Case volume and rate are associated with outcomes in geriatric trauma: A case for geriatric trauma centers? : Journal of Trauma and Acute Care Surgery

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Case volume and rate are associated with outcomes in geriatric trauma: A case for geriatric trauma centers?

Kojima, Mitsuaki MD, PhD; Endo, Akira MD, PhD; Zakhary, Bishoy MPH; Shoko, Tomohisa MD, PhD; Firek, Matthew BS; Coimbra, Raul MD, PhD

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Journal of Trauma and Acute Care Surgery 94(2):p 241-247, February 2023. | DOI: 10.1097/TA.0000000000003838
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The elderly population is growing rapidly in most developed countries.1 According to the National Trauma Data Bank, geriatric trauma patients, defined as those older than 65 years, have increased from 18% to 30% between 2005 and 2015.2 It was also estimated that over 50% of the cases registered in the Japanese nationwide trauma database were elderly patients.3 Since older trauma patients have more comorbidities and a higher rate of complications and mortality than younger patients, medical resources and costs for elderly trauma patients are also increasing rapidly.4 Hence, geriatric trauma care is rapidly becoming a global public health concern.5

Geriatric trauma patients have different physiology, mechanisms of injury, and responses to treatment compared with younger trauma patients.3,6,7 Pediatric trauma care has been centralized, and dedicated pediatric trauma centers have been established to improve outcomes in the United States.8,9 Similar to pediatric trauma care, geriatric trauma patients may require targeted strategies, and there may be benefits from consolidating geriatric trauma care.10 Trauma centers have mainly focused on treating younger patients who have suffered severe injuries, and the benefit of trauma center care for the elderly remains unclear. Previous studies have shown a reduction of approximately 40% in 1-year mortality in younger trauma patients treated at Level I trauma centers; however, no significant difference in mortality among elderly patients has been reported.11 Similarly, a recent study examining Medicare claims data reported that for patients 65 years and older, no benefit in survival from treatment at existing trauma centers was observed.12 Therefore, the current system of trauma centers alone has not improved outcomes for elderly trauma patients, and it would be important to consider specialized care for the elderly.

This study aimed to investigate the association between elderly trauma case volume and rate with outcomes. This study discusses the need to consolidate and unify the care of elderly trauma patients by establishing designated trauma centers focusing on the elderly population.

METHODS

Data Source

This retrospective cohort study utilized the data from the American College of Surgeons (ACS) Trauma Quality Improvement Program (TQIP) database. The observation period was 4 years, between January 2015 and December 2019. The local institutional review committee approved the study and its protocols. This study conforms with the Strengthening the Reporting of Observational Studies in Epidemiology guidelines and a complete checklist has been uploaded as Supplemental Digital Content (SDC) 1 (https://links.lww.com/TA/C789).

Patient Selection

Data from severely injured geriatric patients in the TQIP database, defined as patients ≥65 years, were included in the analyses.13 We excluded patients without exact information on injury mechanisms, outcomes, or hospital characteristics. We also excluded patients with burn injuries, nonsurvivable injuries defined as those with an Abbreviated Injury Scale (AIS) = 6 points, and without signs of life (detectable blood pressure, respiratory or motor effort, cardiac electrical activity, or pupillary activity) on hospital arrival (Fig. 1).

F1
Figure 1:
Study flowchart.

Data Collection

The following variables were included in the analyses: age, sex, comorbidities, mechanism of injury, Injury Severity Score (ISS), AIS for each body region, vital signs, Glasgow Coma Scale (GCS) score upon arrival at the emergency department, hospital characteristics (ACS trauma center level, teaching status, and facility identifier), intensive care unit length of stay (LOS), hospital LOS, in-hospital complications, and survival status at hospital discharge.

Definitions and Outcomes

A severely injured patient was defined as a patient with ISS ≥16. Geriatric case volume (GCV) was defined as the mean annual number of treated geriatric trauma patients, and geriatric case rate (GCR) was defined as the mean annual number of geriatric trauma patients divided by all trauma patients in each center. Hospitals were then classified into tertiles: low-, medium-, and high-volume and rate facilities based on GCV and GCR. The study outcomes were in-hospital mortality rate, the incidence of predetermined adverse events, and prolonged LOS. We defined prolonged LOS as two standard deviations above the mean LOS of the entire study cohort.14 Adverse events developed during hospital stay were defined as cardiac, respiratory, and renal failure, thrombotic events, and sepsis.

Statistical Analysis

After selecting the study cohort, missing values were then imputed using patient characteristics (age, sex), severity upon arrival to the emergency department (Revised Trauma Score [RTS], ISS, and AIS score of each body region), and comorbidities on arrival using the random forest method for each study cohort with the missForest package (version 1.4) of R software (version 3.5.2; R Foundation for Statistical Computing, Vienna, Austria). The association of GCV and GCR with outcomes was assessed using the generalized additive model (GAM) and multivariate generalized linear mixed model (GLMM) adjusted for patient age, sex, injury mechanism (penetrating or blunt), RTS, ISS, modified Frailty Index, and hospital characteristics (ACS verification level and teaching status). The modified Frailty Index is a scale based on five variables, including diabetes, hypertension, chronic obstructive pulmonary disease, congestive heart failure, and functional dependency. It has been proven to adequately reflect frailty in previous studies.15–17 We included a random effect on trauma center characteristics to control for clustering hospitals using GLMM models. We performed Cox proportional hazard regression analyses after adjusting for the aforementioned variables to further evaluate the 28-day risk of mortality among the low, medium, and high GCV/GCR groups. Cox analysis was also performed for the subgroups of high-GCV and GCR groups to determine the mutual influences of GCV and GCR. Finally, we performed sensitivity analyses to determine if the observed relationships were applicable to patients with less severe (ISS < 16) injuries.

χ2 or Fisher's exact test was used for categorical variables, and the Mann-Whitney U test was used for continuous variables. Values are presented as median (25–75% interquartile range) and frequency (percentage). Estimated data are presented as adjusted odds ratios (OR) with 95% confidence intervals (95% CIs). All statistical analyses were performed using R software. The level of significance was defined as a p value <0.05.

RESULTS

Patient and Hospital Characteristics

A total of 164,818 geriatric trauma patients admitted to 812 hospitals were included (Fig. 1). Patient and hospital characteristics are summarized in Tables 1 and 2. The median age of geriatric trauma patients was 77 years, 72.4% were male, 70.1% had a severe head injury, and the median ISS was 20. The mean and standard deviation of LOS was 9.0 ± 9.6 days; thus, prolonged LOS was defined as a LOS greater than 19 days in this study. Most patients were treated at teaching hospitals (84.4%) and Level I or II trauma centers (70.3%). Prolonged LOS, complication, and in-hospital mortality rates for the overall cohort were 8.1%, 21.9%, and 15.8%, respectively (Table 1). A summary of the facilities included in the study is shown in Table 2. The 812 facilities included in the study were divided into three groups based on the GCV and GCR tertiles. The median annual volume of elderly trauma patients in the low-, medium-, and high-GCV facilities were 51.4, 176.0, and 363.8, respectively. The median case rate of the low, medium, and high-GCV groups were 31.0%, 48.0%, and 67.0%, respectively (Table 2). The high-GCV group included significantly more Level I trauma centers than the low- or medium-GCV groups, whereas the opposite trend was observed in the GCR group. A histogram of the average annual volume of geriatric trauma patients per facility and the percentage of elderly patients is shown in SDC 2 (https://links.lww.com/TA/C789).

TABLE 1 - Description of Geriatric Trauma Patients Included in the Analyses
Variables Overall
Overall population n = 164,818
Age, median (IQR) 77.0 (70.0–83.0)
Sex, female 52,272 (37.6%)
Comorbidity
 Liver 641 (0.8%)
 Renal 3,131 (1.9%)
 Cardiovascular 13,773 (8.4%)
 Respiratory 17,709 (10.8%)
 Diabetes mellitus 43,372 (26.5%)
 Hypertension 106,573 (64.9%)
 Frail 59,384 (36.4%)
Mechanism of injury
 Blunt 162,983 (98.9%)
 Penetrating 1,835 (1.1%)
Vital signs on arrival, median (IQR)
 Systolic blood pressure, mm Hg 146.0 (126.0–166.0)
 Heart rate, beats/min 84.0 (72.0–100.0)
 Respiratory rate, breaths/min 18.0 (16.0–20.0)
 GCS 14.0 (14.0–15.0)
 ISS, median (IQR) 20.0 (17.0–26.0)
Injured region, AIS ≥ 3
 Head 112,648 (70.1%)
 Face 1,101 (0.7%)
 Neck 1,495 (0.9%)
 Thorax 45,271 (28.2%)
 Abdomen 9,034 (5.6%)
 Spine 18,948 (11.8%)
 Upper extremities 1,176 (0.7%)
 Pelvis and lower extremities 19,918 (12.4%)
Procedures
 Blood transfusion within 4 h 12,686 (7.7%)
 Angioembolization 2,695 (1.6%)
 Emergency surgery 5,964 (3.6%)
Hospital characteristics
Trauma center level
 I 74,582 (45.3%)
 II 41,138 (25.0%)
 III/not verified 49,098 (29.7%)
Teaching status
 University 61,279 (37.1%)
 Community 78,029 (47.3%)
 Nonteaching 24,982 (15.1%)
Overall trauma volume, median (IQR) 869.6 (560.2–1302.8)
GCV
Geriatric volume, median (IQR) 354.0 (233.4–379.1)
 Low 6,703 (4.1%)
 Medium 39,313 (23.9%)
 High 118,802 (72.0%)
GCR
Proportion, median (IQR) 0.41 (0.32–0.49)
 Low 77,759 (47.2%)
 Medium 68,715 (41.7%)
 High 18,344 (11.1%)
Outcomes
ICU days, median (IQR) 3.0 (2.0–6.0)
Hospital days, median (IQR) 6.0 (4.0–11.0)
Prolonged LOS 13,312 (8.1%)
Adverse events 36,159 (21.9%)
In-hospital mortality 25,987 (15.8%)
Data are presented as median (IQR) or number (%).
IQR interquartile range; ICU, intensive care unit.

TABLE 2 - Hospital Characteristics and Distribution of Geriatric Patients Included in Study Analyses
GCV Low Volume Medium Volume High Volume
n = 271 n = 270 n = 271 p
Geriatric volume/year 51.4 (25.8–81.9) 176.0 (141.1–210.1) 363.8 (294.7–465.7) <0.001
Total volume/year 94.7 (57.1–151.4) 369.8 (257.4–505.9) 868.6 (651.5–1190.0) <0.001
Proportion of geriatrics 0.54 (0.36–0.68) 0.50 (0.36–0.61) 0.44 (0.36–0.52) <0.001
GCR group (%)
 Low 91 (33.6%) 84 (31.1%) 96 (35.4%) <0.001
 Medium 52 (19.2%) 85 (31.5%) 133 (49.1%)
 High 128 (47.2%) 101 (37.4%) 42 (15.5%)
Trauma center level
 I 10 (3.7%) 39 (14.4%) 128 (47.2%) <0.001
 II 38 (14.0%) 110 (40.7%) 85 (31.4%)
 III/not verified 223 (82.3%) 121 (44.8%) 58 (21.4%)
Teaching status <0.001
 Teaching 151 (55.7%) 179 (66.3%) 225 (83.0%)
 Nonteaching 120 (44.3%) 91 (33.7%) 46 (17.0%)
GCR Low rate Medium rate High rate
n = 271 n = 270 n = 271 p
Geriatric volume/year 176.8 (88.4–309.1) 241.5 (133.7–374.7) 115.2 (63.3–195.6) <0.001
Total volume/year 615.5 (327.9–1003.4) 518.8 (264.1–766.5) 168.6 [92.7, 310.8] <0.001
Proportion of geriatrics 0.31 (0.25–0.36) 0.48 (0.44–0.52) 0.67 [0.61, 0.73] <0.001
GCV group (%)
 Low 91 (33.6%) 52 (19.3%) 128 (47.2%) <0.001
 Medium 84 (31.0%) 85 (31.5%) 101 (37.3%)
 High 96 (35.4%) 133 (49.3%) 42 (15.5%)
Trauma center level
 I 111 (41.0%) 57 (21.1%) 9 (3.3%) <0.001
 II 71 (26.2%) 112 (41.5%) 50 (18.5%)
 III/not verified 89 (32.8%) 101 (37.4%) 212 (78.2%)
Teaching status <0.001
 Teaching 221 (81.5%) 190 (70.4%) 144 (53.1%)
 Nonteaching 50 (18.5%) 80 (29.6%) 127 (46.9%)
Data are presented as median (IQR) or number (%).

Association Between GCV, GCR, and Outcomes

Using a nonlinear GAM to analyze the study cohort, the plots showed that the adjusted OR for in-hospital mortality and complication rates decreased according to the increase in GCV after adjusting for multiple covariables (Fig. 2). Although similar trends were observed, the decrease in the odds of mortality and adverse events plateaued with a GCR of approximately 50% (Fig. 2).

F2
Figure 2:
Generalized additive model evaluating the association between GCV/GCR and outcomes. Association of GCV (A, C)/GCR (B, D) and study outcomes. In-hospital mortality (A, B) and adverse events (C, D) were analyzed using the nonlinear logistic generalized additive model adjusted for patient age, gender, injury mechanism, RTS, ISS, modified Frailty Index, hospital characteristics. Adverse events included cardiac, respiratory, and renal failure, thrombotic events and sepsis. The shaded region represents the 95% CIs for the estimated points.

To show the results of the GAM plots numerically, we divided the hospitals into low, medium, and high groups based on GCV and GCR tertiles. As per the GAM plots, the GLMM models revealed that high-GCV and high-GCR centers had lower observed mortality, complication, and prolonged LOS rates than low GCV and GCR centers (Table 3).

TABLE 3 - Association of GCV and GCR With in-Hospital Mortality and Adverse Events Among Geriatric Trauma Patients Using GLMM
In-Hospital Mortality Adverse Events Prolonged LOS
GCV OR (95% CI) p OR (95% CI) p OR (95% CI) p
Low 1.00 (reference) 1.00 (reference) 1.00 (reference)
Medium 0.89 (0.78–1.01) 0.070 0.85 (0.77–0.95) 0.004 0.79 (0.71–0.87) <0.001
High 0.82 (0.72–0.92) <0.001 0.79 (0.71–0.88) <0.001 0.69 (0.62–0.76) <0.001
GCR OR (95% CI) p OR (95% CI) p OR (95% CI) p
Low 1.00 (reference) 1.00 (reference) 1.00 (reference)
Medium 0.86 (0.79–0.92) <0.001 0.84 (0.79–0.90) <0.001 0.76 (0.73–0.80) <0.001
High 0.81 (0.73–0.90) <0.001 0.75 (0.68–0.82) <0.001 0.73 (0.67–0.79) <0.001
Data are presented as OR (95% CI).

When comparing medium and high groups, the high-GCV group showed significantly lower odds of mortality, complication, and prolonged LOS rates (OR [95% CI]: 0.87 [0.83–0.91], 0.89 [0.85–0.92], and 0.88 [0.84–0.92]). However, there was no significant difference in outcomes between the medium- and high-GCR groups (SDC 3, https://links.lww.com/TA/C789).

Cox proportional hazard regression analysis revealed that the high-GCV and high-GCR groups were associated with lower risks of 28-day mortality compared with the low-GCV and low-GCR groups after controlling for multiple confounders (Table 4). When the high-GCV group was subdivided by GCR tertiles, the 28-day mortality rate decreased with each increase in the proportion of elderly patients (OR, low vs. medium and low vs. high, 0.92 [0.88–0.95] and 0.78 [0.73–0.84], respectively; SDC 4, https://links.lww.com/TA/C789). In addition, when the relationship between annual volume in the high-GCR group was examined, a significant correlation between GCV and mortality was found in the high-GCR group compared with the low-GCR group (OR [95% CI]: 0.76 [0.62–0.93]; SDC 4, https://links.lww.com/TA/C789). A reciprocal association was observed in the high-GCV/GCR group.

TABLE 4 - Cox Proportional Hazard Regression Analysis of 28-Day Mortality
GCV HR (95% CI) p
Low 1.00 (reference)
Medium 0.95 (0.88–1.02) 0.161
High 0.91 (0.85–0.98) 0.012
GCR HR (95% CI) p
Low 1.00 (reference)
Medium 0.90 (0.87–0.92) <0.001
High 0.79 (0.75–0.84) <0.001
Data are presented as hazard ratio (95% CI).
HR, hazard ratio.

Sensitivity analyses were performed to evaluate the performance of regression models on outcomes among geriatric patients with less severe injuries (ISS <16). There were significant reductions in the odds of mortality, complications, and prolonged LOS in the high-GCV/GCR groups compared with the low-GCV/GCR groups, showing a similar trend to that observed in the severe injury cohort (SDC 5, https://links.lww.com/TA/C789).

DISCUSSION

In this study, we examined the association between the volume and rate of cases and outcomes of severely injured geriatric patients using the largest national trauma database in the United States. We found that increases in both volume and rate of geriatric trauma cases were significantly associated with decreases in mortality rates. Similar trends were also observed when complications and prolonged hospital stay rates were examined. Furthermore, subgroup analyses revealed that (1) increasing the volume of older patients, even in subgroups with a higher proportion of older patients, was associated with lower mortality; and 2) in high volume of cases involving the elderly, increasing the proportion of elderly patients further reduced mortality rate. Collectively, our findings showed that the rate and volume of cases of geriatric trauma patients were associated with patient outcomes.

Generally, the benefit of care in high-level trauma centers has been demonstrated for severely injured young adults but not the elderly.11 Jarma et al.12 reported that older adults with injuries from low-energy blunt mechanisms would not benefit from receiving care in trauma centers. However, many studies have shown that consolidation into Level I trauma centers improved the prognosis of younger adult trauma patients.2,18,19 Pediatric trauma centers, have shown to have better outcomes than existing adult trauma centers caring for pediatric trauma victims.8,10,20 These observed outcome differences may be explained by the consolidation of pediatric cases with different physiological characteristics from adults cared for by a dedicated team. A previous study using the Japanese trauma database reported that trauma in the elderly differs from trauma in younger patients in terms of mechanism of injury, injured body areas, and prognosis.3 Furthermore, a recent study using the TQIP database also reported that massive blood transfusion with a high rate of plasma, recommended for younger patients, was ineffective in elderly patients with severe trauma.7 Hence, we planned this study to examine the association between the volume and rate of geriatric trauma patients with outcomes based on the premise that, as with pediatric cases, consolidating geriatric care in specialized geriatric trauma centers may have survival benefit.

Case volume and case rate are related to outcomes in emergency surgery for nontraumatic medical diseases in the elderly.21,22 These data support the idea that specialized teams familiar with elderly patients' diseases and physiology practicing under a unified care delivery system may positively impact outcomes. For example, elderly patients with multiple comorbidities, such as cardiac or respiratory diseases, may require specialized intervention by a geriatrician.23,24 In addition, a team approach may also be necessary, including early rehabilitation and delirium prevention programs by trauma surgeons and comedical staff.4,25 Early rehabilitation activity and fall prevention programs for older trauma patients have been reported to reduce the incidence of recurrent falls and fall-related complications.26,27

Previous studies in the field of trauma have focused primarily on the caseload and prognosis of older trauma patients.28–30 For example, Matsushima et al.28 reported that a higher volume of cases of elderly trauma patients correlated with a lower in-hospital mortality rate in Level I and II trauma centers. However, few studies have focused on the case rate of elderly patients as it relates to the total number of institutional trauma cases (GCR) as in our study. Olufajo et al.29 used the California inpatient database and found that an increase in the proportion of elderly trauma patients leads to lower rates of complications and in-hospital mortality. Similarly, our study showed that increasing the rate of older patients significantly decreased mortality and complications rates but included more participants and would have more statistical power. The most important finding in our study is the potential benefit of consolidating care for severely injured geriatric patients, not only by increasing the absolute number of patients treated but also by increasing the rate of elderly patients compared with the overall institutional trauma volume. The number of elderly trauma patients is increasing yearly in many developed countries, and specialized geriatrics care is one of the critical issues among trauma surgeons. This may be the appropriate time to discuss the need to establish trauma centers dedicated to the elderly.

In general, Level I trauma centers have shown better outcomes for critically injured patients; however, the impact of high-level trauma centers on outcomes in the elderly remains controversial. Prabhakaran et al.31 reported that elderly trauma patients have better outcomes when treated at a designated trauma center. However, another study found no significant correlation between the level of ACS-accredited trauma centers and the prognosis of elderly trauma patients.29 In our study, neither trauma center level nor teaching status correlated with mortality of geriatric trauma patients even after adjusting for multiple covariates in the study cohort (SDC 6, https://links.lww.com/TA/C789). This suggests that Level II or even lower level trauma centers can contribute to improving the outcomes of elderly trauma patients through their experience and quality programs in geriatric care. Because it is not realistic to immediately retrofit Level I trauma centers that contribute to saving the lives of young people for the elderly, it may be possible to establish a specialized program for the care of the elderly and consolidate cases regardless of their trauma center levels. Specific criteria for trauma center verification applied specifically to centers with higher GCRs should be considered. These could potentially include specific performance improvement metrics and audit filters, injury prevention programs targeting the elderly population, and research focusing on that population, besides the need to have a geriatrics program involved in trauma care.

This study has several limitations. Although we argue that each facility’s quantitative and qualitative treatment experience with the elderly would improve outcomes, we did not have detailed programs and treatment protocols for each facility. Although elderly patients may have previously expressed wishes regarding do-not-attempt-resuscitation decisions, this study could not assess the presence or absence of do-not-attempt-resuscitation decisions or the timing of treatment discontinuation. These factors may influence early patient mortality. Second, prehospital services and geographical factors of each region could not be considered in this study because of data limitations. For example, factors such as whether the trauma occurred in a densely populated or underpopulated area and whether a Level I trauma center was available nearby a Level III or nontrauma center are important considerations in the timely management of trauma patients. Third, the trauma database used in this study only included patients from the United States, and the generalizability of the current study at a global level is unclear. For further clarification and comparisons, large-scale prospective clinical studies may be needed in different geographical regions.

In conclusion, the present study demonstrated that in-hospital mortality and complication rates may be lower in centers that treat an adequate number and proportion of elderly patients with severe trauma. As the population ages, it is necessary to discuss the creation of protocols specifically for the elderly and the establishment of specialized trauma centers.

AUTHORSHIP

M.K., A.E., B.Z., and M.F. carried out data collection. M.K. and A.E. performed data analysis. M.K., T.S., and R.C. conceived the study, and M.K., A.E., B.Z., T.S., M.F., and R.C. participated in its design and coordination. M.K., A.E., and R.C. drafted the article. All authors read and approved the final article.

DISCLOSURE

The authors declare no funding or conflicts of interest.

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Keywords:

Geriatrics; elderly trauma; trauma registry; trauma centers; outcomes

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