This retrospective study analyzed over 2,500 adult patients to determine if lactate dynamics—including clearance time, trend, and maximum level—offer incremental value in predicting poor outcomes after cardiac surgery, beyond established clinical risk models.

Delayed Clearance is a High-Risk Marker: Patients with delayed lactate clearance (lactate remaining >3 mmol/L for more than 24 hours or never clearing) represented 5% of the cohort and were significantly associated with established risk factors, including older age, pre-operative mechanical support, longer bypass times, and higher pre-operative risk scores (STS-PROM).

Strong Association with Mortality: Delayed clearance was strongly associated with significantly increased operative mortality (adjusted Odds Ratio 9.23).

No Incremental Predictive Value: Crucially, when lactate parameters (like clearance time) were added to the existing Society of Thoracic Surgeons Predicted Risk of Mortality (STS-PROM) score, they did not significantly improve the model’s performance in predicting operative mortality (AUC: 0.83 for STS-PROM vs. 0.84 with lactate; p>0.9).

Although delayed lactate clearance is a powerful indicator associated with poor outcomes and severe illness after cardiac surgery, the study concludes that it functions as a reflective biomarker of established risk and clinical instability, rather than an independent prognostic biomarker that enhances pre-existing risk stratification models (like STS-PROM) for predicting mortality.

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