Carboxyhemoglobin and methemoglobin levels to diagnose hemolysis in patients supported with mechanical circulatory support devices

Abstract

Decreased systemic oxygen delivery derived from gas exchange abnormalities in severe hemolysis may complicate critically ill patients supported with mechanical circulatory support devices such as the Impella device and others. Severe hemolysis releases free hemoglobin in plasma causing elevation of carboxyhemoglobin and methemoglobin levels in blood. Hemolysis induced decline in hemoglobin and oxyhemoglobin saturation may drastically reduce the arterial oxygen content in blood, therefore decreasing systemic oxygen delivery, causing or worsening lactic acidosis. These patients develop significant hypoxemia with misleadingly normal oxygen saturation measured by standard pulse oximetry. The objective of this study is to report two cases that illustrate these physiologic phenomena, emphasizing the value of monitoring carboxyhemoglobin and methemoglobin levels to readily identify and modify the management of ongoing hemolysis secondary to invasive supportive devices.