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While oxygen saturation refers to the percentage of hemoglobin bound to oxygen within red blood cells, mixed venous oxygen saturation (SvO2) refers to the oxygen content of the blood that returns to the heart after meeting tissue needs. Therefore, mixed venous oxygen saturation is a clinically useful parameter when managing patients in the perioperative period, critical care setting, or presenting with shock pathophysiology. Monitoring mixed venous oxygen has significant value in risk stratification, prognosis, and monitoring to recognize tissue hypoxia in the critically ill. Realistically, it is one among several parameters that should be taken into account when assessing adequate tissue perfusion. This activity reviews the indications, contraindications, and methodology for measuring mixed venous saturation and highlights the role of the interprofessional team in managing patients with poor tissue perfusion. Objectives: Describe the technique for measuring mixed venous oxygen saturation. Outline the indications for measuring mixed venous oxygen saturation. Review the clinical relevance of mixed venous oxygen saturation. Explain the importance of clear communication among interprofessional team members to improve care for patients with abnormal mixed venous oxygen saturation. Access free multiple choice questions on this topic.

While oxygen saturation refers to the percentage of hemoglobin bound to oxygen within red blood cells, mixed venous oxygen saturation (SvO2) refers to the oxygen content of the blood that returns to the heart after meeting tissue needs. Therefore, in practice, venous oxygen saturation is a measured value that is a significant parameter when managing patients in the perioperative period, critical care setting, and patients presenting with shock pathophysiology. While its use as a therapeutic endpoint as part of early goal-directed therapy has received study with varying results, abnormal values have been invariably concluded to correlate with higher mortality. Therefore, monitoring mixed venous oxygen has significant value in risk stratification, prognosis, and monitoring to recognize tissue hypoxia in the critically ill. It is one of several parameters that should be considered when assessing adequate tissue perfusion.

The use of catheters is not without complications, and usually, these risks are higher with the more invasive procedure associated with pulmonary artery catheterizations. Complications can result from inserting, manipulating, and maintaining pulmonary artery catheters (PAC). With initial insertion, thrombosis formation is one of the more common complications, with a thrombotic risk of internal jugular catheter placement being 7.6%. There are also relatively fewer common risks of arterial puncture, hematoma formation, AV fistula, thoracic duct injury, air embolization, and pneumothorax. Furthermore, complications of PAC manipulation and maintenance include transient cardiac arrhythmias that happen with an incidence ranging between 12.5% to 70%, with PVCs and VTs being the most commonly observed. A catheter-associated infection is also an ongoing challenge, with the incidence of PAC-associated bacteremia being 1.3% to 2.3%. Cases of pulmonary artery rupture, chamber rupture, malposition in the coronary sinus, pulmonary infarction, and PAC knotting have been reported but are relatively rare.[9]

Observing significant changes in mixed venous oxygen saturation indicates worsening prognosis in critically ill patients and should be one of the parameters used to assess adequate tissue perfusion. Enhancing health outcomes for these patients who need venous monitoring is best accomplished through an interprofessional team-based approach, which includes clinicians, nursing staff, radiologists, and pharmacists. They all perform essential roles in sepsis, perioperative management, critical care, and heart failure by detecting sudden increases or decreases in oxygen delivery and extraction, and they must document their interventions while maintaining open lines of communication with other team members should they note any concerns. This interprofessional approach will yield optimal patient results. When there is a clinical indication for mixed venous oxygen monitoring, the central line and swan catheter should be inserted under strict aseptic precaution. The site should be monitored daily to ensure it's clean and sterile. Only providers credentialed per institutional guidelines should be allowed to insert catheters since risks are significant and can be life-threatening. Once placed position should be confirmed, and the device should be secured and continuously monitored for misplacement. The clinical utility of the catheters is proven by providers trained to interpret data and waveforms. Finally, risks to benefits must be weighed for each patient, and like with any other invasive monitoring; PA catheter should be discontinued when no longer indicated in the management of the patient.