Venous oximetry

Excerpt

The primary physiological task of the cardiovascular system is to deliver enough oxygen (O₂) to meet the metabolic demands of the body. Shock and tissue hypoxia occur when the cardiorespiratory system is unable to cover metabolic demand adequately. Sustained tissue hypoxia is one of the most important cofactors in the pathophysiology of organ dysfunction [1]. Therefore determining the adequacy of tissue oxygenation in critically ill patients is central to ascertain the health of the patient. Unfortunately, normal values in blood pressure, central venous pressure, heart rate, and blood gases do not rule out tissue hypoxia or imbalances between whole-body oxygen supply and demand [2]. This discrepancy has led to increased interest in more direct indicators of adequacy of tissue oxygenation such as mixed and central venous oxygen saturations. Pulmonary artery catheterization allows obtaining true mixed venous oxygen saturation (SvO₂) while measuring central venous oxygen saturation (ScvO₂) via central venous catheter reflects principally the degree of oxygen extraction from the brain and the upper part of the body. This brief review discusses the role and limitations of SvO₂ and ScvO₂ as indicators of the adequacy of tissue oxygenation. …