Lower Mortality for Abdominal Aortic Aneurysm Repair in High-Volume Hospitals Is Contingent upon Nurse Staffing

One of the most consistently observed and frequently reported relationships in health services research is that of the volume–outcomes relationship. Hospitals in which specific surgical procedures are performed more often, or in some cases hospitals in which the volume of specific medical conditions is greater, experience mortality rates for patients that are significantly lower than in other hospitals. This volume–outcomes relationship has led many to endorse referral of high-risk surgeries to high-volume hospitals under the assumption that higher hospital surgical volumes will be associated with better patient outcomes and decreased costs of health care (Leapfrog Group, Evidence Based Hospital Referral 2010). Similarly, a volume–outcomes relationship has been suggested between provider volume and patient outcomes. However, the causal mechanisms that underlie the relationship between volumes, whether it is hospital or surgeon volume, and outcomes are not well understood. This study seeks to examine a potential mediator of the hospital volume–outcomes relationship, specifically nursing. In the hundreds of studies appearing in the literature on the hospital volumes and mortality association, very few have considered nursing. It has been well established that nursing varies considerably across hospitals and that variation is found in nurse staffing, nurse education, and the quality of the nurse practice environment, and all of these characteristics are associated with mortality (Kane et al. 2007; Aiken et al. 2008). As nursing is a major intervention provided by hospitals, this study seeks to determine whether, and to what extent, nurse staffing, nurse education, and the nurse practice environment explain the relationship between increased hospital volumes of high-risk operations and better patient outcomes. Specifically, this article examines the role of nurse staffing, nurse education, and the nurse practice environment and hospital surgical volume after abdominal aortic aneurysm (AAA) repair to further examine the underlying mechanisms leading to the volume–outcomes relationship.