A simple subclassification of American Society of Anesthesiology III patients undergoing peripheral revascularization based on functional capacity

PurposeThe American Society of Anesthesiology (ASA) classification remains the most widely used risk-stratification system in the world. However, it is not practical in patients undergoing revascularization procedures because most are classified as ASA III. We hypothesized that ASA III patients can be subdivided into two subgroups, ASA IIIA and ASA IIIB, simply based on their preoperative functional capacity measured in metabolic equivalents (METS) of <4 or ≥4, which would allow the largest group of vascular surgery patients to be appropriately subgrouped for their predicted early and late postoperative morbidity and mortality.MethodsAll charts of 482 patients (99% men) who underwent revascularization for disabling claudication or critical limb ischemia between June 2001 and October 2006 were reviewed for demographics, comorbidities, operative and interventional details, postoperative complications, and outcomes defined as myocardial infarction, stroke, and death. Preoperative functional capacity information was obtained from the anesthesia records in the electronic charts.ResultsThere were 35 patients (7%) in ASA II, 371 patients (77%) in ASA III (45% in ASA IIIA, 32% in ASA IIIB) and 76 patients (16%) in ASA IV. The age, albumin level, prevalence of coronary artery disease, diabetes mellitus, cerebrovascular disease, renal insufficiency (creatinine >1.5 mg/dL), critical limb ischemia, and length of stay were significantly higher in ASA IIIB than IIIA patients. Significantly more myocardial infarctions and deaths occurred in IIIB than in IIIA patients. The overall survival rate was significantly better in ASA IIIA than in ASA IIIB patients. A univariate Cox proportional model identified coronary artery disease, diabetes mellitus, chronic obstructive pulmonary disease (COPD), renal insufficiency, hypercholesterolemia, presence of critical limb ischemia, and preoperative albumin level of <3 g/dL or ≥3 g/dL as being significantly associated with survival. Multivariate analysis showed being ASA IIIA or IIIB is an independent predictor of survival, after adjusting for age, coronary artery disease, hyperlipidemia, COPD, and preoperative albumin levels.ConclusionFunctional capacity assessment is an integral part of routine preoperative anesthesia evaluation, and we found this to be very reliable in predicting postoperative morbidity and mortality as well as overall survival in ASA III patients undergoing peripheral revascularization. This simple modification allows ASA III patients (approximately 80% of vascular patients) to be unbundled into two very distinct subgroups, which will potentially lead to a more accurate preoperative risk assessment.