- Email: [email protected]
The nebulous relationship between volume and outcome
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 <300 beds compared to those with 300–499 beds.18 There are additional limitations to the data available in VPS, as the authors point out, that may be important determinants of risk of cardiac arrest and outcome after cardiac arrest. There are no data on the training or availability of ICU personnel, nursing factors, and processes such as mock codes, debriefing, or rapid response teams.15 Additionally, selection bias and/or measurement error may at least partially explain the widely reported variation in outcomes among centers. Four centers reported 0% mortality and 11 reported <20% mortality while three centers reported 80% or greater mortality. It is of course impossible to know if these limitations of the database did not exist if the results would be different. What then can one conclude about the volume–outcome relationship in pediatric cardiac arrests? Are high-volume centers on average able to more likely to prevent a cardiac arrest and when an arrest occurs more likely to rescue the patient? At the current time, these important questions seem far from answered. The study by Gupta et al. suggests that the relationship, if it is exists, is likely complex and mediated by factors that are difficult to gauge and frequently not measured including detailed descriptions of processes of care and personnel competency. It has become increasingly important to understand these factors and how they relate to the prevention and treatment of many diseases including pediatric cardiac arrest. Widespread and sustained improvements will likely depend upon it.
Editorial / Resuscitation 85 (2014) 1642–1643
Conflict of interest statement The authors have no conflicts of interest to disclose. References 1. Reineck LA, Kahn JM. Quality measurement in the Affordable Care Act: a reaffirmed commitment to value in health care. Am J Respir Crit Care Med 2013;187:1038–9. 2. Sutton RM, Niles D, French B, et al. First quantitative analysis of cardiopulmonary resuscitation quality during in-hospital cardiac arrests of young children. Resuscitation 2014;85:70–4. 3. Ong ME, Quah JL, Annathurai A, et al. Improving the quality of cardiopulmonary resuscitation by training dedicated cardiac arrest teams incorporating a mechanical load-distributing device at the emergency department. Resuscitation 2013;84:508–14. 4. Luft HS, Bunker JP, Enthoven AC. Should operations be regionalized? The empirical relation between surgical volume and mortality. N Engl J Med 1979;301:1364–9. 5. Ritchie JL, Phillips KA, Luft HS. Coronary angioplasty. Statewide experience in California. Circulation 1993;88:2735–43. 6. Jollis JG, Peterson ED, DeLong ER, et al. The relation between the volume of coronary angioplasty procedures at hospitals treating Medicare beneficiaries and short-term mortality. N Engl J Med 1994;331:1625–9. 7. Hlatky MA, Dudley RA. Operator volume and clinical outcomes of primary coronary angioplasty for patients with acute myocardial infarction. Circulation 2001;104:2155–7. 8. Jenkins KJ, Newburger JW, Lock JE, Davis RB, Coffman GA, Iezzoni LI. In-hospital mortality for surgical repair of congenital heart defects: preliminary observations of variation by hospital caseload. Pediatrics 1995;95:323–30. 9. Pasquali SK, Jacobs JP, He X, et al. The complex relationship between center volume and outcome in patients undergoing the Norwood operation. Ann Thorac Surg 2012;93:1556–62. 10. Hornik CP, He X, Jacobs JP, et al. Relative impact of surgeon and center volume on early mortality after the Norwood operation. Ann Thorac Surg 2012;93:1992–7. 11. Karamlou T, Jacobs ML, Pasquali S, et al. Surgeon and center volume influence on outcomes after arterial switch operation: analysis of the sts congenital heart surgery database. Ann Thorac Surg 2014;98:904–11. 12. Welke KF, O’Brien SM, Peterson ED, Ungerleider RM, Jacobs ML, Jacobs JP. The complex relationship between pediatric cardiac surgical case volumes and mortality rates in a national clinical database. J Thorac Cardiovasc Surg 2009;137:1133–40. 13. Van Bakel AB, Brown RN, Nikolaidis LA, et al. Variations in institutional staffing and clinical practice are predictive of center-specific 1-year survival posttransplant. J Heart Lung Transplant 2013;32:1196–204.
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14. Merchant RM, Yang L, Becker LB, et al. Variability in case-mix adjusted inhospital cardiac arrest rates. Med Care 2012;50:124–30. 15. Gupta P, Tang X, Gall CM, Lauer C, Rice TB, Wetzel RC. Epidemiology and outcomes of in-hospital cardiac arrest in critically ill children across hospitals of varied center volume: a multi-center analysis. Resuscitation 2014. 16. Lowry AW, Knudson JD, Cabrera AG, Graves DE, Morales DL, Rossano JW. Cardiopulmonary resuscitation in hospitalized children with cardiovascular disease: estimated prevalence and outcomes from the kids’ inpatient database. Pediatr Crit Care Med 2013;14:248–55. 17. Knudson JD, Neish SR, Cabrera AG, et al. Prevalence and outcomes of pediatric in-hospital cardiopulmonary resuscitation in the United States: an analysis of the Kids’ Inpatient Database. Crit Care Med 2012;40:2940–4. 18. Ortmann L, Prodhan P, Gossett J, et al. Outcomes after in-hospital cardiac arrest in children with cardiac disease: a report from Get With the Guidelines – resuscitation. Circulation 2011;124:2329–37.
Joseph W. Rossano a,b,∗ The Cardiac Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States b Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
a
Maryam Y. Naim a,b,c The Cardiac Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States b Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States c Department of Anesthesiology and Critical Care Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States a
∗ Corresponding
author at: The Children’s Hospital of Philadelphia, Division of Cardiology, 34th Street and Civic Center Boulevard, Room 6NE 40, Philadelphia, PA 19104, United States. E-mail address: [email protected] (J.W. Rossano)
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 <300 beds compared to those with 300–499 beds.18 There are additional limitations to the data available in VPS, as the authors point out, that may be important determinants of risk of cardiac arrest and outcome after cardiac arrest. There are no data on the training or availability of ICU personnel, nursing factors, and processes such as mock codes, debriefing, or rapid response teams.15 Additionally, selection bias and/or measurement error may at least partially explain the widely reported variation in outcomes among centers. Four centers reported 0% mortality and 11 reported <20% mortality while three centers reported 80% or greater mortality. It is of course impossible to know if these limitations of the database did not exist if the results would be different. What then can one conclude about the volume–outcome relationship in pediatric cardiac arrests? Are high-volume centers on average able to more likely to prevent a cardiac arrest and when an arrest occurs more likely to rescue the patient? At the current time, these important questions seem far from answered. The study by Gupta et al. suggests that the relationship, if it is exists, is likely complex and mediated by factors that are difficult to gauge and frequently not measured including detailed descriptions of processes of care and personnel competency. It has become increasingly important to understand these factors and how they relate to the prevention and treatment of many diseases including pediatric cardiac arrest. Widespread and sustained improvements will likely depend upon it.
Editorial / Resuscitation 85 (2014) 1642–1643
Conflict of interest statement The authors have no conflicts of interest to disclose. References 1. Reineck LA, Kahn JM. Quality measurement in the Affordable Care Act: a reaffirmed commitment to value in health care. Am J Respir Crit Care Med 2013;187:1038–9. 2. Sutton RM, Niles D, French B, et al. First quantitative analysis of cardiopulmonary resuscitation quality during in-hospital cardiac arrests of young children. Resuscitation 2014;85:70–4. 3. Ong ME, Quah JL, Annathurai A, et al. Improving the quality of cardiopulmonary resuscitation by training dedicated cardiac arrest teams incorporating a mechanical load-distributing device at the emergency department. Resuscitation 2013;84:508–14. 4. Luft HS, Bunker JP, Enthoven AC. Should operations be regionalized? The empirical relation between surgical volume and mortality. N Engl J Med 1979;301:1364–9. 5. Ritchie JL, Phillips KA, Luft HS. Coronary angioplasty. Statewide experience in California. Circulation 1993;88:2735–43. 6. Jollis JG, Peterson ED, DeLong ER, et al. The relation between the volume of coronary angioplasty procedures at hospitals treating Medicare beneficiaries and short-term mortality. N Engl J Med 1994;331:1625–9. 7. Hlatky MA, Dudley RA. Operator volume and clinical outcomes of primary coronary angioplasty for patients with acute myocardial infarction. Circulation 2001;104:2155–7. 8. Jenkins KJ, Newburger JW, Lock JE, Davis RB, Coffman GA, Iezzoni LI. In-hospital mortality for surgical repair of congenital heart defects: preliminary observations of variation by hospital caseload. Pediatrics 1995;95:323–30. 9. Pasquali SK, Jacobs JP, He X, et al. The complex relationship between center volume and outcome in patients undergoing the Norwood operation. Ann Thorac Surg 2012;93:1556–62. 10. Hornik CP, He X, Jacobs JP, et al. Relative impact of surgeon and center volume on early mortality after the Norwood operation. Ann Thorac Surg 2012;93:1992–7. 11. Karamlou T, Jacobs ML, Pasquali S, et al. Surgeon and center volume influence on outcomes after arterial switch operation: analysis of the sts congenital heart surgery database. Ann Thorac Surg 2014;98:904–11. 12. Welke KF, O’Brien SM, Peterson ED, Ungerleider RM, Jacobs ML, Jacobs JP. The complex relationship between pediatric cardiac surgical case volumes and mortality rates in a national clinical database. J Thorac Cardiovasc Surg 2009;137:1133–40. 13. Van Bakel AB, Brown RN, Nikolaidis LA, et al. Variations in institutional staffing and clinical practice are predictive of center-specific 1-year survival posttransplant. J Heart Lung Transplant 2013;32:1196–204.
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14. Merchant RM, Yang L, Becker LB, et al. Variability in case-mix adjusted inhospital cardiac arrest rates. Med Care 2012;50:124–30. 15. Gupta P, Tang X, Gall CM, Lauer C, Rice TB, Wetzel RC. Epidemiology and outcomes of in-hospital cardiac arrest in critically ill children across hospitals of varied center volume: a multi-center analysis. Resuscitation 2014. 16. Lowry AW, Knudson JD, Cabrera AG, Graves DE, Morales DL, Rossano JW. Cardiopulmonary resuscitation in hospitalized children with cardiovascular disease: estimated prevalence and outcomes from the kids’ inpatient database. Pediatr Crit Care Med 2013;14:248–55. 17. Knudson JD, Neish SR, Cabrera AG, et al. Prevalence and outcomes of pediatric in-hospital cardiopulmonary resuscitation in the United States: an analysis of the Kids’ Inpatient Database. Crit Care Med 2012;40:2940–4. 18. Ortmann L, Prodhan P, Gossett J, et al. Outcomes after in-hospital cardiac arrest in children with cardiac disease: a report from Get With the Guidelines – resuscitation. Circulation 2011;124:2329–37.
Joseph W. Rossano a,b,∗ The Cardiac Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States b Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
a
Maryam Y. Naim a,b,c The Cardiac Center, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States b Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States c Department of Anesthesiology and Critical Care Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States a
∗ Corresponding
author at: The Children’s Hospital of Philadelphia, Division of Cardiology, 34th Street and Civic Center Boulevard, Room 6NE 40, Philadelphia, PA 19104, United States. E-mail address: [email protected] (J.W. Rossano)