Free hemoglobin concentration in severe sepsis: methods of measurement and prediction of outcome
Critical Care, 07/17/2012
Adamzik M et al. – Free hemoglobin is an important new predictor of survival in severe sepsis.Methods
- Plasma concentration of free hemoglobin was determined in patients with severe sepsis (n=161) and postoperative patients (n=136) on day 1 of diagnosis and surgery.
- For the measurement of free hemoglobin, an enzyme linked immunosorbent assay and three spectrophotometric algorithms were used.
- Moreover, SAPS II– and SOFA scores as well as procalcitonin concentration and outcome were determined.
- Kaplan–Meier analysis was performed and odds ratios were determined after classification of free hemoglobin concentrations in a high and low concentration group according to the median.
- For statistical evaluation the Mann–Whitney test and logistic regression analysis were used.
- In nonsurvivors of severe sepsis, free hemoglobin concentration was twice the concentration compared to survivors.
- 30–day survival of patients, as evidenced by Kaplan–Meier analysis, was markedly lower in patients with high free hemoglobin concentration than in patients with low free hemoglobin concentration.
- Best discrimination of outcome was achieved with the spectrophotometric method of Harboe (51.3 % vs. 86.4 % survival, p<0.001; odds ratio 6.1).
- Multivariate analysis including free hemoglobin, age, SAPS II– and SOFA–scores and procalcitonin demonstrated that free hemoglobin, as determined by all 4 methods, was the best and an independent predictor for death in sepsis (p=0.022 to p<0.001).
- Free hemoglobin concentrations were not significantly different in postoperative and septic patients in three of four assays.
- Thus, free hemoglobin can not be used to diagnose severe sepsis in critical illness.