Injury, Int. J. Care Injured 45 (2014) 478–486
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Review
The relationship between patient volume and mortality in American trauma centres: A systematic review of the evidence Lisa M. Caputo a, Kristin M. Salottolo a, Denetta Sue Slone b, Charles W. Mains c,d, David Bar-Or a,d,* a
Trauma Research Department, Swedish Medical Department, Englewood, CO 80113, United States Trauma Services Department, Swedish Medical Center, Englewood, CO 80113, United States Trauma Services Department, St. Anthony Hospital, Lakewood, CO 80228, United States d Rocky Vista University, Parker, CO 80134, United States b c
A R T I C L E I N F O
A B S T R A C T
Article history: Accepted 21 September 2013
Objective: To synthesise published and unpublished findings examining the relationship between institutional trauma centre volume or trauma patient volume per surgeon and mortality. Background: Evidence on the relationship between patient volume and survival in trauma patients is inconclusive in the literature and remains controversial. Methods: A literature search was performed to identify studies published between 1976 and 2013 via MEDLINE (Pubmed) and the Cumulative Index to Nursing and Allied Health Literature (EbscoHost) as well as footnote chasing. Abstracts from appropriate conferences and ProQuest Dissertations and Theses were also searched. Inclusion criteria required studies to be original research published in English that examined the relationship between mortality and either institutional or per surgeon volume in American trauma centres. We employed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement checklist and flowchart. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was employed to rate the quality of the evidence. Results: Of 1392 studies reviewed, 19 studies met defined inclusion criteria; all studies were retrospective. The definition of volume was heterogeneous across the studies. Patient population and analysis methods also varied across the studies. Sixteen studies (84%) examined the relationship between institutional trauma centre volume and mortality. Of the 16 studies, 12 examined the volume of severely injured patients and eight examined overall trauma patient volume. High institutional volume was associated with at least somewhat improved mortality in ten of 16 studies (63%); however, nearly half of these studies found only some subpopulations experienced benefits. In the remaining six studies, volume was not associated with any benefits. Four studies (25%) analysed the impact of surgeon volume on mortality. High volume per surgeon was associated with improved mortality in only one of four studies (25%). Conclusions: The studies were extremely heterogeneous, thus definitive conclusions cannot be drawn regarding optimal volume before a clear advantage in survival is observed. A prospective study defining volume as a continuous variable is warranted to support current admission criteria for American trauma patients. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Patient volume Volume outcome relationship Trauma centre Volume per surgeon Patient caseload Systematic review Mortality
Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . Methods . . . . . . . . . . . . . . . . . . . . . . . . . . Study identification and selection Quality review. . . . . . . . . . . . . . . . Statistical analysis. . . . . . . . . . . . .
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* Corresponding author at: Swedish Medical Center, Trauma Research Department, 501 East Hampden Avenue Room 4-454, Englewood, CO 80113, United States. Tel.: +1 303 788 4089; fax: +1 303 788 4064. E-mail address: [email protected] (D. Bar-Or). 0020–1383/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.injury.2013.09.038
L.M. Caputo et al. / Injury, Int. J. Care Injured 45 (2014) 478–486
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Patient population . . . . . . . . . . . . . . . . . Definition of patient volume . . . . . . . . . Impact of institutional volume on mortality . . Institutional volume of severely injured Overall institutional volume. . . . . . . . . . Impact of volume per surgeon on mortality. . . Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Role of funding source. . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Introduction Identifying the appropriateness of volume requirements for American trauma centres has been controversial since the American College of Surgeons Committee on Trauma (ACS COT) first suggested a minimum number of admitted trauma patients for Level I accreditation in 1990, and then instituted a mandate in 1999. The ACS COT requires a minimum of 1200 annual trauma patient admissions at each of the 110 American College of Surgeons (ACS) verified Level I facilities in the United States. Of these, 20% (240 patients) must have an Injury Severity Score (ISS) of at least 16; alternatively, individual trauma surgeons must treat at least 35 severely injured trauma patients (ISS 16) per year. The volume requirements are based on evidence produced within other surgical specialties that found an inverse relationship between patient volume and clinical outcomes. Adams and colleagues were the first to demonstrate increased complication rates of coronary arteriography in facilities that performed fewer procedures per annum in 1973 [1]. Other widely cited studies have also found supporting evidence that an increase in practice leads to improved performance [2,3]. However, the relationship between volume and outcomes among trauma centres has been inconclusive. It is possible that the rigorous education, skill building, teaching and research requirements associated with the ACS Level I trauma centre verification process may impact outcomes independent of high patient volume. The majority of states with state-verified Level I trauma centres require their Level I trauma centres to reach the ACS COT volume mandate. However, Alabama, Florida, New York and New Jersey require a lower number of total patients [4]. Pennsylvania requires their Level I trauma centres to treat at least 600 serious trauma patients, with severity not based on ISS1. Colorado requires each Level I trauma centre to treat at least 400 severely injured (ISS 16) patients. Washington and Montana have no mandatory requirement for volume [4]. The adoption of the updated Abbreviated Injury Scale (AIS) in 2008, an integral component of the ISS, is also a substantial factor that has been largely overlooked. The AIS scores were updated in 2005 from the AIS 1998 version, in which codes were added, modified, and removed to improve the functionality of the AIS [5]. In a multicentre study of 2250 trauma patients, the updated AIS scores resulted in changes for nearly half (46.5%) of patients [6]. The mean ISS was significantly lower after implementation of the new AIS codes, resulting in 20.5% reduction in patients with an ISS of at least 16. [6] The ACS has not altered its volume criteria despite 1 ‘‘Serious trauma patients,’’ as defined by the Pennsylvania Trauma Outcomes Survey, is defined as trauma patients meeting at least one of the following criteria: (1) Stay in ICU; (2) admission to a step-down unit; (3) trauma deaths including death pronounced after arrival; (4) patients with a 36–48 h stay with an ISS 9; (5) patients with at least a 48 h stay; (6) predetermined burn criteria; (7) predetermined transfer criteria.
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the reduction in patients with an ISS of at least 16 resulting from the AIS update. This systematic review provides an assessment of studies that have addressed the potential impact of institutional and per surgeon trauma patient volume on survival advantage. It is our hope that by summarising a large and diverse collection of literature, we may present evidence to improve the generalizability of the topic and aid future policymaking as trauma centres continue to proliferate.
Methods Study identification and selection Two authors (L.M.C. and K.M.S.) drafted the inclusion criteria prior to the literature search. Scientific literature was identified through electronic databases Pubmed (MEDLINE) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (EbscoHost) as well as hand-searching citations from appropriate studies. We searched conference abstracts and dissertations to reduce publication bias present in systematic reviews exclusively analysing published data [7]. We searched abstracts from the American Association for the Surgery of Trauma (AAST) using the AAST online collection of past abstracts (2003–2012) and PapersFirst (First Search) (1976–2002). We also searched the ProQuest Dissertations and Theses (1976–2012). We crosschecked the Cochrane Database of Systematic Reviews and the Database of Abstracts of Reviews of Effects to ensure no systematic reviews exclusively examining our topic of interest were published or in progress. Our criteria required studies to: (a) consist of original research addressing the topic of institutional or per surgeon volume on mortality; (b) include data from Level I trauma centres; (c) be English-language publications addressing American trauma centres; (d) published between 1 January 1976 and 1 June 2013; (e) have available abstracts; (f) study a general trauma population. We only included American studies, as the ACS requirements are uniform throughout the country. We chose studies published in 1976 or later, as the ASC COT published its first version of the ‘‘Optimal Hospital Resources for the Care of the Seriously Injured,’’ which guided the development of the modern, tiered American trauma system, in 1976. We excluded studies that only considered demographic-specific populations, such as geriatric or paediatric patients, rather than injury characteristics, and studies examining exclusively burns. The definition of trauma patient was defined by individual studies; most studies established criteria based on International Classification of Disease (ICD) criteria. We recorded all citations in the web-based citation manager Zotero (www.zotero.org; Fairfax, VA, USA) to organise studies and eliminate duplicates.
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Quality review Citations were initially assessed by the first author (L.M.C.), and those that met predetermined criteria were further reviewed by the first and second author (L.M.C. & K.M.S.). Discrepancies were discussed with a third author (D.B.O.) throughout the study identification and selection process and disagreements were settled by consensus. While reviewing, we recorded predetermined characteristics of the studies of interest in a checklist. The Preferred Reporting Items for Systematic Reviews and MetaAnalyses (PRISMA) Statement was used to ensure reviewers collected variables describing the quality of the studies. Variables collected included publication year and source, patient characteristics, patient inclusion and exclusion criteria, study design, study size, the number of institutions involved, volume definition, key results, potential sources of bias, and whether the study controlled for case-mix factors. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was employed to rate the quality of the evidence. Potential sources of bias identified included coding bias and discrepancies that may occur when comparing multiple registries. Further, the inclusion and exclusion criteria of which trauma populations were to be included, often defined by specific ICD codes, varied. Additionally, we included one study that included a patient population from Level I, Level II and ‘‘non trauma’’ trauma centres; we acknowledge this may invite some coding bias. The reviewers were not blinded to the authors or other study characteristics. Statistical analysis The definition of institutional or per surgeon volume was inconsistently applied across studies. Some studies compared high
Table 1 Keywords for electronic literature search. Search term ‘‘Trauma centres/utilization’’ (‘‘patient volume’’ OR ‘‘caseload’’) AND (‘‘mortality’’ OR ‘‘length of stay’’) (‘‘patient volume’’ OR ‘‘caseload’’) AND (‘‘trauma’’ OR ‘‘Wounds, Nonpenetrating/ mortality’’ OR ‘‘Wounds, Penetrating/mortality’’) ((‘‘trauma centre’’ OR ‘‘level I’’) AND (‘‘patient volume’’ OR ‘‘caseload’’ OR ‘‘throughput’’)) (volume outcome relationship) AND (‘‘trauma’’ OR ‘‘Wounds, Nonpenetrating/ mortality’’ OR ‘‘Wounds, Penetrating/mortality’’)
to low volume trauma centres, while others examined high, medium, and low volume, and other studies viewed volume as a continuous variable. Additionally, recognised confounding factors of age and ISS were inconsistently controlled; this inconsistency may limit our ability to draw conclusions from the results of the studies. Lastly, of the six studies that used a sample from the National Trauma Data Bank (NTDB), five used overlapping data from at least two years. As a result, the evidence did not allow for use of a weighted meta-analysis to produce results that can be generalised or scaled. We thereby presented the study characteristics and results descriptively. Results We used original keywords in addition to MeSH terminology, listed in Table 1. We originally retrieved a total of 1371 abstracts through electronic searches, six through a search of conference abstracts, and 15 through hand searching, resulting in a total of 1392 total abstractions (Fig. 1). Three hundred fifty eight duplicates were removed, leaving 1034 studies. The initial review eliminated 971 studies that did not address adult trauma patient
Fig. 1. PRISMA flow chart: STUDY identification and selection process. Flow chart demonstrating the study identification and selection process.
Penetrating (p = 0.99) Severely injured penetrating trauma (p = 0.879)
N/A
N/A
N/A
N/A
N/A + Continuous variable
NTDB
NTDB
Logan et al., 2010 [11]
Lorenzo et al., 2008 [26]
N/A; overall volume
+ Deciles
NTDB Bennett et al., 2011 [10]
469,327; overall volume
Multicentre Marx et al., 2011 [9]
115,358; severely injured (ISS 15)
HV: >480; MV: 240– 480; LV: 1200; LV: 15)
Continuous variable
+
Nathens et al., 2001 [17]
Multicentre
HV: 650 LV: 250; MV: 151–250; LV: 1200; LV: 12, and adult blunt trauma patients, but not in subpopulations including penetrating injuries or paediatric patients. The other three studies found no association between volume per surgeon and survival. One of these studies addressed LOS, complications and the number of preventable/ potentially preventable deaths in addition to mortality; no relationship was found between any outcome and volume. The study that found an association between volume and mortality employed a survival probability model, demonstrating that to improve survival, trauma surgeons should treat a minimum of 35 seriously injured trauma patients, defined as ISS of at least 13, and at least 28 serious blunt trauma adult patients per year. Of note, this study made a vital assumption that all trauma surgeons within institutions treated an evenly distributed number of trauma cases [23]. Each of the three studies that did not find an association between volume per surgeon and mortality employed a different method of analysis. One study utilized a logistic regression model, finding no predictive abilities between surgeon volume and survival [16]. The second study employed the TRISS methodology to compare probability of survival between two cohorts, divided by low and high per surgeon volume, as well as comparing mortality patterns of six preselected injury patterns [21]. The last study compared LOS, complications and the number of preventable/ potentially preventable deaths between surgeons, in addition to evaluating the responses to several ‘‘difficult questions,’’ stratified by surgeon volume [22]. As all studies analysed the relationship
Table 4 Summary of volume per surgeon – mortality studies. Author, year
Sample
Sample size; patient definition
Volume definition
Sava et al. [21] Margulies et al. [16] Richardson et al. [22] Konvolinka et al. [23]
Single centre Multicentre Single centre Multicentre
20,695; ISS > 15 1757; ISS > 15 1077; ISS > 14 36,346; ISS 13; overall trauma population
HV: >35 patients per surgeon; LV 35 Deciles Continuous variable Continuous variable
HV, high volume; MV, medium volume; LV, low volume. +: beneficial relationship with volume;
Outcome
+
Volume Volume Volume Volume
was was was was
not associated with any benefits. not associated with any benefits. not associated with any benefits. beneficial.
: not beneficial relationship with volume; : inconclusive evidence.
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sample sizes; among the studies we examined, several analysed small sample sizes, inviting the potential that some were perhaps inadequately powered to detect an association. A systematic review of general surgery volume and outcome found retrospective studies were more likely to find a significantly beneficial relationship between volume and outcome than a prospective study [28]. The authors of the review postulated this finding might be attributable to the limitations of retrospective data. Our systematic review has several limitations. There were few studies addressing the impact of trauma patient volume on mortality, and we found just nineteen studies eligible for inclusion in our study. Second, the diverse definitions of volume, data sources, analysis methods and patient population did not allow us to produce generalisable results and recommendations. Lastly, we limited our studies to US trauma centres, which restricts external validity and the ability to generalise our findings to other settings. Conclusion In summary, each study’s unique definitions of patient population and volume, and analysis methods limit the conclusions that can be drawn from the aggregate. There appears to be a relationship between higher overall institutional volume and improved mortality, but based on the heterogeneity of the studies, this relationship cannot be quantified using statistical methods. The current literature does not support an optimal volume, defined as overall institutional volume, volume of severely injured trauma patients, or volume per surgeon, associated with survival benefit. As state trauma systems begin to cover the majority of the United States, minimum volume requirements will continue to be controversial. Additional research is required to determine the impact of ACS volume requirements on mortality, demonstrate an optimal minimum volume to improve survival rates, and to evaluate the potential of high volume trauma centres exhausting their resources. Conflict of interest None of the authors have any financial or personal relationships that could inappropriate bias their work to disclose. Role of funding source This study has no funding sources to declare. References [1] Adams DF, Fraser DB, Abrams HL. The complications of coronary arteriography. Circulation 1973;48(3):609–18. [2] Hannan E, Racz M. Coronary angioplasty volume-outcome relationships for hospitals and cardiologists. JAMA 1997;277(11):892–8. [3] Luft H, Bunker J, Enthoven A. Should operations be regionalized? The empirical relation between surgical volume and mortality. N Engl J Med 1979;301(25):1364–9. [4] Colorado Department of Public Health and Environment. Volume Criteria; 2013. Available at: http://www.colorado.gov/cs/Satellite?blobcol=urldata&blobheadername1=Content-Disposition&blobheadername2=Content-Type&blobheadervalue1=inline%3B+filename%3D%22Volume+Criteria+in+Other+States.pdf%22&blobheadervalue2=application%2Fpdf&blobkey=id&blobtable=MungoBlobs&blobwhere=1251855864341&ssbinary=true [accessed 21.06.13].
[5] Association for the advancement of automotive medicine. AIS Update Information. Available at: http://www.aaam1.org/ais/ais_update.php [accessed 21.06.13]. [6] Salottolo K, Settell A, Uribe P, Akin S, Slone DS, O’Neal E, et al. The impact of the AIS 2005 revision on injury severity scores and clinical outcome measures. Injury 2009;40(9):999–1003. [7] McAuley L, Pham B, Tugwell P, Moher D. Does the inclusion of grey literature influence estimates of intervention effectiveness reported in meta-analyses? Lancet 2000;356(9237):1228–31. [8] Villegas CV, Haider AH, Schnedier EB, Haut ER, Efron DT, Chi A, et al. Does trauma center volume for penetrating trauma improve survival among patients with penetrating injuries?In: Annual meeting of the american association for the surgery of trauma and clinical congress of acute care surgery; 2011 [abstract]. [9] Marx WH, Simon R, O’Neill P, Shapiro MJ, Cooper AC, Farrell LS, et al. The relationship between annual hospital volume of trauma patients and in-hospital mortality in New York State. J Trauma 2011;71(2):339–45 [discussion 345–346]. [10] Bennett KM, Vaslef S, Pappas TN, Scarborough JE. The volume-outcomes relationship for United States Level I trauma centers. J Surg Res 2011;167(1):19–23. [11] Logan MS, Watson CM, Stukenborg G, Hranjec T, Young J, Calland JF. Trauma volume and outcome: is bigger always better?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery 2010; 2010 [abstract]. [12] Demetriades D, Martin M, Salim A, Rhee P, Brown C, Chan L. The effect of trauma center designation and trauma volume on outcome in specific severe injuries. Ann Surg 2005;242(4):512–7 [discussion 517–519]. [13] Marcin JP, Romano PS. Impact of between-hospital volume and within-hospital volume on mortality and readmission rates for trauma patients in California. Crit Care Med 2004;32(7):1477–83. [14] Glance LG, Osler TM, Dick A, Mukamel D. The relation between trauma center outcome and volume in the National Trauma Databank. J Trauma 2004;56(3):682–90. [15] London JA, Battistella FD. Is there a relationship between trauma center volume and mortality? J Trauma 2003;54(1):16–24 [discussion 24–25]. [16] Margulies DR, Cryer HG, McArthur DL, Lee SS, Bongard FS, Fleming AW. Patient volume per surgeon does not predict survival in adult level I trauma centers. J Trauma 2001;50(4):597–601 [discussion 601–603]. [17] Nathens AB, Jurkovich GJ, Maier RV, Grossman DC, MacKenzie EJ, Moore M, et al. Relationship between trauma center volume and outcomes. JAMA 2001;285(9):1164–71. [18] Pasquale MD, Peitzman AB, Bednarski J, Wasser TE. Outcome analysis of Pennsylvania trauma centers: factors predictive of nonsurvival in seriously injured patients. J Trauma 2001;50(3):465–72 [discussion 473–474]. [19] Cooper A, Hannan EL, Bessey PQ, Farrell LS, Cayten CG, Mottley L. An examination of the volume-mortality relationship for New York State trauma centers. J Trauma 2000;48(1):16–23 [discussion 23–24]. [20] Smith RF, Frateschi L, Sloan EP, Campbell L, Krieg R, Edwards LC, et al. The impact of volume on outcome in seriously injured trauma patients: two years’ experience of the Chicago Trauma System. J Trauma 1990;30(9):1066–75 [discussion 1075–1076]. [21] Sava J, Kennedy S, Jordan M, Wang D. Does volume matter? The effect of trauma surgeons’ caseload on mortality. J Trauma 2003;54(5):829–33 [discussion 833–834]. [22] Richardson JD, Schmieg R, Boaz P, Spain DA, Wohltmann C, Wilson MA, et al. Impact of trauma attending surgeon case volume on outcome: is more better? J Trauma 1998;44(2):266–71 [discussion 271–272]. [23] Konvolinka CW, Copes WS, Sacco WJ. Institution and per-surgeon volume versus survival outcome in Pennsylvania’s trauma centers. Am J Surg 1995;170(4):333–40. [24] McGwin Jr G, Swain RD, Reiff DA, Rue III LW. Trauma center volume: when is enough, enough?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery; 2008 [abstract]. [25] Green JM, Gunter OL, Nash J, Buchman TG, Schuerer DJE. Too much of a good thing? How increasing trauma volumes are stressing the system?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery; 2008 [abstract]. [26] Lorenzo M, Santerre R, Mangram AJ, Dunn EL, Amos JD, Truitt MS. Should patient volume be a determinant for trauma center level designation?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery; 2008 [abstract]. [27] Tepas III JJ, Patel JC, DiScala C, Wears RL, Veldenz HC. Relationship of trauma patient volume to outcome experience: can a relationship be defined? J Trauma 1998;44(5):827–30 [discussion 830–831]. [28] Chowdhury MM, Dagash H, Pierro A. A systematic review of the impact of volume of surgery and specialization on patient outcome. Br J Surg 2007;94(2):145–61.
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Review
The relationship between patient volume and mortality in American trauma centres: A systematic review of the evidence Lisa M. Caputo a, Kristin M. Salottolo a, Denetta Sue Slone b, Charles W. Mains c,d, David Bar-Or a,d,* a
Trauma Research Department, Swedish Medical Department, Englewood, CO 80113, United States Trauma Services Department, Swedish Medical Center, Englewood, CO 80113, United States Trauma Services Department, St. Anthony Hospital, Lakewood, CO 80228, United States d Rocky Vista University, Parker, CO 80134, United States b c
A R T I C L E I N F O
A B S T R A C T
Article history: Accepted 21 September 2013
Objective: To synthesise published and unpublished findings examining the relationship between institutional trauma centre volume or trauma patient volume per surgeon and mortality. Background: Evidence on the relationship between patient volume and survival in trauma patients is inconclusive in the literature and remains controversial. Methods: A literature search was performed to identify studies published between 1976 and 2013 via MEDLINE (Pubmed) and the Cumulative Index to Nursing and Allied Health Literature (EbscoHost) as well as footnote chasing. Abstracts from appropriate conferences and ProQuest Dissertations and Theses were also searched. Inclusion criteria required studies to be original research published in English that examined the relationship between mortality and either institutional or per surgeon volume in American trauma centres. We employed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement checklist and flowchart. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was employed to rate the quality of the evidence. Results: Of 1392 studies reviewed, 19 studies met defined inclusion criteria; all studies were retrospective. The definition of volume was heterogeneous across the studies. Patient population and analysis methods also varied across the studies. Sixteen studies (84%) examined the relationship between institutional trauma centre volume and mortality. Of the 16 studies, 12 examined the volume of severely injured patients and eight examined overall trauma patient volume. High institutional volume was associated with at least somewhat improved mortality in ten of 16 studies (63%); however, nearly half of these studies found only some subpopulations experienced benefits. In the remaining six studies, volume was not associated with any benefits. Four studies (25%) analysed the impact of surgeon volume on mortality. High volume per surgeon was associated with improved mortality in only one of four studies (25%). Conclusions: The studies were extremely heterogeneous, thus definitive conclusions cannot be drawn regarding optimal volume before a clear advantage in survival is observed. A prospective study defining volume as a continuous variable is warranted to support current admission criteria for American trauma patients. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Patient volume Volume outcome relationship Trauma centre Volume per surgeon Patient caseload Systematic review Mortality
Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . Methods . . . . . . . . . . . . . . . . . . . . . . . . . . Study identification and selection Quality review. . . . . . . . . . . . . . . . Statistical analysis. . . . . . . . . . . . .
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* Corresponding author at: Swedish Medical Center, Trauma Research Department, 501 East Hampden Avenue Room 4-454, Englewood, CO 80113, United States. Tel.: +1 303 788 4089; fax: +1 303 788 4064. E-mail address: [email protected] (D. Bar-Or). 0020–1383/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.injury.2013.09.038
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Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Patient population . . . . . . . . . . . . . . . . . Definition of patient volume . . . . . . . . . Impact of institutional volume on mortality . . Institutional volume of severely injured Overall institutional volume. . . . . . . . . . Impact of volume per surgeon on mortality. . . Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Role of funding source. . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Introduction Identifying the appropriateness of volume requirements for American trauma centres has been controversial since the American College of Surgeons Committee on Trauma (ACS COT) first suggested a minimum number of admitted trauma patients for Level I accreditation in 1990, and then instituted a mandate in 1999. The ACS COT requires a minimum of 1200 annual trauma patient admissions at each of the 110 American College of Surgeons (ACS) verified Level I facilities in the United States. Of these, 20% (240 patients) must have an Injury Severity Score (ISS) of at least 16; alternatively, individual trauma surgeons must treat at least 35 severely injured trauma patients (ISS 16) per year. The volume requirements are based on evidence produced within other surgical specialties that found an inverse relationship between patient volume and clinical outcomes. Adams and colleagues were the first to demonstrate increased complication rates of coronary arteriography in facilities that performed fewer procedures per annum in 1973 [1]. Other widely cited studies have also found supporting evidence that an increase in practice leads to improved performance [2,3]. However, the relationship between volume and outcomes among trauma centres has been inconclusive. It is possible that the rigorous education, skill building, teaching and research requirements associated with the ACS Level I trauma centre verification process may impact outcomes independent of high patient volume. The majority of states with state-verified Level I trauma centres require their Level I trauma centres to reach the ACS COT volume mandate. However, Alabama, Florida, New York and New Jersey require a lower number of total patients [4]. Pennsylvania requires their Level I trauma centres to treat at least 600 serious trauma patients, with severity not based on ISS1. Colorado requires each Level I trauma centre to treat at least 400 severely injured (ISS 16) patients. Washington and Montana have no mandatory requirement for volume [4]. The adoption of the updated Abbreviated Injury Scale (AIS) in 2008, an integral component of the ISS, is also a substantial factor that has been largely overlooked. The AIS scores were updated in 2005 from the AIS 1998 version, in which codes were added, modified, and removed to improve the functionality of the AIS [5]. In a multicentre study of 2250 trauma patients, the updated AIS scores resulted in changes for nearly half (46.5%) of patients [6]. The mean ISS was significantly lower after implementation of the new AIS codes, resulting in 20.5% reduction in patients with an ISS of at least 16. [6] The ACS has not altered its volume criteria despite 1 ‘‘Serious trauma patients,’’ as defined by the Pennsylvania Trauma Outcomes Survey, is defined as trauma patients meeting at least one of the following criteria: (1) Stay in ICU; (2) admission to a step-down unit; (3) trauma deaths including death pronounced after arrival; (4) patients with a 36–48 h stay with an ISS 9; (5) patients with at least a 48 h stay; (6) predetermined burn criteria; (7) predetermined transfer criteria.
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the reduction in patients with an ISS of at least 16 resulting from the AIS update. This systematic review provides an assessment of studies that have addressed the potential impact of institutional and per surgeon trauma patient volume on survival advantage. It is our hope that by summarising a large and diverse collection of literature, we may present evidence to improve the generalizability of the topic and aid future policymaking as trauma centres continue to proliferate.
Methods Study identification and selection Two authors (L.M.C. and K.M.S.) drafted the inclusion criteria prior to the literature search. Scientific literature was identified through electronic databases Pubmed (MEDLINE) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (EbscoHost) as well as hand-searching citations from appropriate studies. We searched conference abstracts and dissertations to reduce publication bias present in systematic reviews exclusively analysing published data [7]. We searched abstracts from the American Association for the Surgery of Trauma (AAST) using the AAST online collection of past abstracts (2003–2012) and PapersFirst (First Search) (1976–2002). We also searched the ProQuest Dissertations and Theses (1976–2012). We crosschecked the Cochrane Database of Systematic Reviews and the Database of Abstracts of Reviews of Effects to ensure no systematic reviews exclusively examining our topic of interest were published or in progress. Our criteria required studies to: (a) consist of original research addressing the topic of institutional or per surgeon volume on mortality; (b) include data from Level I trauma centres; (c) be English-language publications addressing American trauma centres; (d) published between 1 January 1976 and 1 June 2013; (e) have available abstracts; (f) study a general trauma population. We only included American studies, as the ACS requirements are uniform throughout the country. We chose studies published in 1976 or later, as the ASC COT published its first version of the ‘‘Optimal Hospital Resources for the Care of the Seriously Injured,’’ which guided the development of the modern, tiered American trauma system, in 1976. We excluded studies that only considered demographic-specific populations, such as geriatric or paediatric patients, rather than injury characteristics, and studies examining exclusively burns. The definition of trauma patient was defined by individual studies; most studies established criteria based on International Classification of Disease (ICD) criteria. We recorded all citations in the web-based citation manager Zotero (www.zotero.org; Fairfax, VA, USA) to organise studies and eliminate duplicates.
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Quality review Citations were initially assessed by the first author (L.M.C.), and those that met predetermined criteria were further reviewed by the first and second author (L.M.C. & K.M.S.). Discrepancies were discussed with a third author (D.B.O.) throughout the study identification and selection process and disagreements were settled by consensus. While reviewing, we recorded predetermined characteristics of the studies of interest in a checklist. The Preferred Reporting Items for Systematic Reviews and MetaAnalyses (PRISMA) Statement was used to ensure reviewers collected variables describing the quality of the studies. Variables collected included publication year and source, patient characteristics, patient inclusion and exclusion criteria, study design, study size, the number of institutions involved, volume definition, key results, potential sources of bias, and whether the study controlled for case-mix factors. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was employed to rate the quality of the evidence. Potential sources of bias identified included coding bias and discrepancies that may occur when comparing multiple registries. Further, the inclusion and exclusion criteria of which trauma populations were to be included, often defined by specific ICD codes, varied. Additionally, we included one study that included a patient population from Level I, Level II and ‘‘non trauma’’ trauma centres; we acknowledge this may invite some coding bias. The reviewers were not blinded to the authors or other study characteristics. Statistical analysis The definition of institutional or per surgeon volume was inconsistently applied across studies. Some studies compared high
Table 1 Keywords for electronic literature search. Search term ‘‘Trauma centres/utilization’’ (‘‘patient volume’’ OR ‘‘caseload’’) AND (‘‘mortality’’ OR ‘‘length of stay’’) (‘‘patient volume’’ OR ‘‘caseload’’) AND (‘‘trauma’’ OR ‘‘Wounds, Nonpenetrating/ mortality’’ OR ‘‘Wounds, Penetrating/mortality’’) ((‘‘trauma centre’’ OR ‘‘level I’’) AND (‘‘patient volume’’ OR ‘‘caseload’’ OR ‘‘throughput’’)) (volume outcome relationship) AND (‘‘trauma’’ OR ‘‘Wounds, Nonpenetrating/ mortality’’ OR ‘‘Wounds, Penetrating/mortality’’)
to low volume trauma centres, while others examined high, medium, and low volume, and other studies viewed volume as a continuous variable. Additionally, recognised confounding factors of age and ISS were inconsistently controlled; this inconsistency may limit our ability to draw conclusions from the results of the studies. Lastly, of the six studies that used a sample from the National Trauma Data Bank (NTDB), five used overlapping data from at least two years. As a result, the evidence did not allow for use of a weighted meta-analysis to produce results that can be generalised or scaled. We thereby presented the study characteristics and results descriptively. Results We used original keywords in addition to MeSH terminology, listed in Table 1. We originally retrieved a total of 1371 abstracts through electronic searches, six through a search of conference abstracts, and 15 through hand searching, resulting in a total of 1392 total abstractions (Fig. 1). Three hundred fifty eight duplicates were removed, leaving 1034 studies. The initial review eliminated 971 studies that did not address adult trauma patient
Fig. 1. PRISMA flow chart: STUDY identification and selection process. Flow chart demonstrating the study identification and selection process.
Penetrating (p = 0.99) Severely injured penetrating trauma (p = 0.879)
N/A
N/A
N/A
N/A
N/A + Continuous variable
NTDB
NTDB
Logan et al., 2010 [11]
Lorenzo et al., 2008 [26]
N/A; overall volume
+ Deciles
NTDB Bennett et al., 2011 [10]
469,327; overall volume
Multicentre Marx et al., 2011 [9]
115,358; severely injured (ISS 15)
HV: >480; MV: 240– 480; LV: 1200; LV: 15)
Continuous variable
+
Nathens et al., 2001 [17]
Multicentre
HV: 650 LV: 250; MV: 151–250; LV: 1200; LV: 12, and adult blunt trauma patients, but not in subpopulations including penetrating injuries or paediatric patients. The other three studies found no association between volume per surgeon and survival. One of these studies addressed LOS, complications and the number of preventable/ potentially preventable deaths in addition to mortality; no relationship was found between any outcome and volume. The study that found an association between volume and mortality employed a survival probability model, demonstrating that to improve survival, trauma surgeons should treat a minimum of 35 seriously injured trauma patients, defined as ISS of at least 13, and at least 28 serious blunt trauma adult patients per year. Of note, this study made a vital assumption that all trauma surgeons within institutions treated an evenly distributed number of trauma cases [23]. Each of the three studies that did not find an association between volume per surgeon and mortality employed a different method of analysis. One study utilized a logistic regression model, finding no predictive abilities between surgeon volume and survival [16]. The second study employed the TRISS methodology to compare probability of survival between two cohorts, divided by low and high per surgeon volume, as well as comparing mortality patterns of six preselected injury patterns [21]. The last study compared LOS, complications and the number of preventable/ potentially preventable deaths between surgeons, in addition to evaluating the responses to several ‘‘difficult questions,’’ stratified by surgeon volume [22]. As all studies analysed the relationship
Table 4 Summary of volume per surgeon – mortality studies. Author, year
Sample
Sample size; patient definition
Volume definition
Sava et al. [21] Margulies et al. [16] Richardson et al. [22] Konvolinka et al. [23]
Single centre Multicentre Single centre Multicentre
20,695; ISS > 15 1757; ISS > 15 1077; ISS > 14 36,346; ISS 13; overall trauma population
HV: >35 patients per surgeon; LV 35 Deciles Continuous variable Continuous variable
HV, high volume; MV, medium volume; LV, low volume. +: beneficial relationship with volume;
Outcome
+
Volume Volume Volume Volume
was was was was
not associated with any benefits. not associated with any benefits. not associated with any benefits. beneficial.
: not beneficial relationship with volume; : inconclusive evidence.
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sample sizes; among the studies we examined, several analysed small sample sizes, inviting the potential that some were perhaps inadequately powered to detect an association. A systematic review of general surgery volume and outcome found retrospective studies were more likely to find a significantly beneficial relationship between volume and outcome than a prospective study [28]. The authors of the review postulated this finding might be attributable to the limitations of retrospective data. Our systematic review has several limitations. There were few studies addressing the impact of trauma patient volume on mortality, and we found just nineteen studies eligible for inclusion in our study. Second, the diverse definitions of volume, data sources, analysis methods and patient population did not allow us to produce generalisable results and recommendations. Lastly, we limited our studies to US trauma centres, which restricts external validity and the ability to generalise our findings to other settings. Conclusion In summary, each study’s unique definitions of patient population and volume, and analysis methods limit the conclusions that can be drawn from the aggregate. There appears to be a relationship between higher overall institutional volume and improved mortality, but based on the heterogeneity of the studies, this relationship cannot be quantified using statistical methods. The current literature does not support an optimal volume, defined as overall institutional volume, volume of severely injured trauma patients, or volume per surgeon, associated with survival benefit. As state trauma systems begin to cover the majority of the United States, minimum volume requirements will continue to be controversial. Additional research is required to determine the impact of ACS volume requirements on mortality, demonstrate an optimal minimum volume to improve survival rates, and to evaluate the potential of high volume trauma centres exhausting their resources. Conflict of interest None of the authors have any financial or personal relationships that could inappropriate bias their work to disclose. Role of funding source This study has no funding sources to declare. References [1] Adams DF, Fraser DB, Abrams HL. The complications of coronary arteriography. Circulation 1973;48(3):609–18. [2] Hannan E, Racz M. Coronary angioplasty volume-outcome relationships for hospitals and cardiologists. JAMA 1997;277(11):892–8. [3] Luft H, Bunker J, Enthoven A. Should operations be regionalized? The empirical relation between surgical volume and mortality. N Engl J Med 1979;301(25):1364–9. [4] Colorado Department of Public Health and Environment. Volume Criteria; 2013. Available at: http://www.colorado.gov/cs/Satellite?blobcol=urldata&blobheadername1=Content-Disposition&blobheadername2=Content-Type&blobheadervalue1=inline%3B+filename%3D%22Volume+Criteria+in+Other+States.pdf%22&blobheadervalue2=application%2Fpdf&blobkey=id&blobtable=MungoBlobs&blobwhere=1251855864341&ssbinary=true [accessed 21.06.13].
[5] Association for the advancement of automotive medicine. AIS Update Information. Available at: http://www.aaam1.org/ais/ais_update.php [accessed 21.06.13]. [6] Salottolo K, Settell A, Uribe P, Akin S, Slone DS, O’Neal E, et al. The impact of the AIS 2005 revision on injury severity scores and clinical outcome measures. Injury 2009;40(9):999–1003. [7] McAuley L, Pham B, Tugwell P, Moher D. Does the inclusion of grey literature influence estimates of intervention effectiveness reported in meta-analyses? Lancet 2000;356(9237):1228–31. [8] Villegas CV, Haider AH, Schnedier EB, Haut ER, Efron DT, Chi A, et al. Does trauma center volume for penetrating trauma improve survival among patients with penetrating injuries?In: Annual meeting of the american association for the surgery of trauma and clinical congress of acute care surgery; 2011 [abstract]. [9] Marx WH, Simon R, O’Neill P, Shapiro MJ, Cooper AC, Farrell LS, et al. The relationship between annual hospital volume of trauma patients and in-hospital mortality in New York State. J Trauma 2011;71(2):339–45 [discussion 345–346]. [10] Bennett KM, Vaslef S, Pappas TN, Scarborough JE. The volume-outcomes relationship for United States Level I trauma centers. J Surg Res 2011;167(1):19–23. [11] Logan MS, Watson CM, Stukenborg G, Hranjec T, Young J, Calland JF. Trauma volume and outcome: is bigger always better?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery 2010; 2010 [abstract]. [12] Demetriades D, Martin M, Salim A, Rhee P, Brown C, Chan L. The effect of trauma center designation and trauma volume on outcome in specific severe injuries. Ann Surg 2005;242(4):512–7 [discussion 517–519]. [13] Marcin JP, Romano PS. Impact of between-hospital volume and within-hospital volume on mortality and readmission rates for trauma patients in California. Crit Care Med 2004;32(7):1477–83. [14] Glance LG, Osler TM, Dick A, Mukamel D. The relation between trauma center outcome and volume in the National Trauma Databank. J Trauma 2004;56(3):682–90. [15] London JA, Battistella FD. Is there a relationship between trauma center volume and mortality? J Trauma 2003;54(1):16–24 [discussion 24–25]. [16] Margulies DR, Cryer HG, McArthur DL, Lee SS, Bongard FS, Fleming AW. Patient volume per surgeon does not predict survival in adult level I trauma centers. J Trauma 2001;50(4):597–601 [discussion 601–603]. [17] Nathens AB, Jurkovich GJ, Maier RV, Grossman DC, MacKenzie EJ, Moore M, et al. Relationship between trauma center volume and outcomes. JAMA 2001;285(9):1164–71. [18] Pasquale MD, Peitzman AB, Bednarski J, Wasser TE. Outcome analysis of Pennsylvania trauma centers: factors predictive of nonsurvival in seriously injured patients. J Trauma 2001;50(3):465–72 [discussion 473–474]. [19] Cooper A, Hannan EL, Bessey PQ, Farrell LS, Cayten CG, Mottley L. An examination of the volume-mortality relationship for New York State trauma centers. J Trauma 2000;48(1):16–23 [discussion 23–24]. [20] Smith RF, Frateschi L, Sloan EP, Campbell L, Krieg R, Edwards LC, et al. The impact of volume on outcome in seriously injured trauma patients: two years’ experience of the Chicago Trauma System. J Trauma 1990;30(9):1066–75 [discussion 1075–1076]. [21] Sava J, Kennedy S, Jordan M, Wang D. Does volume matter? The effect of trauma surgeons’ caseload on mortality. J Trauma 2003;54(5):829–33 [discussion 833–834]. [22] Richardson JD, Schmieg R, Boaz P, Spain DA, Wohltmann C, Wilson MA, et al. Impact of trauma attending surgeon case volume on outcome: is more better? J Trauma 1998;44(2):266–71 [discussion 271–272]. [23] Konvolinka CW, Copes WS, Sacco WJ. Institution and per-surgeon volume versus survival outcome in Pennsylvania’s trauma centers. Am J Surg 1995;170(4):333–40. [24] McGwin Jr G, Swain RD, Reiff DA, Rue III LW. Trauma center volume: when is enough, enough?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery; 2008 [abstract]. [25] Green JM, Gunter OL, Nash J, Buchman TG, Schuerer DJE. Too much of a good thing? How increasing trauma volumes are stressing the system?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery; 2008 [abstract]. [26] Lorenzo M, Santerre R, Mangram AJ, Dunn EL, Amos JD, Truitt MS. Should patient volume be a determinant for trauma center level designation?In: Annual Meeting of the American Association for the Surgery of Trauma and Clinical Congress of Acute Care Surgery; 2008 [abstract]. [27] Tepas III JJ, Patel JC, DiScala C, Wears RL, Veldenz HC. Relationship of trauma patient volume to outcome experience: can a relationship be defined? J Trauma 1998;44(5):827–30 [discussion 830–831]. [28] Chowdhury MM, Dagash H, Pierro A. A systematic review of the impact of volume of surgery and specialization on patient outcome. Br J Surg 2007;94(2):145–61.
