Carboxyhemoglobin predicts oxygenator performance and imminent oxygenator change in extracorporeal membrane oxygenation

Erlebach, R., Buhlmann, A., Andermatt, R. et al. Carboxyhemoglobin predicts oxygenator performance and imminent oxygenator change in extracorporeal membrane oxygenation. ICMx 12, 41 (2024). https://doi.org/10.1186/s40635-024-00626-7

Summary:

The study investigated the use of carboxyhemoglobin (COHb) levels as a marker for oxygenator dysfunction and imminent oxygenator change in patients undergoing extracorporeal membrane oxygenation (ECMO). The retrospective cohort study analyzed data from 89 patients who required 116 oxygenator changes, with 19,692 arterial COHb measurements. The study found that higher COHb levels were associated with worse oxygenator performance and were predictive of oxygenator change within six hours.

Results:

The study analyzed data from 484 ECMO patients, of which 89 required oxygenator changes. These patients had a median age of 54 years, with 71% being male. The median duration of ECMO support was 17.9 days, and the median time to oxygenator exchange was 9.3 days. The median COHb level was 2.0%, with higher levels observed in veno-venous (V-V) ECMO compared to veno-arterial (V-A) ECMO.

Higher COHb levels correlated with lower post-oxygenator partial pressure of oxygen (PpostO2), indicating worse oxygenator performance. The study showed that COHb levels significantly decreased after oxygenator change, confirming its utility as a marker for oxygenator dysfunction. The predictive value of COHb for oxygenator change within six hours was demonstrated through hierarchical generalized linear mixed-effects models and Cox proportional hazards models.

Discussion:

The study highlighted the importance of timely recognition of oxygenator dysfunction in ECMO patients, emphasizing that COHb could serve as a reliable marker for monitoring oxygenator performance. Traditional markers of hemolysis, such as lactate dehydrogenase (LDH) and bilirubin, have limitations, whereas COHb offers a rapid and routine measure. The study suggested that COHb levels >2% could indicate hemolysis, with >2.7% providing a high specificity for detecting hemolysis.

The findings underscore the need for integrating COHb measurements into routine ECMO monitoring to anticipate oxygenator failures and avoid emergency circuit changes. The study's limitations include its retrospective design, single-center setting, and exclusion of patients who did not require oxygenator changes. Future prospective trials are necessary to establish clear cut-off values for COHb to guide clinical decisions on oxygenator changes.

Conclusion:

The study concluded that rising COHb levels are predictive of reduced oxygenator performance and imminent oxygenator change in ECMO patients. Integrating COHb into routine monitoring protocols could enhance early detection of oxygenator dysfunction and improve patient outcomes by preventing emergency situations.

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Discussion Questions:

1. What are the potential advantages of incorporating COHb measurements into routine ECMO monitoring protocols, and how might this practice impact clinical outcomes and patient safety?
2. How can the findings of this study be applied to develop standardized guidelines for oxygenator change in ECMO patients, and what further research is needed to refine these guidelines?
3. What are the limitations of using COHb as a marker for oxygenator performance, and how can clinicians address these limitations to ensure accurate and reliable monitoring?

Javier Amador-Casta?eda, BHS, RRT, FCCM, PNAP

Interprofessional Critical Care Network (ICCN)

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