Oxygen Consumption and Delivery in Critical Illness

This chapter evaluates the importance of identifying the oxygen delivery and oxygen consumption balance in critically ill patients. Mixed venous oxygen saturation is a valuable marker of oxygen consumption and delivery in an intensive care unit patient. Organ perfusion can be improved by optimizing all components of the oxygen delivery calculation and decreasing oxygen consumption, if indicated. Several tools that aid in this assessment include pulmonary artery catheter–derived mixed venous oxygen saturation, central venous line–derived central venous saturation, cardiac ultrasonography, and laboratory values such as the arterial blood gas and lactate levels. The chapter also discusses hyperlactatemia. Hyperlactatemia can be due to anaerobic metabolism (type A lactic acidosis) or aerobic metabolism (type B lactic acidosis).