Simplified risk stratification in elective colorectal surgery

Audit is a compulsory part of practice and all outcomes are now scrutinized. Raw results may be used to compare performance but these may not accurately reflect case and patient mix. Risk stratification tools, such as American Society of Anaesthesiologists (ASA) and Physiological and Operative Severity Score for the enumeration of Mortality and Morbidity (POSSUM), have been shown to predict morbidity and mortality at the expense of extra data collection. The Special Cooperative Audit of Rural Surgeons reported that two comorbidities increased mortality from 4% to 16, but this finding has not been confirmed. Our aim was to compare risk stratification tools and confirm or refute if comorbidities are accurate predictors of morbidity and mortality.

We made use of an existing colorectal audit, which includes ASA, POSSUM, comorbidities and surgical outcomes. Our anaesthetic department provided data from preoperative cardiopulmonary exercise tests. A poor surgical outcome was defined as death, anastomotic leak and a complication requiring significant intervention.

Data collection was complete for comorbidities, but only 79% cases had ASA scores, 72% completed POSSUM sets and 39% anaerobic threshold. POSSUM >30, ASA III and two comorbidities were all predictors of mortality and grade 3 complications. Anaerobic threshold <11 mL/min/kg did not predict poor surgical outcome. Anastomotic leak was not predicted by any of the scoring systems.

ASA, POSSUM and the presence of two comorbidities were significant predictors of mortality and morbidity, excluding anastomotic leaks. Comorbidities are simple to collect and their correlation with outcome compares favourably with POSSUM. Comorbidities are a simple and quick method of risk stratification for colorectal surgery.