Association of hospital volume with patient selection, risk of complications, and mortality from failure to rescue after open abdominal aortic aneurysm repair

Objective: The association of higher hospital volume with lower mortality after open abdominal aortic aneurysm (OAAA) repair is well known; however, the underlying mechanism for improved outcomes is poorly understood. Better patient selection, lower risk of complications, and improved ability to rescue patients after adverse events are assumed mechanisms, but few data exist to validate this hypothesis. The purpose of this analysis was to determine the association of hospital volume with patient selection, incidence of complications, and failure to rescue (FTR) after adverse events resulting from OAAA repair. Methods: The Vizient (Irving, Tex) database (>95% of all academic hospitals) was reviewed for OAAA repairs (elective, n = 2827; nonelective, n = 1622) performed from 2012 to 2014. Presentation type (elective vs nonelective) was considered in all analyses. Elixhauser comorbidity index and van Walraven weighted scores were assigned to patients and volume-outcome relationships explored. By use of logistic regression, risk-adjusted complications (including preventable complications; Agency for Healthcare Research and Quality patient safety indicators [PSIs]) and FTR rates were determined. Predicted risk scores were assigned to delineate hospital volume association with these outcomes. Results: Overall, no relationship between hospital volume and composite patient comorbidity severity score was identified (Elixhauser comorbidity index and van Walraven weighted scores: Pearson [rho, 0.02], P = .2; [rho, -0.01], P = .4; Spearman correlation coefficient [rho, 0.02], P = .4; [rho, -0.02], P = .2). The lack of correlation persisted in considering elective vs nonelective status. However, for elective cases, differences in specific comorbidities were noted because high-volume hospitals were more likely to repair patients with a history of peripheral vascular disease (P = .01), diabetes (P = .07), obesity (P = .004), and alcohol abuse (P = .05). Lower volume hospitals more frequently repaired patients with hypothyroidism (P = .05), fluid and electrolyte disorders (P = .007), and chronic blood loss anemia (P = .05). No specific individual comorbidity differences were detected for nonelective cases. In examining hospital volume effects on the likelihood for development of any complication (45%), PSIs (12%), and FTR (9%), a significant risk reduction was noted in high-volume institutions. Specifically, a nonlinear relationship between hospital volume and risk of any complication (P = .0004), PSI (P = .0004), and FTR (P = .0003) was present. In exploring the risk of specific complications or PSI events, greater hospital volume was strongly correlated to a lower likelihood of multiple adverse outcomes. Conclusions: Although high-volume institutions performing OAAA repair do not necessarily operate on patients with more comorbidities, there are important differences in the patients selected compared with lower volume hospitals. The risk for development of multiple specific postoperative complications as well as for preventable adverse events preceding FTR is significantly lower in high-volume centers. These findings provide benchmarks for multiple selected quality indicators and further support national initiatives to incentivize regionalization of OAAA care.