Key result
Higher initial ICU lactate linked to ~37% greater postoperative delirium risk per mmol/L after cardiac surgery.
Why the study?
Postoperative delirium frequently complicates cardiac surgery, but the predictive value of initial lactate at ICU admission for this condition remains unclear.
Does initial lactate at ICU admission predict postoperative delirium in adult patients after cardiac surgery?
Cohort (n=358)
Yes
Does initial lactate at ICU admission predict postoperative delirium in adult patients after cardiac surgery?
Effect estimate: OR 1.37 (95% CI 1.11-1.69)
p-value: p=0.003
Initial lactate levels at ICU admission following cardiac surgery are independently associated with an increased risk of postoperative delirium, though the predictive value is modest.
Should not yet change cardiac surgery practice; leaves open if lactate reduction prevents CS-POD.
Background Postoperative delirium is a frequent complication after cardiac surgery. The predictive value of initial lactate at ICU admission for cardiac surgery–associated postoperative delirium (CS-POD) remains unclear. Methods We conducted a retrospective cohort study using the eICU Collaborative Research Database, including adult patients admitted to the ICU after cardiac surgery. Multivariable logistic regression, restricted cubic spline analysis, ROC analysis, and mediation analysis were performed to assess the association between initial lactate and CS-POD and to explore whether disease severity scores (SOFA, APACHE IV) or clinical interventions statistically explained this relationship. Results Among 358 patients, 104 (29.1%) developed CS-POD. Higher initial lactate at ICU admission was independently associated with increased risk of CS-POD after full adjustment (OR per 1 mmol/L increase: 1.37, 95% CI 1.11–1.69; P = 0.003). Restricted cubic spline analysis demonstrated a linear relationship between initial lactate and CS-POD risk (P for nonlinearity = 0.132). Adding initial lactate to the baseline prediction model improved discriminative performance, with the area under the ROC curve (AUC) increasing from 0.661 (95% CI, 0.598–0.723) to 0.717 (95% CI, 0.660–0.775) (DeLong test P = 0.012). The optimal lactate cutoff for predicting CS-POD was 2.385 mmol/L. Mediation analysis indicated that part of the association between initial lactate and CS-POD was statistically explained by SOFA (proportion statistically explained: 17%, P = 0.002) and APACHE IV (proportion statistically explained: 7.7%, P = 0.034), whereas clinical interventions (IABP, RRT, opioid use) did not show significant mediation. Higher initial lactate levels were also associated with increased risks of acute kidney injury (OR 1.27, 95% CI 1.00–1.61) and in-hospital mortality (OR 2.88, 95% CI 1.52–5.46). Conclusions Higher initial lactate at ICU admission is associated with an increased risk of CS-POD and adverse postoperative outcomes. However, its predictive value is modest and should be interpreted cautiously as part of a broader clinical assessment rather than as an independent decision-making tool.
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Yang et al. (2026) conducted a cohort in Cardiac surgery-associated postoperative delirium (n=358). Initial lactate at ICU admission vs. Lower lactate levels was evaluated on Incidence of postoperative delirium (OR 1.37, 95% CI 1.11-1.69, p=0.003). Higher initial lactate at ICU admission was independently associated with an increased risk of postoperative delirium after cardiac surgery (OR 1.37 per 1 mmol/L increase).
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