Use of Mixed Venous Oxygen Saturation in ICU Patients
The hemodynamic resuscitation of patients in shock is aimed at fulfilling therapeutic goals that are predetermined. Classically, these goals are arterial pressure (MAP), urine output, and central venous pressure (CVP) . Despite normalization of these parameters, tissue hypoxia can persist when the cardiorespiratory system is not adapted to metabolic requirements . Prolonged hypoxia must be avoided since it is the main risk factor for multivisceral failure . It is difficult to evaluate tissue hypoxia at the patient’s bedside . It is therefore of great interest to be able to evaluate it with an easy-to-monitor parameter. Mixed venous oxygen saturation (SvO2) depends on the balance between arterial oxygen transport (DO2) to tissue and its consumption (VO2) . However, SvO2 measurement requires the placement of a pulmonary artery catheter (PAC) with a benefit/risk ratio that remains controversial. No study has reported a favorable impact on survival in patients with the use of this type of catheter [5, 6, 7]. Moreover, placement of a PAC is not always possible. Measurement of central venous oxygen saturation in the superior vena cava blood (ScvO2) is possible with the use of a central venous catheter equipped with an optic fiber or using repeated venous samples with traditional catheters. There is a physiological relationship between SvO2 and ScvO2 values with the latter always a little lower (2–3%) in physiologic conditions than the former. Monitoring of ScvO2 is therefore an attractive alternative to that of SvO2 . The aim of this chapter is to define the interest and limits of this hypothesis.
KeywordsCardiac Output Septic Shock Severe Sepsis Pulmonary Artery Catheter Oxygen Extraction
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