Evaluation of reoxygenation slope using Near-infrared spectroscopy in intensive care patients

Objective: To evaluate the reoxygenation slope reactivity in intensive care patients using near-infrared spectrophotometry (NIRS). Design: an observational prospective study. Setting: A 15-beds intensive care unit of a teaching hospital Patients: Consecutive patients admitted to the intensive care unit with severe sepsis (Sepsis; n=25 patients), without sepsis (Control; n=22 patients); a group of healthy volunteers (n=50). Measurements: Baseline thenar muscle tissue oxygen saturation (StO2), Maximal StO2 reperfusion slope and the area under the curve for the hyperhemic response were measured during and after a 150 seconds arterial occlusion. Measurements were performed at the early phase of hospitalization and compared to measurements obtained in healthy volunteers. Results: Mean initial StO2 values were comparable between the 3 groups. During arterial occlusion, maximal StO2 reperfusion slope was higher in healthy volunteers (361 ± 137 %.min-1), as compared to both Sepsis (111.3 ± 56.9 %.min-1; p=0.0002) and Control groups (163.3 ± 120.5 %.min-1; p=0.01). Maximal StO2 reperfusion slope was comparable between Sepsis and Control (p=0.55). In Sepsis, StO2 reperfusion slope and the area under the curve for the hyperemic response were similar whatever the mean arterial pressure or the blood lactate levels. Conclusion: Microvascular postocclusive reactivity assessed by NIRS is significantly altered on admission within ICU patients, as compared to healthy volunteers. However, In contrast to our expectancies, no difference was observed between Sepsis and Control.