Prevalence of hemolysis and metabolic acidosis in patients with circulatory failure supported with extracorporeal life support: a marker for survival?

AIMS: Elevated levels of plasma free hemoglobin (fHb) indicate red blood cell (RBC) damage. The aim of this study was to analyze the prevalence of hemolysis and metabolic acidosis in patients on extracorporeal life support (ECLS) and to investigate whether it is a marker for outcome.

METHODS AND RESULTS: This retrospective analysis included 215 adult patients with cardiac failure treated with ECLS. The cohort was divided into three groups: ECLS (1) during ongoing cardiopulmonary resuscitation (CPR, n = 110); (2) after CPR with return of spontaneous circulation and sustained cardiogenic shock (n = 45); (3) in severe cardiogenic shock without previous CPR (n = 60). Lactate, arterial pH value and fHb were measured daily before (pre-fHb) and during ECLS. CPR caused a pronounced increase in pre-fHb (group1, 318 (138/586) mg/L; group2, 212 (107/439) mg/L; group3, 79 (53/232) mg/L; p < 0.001). Within 24 hours on ECLS, fHb declined significantly. Compared to group 3 without CPR, group1 and 2 had a lower pH value (group1, 7.10 (6.93/7.20); group2, 7.21 (7.16/7.27); group3, 7.28 (7.20/7.35); p < 0.001), and an increased lactate level (group1, 88 (55/129) mg/dL; group2, 76 (36/111) mg/dL; group3, 52 (25/83) mg/dL; p < 0.0001). Multivariante analysis showed that pre-fHb had no prognostic value for survival. Only a low pre-lactate was a surrogate marker for successful weaning (p < 0.0001) and discharge from hospital (p = 0.0028).

CONCLUSIONS: CPR was associated with a strongly increased fHb irrespective of ECLS. Implantation of ECLS did not aggravate hemolysis but instead decreased it within 24 hours. In this study low pre-fHb had no predictive value for survival.