Page 18 - ANZCP Gazette May 2023

CARDIOPULMONARY BYPASS PARAMETERS IMPROVE THE PREDICTION OF 30-DAY MORTALITY FOLLOWING CARDIAC SURGERY
Richard Newland CCP, FANZCP & Rob Baker CCP, FANZCP
Flinders Medical Centre & College of Medicine and Public Health, South Australia On behalf of the Australian and New Zealand Collaborative Perfusion Registry.
Presented at the Australian and New Zealand College of Perfusionists Annual Scientific Meeting, November 2021. Winner of the Terumo award - the best scientific or clinical paper presented by a full ANZCP Member.
Abstract
Currently 30-day mortality is commonly used as a quality indicator for cardiac surgery; however, prediction models have not included the role of cardiopulmonary bypass (CPB). We hypothesized that reproducing currently utilised prediction model methods of 30-day mortality using the Australian and New Zealand Collaborative Perfusion Registry (ANZCPR) would identify relevant CPB predictors. Nine centers in Australia and New Zealand collected data using the ANZCPR between 2011–2020. CPB parameter selection was determined by evaluating association with 30-day mortality. Data were divided into model creation (n = 15,073) and validation sets (n = 15,072). Bootstrap sampling and automated variable selection methods were used to develop candidate models. The final model was selected using prediction mean square error and Bayesian Information Criteria. The average receiver operating characteristic (ROC), p-value for Hosmer—Lemeshow chi-squared test and MSE were obtained. In total, 30,145 patients were included, of which 735 (2.4%) died within 30 days of surgery. The area under the ROC for the model including CPB parameters was significantly greater than preoperative risk factors only (0.829 vs 0.783, p<0.001). CPB parameters included in the predictive model were CPB time, red blood cell transfusion, mean arterial pressure <50mmHg, minimum oxygen delivery, cardiac index <1.6 l/min/m2.CPB parameters improve the prediction of 30-day mortality. Randomised trials designed to evaluate modifiable CPB parameters will determine their impact on mortality.
Introduction
Given the concern of perioperative mortality and morbidity and the demands on hospital resources, accurate assessment of preoperative risk is essential for patients and clinicians prior to cardiac surgery to provide informed consent and support medical management.
Methods to assess preoperative risk have been developed for the Australian population. Billah et al reported a statistical model which includes 18 preoperative risk factors to calculate predicted risk for 30-day mortality following cardiac surgical procedures utilising data from the Australian and New Zealand Society of Cardiothoracic Surgeons (ANZSCTS) registry (1). 30- day mortality is commonly used as a standard performance metric for cardiac surgery, however as predictive models are designed to inform the patient and surgeon prior to surgery they have not included cardiopulmonary bypass (CPB) parameters.
We hypothesized that by reproducing the approach taken by Billah et al (1) to identify predictors of 30- day mortality we could potentially expand the model by identifying relevant CPB predictors. The Australian and New Zealand Collaborative Perfusion Registry (ANZCPR) data definitions for preoperative risk factors are consistent with the ANZSCTS registry allowing the model to be reproduced., The ANZCPR is unique in its integration of electronic perfusion data (EPD) collected intraoperatively from the heart lung machine (HLM) and patient physiological monitoring systems, together with patient preoperative risk factors and outcome data (2). As reporting of modifiable CPB predictors of mortality is limited, the identification of modifiable predictors that can be used as quality indicators will facilitate development of CPB improvement initiatives. Furthermore, the inclusion of intraoperative variables in a cardiac surgery risk prediction model may provide a unique additional source of information to help inform postoperative management. The aim of this study was to identify CPB parameters that impact upon the prediction of 30-day mortality following cardiac surgery.
15 MAY 2023 | www.anzcp.org