Abstract
Central venous oxygen saturation (ScvO2) in the superior vena cava is predominantly determined by cardiac output, arterial oxygen content, and oxygen consumption by the upper body. While abnormal ScvO2 levels are associated with morbidity and mortality in non-uremic populations, ScvO2 has received little attention in hemodialysis patients. From 1/2012 to 8/2015, 232 chronic hemodialysis patients with central venous catheters as vascular access had their ScvO2 monitored during a 6-month baseline period and followed for up to 36 months. Patients were stratified into upper and lower two tertiles by a ScvO2 of 61.1%. Survival analysis employed Kaplan-Meier curves and adjusted Cox proportional hazards models. Patients in the lower tertiles of ScvO2 were older, had longer hemodialysis vintage, lower systolic blood pressure, lower ultrafiltration rates, higher leukocyte counts and neutrophil-to-lymphocyte ratios. Kaplan-Meier analysis indicated a shorter survival time in the lower tertiles of ScvO2 (P = 0.005, log-rank test). In adjusted Cox analysis, a 1 percent point decrease in mean ScvO2 was associated with a 4% increase in mortality (HR 1.04 [95% CI 1.01–1.08], P = 0.044), indicating that low ScvO2 is associated with poor outcomes. Research on the relative contributions of cardiac output and other factors is warranted to further elucidate the pathophysiology underlying this novel finding.
Highlights
Mixed venous oxygen saturation (SmvO2) and central venous oxygen saturation (ScvO2) have been used in critical care to guide fluid resuscitation[8]
ScvO2 is determined by oxygen delivery to and oxygen consumption of the arms, head, and upper portion of the torso; the former depends on the arterial blood oxygen content and the cardiac output (CO)
The initial population comprised of 579 patients with central venous catheters (CVC) as dialysis access, with a total of 15,792 HD treatments with ScvO2 measurements from January 1, 2012 until August 31, 2015
Summary
Mixed venous oxygen saturation (SmvO2) and central venous oxygen saturation (ScvO2) have been used in critical care to guide fluid resuscitation[8]. SmvO2 is the oxygen saturation in the pulmonary artery, which receives blood from the superior vena cava, the inferior vena cava, and the coronary sinus, and reflects – in the absence of arterial venous shunts – the aggregated effects of oxygen delivery to and utilization by the entire body. ScvO2 from upper body central venous catheters (CVC) is the oxygen saturation of blood in the superior vena cava, which reflects the aggregate of oxygen delivery to and utilization by the upper body. While the measurement of SmvO2 requires pulmonary artery catheterization, ScvO2 can be more obtained from a CVC. ScvO2 is determined by oxygen delivery to and oxygen consumption of the arms, head, and upper portion of the torso; the former depends on the arterial blood oxygen content and the cardiac output (CO). One study in healthy subjects found a ScvO2 of 76.8 ± 5.2% during cardiac catheterization[13]
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