Methemoglobin level as an indicator for disease severity in sepsis

Introduction

The objective of our study was to investigate how methemoglobin (MetHb) levels reflect the occurrence and severity of sepsis. MetHb is generated of nitric oxide (NO) through interaction with hemoglobin in a variety of patients [1]. This includes patients in sepsis with a potentially higher NO generation.

Methods

Six hundred and sixty-five patients of a university ICU were included in a retrospective study to analyze data after onset of sepsis (day 0) and 24 hours later (day 1). Eligible for inclusion were sepsis or severe sepsis patients as defined by ACCP/SCCM consensus conference and control ICU patients, both with measured MetHb levels and age >18 years. The recorded SOFA score on day 0 was used to stratify the study population in less severely (≤ 10 points) and more severely (>10 points) patients. After verification of skewness, septic and nonseptic patients and SOFA groups were compared using the Mann–Whitney U test. P < 0.05 was considered significant.

Results

Of 665 patients, 71% (n = 469) had a SOFA score ≤ 10. Forty-five percent (n = 211) of them had sepsis. One hundred and sixty-four out of 196 severely ill patients (SOFA score > 10) had sepsis. MetHb levels were significantly higher in patients with sepsis compared with nonseptic patients on day 0 (SOFA ≤ 10: 0.72 ± 0.27% vs 0.65 ± 0.15% (P < 0.01); SOFA > 10: 0.79 ± 0.21% vs 0.62 ± 0.17% (P < 0.01)). On day 1 similar results comparing septic and nonseptic patients were obtained (SOFA ≤ 10: 0.73 ± 0.24% vs 0.63 ± 0.16% (P < 0.01); SOFA > 10: 0.80 ± 0.24% vs 0.69 ± 0.20% (P < 0.01)). If sepsis was more severe, as defined by SOFA score > 10, significantly higher MetHb levels were observed compared with sepsis patients with SOFA scores ≤ 10 on day 0 and day 1 (P < 0.01).

Conclusion

Our data suggest that increased MetHb levels reflect the severity of disease defined by SOFA score. Furthermore, MetHb levels may have the potential to contribute to the diagnosis of sepsis. This potential of MetHb levels needs prospective validation.