Low tissue oxygen saturation at the end of early goal-directed therapy is associated with worse outcome in critically ill patients

Introduction: The prognostic value of continuous monitoring of tissue oxygen saturation (StO(2)) during early goal- directed therapy of critically ill patients has not been investigated. We conducted this prospective study to test the hypothesis that the persistence of low StO(2) levels following intensive care admission is related to adverse outcome. Methods: We followed 22 critically ill patients admitted with increased lactate levels (>3 mmol/l). Near-infrared spectroscopy (NIRS) was used to measure the thenar eminence StO(2) and the rate of StO(2) increase (R(inc)StO(2)) after a vascular occlusion test. NIRS dynamic measurements were recorded at intensive care admission and each 2-hour interval during 8 hours of resuscitation. All repeated StO(2) measurements were further compared with Sequential Organ Failure Assessment (SOFA), Acute Physiology and Chronic Health Evaluation (APACHE) II and hemodynamic physiological variables: heart rate (HR), mean arterial pressure (MAP), central venous oxygen saturation (ScvO(2)) and parameters of peripheral circulation (physical examination and peripheral flow index (PFI)). Results: Twelve patients were admitted with low StO(2) levels (StO(2) <70%). The mean scores for SOFA and APACHE II scores were significantly higher in patients who persisted with low StO(2) levels (n = 10) than in those who exhibited normal StO(2) levels (n = 12) at 8 hours after the resuscitation period (P < 0.05; median (interquartile range): SOFA, 8 (7 to 11) vs. 5 (3 to 8); APACHE II, 32 (24 to 33) vs. 19 (15 to 25)). There was no significant relationship between StO(2) and mean global hemodynamic variables (HR, P = 0.26; MAP, P 0.51; ScvO(2), P = 0.11). However, there was a strong association between StO(2) with clinical abnormalities of peripheral perfusion (P = 0.004), PFI (P = 0.005) and R(inc)StO(2) (P = 0.002). The persistence of low StO(2) values was associated with a low percentage of lactate decrease (P < 0.05; median (interquartile range): 33% (12 to 43%) vs. 43% (30 to 54%)). Conclusions: We found that patients who consistently exhibited low StO(2) levels following an initial resuscitation had significantly worse organ failure than did patients with normal StO(2) values, and found that StO(2) changes had no relationship with global hemodynamic variables