelet count to its preoperative range by the seventh day and, in a majority of patients, "overshoots" to a level of relative thrombocytosis during the latter part of the second week of convalescence. While it appeai-s that augmented megakaryocyte productivity, as interpreted from observations previously reported from this laboratory, may be responsible for the "high tide" of the platelet response, evidence that marrow function is a significant factor during the "low tide" phase has been inconclusive. Although observations that the average survival time of circulating platelets is at least four days discredit the significance of production and delivery processes in the rapid fall in peripheral platelet counts during operation, a