Elevated postoperative hemolysis index tied to Cardiac Surgery-Associated Acute Kidney Injury, reveals research

Cardiac surgery-associated acute kidney injury (CS-AKI) is common and linked to adverse outcomes. Early prediction and identification of CS-AKI are essential for reducing its effects. One of the factors contributing to CS-AKI is hemolysis. Recent study aimed to assess whether the postoperative plasma level of the hemolysis index (HIpostoperative) could aid in the early recognition of patients at risk for cardiac surgery-associated acute kidney injury (CS-AKI). The researchers also evaluated other hemolysis indicators, including plasma carboxyhemoglobin (COHbpostoperative) and methemoglobin (MetHbpostoperative).

Patient Population and Findings

The study included 1,090 patients who underwent elective cardiac surgery under cardiopulmonary bypass (CPB). CS-AKI occurred in 224 patients (20.6%). The median HIpostoperative was significantly higher in patients who developed CS-AKI compared to those who did not (11 mg/dL vs 7 mg/dL, p<0.001). HIpostoperative refined the early recognition of CS-AKI, with an area under the precision-recall curve (AUPRC) of 37%, whereas the AUPRC associated with no discriminative power was 21%.

Comparison of Biomarkers

Among the 611 patients with measurements for all 3 biomarkers, the AUPRC of HIpostoperative was higher than that of COHbpostoperative or MetHbpostoperative (+6.6% and +7.4% respectively; p<0.0001 for both). Importantly, the incorporation of HIpostoperative into a predictive model for early recognition of CS-AKI significantly enhanced its performance, with a 1.9% (95% CI, 1.6%-2.1%) increase in AUPRC (p<0.0001). In contrast, COHbpostoperative and MetHbpostoperative were not retained in the final predictive model, indicating their limited value for CS-AKI early recognition compared to HIpostoperative.

Conclusion and Implications

In conclusion, elevated HIpostoperative represents an early alert signal for the development of CS-AKI. The findings support the incorporation of HIpostoperative, a readily available biomarker, into predictive scores of CS-AKI.

Key Points

1. The study aimed to assess whether the postoperative plasma level of the hemolysis index (HIpostoperative) could aid in the early recognition of patients at risk for cardiac surgery-associated acute kidney injury (CS-AKI). It also evaluated other hemolysis indicators, including plasma carboxyhemoglobin (COHbpostoperative) and methemoglobin (MetHbpostoperative).

2. The study included 1,090 patients who underwent elective cardiac surgery under cardiopulmonary bypass (CPB). CS-AKI occurred in 224 patients (20.6%). The median HIpostoperative was significantly higher in patients who developed CS-AKI compared to those who did not (11 mg/dL vs 7 mg/dL, p<0.001).

3. HIpostoperative refined the early recognition of CS-AKI, with an area under the precision-recall curve (AUPRC) of 37%, whereas the AUPRC associated with no discriminative power was 21%.

4. Among the 611 patients with measurements for all 3 biomarkers, the AUPRC of HIpostoperative was higher than that of COHbpostoperative or MetHbpostoperative (+6.6% and +7.4% respectively; p<0.0001 for both). Incorporating HIpostoperative into a predictive model for early recognition of CS-AKI significantly enhanced its performance, with a 1.9% (95% CI, 1.6%-2.1%) increase in AUPRC (p<0.0001).

5. In contrast, COHbpostoperative and MetHbpostoperative were not retained in the final predictive model, indicating their limited value for CS-AKI early recognition compared to HIpostoperative.

6. The findings support the incorporation of HIpostoperative, a readily available biomarker, into predictive scores of CS-AKI, as it represents an early alert signal for the development of CS-AKI.

Reference –

Dr Emmanuel Golinvaux et al. (2024). Hemolysis Index, Carboxyhemoglobin, And Methemoglobin For The Early Identification Of Patients At Risk For Cardiac Surgery-Associated Acute Kidney Injury.. *Journal Of Cardiothoracic And Vascular Anesthesia*. https://doi.org/10.1053/j.jvca.2024.09.143