Carboxyhemoglobin in Cardiac Surgery Patients and Its Association with Risk Factors and Biomarkers of Hemolysis.

BACKGROUND

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with hemolysis. Yet, there is no easily available and frequently measured marker to monitor this hemolysis. However, carboxyhemoglobin (CO-Hb), formed by the binding of carbon monoxide (a product of heme breakdown) to hemoglobin, may reflect such hemolysis. We hypothesized that CO-Hb might increase after cardiac surgery and show associations with operative risk factors and indirect markers for hemolysis.

METHODS

We conducted a retrospective descriptive cohort study of data from on-pump cardiac surgery patients. We analyzed temporal changes in CO-Hb levels and applied a generalized linear model to assess patient characteristics associated with peak CO-Hb levels. Additionally, we examined their relationship with red blood cell (RBC) transfusion and bilirubin levels.

RESULTS

We studied 38,487 CO-Hb measurements in 1735 patients. CO-Hb levels increased significantly after cardiac surgery, reaching a peak CO-Hb level 2.1 times higher than baseline ( P < .001) at a median of 17 hours after the initiation of surgery. Several factors were independently associated with higher peak CO-Hb, including age ( P < .001), preoperative respiratory disease ( P = .001), New York Heart Association Class IV ( P = .019), the number of packed RBC transfused ( P < .001), and the duration of CPB ( P = .002). Peak CO-Hb levels also significantly correlated with postoperative total bilirubin levels (Rho = 0.27, P < .001).

CONCLUSIONS

CO-Hb may represent a readily obtainable and frequently measured biomarker that has a moderate association with known biomarkers of and risk factors for hemolysis in on-pump cardiac surgery patients. These findings have potential clinical implications and warrant further investigation.