Algorithm for Reporting Free Hemoglobin in ECMO Patients: Need for a Multidisciplinary Approach

Area of Science:

• Clinical Chemistry
• Biomarkers
• Extracorporeal Membrane Oxygenation (ECMO)

Background:

• Intravascular hemolysis is a frequent complication in ECMO patients.
• Plasma free hemoglobin (pfHb) is a key biomarker for hemolysis detection.
• Lack of standardized protocols challenges accurate pfHb interpretation and reporting.

Purpose of the Study:

• To compare pfHb measurement methods in ECMO patients.
• To evaluate the impact of hemolysis, icterus, and lipemia (HIL) indices on pfHb estimation.
• To develop an algorithm for improved pfHb reporting in ECMO patients.

Main Methods:

• Retrospective observational study of 61 ECMO patient samples.
• Comparison of Harboe method (fHb) with estimated pfHb (efHb) from hemolysis indices on Abbott Alinity c.
• Analysis of bilirubin, HIL indices, and method comparison using Passing-Bablok and Bland-Altman.

Main Results:

• Significant differences observed between fHb (median 261 mg/L) and efHb (median 58 mg/L).
• efHb showed a constant negative bias (-91 mg/L) relative to fHb.
• Method delta increased with higher bilirubin; moderate correlation (rho=0.618) between fHb and efHb.

Conclusions:

• Accurate hemolysis assessment in ECMO necessitates careful interpretation and method selection.
• An algorithm integrating HIL indices enhances pfHb testing utility by addressing interferences.
• Laboratory-clinician collaboration is crucial for informed decision-making in ECMO patient care.