Should We Monitor ScVO(2) in Critically Ill Patients?

Abstract

Hemodynamic monitoring has become a real challenge in the intensive care unit. As an integrative parameter for oxygen supply/demand, venous oxygen saturation (SvO(2)) provided by pulmonary artery catheterization is one of the most popular parameters to assess the adequacy of cardiac output. However, technical limitations and potential iatrogenic complications constitute important limits for a widespread use. Regular central venous catheters coupled with a fiberoptic lumen for central venous oxygen saturation (ScvO(2)) monitoring have been proposed as a surrogate for SvO(2) monitoring. The purpose of the present article is to review the physiological backgrounds of circulation, the pathophysiology of circulatory failure and subsequent venous oxygen saturation alterations, and finally the merits and the limits of the use of ScvO(2) in different clinical situations.

Figure 1

Evolution of oxygen consumption when oxygen delivery decreases. From Vincent and De Backer [5] with permission. Note the presence of a DO₂ threshold located at approximately 100 mL/min. Below this value, oxygen consumption begins to fall and lactate concentration increases, indicating a switch from aerobic to anaerobic metabolism.