Objectives To determine the derangement of muscle tissue oxygen saturation (StO₂) in the early phase of emergency department (ED) sepsis management and its relationship to 30-day mortality in patients with severe sepsis or septic shock.

Methods A prospective cohort study conducted in the ED of a university hospital. Patients were included if they had a clinical diagnosis of severe sepsis or septic shock. Thenar muscle tissue StO₂ on arrival in the ED and its change with usual ED sepsis management was measured using near-infrared spectroscopy. A follow-up measurement was obtained after 24 h of treatment. All patients were followed for 30 days.

Results 49 patients were included, of which 24 (49%) died. There was no difference in mean StO₂ on arrival in the ED between survivors and non-survivors (72% vs 72%; p=0.97). Following ED treatment the mean StO₂ of survivors improved significantly to 78% (p<0.05) while StO₂ remained persistently low in non-survivors (p=0.94). Persistently low StO₂ (<75%) despite initial resuscitative treatment was associated with a twofold increase in mortality (RR of death 2.1%; 95% CI 1.2% to 3.5%).

Conclusion Patients with severe sepsis/septic shock have abnormal muscle tissue StO₂ upon arrival in the ED. Inability to normalise StO₂ with ED sepsis management is associated with a poor outcome. The role of StO₂ as an early prognostic and potential therapeutic biomarker in severe sepsis or septic shock warrants further exploration.