Lactate level and unplanned readmission to the surgical intensive care unit: a retrospective cohort study

Background: This study aimed to investigate the association between lactate levels during intensive care unit (ICU) stay and unplanned ICU readmission rates within 48 and 120 h in surgical patients. Methods: This single-center retrospective cohort study evaluated adult patients who were discharged from the ICU between January 2012 and December 2018. The association between lactate levels (initial lactate at ICU admission, peak level during ICU stay, and last level before ICU discharge) and unplanned ICU readmission was investigated using uni- and multivariable logistic regression analyses. Results: The cohort included 3,707 patients. The unplanned ICU readmission rate within 48 and 120 h was 2.1% (n=78 patients) and 4.5% (n=166 patients), respectively. In the multivariable model, 1 mg dL(-1) increase in the peak lactate level during ICU stay was associated with 1.1-fold increase in unplanned ICU readmission within 48 h (odds ratio: 1.10; 95% confidence interval: 1.02 to 1.2; P=0.016). In contrast, both initial and last lactate levels during ICU stay were not significantly associated. A similar trend was observed for unplanned ICU readmission within 120 h. On receiver operating characteristic analysis, the areas under the curve (AUC) of the initial, last, and peak lactate levels were 0.61, 0.53, and 0.63, respectively. Conclusions: The peak lactate level during ICU admission is independently associated with unplanned ICU readmission within both, 48 and 120 h among surgical ICU patients. However, the lactate level has relatively poor predictive capability for unplanned ICU readmissions, and a new model is needed to predict unplanned ICU readmissions among surgical patients.