Hemolysis, characterized by increased carboxyhemoglobin (COHb) and methemoglobin (MetHb) levels, is a complication of extracorporeal membrane oxygenation (ECMO).

This prospective single-center study aimed to investigate the correlation between COHb and MetHb levels and hemolysis during ECMO. This study included 32 patients requiring ECMO for circulatory or respiratory failure. Plasma-free hemoglobin (pfHb), COHb, and MetHb levels were measured simultaneously within 6 h of ECMO induction, daily during ECMO, within 6 h after decannulation, and 2 days after decannulation unless death occurred before. Patients were classified into hemolysis and non-hemolysis groups based on whether the maximum pfHb level during ECMO was ⩾50 mg/dL.

No significant difference in maximum COHb levels during ECMO (COHb_ECMO) was observed between the hemolysis and non-hemolysis groups (2.15% [interquartile range (IQR) = 1.83, 2.60] vs 1.65% [IQR = 1.40, 2.10], p = 0.159). However, maximum MetHb levels during ECMO (MetHb_ECMO) were significantly higher in the hemolysis group (1.35% [IQR = 1.12, 1.78] vs 1.10% [IQR = 0.90, 1.37], p = 0.045). The Spearman’s correlation coefficients for COHb_ECMO and MetHb_ECMO were 0.39 (95% confidence interval [CI] = 0.456–0.649) and 0.66 (95% CI = 0.404–0.820), respectively.

Elevated MetHb levels in patients undergoing ECMO may be associated with hemolysis.