Resuscitation 85 (2014) 1642–1643
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Editorial
The nebulous relationship between volume and outcome
Improved healthcare quality is a central tenet of the Affordable Care Act, and a key component of improved healthcare quality is understanding and reducing variability in outcomes.1–3 It has been long recognized that there is tremendous variability in outcomes across centers for many diseases. In 1979, Luft et al. examined the mortality for 12 different operations performed on over 400,000 patients undergoing surgery at nearly 1500 hospitals across the United States.4 The authors found that hospitals performing 200 or more operations experienced 25–41 percent lower mortality than lower volume centers and argued that care should be regionalized.4 This notion of a volume–outcome relationship has been extended in many other areas including acute myocardial infarction, congenital heart surgery, and adult cardiopulmonary resuscitation, though the relationship may be quite complex and only partially explain discrepancies in outcome.5–13 Merchant et al. evaluated 103, 117 adult in hospital cardiac arrests from the Get With Guidelines-Resuscitation database and found that smaller hospitals had a higher rates of in-hospital cardiac arrest compared to larger hospitals, with the differences seemingly not related to factors such as nurse to bed ratios, percent of ICU beds, or whether the hospital was an academic institution.14 An attempt to understand this volume–outcome relationship for pediatric in-hospital cardiac arrests is the subject of the manuscript by Gupta et al. in this issue of Resuscitation.15 The authors used the Virtual PICU System (VPS) database to study the epidemiology and outcomes of in hospital pediatric cardiac arrest to address the question of whether there are improved outcomes between higher hospital volume and cardiac arrest outcome. In this study, cardiac and non-cardiac patients less than 18 years of age were included and primary outcome variables included the variation in incidence of cardiac arrest and the rate of death across centers of varying volume for a 5 year period between 2009 and 2013. Centers were divided into low, low-medium, high-medium and high volume groups depending on the number of discharges, average annual ECMO and average annual conventional mechanical ventilation per center. A total of 329,982 patients from 108 centers were included with a 2.2% (n = 7,390) incidence of cardiac arrest with an overall associated mortality of 35%, with significant variability among centers (range 0–100%). While there was no difference in PIM 2 scores across centers, PRISM 3 scores were highest in low medium volume centers. In an unadjusted analysis the rate of cardiac arrest was lower in low and low-medium volume centers as compared to high-volume centers; however, when adjusted for patient level covariates and center level covariates, on multivariable analysis there was no difference in incidence http://dx.doi.org/10.1016/j.resuscitation.2014.09.002 0300-9572/© 2014 Elsevier Ireland Ltd. All rights reserved.
of cardiac arrest across centers. Similarly in unadjusted analysis there was a higher mortality in high-medium volume centers compared to high volume centers but no difference across centers on adjusted analysis. Interestingly, there was no difference in outcomes with stratifying patients by non-cardiac vs. cardiac diagnosis. Some of the findings from this study are in contrast to previous studies, and may in part be due to differences and limitations in the databases utilized. Previous studies reported that among children with cardiac disease, there is substantial variation in the frequency and outcome of cardiac arrest depending on the type of cardiac disease and whether the patient underwent a cardiac operation.16–18 Understanding the variability in cardiac diseases treated at contributing centers may aid in understanding the relationship between volume and outcome. Using the Get with the Guidelines-Resuscitation database, Ortmann et al. found that overall survival after pediatric cardiac arrest was highest among surgical-cardiac patients compared to medical-cardiac and non-cardiac patients.18 Also, among surgical-cardiac patients, mortality was lowest in hospitals with
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Editorial
The nebulous relationship between volume and outcome
Improved healthcare quality is a central tenet of the Affordable Care Act, and a key component of improved healthcare quality is understanding and reducing variability in outcomes.1–3 It has been long recognized that there is tremendous variability in outcomes across centers for many diseases. In 1979, Luft et al. examined the mortality for 12 different operations performed on over 400,000 patients undergoing surgery at nearly 1500 hospitals across the United States.4 The authors found that hospitals performing 200 or more operations experienced 25–41 percent lower mortality than lower volume centers and argued that care should be regionalized.4 This notion of a volume–outcome relationship has been extended in many other areas including acute myocardial infarction, congenital heart surgery, and adult cardiopulmonary resuscitation, though the relationship may be quite complex and only partially explain discrepancies in outcome.5–13 Merchant et al. evaluated 103, 117 adult in hospital cardiac arrests from the Get With Guidelines-Resuscitation database and found that smaller hospitals had a higher rates of in-hospital cardiac arrest compared to larger hospitals, with the differences seemingly not related to factors such as nurse to bed ratios, percent of ICU beds, or whether the hospital was an academic institution.14 An attempt to understand this volume–outcome relationship for pediatric in-hospital cardiac arrests is the subject of the manuscript by Gupta et al. in this issue of Resuscitation.15 The authors used the Virtual PICU System (VPS) database to study the epidemiology and outcomes of in hospital pediatric cardiac arrest to address the question of whether there are improved outcomes between higher hospital volume and cardiac arrest outcome. In this study, cardiac and non-cardiac patients less than 18 years of age were included and primary outcome variables included the variation in incidence of cardiac arrest and the rate of death across centers of varying volume for a 5 year period between 2009 and 2013. Centers were divided into low, low-medium, high-medium and high volume groups depending on the number of discharges, average annual ECMO and average annual conventional mechanical ventilation per center. A total of 329,982 patients from 108 centers were included with a 2.2% (n = 7,390) incidence of cardiac arrest with an overall associated mortality of 35%, with significant variability among centers (range 0–100%). While there was no difference in PIM 2 scores across centers, PRISM 3 scores were highest in low medium volume centers. In an unadjusted analysis the rate of cardiac arrest was lower in low and low-medium volume centers as compared to high-volume centers; however, when adjusted for patient level covariates and center level covariates, on multivariable analysis there was no difference in incidence http://dx.doi.org/10.1016/j.resuscitation.2014.09.002 0300-9572/© 2014 Elsevier Ireland Ltd. All rights reserved.
of cardiac arrest across centers. Similarly in unadjusted analysis there was a higher mortality in high-medium volume centers compared to high volume centers but no difference across centers on adjusted analysis. Interestingly, there was no difference in outcomes with stratifying patients by non-cardiac vs. cardiac diagnosis. Some of the findings from this study are in contrast to previous studies, and may in part be due to differences and limitations in the databases utilized. Previous studies reported that among children with cardiac disease, there is substantial variation in the frequency and outcome of cardiac arrest depending on the type of cardiac disease and whether the patient underwent a cardiac operation.16–18 Understanding the variability in cardiac diseases treated at contributing centers may aid in understanding the relationship between volume and outcome. Using the Get with the Guidelines-Resuscitation database, Ortmann et al. found that overall survival after pediatric cardiac arrest was highest among surgical-cardiac patients compared to medical-cardiac and non-cardiac patients.18 Also, among surgical-cardiac patients, mortality was lowest in hospitals with
