The revised-risk analysis index as a predictor of major morbidity and mortality in older patients after abdominal surgery: a retrospective cohort study

Background The revised-Risk Analysis Index (RAI-rev) can accurately predict postoperative mortality risk. However, the association of RAI-rev with composite outcome of major morbidity and mortality (MMM) among older surgical patients is largely unknown. This study investigated the association between RAI-rev and postoperative MMM in older patients undergoing abdominal surgery. It also assessed the predictive value of RAI-rev combined with other preoperative risk factors. Methods This retrospective cohort study reviewed the medical records of all patients aged 65 and older who underwent abdominal surgery between January 2018 and December 2019. The primary outcome was the postoperative MMM during hospitalization, and its association with preoperative RAI-rev scores was assessed using multivariable logistic regression analysis. The prediction of postoperative outcomes was used the receiver-operating characteristic curve analysis. Results A total of 2225 older patients were analyzed, and 258 (11.6%) developed postoperative MMM. After adjusting for confounders, each unit increase in RAI-rev scores resulted in a 2.3% increase in the MMM risk and a 3.0% increase in the odds of life-threatening complications and mortality (both P < 0.05). The area under the curves (AUCs) of RAI-rev scores in predicting MMM and life-threatening complications and mortality was 0.604 (95% CI: 0.567 to 0.640) and 0.633 (95% CI: 0.592 to 0.675), respectively (both P < 0.001); when the RAI-rev was combined with age, gender, American Society of Anesthesiologists (ASA) classification, operative stress, and urgency status of surgery (emergency or elective), the AUCs were 0.694 (95% CI: 0.659 to 0.729) and 0.739 (95% CI: 0.702 to 0.777), respectively (both P < 0.001). Conclusions Higher RAI-rev scores were independently associated with increased risk of MMM. When combined with age, gender, ASA classification, operative stress, and urgency status of surgery, RAI-rev had improved performance in predicting the risk of MMM, particularly the life-threatening complications and mortality.