ORIGINAL ARTICLE
Shock index predicts mortality in geriatric trauma patients: An analysis of the National Trauma Data Bank Viraj Pandit, MD, Peter Rhee, MD, Ammar Hashmi, MD, Narong Kulvatunyou, MD, Andrew Tang, MD, Mazhar Khalil, MD, Terence O’Keeffe, MbChB, Donald Green, MD, Randall S. Friese, MD, and Bellal Joseph, MD Heart rate and systolic blood pressure are unreliable in geriatric trauma patients. Shock index (SI) (heart rate/systolic blood pressure) is a simple marker of worse outcomes after injury. The aim of this study was to assess the utility of SI in predicting outcomes. We hypothesized that SI predicts mortality in geriatric trauma patients. METHODS: We performed a 4-year (2007Y2010) retrospective analysis using the National Trauma Data Bank. Patients 65 years or older were included. Transferred patients, patients dead on arrival, missing vitals on presentation, and patients with burns and traumatic brain injury were excluded. A cutoff value of SI greater than or equal to 1 (sensitivity, 81%; specificity, 79%) was used to define hemodynamic instability. The primary outcome measure was mortality. Secondary outcome measures were need for blood transfusion, need for exploratory laparotomy, and development of in-hospital complications. Multiple logistic regressions were performed. RESULTS: A total of 485,595 geriatric patients were reviewed, of whom 217,190 were included. The mean (SD) age was 77.7 (7.1) years, 60% were males, median Glasgow Coma Scale (GCS) score was 14 (range, 3Y15), median Injury Severity Score (ISS) was 9 (range, 4Y18), and mean (SD) SI was 0.58 (0.18). Three percent (n = 6,585) had an SI greater than or equal to 1. Patients with SI greater than or equal to 1 were more likely to require blood product requirement ( p = 0.001), require an exploratory laparotomy ( p = 0.01), and have in-hospital complications ( p = 0.02). The overall mortality rate was 4.1% (n = 8,952). SI greater than or equal to 1 was the strongest predictor for mortality (odds ratio, 3.1; 95% confidence interval, 2.6Y3.3; p = 0.001) in geriatric trauma patients. Systolic blood pressure ( p = 0.09) and heart rate ( p = 0.2) were not predictive of mortality. CONCLUSION: SI is an accurate and specific predictor of morbidity and mortality in geriatric trauma patients. SI is superior to heart rate and systolic blood pressure for predicting mortality in geriatric trauma patients. Geriatric trauma patients with SI greater than or equal to 1 should be transferred to a Level 1 trauma center. (J Trauma Acute Care Surg. 2014;76: 1111Y1115. Copyright * 2014 by Lippincott Williams & Wilkins) LEVEL OF EVIDENCE: Prognostic/epidemiologic study, level III. KEY WORDS: Geriatric; shock index; vitals on presentation; mortality; blood transfusion. BACKGROUND:
T
rauma is one of the leading causes of death among geriatric (age Q 65 years) individuals.1 Assessment of injury severity and hemodynamic instability in geriatric patients is often difficult owing to their altered response to injury.1,2 The low physiologic capacity in these patients masks the clinical exacerbation of injury, which makes management of these patients challenging.3 Traditional vital signs such as systolic blood pressure (SBP) and heart rate (HR) are routinely used for the assessment of trauma patients.4,5 Numerous cutoff points based on blood pressure and HR have been defined as threshold for transferring patients to a Level 1 trauma center.6 Complex laboratory tests using specialized equipment have also been implicated for early identification of patients at a higher risk of death from
Submitted: October 24, 2013, Revised: December 2, 2013, Accepted: November 29, 2013. From the Division of Trauma, Critical Care, Emergency Surgery, and Burns, Department of Surgery, University of Arizona, Tucson, Arizona. Supplemental digital content is available for this article. Direct URL citations appear in the printed text, and links to the digital files are provided in the HTML text of this article on the journal’s Web site (www.jtrauma.com). Address for reprints: Bellal Joseph, MD, Division of Trauma, Critical Care, And Emergency Surgery, Department of Surgery, University of Arizona, 1501 N Campbell Ave, Room 5411, PO Box 245063, Tucson, AZ 85724; email: [email protected]. DOI: 10.1097/TA.0000000000000160
hemorrhagic shock; however, such resources may not always be available in the field or the emergency department.7 In addition, the applicability, reliability, and cost-effectiveness of these parameters to identify hemodynamic instability in geriatric trauma patients remain unclear.8 Shock index (SI) is a simple ratio of HR over SBP, which can be easily calculated in the field.9 SI has been shown to be an accurate indicator of hemodynamic instability and need for blood transfusion in trauma patients;10 however, the role of SI as an assessment tool in geriatric trauma patients is not well defined. The aim of this study was to identify the utility of SI in predicting outcomes in geriatric trauma patients. We hypothesized that SI is a predictor of mortality in geriatric trauma patients.
PATIENTS AND METHODS We performed a 4-year (2007Y2010) retrospective analysis using the National Trauma Data Bank (NTDB), version 7.2. The NTDB is the largest collection of trauma index cases, which is maintained by the American College of Surgeons (Chicago, IL). The NTDB contains more than 1.8 million patients, which are contributed by more than 900 trauma centers across the United States. Patients older than 65 years were included. Patients
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transferred from another institutions; patients dead on presentation; patients with burn injuries, isolated traumatic brain injury (head Abbreviated Injury Scale [AIS] score Q 3 and other body regions AIS score G 3), or recorded comorbidity of hypertension; and patients with missing data on vital parameters (HR or SBP) were excluded from our study. We abstracted the following data points from the NTDB database: demographics (age, sex, race, and ethnicity), vitals on presentation (HR, SBP, respiratory rate, and temperature), mechanism of injury (blunt and penetrating), Glasgow Coma Scale (GCS) score on presentation, requirement of blood transfusion, operative intervention, hospital and intensive care unit lengths of stay, in-hospital complications, and in-hospital mortality. Patient’s injury characteristics were abstracted using the Injury Severity Score (ISS) and the AIS score. SI was calculated in each patient based on the ratio of HR and SBP. Hemodynamic instability was defined by an SI greater than or equal to 1.11,12 Patients were stratified into two groups based on their hemodynamic instability: patients with SI greater than or equal to 1 and patients with SI less than 1. Our primary outcome measure was in-hospital mortality. The secondary outcome measures were blood transfusion requirement, need for exploratory laparotomy, and in-hospital complications. We defined blood transfusion requirement as transfusion of packed red blood cells, whole blood, blood plasma, and human fibrinogen. Blood transfusions (P Code, 964.7) and need for exploratory laparotomy (P Code, 54.11) were abstracted from the NTDB using the DRG International Classification of DiseasesV9th Rev. procedure codes. In-hospital complications are defined as infectious complications (sepsis, pneumonia, and urinary tract infections) or hematologic complications (deep venous thrombosis and disseminated intravascular coagulation). Data are reported as mean (SD) for continuous variables, median (range) for ordinal variables, and as proportions for categorical variables. We performed Mann-Whitney U-test and Student’s t test to explore for differences in the two groups (SI 9 1 and SI G 1) for continuous variables. We used W2 test for identifying differences between patients with SI greater than or equal to 1 and SI less than 1 for categorical variables. Univariate analysis was performed to assess factors predicting mortality in geriatric trauma patients. Factors with p e 0.2 on univariate analysis were used in a multivariate regression analysis. p G 0.05 on multivariate regression analysis was considered statistically significant. All statistical analyses were performed using SPSS version 20 (SPSS, Inc., Chicago, IL).
RESULTS A total of 485,595 geriatric trauma patients were identified, of whom 217,190 patients were included. Figure 1 (Supplemental Digital Content 1, at http://links.lww.com/TA/A394) demonstrates the algorithm for patient selection. The mean (SD) age was 77.7 (51.1) years, 60% were males, median GCS score was 14 (range, 13Y15), median ISS was 9 (range, 4Y18), and the mean (SD) SI 0.58 (0.18). Three percent of the patients (n = 6,585) were hemodynamically unstable on presentation. Patients with SI greater than or equal to 1 were likely to be hypotensive ( p = 0.001) and tachycardiac ( p = 0.001) on presentation, with severe injury 1112
( p = 0.001) compared with patients with SI less than 1. Table 1 demonstrates the demographics of the study population. Patients with SI greater than or equal to 1 were more likely to receive blood transfusion ( p = 0.001), require an exploratory laparotomy ( p = 0.01), and develop in-hospital complications ( p = 0.02). The overall mortality rate was 4.1% (n = 8,905). Patients with SI greater than or equal to 1 ( p = 0.001) had a higher mortality rate compared with patients with SI less than 1. Table 2 demonstrates the outcomes between the patients with SI greater than or equal to 1 and patients with SI less than 1. On univariate analysis, age ( p = 0.01), male sex ( p = 0.04), emergency department (ED) SBP ( p = 0.01), ED HR ( p = 0.01), ISS ( p = 0.02), blunt injury ( p = 0.04), and SI greater than 1 ( p = 0.001) were associated with mortality. After adjusting for factors associated with mortality in a multivariate regression analysis, SI greater than or equal to 1 was the strongest predictor for mortality (odds ratio [OR], 3.1; 95% confidence interval [CI], 2.6Y3.3). SBP (OR, 1.1; 95% CI, 0.8Y1.3) and HR (OR, 1.1; 95% CI, 0.9Y1.3) were not predictive of mortality in geriatric trauma patients. Table 3 demonstrates the univariate and multivariate regression analysis for factors associated with mortality in geriatric trauma patients. On subanalysis of patients based on blunt and penetrating injury, SI greater than 1 was an independent predictor of mortality in patients with blunt injury and patients with
TABLE 1. Demographics Variables Demographics Age, mean (SD), y 65Y74 y, % (n) 75Y84 y, % (n) 985 y, % (n) Males, % (n) Race, % (n) White Black Hispanics Physiologic parameters ED SBP, mean (SD) Hypotensive (SBP G 110), % (n) ED HR, mean (SD) Tachycardia (HR 9 100), % (n) ED temperature, mean (SD) SI, mean (SD) Injury severity Mechanism of injury Blunt, % (n) Penetrating, % (n) ISS, median (interquartile range) ISS Q 16, % (n) GCS score, median (interquartile range) GCS score e 8, % (n)
SI Q 1
SI G 1
(n = 6,585)
(n = 210,605)
p
77.8 (51) 34.4 (2,265) 43.5 (2,864) 22.1 (1,456) 65.8 (4,333)
76 (51.1) 39.5 (83,189) 45.4 (95,615) 15.1 (31,801) 61.2 (128,890)
0.09 0.4 0.1 0.09 0.1
82.9 (5,459) 5.3 (349) 4 (263)
80.4 (169,326) 6.4 (13,479) 5.2 (10,951)
0.4 0.6 0.9
95.6 (21.6) 78.3 (4,794)
138.8 (27.9) 7.9 (16,637)
0.01 0.001
113.1 (23.8) 72.8 (4,794)
81.9 (16) 14.1 (29,695)
0.01 0.001
37.6 (0.08) 1.21 (0.25)
37.5 (0.04) 0.56 (0.14)
0.5 0.001
62 (4,083) 32.5 (2,142) 13 (9Y24) 33.9 (2,232) 15(3Y15)
59.8 (125,942) 33.1 (69,710) 10 (8Y18) 13.8 (2,906) 15 (3Y15)
0.04 0.09 0.01 0.001 0.5
12.2 (803)
11.9 (25,062)
0.7
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TABLE 2. Comparison in Outcomes in Patients Variables Blood transfusion, % (n) Exploratory laparotomy, % (n) In-hospital complications Length of stay, mean (SD) Hospital length of stay ICU length of stay Ventilator days Mortality, % (n)
SI 9 1
SI G 1
(n = 6,585)
(n = 210,605)
TABLE 4. Multivariate Logistic Regression for Mortality Stratified by Mechanism of Injury
17.3 (927) 6 (395) 13.6 (896)
9.3 (15,053) 2.3 (4,843) 9.2 (19,376)
G0.001 0.01 0.02
9.2 (7.1) 7.3 (5.9) 4.4 (2.6) 19.2 (1,133)
6.4 (4.8) 5.1 (4.4) 3.1 (2.3) 4.1 (7,819)
0.02 0.03 0.08 G0.001
penetrating injury. Table 4 highlights the subanalysis for factors associated with mortality in patients with blunt and penetrating injuries. After stratifying patients into three groups based on age (65Y74 years, 75Y84 years, and 985 years), SI still remained an independent predictor for mortality in geriatric trauma patients. Table 5 demonstrates the subanalysis for factors associated with mortality based on each age group. Table 6 demonstrates the subanalysis for factors associated with mortality based on ISS. SI greater than 1 remained an independent predictor of mortality after stratifying patients into groups based on injury severity. SI greater than or equal to 1 has 97% specificity and 85% accuracy to predict mortality in geriatric trauma patients. The sensitivity was 45%, positive predictive value was 82%, and negative predictive value was 67% to predict mortality in geriatric trauma patients.
DISCUSSION Guidelines based on clinical parameters for defining acute resuscitation in geriatric trauma patients remain unclear.13 TABLE 3. Univariate and Multivariate Analyses of Factors Predicting Mortality Variables Age, y 75Y84 985 Male White Hispanic ED SBP ED HR ED temperature SI 9 1 GCS score 9Y12 G8 Blunt mechanism ISS 19Y15 16Y24 925
Blunt Injury
p
OR (95% CI)
p
OR (95% CI)
p
1.62 (1.52Y1.73) 1.14 (1.1Y1.2) 2.1 (2Y2.2) 1.6 (0.9Y1.8) 1.1 (0.7Y2.1) 1.5 (1.1Y2.3) 1.2 (1.05Y2.6) 1.2 (0.8Y1.6) 3.8 (1.6Y4.6)
0.01 0.01 0.04 0.3 0.9 0.01 0.01 0.6 0.001
1.3 (1.52Y1.73) 1.2 (1.1Y1.2) 1.2 (2Y2.2) V V 1.15 (1.1Y2.3) 1.1 (1.05Y2.6) V 3.1 (2.6Y3.3)
0.04 0.02 0.3 V V 0.09 0.2 V 0.001
1.8 (1.2Y2.6) 2.3 (1.9Y2.8) 1.4 (1.05Y1.9)
0.04 0.02 0.04
1.8 (0.9Y3.1) 1.6 (0.5Y2.4) 1.2 (0.9Y2.8)
0.2 0.09 0.1
2.1 (1.4Y3.1) 2.8 (1.9Y4.6) 3.6 (2.2Y5.1)
0.04 0.02 0.02
1.6 (0.6Y2.9) 2.6 (2.1Y4.1) 3.8 (2.1Y5.6)
0.2 0.01 0.001
SI 9 1 Age 75Y84 y 985 y Male SBP HR GCS score 9Y12 G8 ISS 9Y15 16Y24 925
Penetrating Injury
OR (95% CI)
p
OR (95% CI)
p
3.1 (1.6Y7.1)
0.01
2.4 (1.7Y5.8)
0.01
1.09 (0.8Y1.9) 1.1 (1.06Y2.7) 1.06 (0.9Y1.5) 1.3 (0.92Y1.8) 1.2 (0.8Y2.5)
0.2 0.04 0.5 0.08 0.1
1.08 (1.02Y2.4) 1.06 (0.99Y2.1) 1.1 (0.9Y1.9) 1.5 (0.98Y4.5) 1.07 (0.6Y3.2)
0.04 0.09 0.4 0.09 0.6
1.09 (0.7Y2.2) 1.15 (0.85Y1.6)
0.7 0.4
1.2 (0.6Y1.9) 1.4 (0.8Y3.2)
0.3 0.6
1.2 (0.95Y2.1) 1.5 (1.3Y3.8) 2.1 (1.1Y5.1)
0.1 0.04 0.03
1.1 (0.98Y1.9) 1.7 (1.3Y5.8) 2 (1.2Y6.1)
0.09 0.01 0.01
This study demonstrates that SI is a vital tool for the identification of hemodynamic instability in geriatric trauma patients. Patients with SI greater than or equal to 1 have higher mortality rate, blood transfusion requirement, and exploratory laparotomy rates compared with patients with SI less than 1. Moreover, traditional vital parameters such as HR and SBP are not associated with mortality. As guidelines for managing geriatric trauma patients continue to be redefined, SI can be a useful clinical tool to predict the risk of mortality and guide therapeutic management in geriatric trauma patients. Geriatric patients form a special cohort of trauma patients owing to their low physiologic reserve and altered response to injury.3 Vital signs are an inaccurate measurement of hemodynamic instability in these patients, resulting in undertriage and adverse outcomes.4,5 The Eastern Association for the Surgery of Trauma has emphasized on the establishment of a predictive model to facilitate the management decisions in geriatric trauma patients.13 The results of our study demonstrate that
TABLE 5. Multivariate Logistic Regression for Mortality Stratified by Age Age 65Y74 y
SI 9 1 Male SBP HR GCS score 9Y12 G8 ISS 9Y15 16Y24 925
Age 9 85 y
Age 75Y84 y
OR (95% CI)
p
OR (95% CI)
3.6 (1.8Y5.4) 1.1 (0.7Y1.8) 1.4 (0.9Y2.9) 1.1 (0.9Y1.9)
0.001 0.4 0.09 0.6
3.2 (2.1Y4.6) 1.3 (0.9Y2.3) 1.6 (0.6Y3.1) 1.1 (0.8Y2.1)
p
OR (95% CI)
p
0.001 2.1 (1.4Y3.9) 0.01 0.2 1.15 (0.9Y2.5) 0.7 0.1 1.2 (0.7Y1.8) 0.4 0.5 1.4 (0.8Y3.2) 0.2
1.1 (0.2Y3.4) 0.5 1.4 (0.9Y2.4) 0.1
1.3 (0.7Y2.6) 0.2 1.8 (0.6Y4.5) 0.4
1.1 (0.9Y2.1) 0.1 1.4 (0.2Y3.6) 0.2
1.1 (0.9Y2.4) 0.1 1.8 (1.2Y2.8) 0.04 2.6 (1.4Y4.5) 0.02
1.5 (1.1Y3.4) 0.04 2.2 (1.5Y4.5) 0.01 3.2 (1.8Y5.2) 0.001
2.4 (1.3Y5.4) 0.01 3.1 (2.5Y8.4) 0.01 4.1 (1.9Y7.2) 0.001
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TABLE 6. Multivariate Logistic Regression for Mortality Stratified by Injury Severity ISS 0Y8
SI 9 1 Age 75Y84 y 9 85 y Male SBP HR GCS score 9Y12 G8
ISS 9Y15 p
OR (95% CI)
p
OR (95% CI)
p
OR (95% CI)
p
1.3 (1.1Y7.2)
0.04
2.4 (1.4Y3.9)
0.01
3.4 (1.7Y6.5)
0.001
3.8 (1.8Y5.1)
0.001
1.15 (0.57Y3.1) 1.07 (0.65Y2.5) 1.06 (0.87Y2.4) 1.2 (0.8Y3.5) 1.04 (0.75Y2.3)
0.9 0.5 0.5 0.4 0.5
1.18 (0.8Y2.5) 1.2 (0.7Y1.7) 1.2 (0.79Y1.8) 1.3 (0.7Y2.1) 1.12 (0.82Y3.6)
0.5 0.3 0.3 0.3 0.2
1.1 (0.8Y2.1) 1.08 (1.05Y2.8) 1.25 (0.6Y3.1) 1.09 (0.91Y2.5) 1.15 (0.9Y2.2)
0.09 0.03 0.2 0.09 0.1
1.05 (1.02Y2.2) 1.18 (1.09Y3.4) 1.1 (0.94Y1.9) 1.1 (1.05Y4.1) 1.2 (0.93Y3.6)
0.01 0.001 0.1 0.03 0.09
1.05 (0.6Y2.5) 1.09 (0.7Y1.8)
0.2 0.4
1.07 (0.8Y1.6) 1.1 (0.8Y2.2)
0.3 0.1
1.1 (0.85Y1.8) 1.2 (0.7Y2.4)
0.1 0.4
1.1 (0.97Y2.4) 1.2 (1.02Y2.9)
0.09 0.04
SI is a simple and accurate tool for predicting hemodynamic instability and subsequent adverse outcomes in geriatric trauma patients. We believe that SI can be used to define resuscitation guidelines. SI is a known predictor of mortality and adverse outcomes in trauma patients.10 Cannon et al.14 and McNab et al.15 demonstrated higher mortality rates in hemodynamically unstable patients defined by SI greater than or equal to 0.9 compared with stable patients. Similarly, Vandromme et al.16 highlighted the significant association between increasing SI and mortality in trauma patients. However, these studies had relatively small sample size and fewer numbers of hemodynamically unstable patients. In addition, all these studies had a heterogeneous population consisting of young and elderly trauma patients. In our study of 210,605 geriatric trauma patients, we found that patients with SI greater than or equal to 1 were four times more likely to die compared with patients with SI less than 1. These results demonstrate that SI can be implemented in geriatric trauma patients with results similar to those of young trauma patients. Studies assessing postinjury mortality in geriatric trauma patients have used a modified SI defined as age SI as a predictor of mortality. Zarzaur et al.17 analyzed the NTDB and concluded that modified SI should be used as a predictor of mortality in older patients. However, old patients were defined by age greater than or equal to 55 years, and there was a minimal difference in the predictive ability of SI and modified SI in these patients. In our study, we assessed the role of simple SI as a predictor of mortality in geriatric (Q65 years) trauma patients. We did not assess modified SI because adding age as another parameter would increase the complexity of calculating SI and prevent its wider applicability. Second, the accurate age of the patients is routinely unknown at the time of injury. Given the minimal difference in the predictive ability between SI and modified SI, we chose to simplify the situation by only assessing the utility of SI alone. Studies assessing mortality in trauma patients have highlighted the role of old age and injury severity as predictors of mortality. We recently a published meta-analysis of factors associated with mortality and demonstrated that increasing age and severity of injury were the only significant factors associated with mortality in geriatric trauma patients.18 We could 1114
ISS 9 25
ISS 16Y24
OR (95% CI)
not evaluate the role of SI in predicting mortality because data assessing the role of SI as a predictor of mortality in geriatric trauma patients were lacking. In the current study, we found that although increasing age and injury severity were associated with mortality, SI was the strongest predictor for mortality in geriatric trauma patients. Even after stratifying patients based on age and injury severity, SI remained a significant predictor of mortality. As injury severity cannot be assessed in the field, we think that SI can be a reliable tool for guiding the resuscitation of geriatric trauma patients. SI has been widely reported as a more sensitive marker of hemodynamic instability compared with traditional vital signs such as HR and SBP.12,19Y21 Birkhahn et al.20 in a prospective study confirmed that SI was a more accurate predictor of acute changes in blood volume compared with both HR and SBP. Similarly, Rady et al.22 also demonstrated SI to be superior to traditional vital signs in predicting intensive therapy after admission in critically ill patients. Our results on SI are in concordance with these previous studies and further validate its utility in predicting the requirement for blood transfusion, need for exploratory laparotomy, and mortality in geriatric trauma patients. Our study should be interpreted in the context of its inherent limitations, being a retrospective analysis. The NTDB is a convenience sample and is not a comprehensive representation of the population and thus may not be generalizable. Moreover, underreporting and limited quality control of data entered into the registry may reflect in the composite data set under study. We were not able to control for the preinjury use of medication such as A-blocker, which is known to affect HR and SBP. However, we did exclude all patients with known comorbidity of hypertension to control for the use of A-blockers. Despite these limitations, our study is the largest study to assess the utility of SI in geriatric trauma patients. SI is a simple and reliable tool for predicting hemodynamic instability by using the already available vitals on presentation and further guiding the management in geriatric trauma patients.
CONCLUSION SI, which is a simple ratio of HR and blood pressure, is an accurate and specific predictor of morbidity and mortality in * 2014 Lippincott Williams & Wilkins
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geriatric trauma patients. It allows accurate assessment of these patients and is an effective tool that can be implemented in a prehospital setting for the triage of geriatric trauma patients. SI is superior to HR and SBP for predicting mortality in geriatric trauma patients. Geriatric trauma patients with SI greater than or equal to 1 should be transferred to a Level 1 trauma center. AUTHORSHIP V.P., P.R., N.K., R.S.F., and B.J. designed this study. V.P., A.H., M.K., A.T., D.G., R.S.F., and B.J. searched the literature. V.P., A.H., N.K., M.K., T.O., and B.J. collected the data. V.P., A.H., N.K., T.O., R.S.F., and P.R. analyzed the data. All other authors participated in data interpretation and manuscript preparation.
DISCLOSURE The authors declare no conflicts of interest.
REFERENCES 1. Broos PL, D’Hoore A, Vanderschot P, Rommens PM, Stappaerts KH. Multiple trauma in elderly patients. Factors influencing outcome: importance of aggressive care. Injury. 1993;24(6):365Y368. 2. Joseph B, Pandit V, Rhee P, Aziz H, Sadoun M, Wynne J, Friese RS, Predicting outcomes in geraitric trauma patients: Is frailty the answer? J Trauma Care Surg. 2014;76(1):196Y200. 3. Rogers A, Rogers F, Bradburn E, Krasne M, Lee J, Wu D, Edavettal M, Horst M. Old and undertriaged: a lethal combination. Am Surg. 2012; 78(6):711Y715. 4. Victorino GP, Battistella FD, Wisner DH. Does tachycardia correlate with hypotension after trauma? J Am Coll Surg. 2003;196(5):679Y684. 5. Eastridge BJ, Salinas J, McManus JG, Blackburn L, Bugler EM, Cooke WH, Convertino VA, Concertino VA, Wade CE, Holcomb JB. Hypotension begins at 110 mm Hg: redefining ‘‘hypotension’’ with data. J Trauma. 2007; 63(2):291Y297; discussion 297Y279. 6. Oyetunji TA, Chang DC, Crompton JG, Greene WR, Efron DT, Haut ER, Cornwell EE, Haider AH. Redefining hypotension in the elderly: normotension is not reassuring. Arch Surg. 2011;146(7):865Y869. 7. Summers RL, Ward KR, Witten T, Convertino VA, Ryan KL, Coleman TG, Hester RL. Validation of a computational platform for the analysis of the physiologic mechanisms of a human experimental model of hemorrhage. Resuscitation. 2009;80(12):1405Y1410.
8. Cancio LC, Batchinsky AI, Salinas J, Kuusela T, Convertino VA, Wade CE, Holcomb JB. Heart-rate complexity for prediction of prehospital lifesaving interventions in trauma patients. J Trauma. 2008;65(4):813Y819. 9. Rady MY, Smithline HA, Blake H, Nowak R, Rivers E. A comparison of the shock index and conventional vital signs to identify acute, critical illness in the emergency department. Ann Emerg Med. 1994;24(4):685Y690. 10. Rady MY, Nightingale P, Little RA, Edwards JD. Shock index: a reevaluation in acute circulatory failure. Resuscitation. 1992;23(3):227Y234. 11. Allgo¨wer M, Burri C. [‘‘Shock index’’] [in German]. Dtsch Med Wochenschr. 1967;92(43):1947Y1950. 12. King RW, Plewa MC, Buderer NM, Knotts FB. Shock index as a marker for significant injury in trauma patients. Acad Emerg Med. 1996;3(11): 1041Y1045. 13. Calland JF, Ingraham AM, Martin N, Marshall GT, Schulman CI, Stapleton T, Barraco RD; Eastern Association for the Surgery of Trauma. Evaluation and management of geriatric trauma: an Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012;73(5 Suppl 4):S345YS350. 14. Cannon CM, Braxton CC, Kling-Smith M, Mahnken JD, Carlton E, Moncure M. Utility of the shock index in predicting mortality in traumatically injured patients. J Trauma. 2009;67(6):1426Y1430. 15. McNab A, Burns B, Bhullar I, Chesire D, Kerwin A. An analysis of shock index as a correlate for outcomes in trauma by age group. Surgery. 2013; 154(2):384Y387. 16. Vandromme MJ, Griffin RL, Kerby JD, McGwin G. Jr, Rue LW. III, Weinberg JA. Identifying risk for massive transfusion in the relatively normotensive patient: utility of the prehospital shock index. J Trauma Acute Care. 2011;70:384Y390. 17. Zarzaur BL, Croce MA, Magnotti LJ, Fabian TC. Identifying lifethreatening shock in the older injured patient: an analysis of the National Trauma Data Bank. J Trauma. 2010;68(5):1134Y1138. 18. Hashmi A, Ibrahim-Zada I, Rhee P, et al. Predictors of mortality in geriatric trauma patients: A systematic review and meta-analysis. [Accepted for publication in The journal of trauma and acute care surgery 2014]. 19. Allgo¨wer M, Burri C. Shock-index. Ger Med Mon. 1968;13(1):14Y19. 20. Birkhahn RH, Gaeta TJ, Terry D, Bove JJ, Tloczkowski J. Shock index in diagnosing early acute hypovolemia. Am J Emerg Med. 2005;23(3): 323Y326. 21. Birkhahn RH, Gaeta TJ, Van Deusen SK, Tloczkowski J. The ability of traditional vital signs and shock index to identify ruptured ectopic pregnancy. Am J Obstet Gynecol. 2003;189(5):1293Y1296. 22. Rady MY, Rivers EP, Nowak RM. Resuscitation of the critically ill in the ED: responses of blood pressure, heart rate, shock index, central venous oxygen saturation, and lactate. Am J Emerg Med. 1996;14(2):218Y225.
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Shock index predicts mortality in geriatric trauma patients: An analysis of the National Trauma Data Bank Viraj Pandit, MD, Peter Rhee, MD, Ammar Hashmi, MD, Narong Kulvatunyou, MD, Andrew Tang, MD, Mazhar Khalil, MD, Terence O’Keeffe, MbChB, Donald Green, MD, Randall S. Friese, MD, and Bellal Joseph, MD Heart rate and systolic blood pressure are unreliable in geriatric trauma patients. Shock index (SI) (heart rate/systolic blood pressure) is a simple marker of worse outcomes after injury. The aim of this study was to assess the utility of SI in predicting outcomes. We hypothesized that SI predicts mortality in geriatric trauma patients. METHODS: We performed a 4-year (2007Y2010) retrospective analysis using the National Trauma Data Bank. Patients 65 years or older were included. Transferred patients, patients dead on arrival, missing vitals on presentation, and patients with burns and traumatic brain injury were excluded. A cutoff value of SI greater than or equal to 1 (sensitivity, 81%; specificity, 79%) was used to define hemodynamic instability. The primary outcome measure was mortality. Secondary outcome measures were need for blood transfusion, need for exploratory laparotomy, and development of in-hospital complications. Multiple logistic regressions were performed. RESULTS: A total of 485,595 geriatric patients were reviewed, of whom 217,190 were included. The mean (SD) age was 77.7 (7.1) years, 60% were males, median Glasgow Coma Scale (GCS) score was 14 (range, 3Y15), median Injury Severity Score (ISS) was 9 (range, 4Y18), and mean (SD) SI was 0.58 (0.18). Three percent (n = 6,585) had an SI greater than or equal to 1. Patients with SI greater than or equal to 1 were more likely to require blood product requirement ( p = 0.001), require an exploratory laparotomy ( p = 0.01), and have in-hospital complications ( p = 0.02). The overall mortality rate was 4.1% (n = 8,952). SI greater than or equal to 1 was the strongest predictor for mortality (odds ratio, 3.1; 95% confidence interval, 2.6Y3.3; p = 0.001) in geriatric trauma patients. Systolic blood pressure ( p = 0.09) and heart rate ( p = 0.2) were not predictive of mortality. CONCLUSION: SI is an accurate and specific predictor of morbidity and mortality in geriatric trauma patients. SI is superior to heart rate and systolic blood pressure for predicting mortality in geriatric trauma patients. Geriatric trauma patients with SI greater than or equal to 1 should be transferred to a Level 1 trauma center. (J Trauma Acute Care Surg. 2014;76: 1111Y1115. Copyright * 2014 by Lippincott Williams & Wilkins) LEVEL OF EVIDENCE: Prognostic/epidemiologic study, level III. KEY WORDS: Geriatric; shock index; vitals on presentation; mortality; blood transfusion. BACKGROUND:
T
rauma is one of the leading causes of death among geriatric (age Q 65 years) individuals.1 Assessment of injury severity and hemodynamic instability in geriatric patients is often difficult owing to their altered response to injury.1,2 The low physiologic capacity in these patients masks the clinical exacerbation of injury, which makes management of these patients challenging.3 Traditional vital signs such as systolic blood pressure (SBP) and heart rate (HR) are routinely used for the assessment of trauma patients.4,5 Numerous cutoff points based on blood pressure and HR have been defined as threshold for transferring patients to a Level 1 trauma center.6 Complex laboratory tests using specialized equipment have also been implicated for early identification of patients at a higher risk of death from
Submitted: October 24, 2013, Revised: December 2, 2013, Accepted: November 29, 2013. From the Division of Trauma, Critical Care, Emergency Surgery, and Burns, Department of Surgery, University of Arizona, Tucson, Arizona. Supplemental digital content is available for this article. Direct URL citations appear in the printed text, and links to the digital files are provided in the HTML text of this article on the journal’s Web site (www.jtrauma.com). Address for reprints: Bellal Joseph, MD, Division of Trauma, Critical Care, And Emergency Surgery, Department of Surgery, University of Arizona, 1501 N Campbell Ave, Room 5411, PO Box 245063, Tucson, AZ 85724; email: [email protected]. DOI: 10.1097/TA.0000000000000160
hemorrhagic shock; however, such resources may not always be available in the field or the emergency department.7 In addition, the applicability, reliability, and cost-effectiveness of these parameters to identify hemodynamic instability in geriatric trauma patients remain unclear.8 Shock index (SI) is a simple ratio of HR over SBP, which can be easily calculated in the field.9 SI has been shown to be an accurate indicator of hemodynamic instability and need for blood transfusion in trauma patients;10 however, the role of SI as an assessment tool in geriatric trauma patients is not well defined. The aim of this study was to identify the utility of SI in predicting outcomes in geriatric trauma patients. We hypothesized that SI is a predictor of mortality in geriatric trauma patients.
PATIENTS AND METHODS We performed a 4-year (2007Y2010) retrospective analysis using the National Trauma Data Bank (NTDB), version 7.2. The NTDB is the largest collection of trauma index cases, which is maintained by the American College of Surgeons (Chicago, IL). The NTDB contains more than 1.8 million patients, which are contributed by more than 900 trauma centers across the United States. Patients older than 65 years were included. Patients
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transferred from another institutions; patients dead on presentation; patients with burn injuries, isolated traumatic brain injury (head Abbreviated Injury Scale [AIS] score Q 3 and other body regions AIS score G 3), or recorded comorbidity of hypertension; and patients with missing data on vital parameters (HR or SBP) were excluded from our study. We abstracted the following data points from the NTDB database: demographics (age, sex, race, and ethnicity), vitals on presentation (HR, SBP, respiratory rate, and temperature), mechanism of injury (blunt and penetrating), Glasgow Coma Scale (GCS) score on presentation, requirement of blood transfusion, operative intervention, hospital and intensive care unit lengths of stay, in-hospital complications, and in-hospital mortality. Patient’s injury characteristics were abstracted using the Injury Severity Score (ISS) and the AIS score. SI was calculated in each patient based on the ratio of HR and SBP. Hemodynamic instability was defined by an SI greater than or equal to 1.11,12 Patients were stratified into two groups based on their hemodynamic instability: patients with SI greater than or equal to 1 and patients with SI less than 1. Our primary outcome measure was in-hospital mortality. The secondary outcome measures were blood transfusion requirement, need for exploratory laparotomy, and in-hospital complications. We defined blood transfusion requirement as transfusion of packed red blood cells, whole blood, blood plasma, and human fibrinogen. Blood transfusions (P Code, 964.7) and need for exploratory laparotomy (P Code, 54.11) were abstracted from the NTDB using the DRG International Classification of DiseasesV9th Rev. procedure codes. In-hospital complications are defined as infectious complications (sepsis, pneumonia, and urinary tract infections) or hematologic complications (deep venous thrombosis and disseminated intravascular coagulation). Data are reported as mean (SD) for continuous variables, median (range) for ordinal variables, and as proportions for categorical variables. We performed Mann-Whitney U-test and Student’s t test to explore for differences in the two groups (SI 9 1 and SI G 1) for continuous variables. We used W2 test for identifying differences between patients with SI greater than or equal to 1 and SI less than 1 for categorical variables. Univariate analysis was performed to assess factors predicting mortality in geriatric trauma patients. Factors with p e 0.2 on univariate analysis were used in a multivariate regression analysis. p G 0.05 on multivariate regression analysis was considered statistically significant. All statistical analyses were performed using SPSS version 20 (SPSS, Inc., Chicago, IL).
RESULTS A total of 485,595 geriatric trauma patients were identified, of whom 217,190 patients were included. Figure 1 (Supplemental Digital Content 1, at http://links.lww.com/TA/A394) demonstrates the algorithm for patient selection. The mean (SD) age was 77.7 (51.1) years, 60% were males, median GCS score was 14 (range, 13Y15), median ISS was 9 (range, 4Y18), and the mean (SD) SI 0.58 (0.18). Three percent of the patients (n = 6,585) were hemodynamically unstable on presentation. Patients with SI greater than or equal to 1 were likely to be hypotensive ( p = 0.001) and tachycardiac ( p = 0.001) on presentation, with severe injury 1112
( p = 0.001) compared with patients with SI less than 1. Table 1 demonstrates the demographics of the study population. Patients with SI greater than or equal to 1 were more likely to receive blood transfusion ( p = 0.001), require an exploratory laparotomy ( p = 0.01), and develop in-hospital complications ( p = 0.02). The overall mortality rate was 4.1% (n = 8,905). Patients with SI greater than or equal to 1 ( p = 0.001) had a higher mortality rate compared with patients with SI less than 1. Table 2 demonstrates the outcomes between the patients with SI greater than or equal to 1 and patients with SI less than 1. On univariate analysis, age ( p = 0.01), male sex ( p = 0.04), emergency department (ED) SBP ( p = 0.01), ED HR ( p = 0.01), ISS ( p = 0.02), blunt injury ( p = 0.04), and SI greater than 1 ( p = 0.001) were associated with mortality. After adjusting for factors associated with mortality in a multivariate regression analysis, SI greater than or equal to 1 was the strongest predictor for mortality (odds ratio [OR], 3.1; 95% confidence interval [CI], 2.6Y3.3). SBP (OR, 1.1; 95% CI, 0.8Y1.3) and HR (OR, 1.1; 95% CI, 0.9Y1.3) were not predictive of mortality in geriatric trauma patients. Table 3 demonstrates the univariate and multivariate regression analysis for factors associated with mortality in geriatric trauma patients. On subanalysis of patients based on blunt and penetrating injury, SI greater than 1 was an independent predictor of mortality in patients with blunt injury and patients with
TABLE 1. Demographics Variables Demographics Age, mean (SD), y 65Y74 y, % (n) 75Y84 y, % (n) 985 y, % (n) Males, % (n) Race, % (n) White Black Hispanics Physiologic parameters ED SBP, mean (SD) Hypotensive (SBP G 110), % (n) ED HR, mean (SD) Tachycardia (HR 9 100), % (n) ED temperature, mean (SD) SI, mean (SD) Injury severity Mechanism of injury Blunt, % (n) Penetrating, % (n) ISS, median (interquartile range) ISS Q 16, % (n) GCS score, median (interquartile range) GCS score e 8, % (n)
SI Q 1
SI G 1
(n = 6,585)
(n = 210,605)
p
77.8 (51) 34.4 (2,265) 43.5 (2,864) 22.1 (1,456) 65.8 (4,333)
76 (51.1) 39.5 (83,189) 45.4 (95,615) 15.1 (31,801) 61.2 (128,890)
0.09 0.4 0.1 0.09 0.1
82.9 (5,459) 5.3 (349) 4 (263)
80.4 (169,326) 6.4 (13,479) 5.2 (10,951)
0.4 0.6 0.9
95.6 (21.6) 78.3 (4,794)
138.8 (27.9) 7.9 (16,637)
0.01 0.001
113.1 (23.8) 72.8 (4,794)
81.9 (16) 14.1 (29,695)
0.01 0.001
37.6 (0.08) 1.21 (0.25)
37.5 (0.04) 0.56 (0.14)
0.5 0.001
62 (4,083) 32.5 (2,142) 13 (9Y24) 33.9 (2,232) 15(3Y15)
59.8 (125,942) 33.1 (69,710) 10 (8Y18) 13.8 (2,906) 15 (3Y15)
0.04 0.09 0.01 0.001 0.5
12.2 (803)
11.9 (25,062)
0.7
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TABLE 2. Comparison in Outcomes in Patients Variables Blood transfusion, % (n) Exploratory laparotomy, % (n) In-hospital complications Length of stay, mean (SD) Hospital length of stay ICU length of stay Ventilator days Mortality, % (n)
SI 9 1
SI G 1
(n = 6,585)
(n = 210,605)
TABLE 4. Multivariate Logistic Regression for Mortality Stratified by Mechanism of Injury
17.3 (927) 6 (395) 13.6 (896)
9.3 (15,053) 2.3 (4,843) 9.2 (19,376)
G0.001 0.01 0.02
9.2 (7.1) 7.3 (5.9) 4.4 (2.6) 19.2 (1,133)
6.4 (4.8) 5.1 (4.4) 3.1 (2.3) 4.1 (7,819)
0.02 0.03 0.08 G0.001
penetrating injury. Table 4 highlights the subanalysis for factors associated with mortality in patients with blunt and penetrating injuries. After stratifying patients into three groups based on age (65Y74 years, 75Y84 years, and 985 years), SI still remained an independent predictor for mortality in geriatric trauma patients. Table 5 demonstrates the subanalysis for factors associated with mortality based on each age group. Table 6 demonstrates the subanalysis for factors associated with mortality based on ISS. SI greater than 1 remained an independent predictor of mortality after stratifying patients into groups based on injury severity. SI greater than or equal to 1 has 97% specificity and 85% accuracy to predict mortality in geriatric trauma patients. The sensitivity was 45%, positive predictive value was 82%, and negative predictive value was 67% to predict mortality in geriatric trauma patients.
DISCUSSION Guidelines based on clinical parameters for defining acute resuscitation in geriatric trauma patients remain unclear.13 TABLE 3. Univariate and Multivariate Analyses of Factors Predicting Mortality Variables Age, y 75Y84 985 Male White Hispanic ED SBP ED HR ED temperature SI 9 1 GCS score 9Y12 G8 Blunt mechanism ISS 19Y15 16Y24 925
Blunt Injury
p
OR (95% CI)
p
OR (95% CI)
p
1.62 (1.52Y1.73) 1.14 (1.1Y1.2) 2.1 (2Y2.2) 1.6 (0.9Y1.8) 1.1 (0.7Y2.1) 1.5 (1.1Y2.3) 1.2 (1.05Y2.6) 1.2 (0.8Y1.6) 3.8 (1.6Y4.6)
0.01 0.01 0.04 0.3 0.9 0.01 0.01 0.6 0.001
1.3 (1.52Y1.73) 1.2 (1.1Y1.2) 1.2 (2Y2.2) V V 1.15 (1.1Y2.3) 1.1 (1.05Y2.6) V 3.1 (2.6Y3.3)
0.04 0.02 0.3 V V 0.09 0.2 V 0.001
1.8 (1.2Y2.6) 2.3 (1.9Y2.8) 1.4 (1.05Y1.9)
0.04 0.02 0.04
1.8 (0.9Y3.1) 1.6 (0.5Y2.4) 1.2 (0.9Y2.8)
0.2 0.09 0.1
2.1 (1.4Y3.1) 2.8 (1.9Y4.6) 3.6 (2.2Y5.1)
0.04 0.02 0.02
1.6 (0.6Y2.9) 2.6 (2.1Y4.1) 3.8 (2.1Y5.6)
0.2 0.01 0.001
SI 9 1 Age 75Y84 y 985 y Male SBP HR GCS score 9Y12 G8 ISS 9Y15 16Y24 925
Penetrating Injury
OR (95% CI)
p
OR (95% CI)
p
3.1 (1.6Y7.1)
0.01
2.4 (1.7Y5.8)
0.01
1.09 (0.8Y1.9) 1.1 (1.06Y2.7) 1.06 (0.9Y1.5) 1.3 (0.92Y1.8) 1.2 (0.8Y2.5)
0.2 0.04 0.5 0.08 0.1
1.08 (1.02Y2.4) 1.06 (0.99Y2.1) 1.1 (0.9Y1.9) 1.5 (0.98Y4.5) 1.07 (0.6Y3.2)
0.04 0.09 0.4 0.09 0.6
1.09 (0.7Y2.2) 1.15 (0.85Y1.6)
0.7 0.4
1.2 (0.6Y1.9) 1.4 (0.8Y3.2)
0.3 0.6
1.2 (0.95Y2.1) 1.5 (1.3Y3.8) 2.1 (1.1Y5.1)
0.1 0.04 0.03
1.1 (0.98Y1.9) 1.7 (1.3Y5.8) 2 (1.2Y6.1)
0.09 0.01 0.01
This study demonstrates that SI is a vital tool for the identification of hemodynamic instability in geriatric trauma patients. Patients with SI greater than or equal to 1 have higher mortality rate, blood transfusion requirement, and exploratory laparotomy rates compared with patients with SI less than 1. Moreover, traditional vital parameters such as HR and SBP are not associated with mortality. As guidelines for managing geriatric trauma patients continue to be redefined, SI can be a useful clinical tool to predict the risk of mortality and guide therapeutic management in geriatric trauma patients. Geriatric patients form a special cohort of trauma patients owing to their low physiologic reserve and altered response to injury.3 Vital signs are an inaccurate measurement of hemodynamic instability in these patients, resulting in undertriage and adverse outcomes.4,5 The Eastern Association for the Surgery of Trauma has emphasized on the establishment of a predictive model to facilitate the management decisions in geriatric trauma patients.13 The results of our study demonstrate that
TABLE 5. Multivariate Logistic Regression for Mortality Stratified by Age Age 65Y74 y
SI 9 1 Male SBP HR GCS score 9Y12 G8 ISS 9Y15 16Y24 925
Age 9 85 y
Age 75Y84 y
OR (95% CI)
p
OR (95% CI)
3.6 (1.8Y5.4) 1.1 (0.7Y1.8) 1.4 (0.9Y2.9) 1.1 (0.9Y1.9)
0.001 0.4 0.09 0.6
3.2 (2.1Y4.6) 1.3 (0.9Y2.3) 1.6 (0.6Y3.1) 1.1 (0.8Y2.1)
p
OR (95% CI)
p
0.001 2.1 (1.4Y3.9) 0.01 0.2 1.15 (0.9Y2.5) 0.7 0.1 1.2 (0.7Y1.8) 0.4 0.5 1.4 (0.8Y3.2) 0.2
1.1 (0.2Y3.4) 0.5 1.4 (0.9Y2.4) 0.1
1.3 (0.7Y2.6) 0.2 1.8 (0.6Y4.5) 0.4
1.1 (0.9Y2.1) 0.1 1.4 (0.2Y3.6) 0.2
1.1 (0.9Y2.4) 0.1 1.8 (1.2Y2.8) 0.04 2.6 (1.4Y4.5) 0.02
1.5 (1.1Y3.4) 0.04 2.2 (1.5Y4.5) 0.01 3.2 (1.8Y5.2) 0.001
2.4 (1.3Y5.4) 0.01 3.1 (2.5Y8.4) 0.01 4.1 (1.9Y7.2) 0.001
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TABLE 6. Multivariate Logistic Regression for Mortality Stratified by Injury Severity ISS 0Y8
SI 9 1 Age 75Y84 y 9 85 y Male SBP HR GCS score 9Y12 G8
ISS 9Y15 p
OR (95% CI)
p
OR (95% CI)
p
OR (95% CI)
p
1.3 (1.1Y7.2)
0.04
2.4 (1.4Y3.9)
0.01
3.4 (1.7Y6.5)
0.001
3.8 (1.8Y5.1)
0.001
1.15 (0.57Y3.1) 1.07 (0.65Y2.5) 1.06 (0.87Y2.4) 1.2 (0.8Y3.5) 1.04 (0.75Y2.3)
0.9 0.5 0.5 0.4 0.5
1.18 (0.8Y2.5) 1.2 (0.7Y1.7) 1.2 (0.79Y1.8) 1.3 (0.7Y2.1) 1.12 (0.82Y3.6)
0.5 0.3 0.3 0.3 0.2
1.1 (0.8Y2.1) 1.08 (1.05Y2.8) 1.25 (0.6Y3.1) 1.09 (0.91Y2.5) 1.15 (0.9Y2.2)
0.09 0.03 0.2 0.09 0.1
1.05 (1.02Y2.2) 1.18 (1.09Y3.4) 1.1 (0.94Y1.9) 1.1 (1.05Y4.1) 1.2 (0.93Y3.6)
0.01 0.001 0.1 0.03 0.09
1.05 (0.6Y2.5) 1.09 (0.7Y1.8)
0.2 0.4
1.07 (0.8Y1.6) 1.1 (0.8Y2.2)
0.3 0.1
1.1 (0.85Y1.8) 1.2 (0.7Y2.4)
0.1 0.4
1.1 (0.97Y2.4) 1.2 (1.02Y2.9)
0.09 0.04
SI is a simple and accurate tool for predicting hemodynamic instability and subsequent adverse outcomes in geriatric trauma patients. We believe that SI can be used to define resuscitation guidelines. SI is a known predictor of mortality and adverse outcomes in trauma patients.10 Cannon et al.14 and McNab et al.15 demonstrated higher mortality rates in hemodynamically unstable patients defined by SI greater than or equal to 0.9 compared with stable patients. Similarly, Vandromme et al.16 highlighted the significant association between increasing SI and mortality in trauma patients. However, these studies had relatively small sample size and fewer numbers of hemodynamically unstable patients. In addition, all these studies had a heterogeneous population consisting of young and elderly trauma patients. In our study of 210,605 geriatric trauma patients, we found that patients with SI greater than or equal to 1 were four times more likely to die compared with patients with SI less than 1. These results demonstrate that SI can be implemented in geriatric trauma patients with results similar to those of young trauma patients. Studies assessing postinjury mortality in geriatric trauma patients have used a modified SI defined as age SI as a predictor of mortality. Zarzaur et al.17 analyzed the NTDB and concluded that modified SI should be used as a predictor of mortality in older patients. However, old patients were defined by age greater than or equal to 55 years, and there was a minimal difference in the predictive ability of SI and modified SI in these patients. In our study, we assessed the role of simple SI as a predictor of mortality in geriatric (Q65 years) trauma patients. We did not assess modified SI because adding age as another parameter would increase the complexity of calculating SI and prevent its wider applicability. Second, the accurate age of the patients is routinely unknown at the time of injury. Given the minimal difference in the predictive ability between SI and modified SI, we chose to simplify the situation by only assessing the utility of SI alone. Studies assessing mortality in trauma patients have highlighted the role of old age and injury severity as predictors of mortality. We recently a published meta-analysis of factors associated with mortality and demonstrated that increasing age and severity of injury were the only significant factors associated with mortality in geriatric trauma patients.18 We could 1114
ISS 9 25
ISS 16Y24
OR (95% CI)
not evaluate the role of SI in predicting mortality because data assessing the role of SI as a predictor of mortality in geriatric trauma patients were lacking. In the current study, we found that although increasing age and injury severity were associated with mortality, SI was the strongest predictor for mortality in geriatric trauma patients. Even after stratifying patients based on age and injury severity, SI remained a significant predictor of mortality. As injury severity cannot be assessed in the field, we think that SI can be a reliable tool for guiding the resuscitation of geriatric trauma patients. SI has been widely reported as a more sensitive marker of hemodynamic instability compared with traditional vital signs such as HR and SBP.12,19Y21 Birkhahn et al.20 in a prospective study confirmed that SI was a more accurate predictor of acute changes in blood volume compared with both HR and SBP. Similarly, Rady et al.22 also demonstrated SI to be superior to traditional vital signs in predicting intensive therapy after admission in critically ill patients. Our results on SI are in concordance with these previous studies and further validate its utility in predicting the requirement for blood transfusion, need for exploratory laparotomy, and mortality in geriatric trauma patients. Our study should be interpreted in the context of its inherent limitations, being a retrospective analysis. The NTDB is a convenience sample and is not a comprehensive representation of the population and thus may not be generalizable. Moreover, underreporting and limited quality control of data entered into the registry may reflect in the composite data set under study. We were not able to control for the preinjury use of medication such as A-blocker, which is known to affect HR and SBP. However, we did exclude all patients with known comorbidity of hypertension to control for the use of A-blockers. Despite these limitations, our study is the largest study to assess the utility of SI in geriatric trauma patients. SI is a simple and reliable tool for predicting hemodynamic instability by using the already available vitals on presentation and further guiding the management in geriatric trauma patients.
CONCLUSION SI, which is a simple ratio of HR and blood pressure, is an accurate and specific predictor of morbidity and mortality in * 2014 Lippincott Williams & Wilkins
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J Trauma Acute Care Surg Volume 76, Number 4
Pandit et al.
geriatric trauma patients. It allows accurate assessment of these patients and is an effective tool that can be implemented in a prehospital setting for the triage of geriatric trauma patients. SI is superior to HR and SBP for predicting mortality in geriatric trauma patients. Geriatric trauma patients with SI greater than or equal to 1 should be transferred to a Level 1 trauma center. AUTHORSHIP V.P., P.R., N.K., R.S.F., and B.J. designed this study. V.P., A.H., M.K., A.T., D.G., R.S.F., and B.J. searched the literature. V.P., A.H., N.K., M.K., T.O., and B.J. collected the data. V.P., A.H., N.K., T.O., R.S.F., and P.R. analyzed the data. All other authors participated in data interpretation and manuscript preparation.
DISCLOSURE The authors declare no conflicts of interest.
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