Marked hyperlactatemia associated with severe alkalemia in a patient with thrombotic thrombocytopenic purpura.

This report describes a case of severe alkalemia associated with a blood lactate level greater than 13 mEq/L in a patient without evidence of hypotension or hypoxemia. The patient, who had the clinical manifestations of thrombotic thrombocytopenic purpura (TTP), developed the alkalemia from an acute respiratory alkalosis superimposed on an existing metabolic alkalosis. Profound alkalemia may impair oxygen delivery because of stronger hemoglobin-oxygen affinity, vasoconstriction, and alterations in the redox potential of cytochrome c. We suggest that the synergistic effects of a sudden, extreme alkalemia and the localized tissue hypoxia that resulted from extensive microvascular thrombi secondary to TTP caused the patient's hyperlactatemia.