Prognostic implications of tissue oxygen saturation in human septic shock

Abstract

To analyze the prognostic value of tissue oxygen saturation (StO(2)) in septic shock patients with restored mean arterial pressure (MAP). This was a prospective observational study of patients admitted to the ICU in the early phase of septic shock, after restoration of MAP. Demographic data, severity score, hemodynamics, blood lactate, acid-base status, and StO(2) were measured at inclusion followed by a transient vascular occlusion test (VOT) to obtain the StO(2)-deoxygenation (DeOx) and StO(2)-reoxygenation (ReOx) rates. Sequential organ failure assessment (SOFA) score was measured at inclusion and after 24 h. Thirty-three patients were studied. StO(2) was 76 ± 10%, DeOx -12.2 ± 4.2%/min, and ReOx 3.02 ± 1.70%/s. MAP showed a significant correlation with VOT-derived slopes (r = -0.4, p = 0.04 for DeOx; and r = 0.55, p < 0.01 for ReOx). After 24 h, 17 patients (52%) had improved SOFA scores. Patients who did not improve their SOFA showed less negative DeOx values at inclusion. The association between DeOx and SOFA evolution was not affected by MAP. Both DeOx and ReOx impairment correlated with longer ICU stay (r = 0.44, p = 0.05; and r = -0.43, p = 0.05, respectively). In a population of septic shock patients with restored MAP, impaired DeOx was associated with no improvement in organ failures after 24 h. Decrements in DeOx and ReOx were associated with longer ICU stay. DeOx and ReOx were linked to MAP, and thus, their interpretation needs to be made relative to MAP.