Methemoglobin in critically ill septic patients.

Higher nitric oxide (NO) levels correlate with adverse sepsis outcomes but are challenging to measure. Methemoglobin (MetHb), a measurable product of NO, has not been utilized for risk stratification. All patients with sepsis admitted to the intensive care unit (ICU) that had at least one MetHb measurement within 24 h of ICU admission were retrospectively analyzed. We assessed the epidemiology and associations of MetHb with hospital mortality. Among 7724 patients, 1046 qualified. Those with MetHb ≥1.6% showed significantly higher mortality and fewer days alive outside the hospital by day 28. MetHb levels ≥1.6% independently predicted increased 28-day mortality. Our findings suggest MetHb, easily obtainable from arterial blood gases, can significantly enhance sepsis risk stratification.