HBOCs and cardiac integrity

Abstract

Increased incidence of myocardial infarction (MI) associated with the use of hemoglobin based oxygen carriers (HBOCs) is a concern arising from the clinical evaluation of these formulations. Many characteristics of HBOCs may affect cardiac performance, as will specifics of treatment protocols. The vasoactivity of HBOCs affects the hemodynamic response to their infusion, but tissue oxygenation and blood flow to the heart is maintained or enhanced in a variety of circumstances, even when cardiac output is decreased. HBOC infusions are protective in several preclinical models of cardiac ischemia/reperfusion injury and supportive or restorative of cardiac function in models of hemodilution and resuscitation from hemorrhagic shock. Microscopic cardiac lesions observed during the preclinical testing of some HBOCs are a consequence of nitric oxide scavenging, but this mechanism is unlikely to be clinically significant unless humans are unusually sensitive. Understanding the reason(s) for the observed clinical imbalance in MI is hampered by the lack of detailed information concerning the physiologic and biochemical responses of the human cardiovascular system to HBOC infusion and appreciation for the degree to which suboptimal patient management in the presence of these unique solutions has contributed to the observed results.