Importance of Svo₂ Monitoring and Plasma Lactate Level in Critical Care Management

Abstract

  Although assessment of cardiac function using the Starling curve has been widely accepted for management of critically ill patients, the method does not contain the idea of oxygen demand and supply. The mixed venous oxygen saturation (Svo₂) is determined by arterial oxygen saturation (Sao₂) , oxygen consumption (Vo₂) , hemoglobin (Hb) , and cardiac output (CO) . Then, since Svo₂ can assess the abnormal balance between oxygen demand (Vo₂) and supply (Sao₂, Hb, CO) , it is useful for cardiac and metabolic management, i.e., during anesthesia as a lower oxygen demand state or in septic shock as a higher oxygen demand state. High Svo₂ does not always means a good condition because arterio-venous shunt or impaired oxygen utilization in septic shock increases Svo₂. Plasma lactate level can complement the disadvantages of Svo₂ in such pathological states. The meaning and utility of Svo₂ and lactate monitoring are discussed in the text.