Predictors of operative mortality following major lower extremity amputations using the National Surgical Quality Improvement Program public use data

Background: The most definitive outcome data on lower extremity amputation (LEA) comes from the Veterans Administration (VA) system. Because of the unique nature of VA patients (more chronic disease, greater functional disability, and lower socioeconomic status), it is not clear these results can be generalized to the private sector. This study was undertaken to determine the short-term outcome of LEA in private sector patients and to define predictors of operative mortality. Methods: After Institutional Review Board approval and under the National Surgical Quality Improvement Program public use agreement, a data set of LEA based on Current Procedural Terminology coding was assembled for the years 2005 to 2008. Patient demographics, comorbidities, and laboratory values were compiled and linked to operative mortality. Dichotomous variables were analyzed using chi(2) test with odds ratios (ORs) and continuous variables with Student t-test. Predictive modeling was done using stepwise logistic regression. Data were analyzed in SPSS. Results: A total of 6839 patients underwent 4001 amputations below-knee (BK) and 2838 above-knee (AK) with a 9.1% operative mortality (6.5% BK, 12.7% AK; P < .001). Age >60 years (OR, 2.4; 95% confidence interval [CI], 1.9-2.9), white race (OR, 1.2; 95% CI, 1.0-1.4), and American Society of Anesthesiologists classification (II, 2.3% vs IV, 13.8%) were significant predictors of mortality. Preoperative functional status (20% for totally dependent vs 4.3% for independent), renal failure (OR, 2.3; 95% CI, 1.7-3.2), and congestive heart failure (OR, 2.6; 95% CI, 2.1-3.3) also predicted death. Postoperative complications associated with mortality included pneumonia (OR, 5.4; 95% CI, 4.1-7.0), ventilator dependence (OR, 5.1; 95% CI, 3.8-6.8), and need for transfusion (OR, 3.7; 95% CI, 2.0-6.7). Hispanic and African-American race (OR, 0.6; 95% CI, 0.4-0.9 and OR, 0.8; 95% CI, 0.7-1), history of peripheral arterial disease (OR, 0.6; 95% CI, 0.5-0.8), and smoking (OR, 0.5; 95% CI, 0.4-0.7) were protective (all ORs had P values < .001). Conclusions: The mortality of LEA in private sector patients remains high, with risk factors similar to those identified in previous studies of VA patients. These results should serve as a benchmark for future attempts to improve the outcome of LEA and serve to improve patient and family counseling.