eAppendix. Imputation Procedure
Rachel B. Webman, Elizabeth A. Carter, Sushil Mittal, Jichaun Wang, Chethan Sathya, Avery B. Nathens, Michael L. Nance, David Madigan, Randall S. Burd. Association Between Trauma Center Type and Mortality Among Injured Adolescent Patients. JAMA Pediatr. 2016;170(8):780–786. doi:10.1001/jamapediatrics.2016.0805
Although data obtained from regional trauma systems demonstrate improved outcomes for children treated at pediatric trauma centers (PTCs) compared with those treated at adult trauma centers (ATCs), differences in mortality have not been consistently observed for adolescents. Because trauma is the leading cause of death and acquired disability among adolescents, it is important to better define differences in outcomes among injured adolescents by using national data.
To use a national data set to compare mortality of injured adolescents treated at ATCs, PTCs, or mixed trauma centers (MTCs) that treat both pediatric and adult trauma patients and to determine the final discharge disposition of survivors at different center types.
Design, Setting, and Participants
Data from level I and II trauma centers participating in the 2010 National Trauma Data Bank (January 1 to December 31, 2010) were used to create multilevel models accounting for center-specific effects to evaluate the association of center characteristics (PTC, ATC, or MTC) on mortality among patients aged 15 to 19 years who were treated for a blunt or penetrating injury. The models controlled for sex; mechanism of injury (blunt vs penetrating); injuries sustained, based on the Abbreviated Injury Scale scores (post-dot values <3 or ≥3 by body region); initial systolic blood pressure; and Glasgow Coma Scale scores. Missing data were managed using multiple imputation, accounting for multilevel data structure. Data analysis was conducted from January 15, 2013, to March 15, 2016.
Type of trauma center.
Main Outcomes and Measures
Mortality at each center type.
Among 29 613 injured adolescents (mean [SD] age, 17.3 [1.4] years; 72.7% male), most were treated at ATCs (20 402 [68.9%]), with the remainder at MTCs (7572 [25.6%]) or PTCs (1639 [5.5%]). Adolescents treated at PTCs were more likely to be injured by a blunt than penetrating injury mechanism (91.4%) compared with those treated at ATCs (80.4%) or MTCs (84.6%). Mortality was higher among adolescents treated at ATCs and MTCs than those treated at PTCs (3.2% and 3.5% vs 0.4%; P < .001). The adjusted odds of mortality were higher at ATCs (odds ratio, 4.19; 95% CI, 1.30-13.51) and MTCs (odds ratio, 6.68; 95% CI, 2.03-21.99) compared with PTCs but was not different between level I and II centers (odds ratio, 0.76; 95% CI, 0.59-0.99).
Conclusion and Relevance
Mortality among injured adolescents was lower among those treated at PTCs, compared with those treated at ATCs and MTCs. Defining resource and patient features that account for these observed differences is needed to optimize adolescent outcomes after injury.
As adolescents transition into adulthood, their medical care changes from delivery by pediatric to adult health care professionals. This transition also occurs for adolescents’ hospital-based treatment after injury, with more adolescent trauma patients being treated at centers that primarily treat injured adults. Pediatric trauma centers (PTCs) are unique in that these centers provide care that addresses the specific physiological, anatomical, and social needs of children.1 As adolescents move into adulthood, however, the perceived need for these resources decreases. The largest proportion of patients seen at trauma centers are young adults, a population with physiological, anatomical and social needs similar to older adolescents.2 Because the resources of PTCs are comparatively scarce and may not be needed for older adolescents, injured adolescents may also be treated either at an adult trauma center (ATC) or a mixed trauma center (MTC) that treats both adults and children, rather than at a PTC.
Trauma systems in which PTCs and either ATCs or MTCs are found typically define a cutoff age for triage to either a pediatric or primarily adult trauma center. This cutoff age varies in different trauma systems based on local preferences and practice patterns and is usually not based on outcome differences at different center types. Previous studies examining the optimal trauma center type for children have mostly shown an outcome advantage for children treated at a PTC or MTC compared with those treated at an ATC.3- 9 Although a consensus is forming for the optimal treatment center for younger children, controversy still remains about the optimal location for treating injured adolescents.10- 14
Few studies have evaluated the outcome for adolescents at different trauma center types after injury.7,13,14 Studies evaluating outcome among adolescents treated at different types of trauma centers have shown conflicting results, with some showing different frequencies of interventions (eg, laparotomy and blood transfusion) and no difference in mortality, and others showing improved mortality.7,13,14 These previous studies, however, used regional data obtained from mature trauma systems and did not address this issue in a larger national cohort in which more diversity in care and resource availability may exist. Although patient demographics and injury patterns have been proposed as explanations for differences in mortality, these differences were not consistently observed even after controlling for patient and injury features.3,4,6,8,9,15,16
The objectives of this article are to determine whether type of trauma center designation (PTC, MTC, or ATC) is associated with mortality among adolescent trauma patients in a sample obtained from the National Trauma Data Bank and to determine differences among patients presenting to different center types. A second objective was to determine the final discharge disposition of survivors at different center types.
Question Is there a difference in the mortality rate for injured adolescents treated at pediatric trauma centers compared with those treated at adult trauma centers or mixed trauma centers that treat both adults and children?
Findings In this study, after controlling for patient and injury characteristics, adolescents treated at adult trauma centers and mixed trauma centers had a higher risk of death than did adolescents treated at pediatric trauma centers.
Meaning Injured adolescents treated at pediatric trauma centers have a lower risk of death than those treated at mixed trauma centers and adult trauma centers.
This study was approved by the Children’s National Medical Center Institutional Review Board. Because this study was conducted using deidentified data, patient consent was not necessary. All patient data were deidentified. Data were derived from the 2010 National Trauma Data Bank (January 1 to December 31, 2010), a database maintained by the American College of Surgeons that contains medical records of injured children and adults treated at reporting trauma centers. Patients who were aged 15 to 19 years and treated at a level I or level II trauma center for a blunt or penetrating injury were included. Patients who were transferred to a short-term general stay hospital were excluded because their outcome was unknown. Of the 29 658 records obtained, 45 were missing data for the primary outcome (mortality) and were excluded, for a final analysis data set of 29 613 records.
Data analysis was conducted from January 15, 2013, to March 15, 2016. We performed multilevel logistic regression to identify the effect of trauma center type and trauma center level on mortality and discharge disposition among survivors. We separately evaluated overall mortality that included deaths that occurred in the emergency department and in the hospital after admission as well as in-hospital mortality. We defined discharge to rehabilitation as disposition to an intermediate, long-term, or skilled nursing facility. Patient factors modeled included sex, mechanism of injury, transfer status (transported directly from scene vs seen at another hospital before arrival), initial systolic blood pressure less than 90 mm Hg, the initial motor score component of the Glasgow Coma Scale (modeled as 5 binary variables representing 6 values), and Abbreviated Injury Scale [AIS] post-dot values for each of 9 body regions (treated as binary variables for values <3 or ≥3 within each of 9 body regions). Hospital-level variables included the type of center (PTC, ATC, or MTC) and trauma center verification level (I or II).
The amount of missingness among the covariates modeled was between 0% and 4.5%. To manage missingness in the covariates, we performed multiple imputation using a procedure that accounted for the hierarchical structure of the data set, creating 10 imputed data sets (eAppendix in the Supplement). Because multiple imputation was performed, some percentages are estimates of the true percentage and do not have associated exact numbers of patients. The 10 multiple imputation data sets were analyzed using Mplus, version 7.3.17 Parameter estimates were averaged across the 10 analyses, and their SEs were computed using the Rubin method.18,19 Multilevel logistic regression was used for model estimation, with mortality or discharge to rehabilitation as the dependent variable. Standard errors were computed using a robust sandwich estimator. Models with a random intercept were used to account for the hierarchical data structure (patients nested within hospitals). Comparisons of patient and center characteristics between the 3 types of trauma centers were performed using either 1-way analysis of variance or χ2 test as appropriate using imputed data to obtain estimates for variables with missing values (SAS, version 9.3, SAS Institute Inc). P < .05 was considered significant. Model diagnostics were performed measuring discrimination with area under the receiver operator curve and measuring calibration with the Hosmer-Lemeshow statistic, dividing records in deciles of estimated probability of mortality.
Among the 29 613 patients, most were treated at an ATC (20 402 [68.9%]). The remaining patients were treated at either an MTC (7572 [25.6%]) or a PTC (1636 [5.5%]). More adolescents were treated at a level I trauma center (63.3%) than at a level II trauma center (36.7%). Treatment at a level I center was more common among patients at an MTC (81.9%) compared with those at a PTC (76.1%) and was least common among patients at an ATC (55.3%) (Table 1). Patients treated at a PTC were less likely to arrive directly from the injury scene than be transferred from another hospital compared with those treated at either an ATC or MTC. Adolescents treated at ATCs and MTCs were older than those treated at PTCs (mean [SD] age, 17.4 [1.3], 17.1 [1.4], and 16.0 [1.0], respectively) and were more severely injured, including more frequent hypotension (patients with initial blood pressure <90 mm Hg: 3.2%, 2.3%, and 1.4%, respectively), lower Glasgow Coma Scale motor scores (11.2, 10.5, and 6.4, respectively), higher injury severity scores (19.7, 20.3, and 11.1, respectively), and more frequent severe injuries of the head (AIS post-dot value ≥3: 15.2, 15.6, and 11.3, respectively), chest (AIS post-dot value ≥3: 17.1, 17.2, and 7.9, respectively), and upper extremity (AIS post-dot value ≥3: 2.1, 1.8, and 1.0, respectively) (Table 1). Patients treated at a PTC were less commonly discharged to rehabilitation (3.3%) than adolescents treated at either ATCs (5.0%) or MTCs (6.0%) (Table 1).
Adolescents treated at PTCs were more likely to be injured by a blunt than penetrating injury mechanism (91.4%) compared with those treated at ATCs (80.4%) or MTCs (84.6%) (Table 2). Unintentional injuries were most common at all center types but were less frequent among patients treated at ATCs (75.6%) and MTCs (81.4%) compared with those treated at PTCs (86.5%). Injury by assault was less frequent among patients treated at PTCs (11.5%) compared with those treated at ATCs (21.5%) and MTCs (16.2%). Patients injured in a fall (25.9%) or when struck (26.1%) were most common at PTCs compared with ATCs (fall, 12.9%; struck, 12.3%) and MTCs (fall, 15.1%; struck, 13.2%), while patients injured as motor vehicle occupants were most common at ATCs (32.6%) and MTCs (34.3%) compared with PTCs (18.5%). Penetrating injury mechanisms (firearm and cut or pierce) were more common at ATCs (firearm, 12.0%; cut or pierce, 7.3%) and MTCs (firearm, 8.3%; cut or pierce, 7.1%) than at PTCs (firearm, 4.5%; cut or pierce, 4.1%), as were motorcyclist injuries (ATC, 3.0%; MTC, 2.7%; PTC, 1.2%).
Unadjusted emergency department and overall mortality was higher among adolescents treated at ATCs (emergency department, 1.2%; overall, 3.2%) and MTCs (emergency department, 1.0%; overall, 3.5%) compared with those treated at PTCs (emergency department, 0.2%; overall, 0.4%) (Table 1). The emergency department mortality of adolescents arriving from the injury scene was higher among adolescents treated at ATCs (1.5%) and MTCs (1.4%) than among those treated at PTCs (0.3%), but was similar among those transferred from another hospital at each center type (ATC, 0.3%; MTC, 0.4%; and PTC, 0.1%) (Table 1). After adjusting for patient and center variables, overall mortality remained higher at ATCs (odds ratio, 4.19; 95% CI, 1.30-13.51) and MTCs (odds ratio, 6.68; 95% CI, 2.03-21.99) compared with PTCs but was not different between level I and II centers (odds ratio, 0.76; 95% CI, 0.59-0.99) (Table 3). The model derived for these results show excellent discrimination and was well calibrated, overall and among subgroups of patients (Table 4). Similar significant differences in mortality between adolescents treated at PTCs and other center types was observed in the subgroup of adolescents who were admitted to the hospital and in the subgroup of adolescents sustaining only penetrating injuries (Table 3 and Table 5). After adjusting for patient and center variables, no difference in disposition to rehabilitation was observed among the 3 center types (Table 3).
Injury is the leading cause of death and acquired disability among adolescents.20 To reduce the effect of trauma in this age group, it is essential to determine optimal treatment strategies. Because adolescents straddle the gap between pediatric and adult medicine, identifying differences in care among PTCs, ATCs, and MTCs will help determine the most appropriate triage strategies or identify practice strategies that can optimize the outcome for patients in this age group. We assessed the populations presenting to PTCs vs ATCs and MTCs and evaluated mortality at PTCs and other center types, controlling for these differences. We found that trauma center verification level differed among these center types and that the adolescent patients treated at PTCs were different from those treated at ATCs and MTCs based on injury type, mechanism of injury, severity of injury, and demographics.
After controlling for these differences, lower mortality was observed among adolescents treated at PTCs compared with those treated at ATCs and MTCs. This finding is similar to that of studies that evaluated mortality differences among children of all ages (including adolescents) and among younger children only.3,4,6,7,21 Previous studies that have examined outcomes for only adolescents did not find mortality differences among center types.13,14 Both studies were performed using state registry data (Ohio14 and Pennsylvania13) rather than data obtained from a national sample. The study using data from Ohio used propensity case matching, rather than multivariable regression analysis, and combined data from level I and II PTCs to avoid identification of specific centers.14 Although propensity case matching is an appropriate method when the ratio between the number of predictors and outcome is low, multivariable regression is preferred when this ratio is higher, as in the cohort that we examined.22 Combining trauma center designation levels could also have influenced the outcome observed in the PTC cohort.14 The analysis that we used differed from that in previous studies by using imputation rather than data exclusion to manage missing data and by considering the hierarchical structure of the data (patients nested in hospitals) in model development. Another difference is that we separately evaluated mortality in adolescents surviving to hospital admission.
Adolescent patients treated at ATCs and MTCs may have features different from those treated at PTCs. Patients treated at PTCs were younger, more likely to be transferred from other hospitals, less severely injured, and had a different distribution of injury mechanisms. The demographic and injury severity differences are consistent with most previous studies including data from children of all ages3,9,16,23 and those containing only adolescent data.13,14 The patient population differences observed between those treated at PTCs and either ATCs or MTCs may be explained by either first-responder triage decision making or local triage criteria. For example, adolescents injured by firearms may be preferentially brought to ATCs or MTCs regardless of a given adolescent’s age because this mechanism is more likely to be treated at facilities that also treat adult trauma patients.
Although more adolescents treated at PTCs were transferred from another hospital, the emergency department mortality of adolescents arriving at PTCs was similar to that of patients arriving at ATCs and MTCs. In addition, differences in mortality between centers were similar when including and excluding patients who died in the emergency department. These results suggest that differences in mortality cannot be explained by the stability of those transferred to different center types. The greater injury severity of children and adolescents seen at ATCs and MTCs compared with those seen at PTCs has been previously observed.6,10,11 Our study further defines this difference by showing that higher injury severity is related to more severe injuries in the head, thorax, and upper-extremity body regions. Although a previous study suggested improved functional outcome at PTCs vs other center types,5 we observed no differences in disposition to a rehabilitation facility. This finding shows that the observed differences in mortality may not be associated with other outcome measures and warrants separate analysis.
Without finding the cause of the mortality differences between center types, we cannot take appropriate steps to improving outcomes at all centers. Other groups have found that operative interventions, such as spleen and liver procedures, were increased in children of all ages at ATCs and compared with those at PTCs.4,24 In the adolescent patient population, overall intervention rates, not limited to operative management of solid organ injury, were higher at ATCs than PTCs.13 Determining differences in treatment practices between center types will be necessary to show the reasons for differences in mortality rates and may suggest areas in patient management that can be modified to improve outcomes.
This study has several limitations. First, our analysis is based on data from the National Trauma Data Bank that collects data only from participatory centers. Because this data set does not represent all trauma centers, it may result in response bias. Second, although we observed a difference in mortality between those treated at PTCs and other center types, our study does not provide information about what may account for these differences. Although we controlled for several potential confounders that may contribute to mortality differences at different center types and observed excellent model fit, other unknown factors that we did not control for may account for these differences. Finally, although we used a large sample from the National Trauma Data Bank, mortality was sparsely represented in each center type. Our findings will need to be evaluated in a larger cohort of patients to further support our findings.
Trauma centers dedicated to the treatment of pediatric patients see a different adolescent population than do ATCs and MTCs. After controlling for these differences, we observed that adolescent trauma patients have lower overall and in-hospital mortality when treated at PTCs. The optimal care of adolescents at all center types requires the identification of either additional patient differences or treatment practices that account for this mortality difference. Analysis of the association of specific care processes with mortality at center types will be needed to further clarify the etiology of these differences in mortality.
Accepted for Publication: March 17, 2016.
Corresponding Author: Randall S. Burd, MD, PhD, Division of Trauma and Burn Surgery, Children’s National Medical Center, 111 Michigan Ave NW, Washington, DC 20010 (email@example.com).
Published Online: June 27, 2016. doi:10.1001/jamapediatrics.2016.0805.
Author Contributions: Drs Webman and Burd had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Carter, Sathya, Nathens, Nance, Burd.
Acquisition, analysis, or interpretation of data: Webman, Carter, Mittal, Wang, Nathens, Nance, Madigan, Burd.
Drafting of the manuscript: Webman, Wang, Burd.
Critical revision of the manuscript for important intellectual content: Carter, Mittal, Sathya, Nathens, Nance, Madigan, Burd.
Statistical analysis: Webman, Carter, Mittal, Wang, Sathya, Madigan, Burd.
Obtained funding: Burd.
Administrative, technical, or material support: Nathens, Burd.
Study supervision: Nance, Burd.
Conflict of Interest Disclosures: None reported.
Funding/Support: Research reported in this publication was supported by award R01GM087600-03 from the National Institute of General Medical Sciences of the National Institutes of Health.
Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, or interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.