Prediction of postoperative hypokalemia in patients with severe carotid artery stenosis undergoing standard carotid endarterectomy: a retrospective cohort study

BACKGROUND: Postoperative hypokalemia is a common electrolyte disturbance associated with adverse outcomes, particularly in older adults. This study aimed to identify risk factors and develop predictive models for hypokalemia within 24 hours after carotid endarterectomy (CEA) for severe carotid artery stenosis, a condition that primarily affects older patient populations. METHODS: A retrospective cohort of 1,076 CEA patients (October 2021 to May 2023) was analyzed. Risk factors were identified using univariate and multivariate logistic regression. A predictive nomogram was developed and internally validated via bootstrapping. Machine learning models (Random Forest and XGBoost) were developed and interpreted using SHAP (SHapley Additive exPlanations) analysis. Subgroup analyses were performed in patients aged ≥70 years and by comparing postoperative potassium levels >4.0 mmol/L versus 3.5-4.0 mmol/L. RESULTS: The cohort had a median age of 65 years. Multivariate analysis identified preoperative potassium (odds ratio OR=0.60, 95% confidence interval CI 0.50-0.72), hemoglobin (OR=0.74, 95% CI 0.63-0.88), BMI (OR=0.74, 95% CI 0.63-0.88), and postoperative visual analogue scale score (OR=1.28, 95% CI 1.09-1.51) as independent predictors. Frailty showed borderline significance (OR=1.56, 95% CI 1.00-2.44, p=0.05). The nomogram achieved an area under the curve (AUC) of 0.710, demonstrating good discrimination and calibration. Machine learning models similarly performed well (AUC 0.707-0.709). CONCLUSION: We developed a validated tool to predict postoperative hypokalemia after CEA. The model highlights that in addition to biochemical and surgical factors, geriatric syndromes like frailty and nutritional status are pivotal risk determinants. This facilitates early, individualized management, including tailored potassium supplementation, nutritional support, and pain control, especially for vulnerable older adults, to mitigate complications and promote recovery.