Predictive role of central venous oxygen saturation in patients with acute type i respiratory failure

Abstract

Background Global oxygenation can be indirectly measured by the measurement of venous oxygen saturation.Objective To estimate the value of central venous oxygen saturation (ScvO2) to predict the outcome in type 1 acute respiratory failure (ARF) patients admitted to the respiratory ICU and to assess its potential association with mortality.Patients and methods The study included 62 type 1 ARF patients admitted to respiratory ICU with indication for a central venous catheter. ScvO2 was measured from right atrium blood samples at admission, 3 and 7 days later. Arterial blood gas was assessed simultaneously. The patients were classified into three groups according to the ScvO2 level (at admission): high more than 75%, normal 65–75%, and low less than 65% (9, 34, and 19 patients, respectively). The best ScvO2 cutoff value associated with the mortality was considered the critical value of ScvO2. Acute physiology and chronic health evaluation (APACHE) II score severity, ICU, and hospital stay, and hospital mortality were reported.Results Sixty-two type 1 ARF patients with a mean age of 60±17.4 years were included. Seventy-nine percent patients had pneumonia. Mechanical ventilation was indicated in 77.4% of the patients with a mean duration of 6±3.6 days. The mean ScvO2 at day 0, 3, and 7 were 67.7±8.1, 66±11, and 69.3±9.3, respectively. The mean hospital stay was 6.8±4 days; 72.6% of the patients died in the hospital. Overall mortality in patients with low, normal, and high ScvO2 (at admission) were 42.2, 40, and 17.8%, respectively. Abnormal low and high ScvO2 was significantly related to mortality (P<0.0001). The cutoff point of ScvO2 at admission for mortality prediction was less than or equal to 65% (P=0.0008), 100 specificity, 49 sensitivity, 100 positive predictive value, and 42.5 negative predictive value. Mechanical ventilation, APACHE II score more than 27, development of complications, low initial arterial oxygen saturation and partial arterial oxygen pressure, the ScvO2 cutoff point less than or equal to 65% at admission, less than or equal to 70% at third and less than or equal to 66% at seventh day were significantly related to the mortality (<0.0001, <0.0001, <0.0001, 0.01, 0.03, 0.0008, 0.04 and 0.04, respectively).Conclusion In type1 ARF patients, abnormal low and high ScvO2 after day 0, 3, and 7, % of ScvO2 change in third and seventh day, and high APACHE II score were significantly linked to high mortality.Clinical implications In critically ill patients, ScvO2 is useful in the estimation of tissue oxygenation and may replace the use of mixed venous oxygen saturation.