Effect of regional trauma centralization on volume, injury severity and outcomes of injured patients admitted to trauma centres

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    Effect of regional trauma centralization on volume, injuryseverity and outcomes of injured patients admitted to traumacentres

    D. Metcalfe1,2, O. Bouamra3, N. R. Parsons1, M.-O. Aletrari4, F. E. Lecky3,5 and M. L. Costa1

    1Warwick Medical School, University of Warwick, Coventry, 2College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh,3Trauma Audit and Research Network, University of Manchester, Salford, Manchester, 4Faculty of Medicine, Imperial College London, London, and5Emergency Medicine Research in Sheffield (EMRiS), School of Health and Related Research, University of Sheffield, Sheffield, UKCorrespondence to: Mr D. Metcalfe, Warwick Medical School, Clinical Sciences Building, University Hospital Coventry and Warwickshire,Coventry CV2 2DX, UK (e-mail: d.metcalfe@warwick.ac.uk)

    Background: Centralization of complex healthcare services into specialist high-volume centres isbelieved to improve outcomes. For injured patients, few studies have evaluated the centralization ofmajor trauma services. The aim of this study was to evaluate how a regional trauma network affectedtrends in admissions, case mix, and outcomes of injured patients.Methods: A retrospective beforeafter study was undertaken of severely injured patients attending fourhospitals that became major trauma centres (MTCs) in March 2012. Consecutive patients with majortrauma were identified from a national registry and divided into two groups according to injury beforeor after the launch of a new trauma network. The two cohorts were compared for differences in casemix, demand on hospital resources, and outcomes.Results: Patient volume increased from 442 to 1326 (200 per cent), operations from 349 to 1231 (253per cent), critical care bed-days from 1100 to 3704 (237 per cent), and total hospital bed-days from 7910to 22 772 (188 per cent). Patient age increased on MTC designation from 450 years before March 2012to 482 years afterwards (P = 0021), as did the proportion of penetrating injuries (18 versus 41 per cent;P = 0025). Injury severity fell as measured by median Injury Severity Score (16 versus 14) and RevisedTrauma Score (41 versus 78). Fewer patients required secondary transfer to a MTC from peripheralhospitals (199 versus 161 per cent; P =0100). There were no significant differences in total durationof hospital stay, critical care requirements or mortality. However, there was a significant increase, from555 to 623 per cent (P

  • 960 D. Metcalfe, O. Bouamra, N. R. Parsons, M.-O. Aletrari, F. E. Lecky and M. L. Costa

    described the effect of centralizing major trauma serviceswithin an English setting. However, in early 2012, a seriesof regional trauma networkswere launched across England,each centred on dedicated major trauma centres (MTCs).

    The aim of the present study was to analyse data from asingle regional trauma network to evaluate the early impactof MTC designation on case mix, hospital resources andshort-term patient outcomes.


    An observational beforeafter study was conductedusing registry data from all four hospitals in a singleregion (West Midlands, UK) that became MTCs inMarch 2012. The West Midlands is a region of 27million people; its designated MTCs are UniversityHospital Birmingham, University Hospital Coventry andWarwickshire, University Hospital of North Staffordshireand Birmingham Childrens Hospital, which serves as theregional paediatric MTC.

    Data source and case selection

    All patients with major trauma presenting within a 200-dayperiod before and after launch of the trauma networkon 26 March 2012 were included in the study. Datawere extracted from nationally collected Trauma Auditand Research Network (TARN) submissions. The studyinclusion criteria are therefore identical to those used toidentify cases that should be reported to TARN: all injuredpatients regardless of age who were inpatients for 72 h ormore, or were admitted to a high-dependency area, or diedafter reaching hospital, and who sustained a severe injury asdefined in the TARNprocedures manual (such as a femoralfracture excluding femoral neck fracture in patients aged65 years or more)13.

    Patient outcomes recorded within TARN include deathand functional recovery at discharge, which is coded usingthe Glasgow Outcome Scale. This is a five-point scale thatincludes death, persistent vegetative state, severe disability,moderate disability, and good recovery14. Patients withinTARN are recorded as having a good recovery if theywere discharged home to live independently, with no newarrangements for domiciliary care.

    The comprehensiveness of TARN is estimated byreporting the number of submissions from each hospitalas a proportion of patients with a primary diagnosisof International Classification of Diseases tenth revision(ICD-10) code range S00T75 contained within HospitalEpisode Statistics. These values for the four MTCs in thepresent study ranged from 67 to 88 per cent in 2012.

    Statistical analysis

    All statistical analyses were performed using GraphPadPrism 6 (GraphPad Software, San Diego, California,USA). Continuous variables were compared between 200-day periods before and after launch of the trauma networkusing unpaired t tests for normally distributed data andMannWhitneyU tests for non-normally distributed data.Categorical variables were compared using the 2 test withYates continuity correction.

    Revised Trauma Score (RTS) values, which lie alonga physiological severity scale from zero (most injured)to 12 (least injured)15, were calculated using individualcomponents recorded on arrival at hospital: GlasgowComa Scale (GCS) score, systolic blood pressure andrespiratory rate.

    Outcome data are presented both for all injured patientsand for the most severely injured patients (defined as InjurySeverity Score (ISS) of 15 or above). Specific outcomemeasures such as hospital and critical care length of stayexcluded patients who had died, to avoid these measuresbeing downwardly biased by the inclusion of patients whodied at an early stage.

    Adjusted mortality statistics (W andW s) were calculatedfor the two groups. Initial sample sizes were 442 and 1326respectively, but patients transferred to other centres wereexcluded as their final outcome was unknown. The Wstatistic16 represents the excess number of survivors per100 cases and is defined as: W = 100 [(observed no. ofsurvivors expected no. of survivors)/no. of patients]. W sis a further standardization of the W statistic that is usefulwhen hospitals with different case mix are compared16. Inthis case, W is most valuable because it allows comparisonover time of the same group of hospitals.

    Expected survival was calculated using the sum ofsurvival probability obtained from the risk-adjusted modelused in TARN17. Missing GCS scores in the emergencydepartment were replaced by the prehospital GCS score, ifrecorded, or imputed using a locally determined multipleimputation technique. Statistical significance was set for Pvalues of less than 0050.


    The total number of patients with major injury increasedsubstantially from 442 (mean 22 per day) to 1326 (mean66 per day) following the launch of the trauma network;this represents a 200 per cent increase. Mean age increasedsignificantly from 450 (95 per cent confidence interval(c.i.) 427 to 473) to 482 (469 to 495) years (P= 0021,t test). The proportion of penetrating injuries increasedfrom 18 to 41 per cent (P= 0025).

    2014 BJS Society Ltd www.bjs.co.uk BJS 2014; 101: 959964Published by John Wiley & Sons Ltd

  • Effect of regional trauma centralization on outcomes 961

    Falls from height were the leading cause of severe injuryin both groups, although the proportion did not changesignificantly in the two time periods (498 versus 485 percent; P= 0641). The proportion of injuries caused by roadtraffic collisions was similar (367 versus 368 per cent;P= 0955), as was the proportion of intentional injuries(129 versus 107 per cent; P= 0972).

    The proportion of patients transferred from otherhospitals decreased (199 versus 161 per cent), althoughthis change was not statistically significant (P= 0100).Similarly, there was no significant difference in theproportion transported by air ambulance (218 versus 235per cent; P= 0516).

    Median ISS fell from 16 to 14, and the proportion ofseverely injured patients (ISS 15 or more) fell from 523to 481 per cent (P= 0131). The median RTS increasedfrom 41 to 78, indicating a reduction in physiologicaldisturbance among patients in the later group. Theproportions of patients with tachycardia (heart rate 100beats permin ormore) (289 versus 281 per cent;P= 0783)and hypotension (systolic blood pressure 100mmHg orless) (53 versus 60 per cent; P= 0630) did not change.

    The overwhelming majority had a GCS score of 15 onarrival, and the proportion of those scoring 8 or less did notincrease significantly (85 versus 100 per cent; P= 0475).There were, however, ten patients with an ISS of 59 ormore in the later group whereas no such patients wereidentified before institution of the trauma network. Thedistribution of ISS is shown in Fig. 1.

    Resource demands

    The proportion of patients requiring surgery increasednon-significantly from 502 to 550 per cent (P= 0083)and the mean number of operations per patient remainedconstant (16 versus 17; P= 0286, MannWhitney Utest). In keeping with the increased volume of patients, theabsolute number of operations increased by 253 per cent,from 349 (17 per day) to 1231 (62 per day).

    The proportion of patients requiring hospital admissionwas unchanged (957 versus 965 per cent; P= 0469).However, the total number of hospital bed-days increasedby 188 per cent, from 7910 to 22 772 after launch of thetrauma network. The proportion of patients admitted to a



    ry S


    ity S





    0Before After

    Fig. 1 Scatter plot showing the distribution of the Injury Severity Score in injured patients before and after institution of the traumanetwork. Each point represents a severely injured patient reported to the Trauma Audit and Research Network. The central bardenotes the group median and the error bars show the range

    2014 BJS Society Ltd www.bjs.co.uk BJS 2014; 101: 959964Published by John Wiley & Sons Ltd

  • 962 D. Metcalfe, O. Bouamra, N. R. Parsons, M.-O. Aletrari, F. E. Lecky and M. L. Costa

    critical care area did not change (290 versus 314 per cent;P= 0341), although total bed occupancy increased by 237per cent, from 1100 to 3704 days.


    Outcomes in the two groups for all injured patients andfor the severely injured (ISS 15 or above) are shown inTables 1 and 2 respectively. Critical care length of stay wascalculated only for patients admitted to a high-dependencyarea during their admission.

    Duration of hospital and critical care stay did not differbetween the groups. However, the proportion of patientscoded as having a good recovery at discharge increasedsignificantly, from 555 to 623 per cent (P< 0001).Although the proportion of patients with an ISS of 15 orabove coded as having a good recovery appeared to increaseby an even greater amount, from 443 to 555 per cent, thisdifference was not statistically significant (P= 0821).

    The crude mortality rate for all injured patients fellfrom 79 to 63 per cent following the launch of thetrauma network, although this change was not significant(P= 0298). Similarly, the mortality rate in the subgroupof patients with an ISS of 15 or above fell from 126

    Table 1 Outcomes for all injured patients before and afterinstitution of the trauma network


    Aftercentralization P

    Duration of hospitalstay (days)*

    90 (160, 219) 110 (166, 188) 0068

    Duration of criticalcare stay (days)*

    50 (72, 114) 50 (81, 105) 0306

    Good recovery atdischarge

    172 of 310 (555) 308 of 494 (623) < 0001

    Crude mortality 35 of 443 (79) 84 of 1325 (63) 0298

    Values in parentheses are percentages unless indicated otherwise; *valuesare median (95 per cent confidence interval). MannWhitney U test,except 2 test.

    Table 2 Outcomes for patients with an Injury Severity Score of15 or above before and after institution of the trauma network


    Aftercentralization P

    Duration of hospitalstay (days)*

    120 (204, 288) 140 (203, 242) 0599

    Duration of criticalcare stay (days)*

    60 (79, 127) 60 (94, 123) 0181

    Good recovery atdischarge

    90 of 203 (443) 254 of 458 (555) 0821

    Crude mortality 29 of 230 (126) 65 of 639 (102) 0385

    Values in parentheses are percentages unless indicated otherwise; *valuesare median (95 per cent confidence interval). MannWhitney U testtest, except 2 test.

    to 102 per cent (P= 0385). The W statistic increasedfrom 180 (95 per cent c.i. 044 to 405) to 373 (244to 502), indicating that following MTC designation193 lives were saved per 100 patients beyond thatexpected, although the overlapping confidence intervalspoint to no statistically significant difference. The W sstatistic also increased, from 133 (049 to 315) to256 (154 to 358).


    This study describes a longitudinal evaluation of traumaservice centralization and demonstrates an increasedvolume of severely injured patients with predictableimplications for operating theatre capacity, hospital bed,and critical care bed occupancy in trauma centres. Areduction in overall injury severity (ISS) and physiologicaldisturbance (RTS) was noted, perhaps due to expandedambulance triage criteria, for example based onmechanismof injury. A greater proportion of penetrating injuries areseen in trauma centres, as well as a group of criticallyinjured patients who might previously have been triageddirectly to the nearest resuscitation facility.

    Following their designation as MTCs, the four hospitalscontributing to this analysis shouldered an additional14 862 hospital bed-days and 2604 critical care bed-days ina single 6-month period. Fewer patients required secondarytransfer from other hospitals following the launch ofthe trauma network, although this reduction was notstatistically significant.

    Possible advantages of prehospital triage to a MTCinclude avoiding complex transfer arrangements, delayedoperative intervention (such as wound closure) and reducedtotal length of stay. Evidence from theUSA6,7,18,19 suggeststhat outcomes are improved for patients triaged directly toan appropriate facility compared with those transferred ata later time.

    In this analysis, no statistically significant improvementswere identified for hospital length of stay, critical carelength of stay, or mortality. Importantly, one institutionreported atypical mortality data to TARN: no traumadeaths after becoming a MTC. The mortality data shouldtherefore be interpreted cautiously, although the datafrom this hospital seem unlikely to have influenced theoverall finding of no statistically significant improvementin mortality rate. There was a highly significant (P< 0001)improvement in the proportion of patients dischargedwith a coded outcome of good recovery compared againstall other outcomes (moderate disability, severe disability,persistent vegetative...


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