Statin use and other factors associated with mortality after major lower extremity amputation.

OBJECTIVE

Above-knee amputations (AKAs) and below-knee amputations (BKAs) are associated with high postoperative mortality rates. In this study, we examined factors associated with 30-day, 90-day, and 1-year mortality in patients who underwent a major lower extremity amputation.

METHODS

We queried a prospectively collected institutional database for all patients who underwent AKA or BKA with primary or secondary closure, during a 5-year period, between November 2009 and November 2014. Predictors of 30- and 90-day mortality were determined by multivariable logistic regression, and risk indexes for 1-year mortality were determined with Cox proportional hazards model.

RESULTS

We identified 811 patients who underwent AKA (n = 325) or BKA (n = 486). The 30-day mortality was 8.4% (AKA, 13.5%; BKA, 4.9%; P < .001) and 90-day mortality was 15.4% (AKA, 24.3%; BKA, 9.45%; P < .001). Predictors of 30-day mortality included AKA (odds ratio [OR], 3.09; 95% confidence interval [CI], 1.76-5.53), emergency operation (OR, 2.86; 95% CI, 1.56-5.14), chronic obstructive pulmonary disease (OR, 3.09; 95% CI, 1.07-7.81), end-stage renal disease (ESRD) on hemodialysis (HD; OR, 2.35; 95% CI, 1.24-4.33), and chronic kidney disease stages 3 (OR, 1.84; 95% CI, 1.00-3.37) and 4 (OR, 2.33; 95% CI, 1.01-4.98). Predictors of 90-day mortality included age (OR, 1.02; 95% CI, 1.00-1.04), ESRD on HD (OR, 2.56; 95% CI, 1.55-4.22), AKA (OR, 2.61; 95% CI, 1.70-4.05), history of coronary artery bypass grafting (OR, 2.04; 95% CI, 1.06-3.87), and medium-intensity or high-intensity statin (OR, 0.46; 95% CI, 0.29-0.73). One-year survival for the overall cohort was 73.7% (95% CI, 70.8%-76.8%). Predictors of 1-year mortality included AKA (hazard ratio [HR], 2.07; 95% CI, 1.54-2.77), coronary artery bypass grafting (HR, 1.57; 95% CI, 1.07-2.32), age >70 years (HR, 1.39; 95% CI, 1.02-1.88), gangrene (HR, 1.44; 95% CI, 1.07-1.94), ESRD on HD (HR, 1.96; 95% CI, 1.42-2.70), chronic obstructive pulmonary disease (HR, 2.54; 95% CI, 1.52-4.25), Caucasian race (HR, 1.62; 95% CI, 1.18-2.22), history of open lower extremity revascularization (HR, 0.71; 95% CI, 0.51-1.00) and undergoing bilateral amputations (HR, 2.10; 95% CI, 1.06-4.15). In the year after amputation, medium-intensity statin (HR, 0.64; 95% CI, 0.47-0.87) and high-intensity statin (HR, 0.56; 95% CI, 0.33-0.95) conferred a mortality benefit. Low-intensity statins did not confer protection from mortality. At 1 year after amputation, only 44.7% of patients were receiving appropriate statin therapy.

CONCLUSIONS

AKA and BKA have historically been associated with high mortality rates. Medium-intensity and high-intensity statin therapies were associated with a mortality benefit at 1 year. We have identified initiation of statin therapy in this high-risk population as a gap in patient care.