Factors associated with death 1 year after lower extremity bypass in Northern New England

Background

Using 30-day operative mortality reported with lower extremity bypass (LEB) in preoperative decision making may underestimate the actual death rate encountered before patients have truly recovered from surgery, especially in elderly, debilitated patients with significant tissue loss. Therefore, we examined preoperative, patient-level risk factors that predict survival within the first year following LEB.

Methods

Using our regional quality improvement initiative in 11 hospitals in Northern New England, we studied 2306 LEB procedures performed in 2031 patients between January 2003 and December 2007. Sixty surgeons contributed to our database, and over 100 demographic and clinical variables were abstracted by trained researchers. Cox proportional hazards models were used to generate hazard ratios (HR) and surrounding 95% confidence intervals (CI) for our combined outcome measure of death occurring within the first year postoperatively.

Results

We found that within our cohort of 2306 bypass procedures, 11% of patients died within 1 year of surgery (2% prior to discharge, 9% prior to 1-year follow-up). We identified six preoperative patient characteristics associated with higher risk of death in multivariate analysis: congestive heart failure (HR 1.3, 95% CI 1.0-1.8), diabetes (HR 1.5, 95% CI 1.1-2.1), critical limb ischemia (CLI) (HR 1.7, 95% CI 1.3-2.4), lack of single-segment saphenous vein (HR 1.9, 95% CI 1.5-2/5), age over 80 (HR 2.0, 95% CI 1.5-2.7), dialysis dependence (HR 2.7, 95% CI 1.9-3.6), and emergent nature of the procedure (HR 3.4, 95% CI 1.7-6.8). While patients with no risk factors had 1-year death rates that were less than 5%: patients with three or more risk factors had a 28% chance of dying before 1 year postoperatively. When we compared risk-adjusted survival across centers, we found that one center in our region performed significantly better than expected (observed-to-expected outcome ratio 0.7, 95% CI 0.6-0.9, P = .04).

Conclusions

Preoperative risk factors allow surgeons to predict survival in the first year following LEB, and to more precisely inform patients about their operative risk with LEB. Additionally, our model facilitates benchmarking comparison of risk-adjusted outcomes across our region. We believe quality improvement measures such as these will allow surgeons to identify best practices and thereby improve outcomes with LEB across centers.