The prognostic value of muscle StO₂ in septic patients

To quantify sepsis-induced alterations in changes in muscle tissue oxygenation (StO₂) after an ischemic challenge using near-infrared spectroscopy (NIRS), and to test the hypothesis that these alterations are related to outcome.

Prospective study.

Thirty-one-bed, university hospital Department of Intensive Care.

Seventy-two patients with severe sepsis or septic shock, 18 hemodynamically stable, acutely ill patients without infection, and 18 healthy volunteers.

Three-minute occlusion of the brachial artery using a cuff inflated 50 mmHg above systolic arterial pressure.

Thenar eminence StO₂ was measured continuously by NIRS before (StO₂baseline), during, and after the 3-min occlusion. Changes in StO₂ were assessed by the slope of increase in StO₂ during the first 14 s following the ischemic period and by the difference between the maximum StO₂ and StO₂baseline (Δ). The slope was lower in septic patients than in controls and volunteers [2.3 (1.3–3.6), 4.8 (3.5–6.0), and 4.7 (3.2–6.3) %/s, p < 0.001]. Δ was also significantly lower in septic patients than in the other groups. Slopes were lower in septic patients with than without shock [2.0 (1.2–2.9) vs 3.2 (1.8–4.5) %/s, p < 0.05]. In 52 septic patients, in whom the slope was obtained every 24 h for 48 h, slopes were higher in survivors than in non-survivors and tended to increase in survivors but not in non-survivors.

Altered recovery in StO₂ after an ischemic challenge is frequent in septic patients and more pronounced in the presence of shock. The presence and persistence of these alterations in the first 24 h of sepsis are associated with worse outcome.