Predicting Postoperative Cardiac Events and Mortality for People with Kidney Failure Having Non-Cardiac Surgery: An External Validation Study.

Background: Patients with kidney failure undergoing non-cardiac surgery are at high risk of adverse cardiac events and mortality, however existing perioperative risk prediction tools for these outcomes are not valid in these patients. Recently, three models were developed from a kidney failure cohort in Alberta, Canada. In this study, we evaluated these Alberta models in a kidney failure cohort that had surgery in Manitoba, Canada.

Methods: The cohort included adults from Manitoba, Canada (≥ 18 years) with pre-existing kidney failure (estimated glomerular filtration rate < 15 mL/min/1.73m2 or receiving maintenance dialysis) undergoing non-cardiac surgeries between 2007-2019. The primary outcome was a composite of acute myocardial infarction, cardiac arrest, ventricular arrhythmia, and all-cause mortality within 30 days. The three models included an increasing number of variables: demographics and surgical characteristics (model 1), comorbidities (model 2), and preoperative albumin and hemoglobin (model 3). Model performance was evaluated using Area Under the Receiver Operating Characteristic Curve (AUC-ROC), calibration, and Brier score on Manitoba data. This was evaluated by applying Alberta model coefficients for all three models to predict outcomes on Manitoba data, and also by re-estimating the Alberta model predictor coefficients using logistic regression on Manitoba data.

Results: We identified 12,082 surgeries performed in 4,175 participants; 569 outcomes were observed (4.7%). All three models performed well with both approaches, with AUC-ROC ranging from 0.821 (model 1) to 0.874 (model 3) using the models with Alberta coefficients. Calibration slopes were 1.32, 1.40, and 1.24 for models 1, 2, and 3, respectively. Upon refitting, AUC-ROC ranged from 0.830 (model 1) to 0.861 (model 3). Calibration slopes approximated 1 across all the re-estimated models. Brier scores remained < 0.1 across all original and re-estimated models.

Conclusions: Our external validation study confirmed that the kidney failure specific postoperative outcome models developed in Alberta, Canada, performed well in a geographically distinct Canadian population. Future research should explore the performance of these models in different settings and evaluate their clinical impact with prospective implementation.