- Email: [email protected]
Validating the ATLS Shock Classification for Predicting Death, Transfusion, or Urgent Intervention
j o u r n a l o f s u r g i c a l r e s e a r c h j a n u a r y 2 0 2 0 ( 2 4 5 ) 1 6 3 e1 6 7
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.JournalofSurgicalResearch.com
Association for Academic Surgery
Validating the ATLS Shock Classification for Predicting Death, Transfusion, or Urgent Intervention Jonathan Parks, MD,a,* Georgia Vasileiou, MD,a Joshua Parreco, MD,a Gerd D. Pust, MD,a Rishi Rattan, MD,a Tanya Zakrison, MD,b Nicholas Namias, MD, MBA,a and D. Dante Yeh, MDa a b
Ryder Trauma Center, University of Miami, Miami, Florida The University of Chicago Medicine, Section for Trauma and Acute Care Surgery, Chicago, Illinois
article info
abstract
Article history:
Background: The Advanced Trauma Life Support (ATLS) shock classification has been
Received 1 March 2019
accepted as the conceptual framework for clinicians caring for trauma patients. We sought
Received in revised form
to validate its ability to predict mortality, blood transfusion, and urgent intervention.
19 June 2019
Materials and methods: We performed a retrospective review of trauma patients using the
Accepted 16 July 2019
2014 National Trauma Data Bank. Using initial vital signs data, patients were categorized
Available online xxx
into shock class based on the ATLS program. Rates for urgent blood transfusion, urgent operative intervention, and mortality were compared between classes. Results: 630,635 subjects were included for analysis. Classes 1, 2, 3, and 4 included 312,404, 17,133, 31, and 43 patients, respectively. 300,754 patients did not meet criteria for any ATLS shock class. Of the patients in class 1 shock, 2653 died (0.9%), 3123 (1.0%) were transfused blood products, and 7115 (2.3%) underwent an urgent procedure. In class 2, 219 (1.3%) died, 387 (2.3%) were transfused, and 1575 (9.2%) underwent intervention. In class 3, 7 (22.6%) died, 10 (32.3%) were transfused, and 13 (41.9%) underwent intervention. In class 4, 15 (34.9%) died, 19 (44.2%) were transfused, and 23 (53.5%) underwent intervention. For uncategorized patients, 21,356 (7.1%) died, 15,168 (5.0%) were transfused, and 23,844 (7.9%) underwent intervention. Conclusions: Almost half of trauma patients do not meet criteria for any ATLS shock class. Uncategorized patients had a higher mortality (7.1%) than patients in classes 1 and 2 (0.9% and 1.3%, respectively). Classes 3 and 4 only accounted for 0.005% and 0.007%, respectively, of patients. The ATLS classification system does not help identify many patients in severe shock. ª 2019 Elsevier Inc. All rights reserved.
* Corresponding author. Division of Trauma, Emergency Surgery and Surgical Critical Care, Harvard Medical School, 165 Cambridge Street, Suite 810, Boston, MA 02114. Tel: þ1 6176432714; fax: þ1 6176432927. E-mail address: [email protected] (J. Parks). 0022-4804/$ e see front matter ª 2019 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jss.2019.07.041
164
j o u r n a l o f s u r g i c a l r e s e a r c h j a n u a r y 2 0 2 0 ( 2 4 5 ) 1 6 3 e1 6 7
Introduction Hemorrhage is the leading cause of preventable death in trauma patients.1 The identification and early treatment of trauma patients who are in hemorrhagic shock depends on many factors, including mechanism, reports from Emergency Medical Services and law enforcement, testimony from the patient and witnesses if available, and the physical examination. The most important aspect of the initial evaluation is the patient’s vital signs, combined with classic signs and symptoms of severe shock, including mental status, pallor, and diaphoresis.2,3 The Advanced Trauma Life Support (ATLS) program of the American College of Surgeons Committee on Trauma details an algorithmic approach to the initial management of the trauma patient. This program has been accepted internationally as the de facto conceptual framework for most clinicians caring for trauma patients.4 The 9th edition of ATLS classifies shock into four classes of severity based on the patient’s vital signs combined with symptoms of shock, such as mental status changes. A simplified table of the definitions for each class is shown in Table 1.4 Depending on shock class, ATLS then makes treatment recommendations; for example, patients in classes 1 and 2 should be given intravenous crystalloid, whereas patients in classes 3 and 4 should instead be transfused blood products.4 Although the ATLS shock classification system is used primarily as an educational tool, the definitions for ATLS shock class are not evidence based, and the thresholds for each category are somewhat arbitrary.5 In addition, other factors frequently affect the presenting vital signs, including concomitant traumatic brain injury or spinal cord injury, medication or illicit drug use, medical history, and so forth.2,6 Trauma practitioners consider these variables in practice, and among surveyed practitioners, only approximately 10% considered ATLS shock classification a valuable guide for evaluation and management of patients in hemorrhagic shock.6 We hypothesized that the ATLS shock classification is a poor predictor of actual clinical status and outcomes. We sought to validate its usefulness and ability to predict mortality, blood transfusion, and urgent intervention.
Material and methods We performed a retrospective review using the 2014 National Trauma Data Bank (NTDB). The NTDB is supported by the American College of Surgeons and collects detailed data from over 900 trauma centers in the United States.7 The Institutional Review Board of the University of Miami waived the requirement for approval of this study because the NTDB contains deidentified, publicly available data and is not considered human subjects research. Entries were queried for age, sex, presenting vital signs (heart rate [HR], systolic blood pressure [SBP], respiratory rate [RR]) in the emergency department, presenting Glasgow Coma Scale (GCS), and discharge disposition. Patients younger than 18 y, as well as patients with missing values for any of these
variables, were excluded from the analysis. Patients were also excluded if they were transferred to another hospital as final disposition was ultimately unknown. Patients were then classified by ATLS 9th edition shock class according to the values in Table 1. It was necessary to interpret some of the descriptions in Table 1. An SBP “decrease” was taken to indicate values from 90 to 110 mmHg. “Greatly decreased” was taken to indicate values less than 90 mmHg. NTDB does not collect information on “anxiety,” thus anxious was taken as a GCS of 15. Confusion would be indicative of a score of 4 in the GCS verbal component, so “anxious/confused” was interpreted as a GCS of 14. Lethargy indicates decreased score in the eye component of the GCS so “confused/lethargic” was interpreted as a GCS of 13 or less. Similar interpretations were used by Guly et al.5 and Mutschler et al.8 Patients were only included in a classification group if all variables met the definition for the group. Patients who did not fit the definition for any shock classification were classified as “uncategorized.” Outcomes for mortality, urgent intervention, and urgent blood transfusion were then determined for each record. Mortality was defined as in-hospital and determined if hospital or emergency department disposition for the patient was classified as deceased/expired. Urgent intervention was defined as laparotomy, thoracotomy, or embolization procedure within 24 h of admission. Urgent blood transfusion was defined as transfusion of any blood products within 4 h of admission. Median age, sex distribution, and Injury Severity Score were calculated for each group. Median values for vital signs and GCS were reported to validate proper classification of patients into appropriate ATLS shock class. Rates for each outcome were then compared between shock classes. Analysis was performed using RStudio (RStudio 2016, Boston, MA).9
Results After exclusions, 630,635 subjects were included for analysis. Classes 1, 2, 3, and 4 included 312,404 (49.6%), 17,133 (2.7%), 31 (0.005%), and 43 (0.007%) patients, respectively. A total of 300,754 (47.7%) patients did not meet the criteria for any shock class per the ATLS paradigm and were not categorized. Demographic data are shown in Table 2. Of the patients in class 1 shock, 2653 died (0.9%), 3123 (1.0%) were urgently transfused blood products, and 7115 (2.3%) underwent an urgent operative procedure. In class 2, 219 (1.3%) died, 387 (2.3%) were transfused, and 1575 (9.2%) underwent operative intervention. In class 3, 7 (22.6%) died, 10 (32.3%) were transfused, and 13 (41.9%) underwent operative intervention. In class 4, 15 (34.9%) died, 19 (44.2%) were transfused, and 23 (53.5%) underwent operative intervention. For the uncategorized patients, 21,356 (7.1%) died, 15,168 (5.0%) were transfused, and 23,844 (7.9%) underwent operative intervention. Results are shown in Table 3.
Discussion The results of this analysis of over 630,000 trauma patients demonstrates that the shock classification scheme defined by
165
parks et al validating atls shock class
Table 1 e ATLS shock classification (9th edition). Parameter
Class 1
Class 2
Class 3
Class 4
Blood loss (mL)
<750
750-1500
1500-2000
>2000
Blood loss (% volume)
<15
15-30
30-40
>40
<100
100-120
120-140
>140
Normal
Normal
Decreased
Greatly decreased
Heart rate Systolic blood pressure
14-20
20-30
30-40
>35
Slightly anxious
Mildly anxious
Anxious, confused
Confused, lethargic
Respiratory rate Mental status
ATLS 9th edition did not help identify almost half of patients in severe shock nor did it correlate with the clinical outcomes of mortality, urgent procedure, or urgent transfusion. However, for those patients who did fall into the defined class 1 through 4 categories, there was a stepwise increase in urgent transfusion, need for procedure, and mortality, thus validating the construct for a subset of trauma patients. Although patients in ATLS shock classes 3 and 4 had higher rates for mortality, urgent transfusion, and emergency procedures, the number of patients that fits the definition of classes 3 and 4 shock was low, accounting for only 0.01% of all patients. Furthermore, nearly half of all patients (47.7%) were uncategorizable by the ATLS definitions. This uncategorized group had a much higher mortality rate and urgent transfusion rate than both classes 1 and 2, as well as a higher rate of urgent intervention than class 1. This shows that a large number of hemodynamically compromised patients are not captured by the classification scheme. These results demonstrate poor predictive validity for the classification system, as it fails to accurately predict outcomes for a large proportion of patients. Moreover, the ATLS shock definitions lack content validity; that is, the included variables are not sufficient to accurately diagnose hemorrhagic shock or measure actual shock severity in a stepwise fashion. To be clinically useful, the categories should include all patients with shock and also be mutually exclusive, as in the American Association for the Surgery of Trauma Organ Injury scale or the American Joint Committee on Cancer TNM cancer staging system. Several confounders affect hemodynamics, that is, presence of traumatic brain injury or spinal cord injury,
medication or illicit drug use, and the medical history, and so forth. In addition, we know that the compensatory response to hemorrhagic shock is variable in different cohorts of patients, that is, the elderly, athletes, and in pregnancy.2 There may be other factors or clinical signs that should play a greater role in the evaluation of hemorrhagic shock. Considerations about change from baseline for the individual could provide more insight but present a challenge when evaluating a patient with altered mental status in the acute setting. Other measures, such as shock index (HR/SBP), base deficit, or serum lactate level may prove useful in predicting severity of shock and poor outcomes or intervention.10-13 Further analysis may provide insight into what factors should be emphasized. In 2010, Guly et al. performed an analysis of the shock classification from the 8th edition of ATLS. Their study included 107,649 adult trauma patients treated at trauma centers in England and Wales from 1989 to 2007 who were reported to the Trauma Audit and Research Network database. They categorized patients into ATLS shock class by individual vital sign rather than for all vital sign targets as in our analysis. When considering each vital sign, they demonstrated that absence of tachycardia did not rule out hemorrhagic shock. They went on to note that severe hemorrhagic shock can be associated with bradycardia. They concluded that in trauma patients there is an interrelationship between derangements of HR, SBP, RR, and GCS but not to the same degree as that suggested by the ATLS classification of shock.5 In 2013, Mutschler et al. analyzed records from the TraumaRegister DGU of the German Society for Trauma Surgery to perform a similar analysis on German adult trauma patients from 2002 to 2010. Again they used definitions from ATLS 8th
Table 2 e Characteristics by shock class. Parameter
Class 1
Class 2
No. of patients
Class 3
Class 4
Uncategorized 300,754
312,404
17,133
31
43
% of Total
49.6
2.7
0.005
0.007
47.7
% Male
60.4
64.7
51.6
62.8
65.2
Median age
55 (38-72)
40 (25-55)
43 (27-59)
34 (23-45)
47 (30-65)
Median HR
80 (72-89)
107 (103-112)
127 (122-132)
152 (144-160)
96 (81-111)
Median SBP
141 (127-155)
141 (128-155)
98 (93-103)
77 (65-90)
134 (117-151)
Median RR
18 (17-19)
23 (22-25)
33 (31-36)
41 (38-44)
18 (15-21)
Median GCS
15
15
14
10 (6-13)
15 (14-15)
Median ISS
5 (4-10)
8 (4-13)
18 (13-25)
22 (9-34)
9 (4-16)
166
j o u r n a l o f s u r g i c a l r e s e a r c h j a n u a r y 2 0 2 0 ( 2 4 5 ) 1 6 3 e1 6 7
Table 3 e Mortality, urgent transfusion, and urgent procedure by ATLS shock class. Parameter
Class 1
Class 2
No. of patients
312,404
17,133
31
43
300,754
2653
219
7
15
21,356
No. of deaths Mortality (%) No. of urgent transfusions % of urgent transfusion No. of urgent procedures % of urgent procedure
0.9
Class 3
1.3
7141
618
2.3
3.6
7115
1575
2.3
9.2
edition to classify patients into shock class, using HR, SBP, and GCS. Of the 36,504 patients included in their analysis, only 3411 (9.3%) could be categorized into ATLS shock class by matching the combination of all three parameters. The vast majority of categorizable patients were allocated to class 1 shock (91%, n ¼ 3411), presenting with normal HR, SBP, and GCS. The authors concluded that the ATLS shock classification does not seem to reflect clinical reality accurately.8 In our study, we analyzed over 630,000 patients. We categorized patients similar to the Mutschler group, requiring the combination of HR, SBP, RR, and GCS to match the ATLS shock class definition. We used the updated ATLS 9th edition definitions for our analysis. This resulted in a much larger proportion of categorizable patients but still left almost half uncategorizable. Although both previous studies compared mortality rates and blood transfusion rates between groups, we also analyzed the need for urgent procedure, an important clinical outcome and one in which the initial assessment of the patient is paramount. In concordance with the studies by Guly and Mutschler, our analysis confirms that the ATLS classification system for hemorrhagic shock does not apply to a large proportion of trauma patients and can be misleading if strictly interpreted. In the summer of 2018, the ACS published the 10th edition of the ATLS course. The new program included an updated version of the hemorrhagic shock classification (Table 4), which replaced the vital sign threshold values with arrows to indicate an increase, decrease, or unchanged value.14 The new changes, however, provide no reference value, and it must be assumed that they reflect a change from the patient’s baseline, which is almost never known during the initial evaluation of trauma patient. These new definitions may only add to the confusion about how to grade the severity of hemorrhagic shock for a given patient.
Class 4
22.6
34.9
10
19
32.3
44.2
13
23
41.9
53.5
Uncategorized
7.1 20,887 6.9 23,844 7.9
To be fair, the shock classification system taught in the ATLS program is not only intended for clinical use but also serves an important role in education, providing a framework to understand the physiologic changes that accompany hemorrhagic shock. In addition, the program is not only taught to advanced trauma practitioners but also to students and other health care providers that may not encounter hemorrhagic shock frequently. The point cannot be emphasized enough, although, that a great proportion of patients will not completely fit in any category and a high degree of suspicion should be maintained when evaluating the trauma patient. The question arises of what to do with the large number of uncategorizable patientsdby our analysis, these patients lie between class 2 and class 3 shock in terms of clinically significant outcomes. Perhaps the point that should be considered is that these patients do not fit into class 1 or class 2 shock for a reason, for example, beta-blockade precluding tachycardia. Thus, if a patient is not categorizable by all strict criteria, a higher index of suspicion should be maintained, as this uncategorizable patient has a higher potential for worse outcome than someone who fits into class 1 or 2. Further study is necessary to delineate if this is true or if there are other criteria that may more clearly indicate the direction the patient is heading. Clinical judgment and expertise are needed here as well.
Limitations The limitations of our study must be acknowledged. First, the quality of our analysis is dependent on the quality of data submitted by trauma centers to the NTDB and is subject to several limitations. The registry process at every hospital differs slightly and may result in some variation on how
Table 4 e ATLS shock classification (10th edition). Parameter
Class 1
Class 2
Class 3
Class 4
<15%
15%-30%
30%-40%
>40%
Heart rate
4
4/[
[
[/[[
Blood pressure
4
4
4/Y
Y
Respiratory rate
4
4
4/[
[
Glasgow Coma Scale score
4
4
Y
Y
Approximate blood loss
parks et al validating atls shock class
records are coded. In addition, the NTDB includes a disproportionate number of large trauma centers with younger and more severely injured patients and may not be representative of the population at large. Furthermore, participation in the NTDB is voluntary, and hospitals submitting data have demonstrated a commitment to monitoring and quality improvement that may not be representative of all hospitals treating injured patients. Because our data rely on vital signs at presentation, we believe it is somewhat protected from this bias, as the ATLS shock classification solely depends on the presenting vital signs. Coding variations would affect patients in all groups. Another potential limitation is that our analysis is based on the ATLS ninth edition, which is no longer the most current edition. However, as stated earlier, the ATLS 10th edition replaces the numeric thresholds with arrows pointing up, down, and sideways. Although more reflective of clinical reality and the difficulties of relying on traditional vital signs to diagnose shock, it is impossible to reliably and accurately classify a patient into a discrete shock severity in this updated framework without knowing the patient’s baseline vital signs. Even if this were possible, the NTDB does not include base deficit or lactate, and therefore, we cannot use this data set to validate the ATLS 10th edition shock severity classification. We acknowledge that nearly half of the subjects in the sample fell into the “uncategorized” cohort. Due to limitations of the data set, we are unable to provide more data on the populations to compare the cohorts to one another. Despite these limitations, we have demonstrated a clear deficit in the ability of the ATLS shock classification definitions to determine which patients are critically ill. Hemorrhagic shock is the most common cause of preventable mortality in trauma patients, and further research is needed to identify additional factors that can help in its expedient and accurate identification. This is a critical step in reducing preventable trauma deaths.
Conclusions Although mortality, urgent transfusion, and urgent procedure rates increased as ATLS hemorrhagic shock class severity increased, almost half of all trauma patients do not meet the criteria for any category of shock according to the ATLS. These uncategorized patients had a higher mortality (7.1%) than the patients in shock classes 1 and 2 (0.85% and 1.28%, respectively). In addition, shock classes 3 and 4 each only accounted for 0.005% and 0.007%, respectively, of the categorizable patients. Given these results, the current classification system defined by ATLS does not help the clinician identify many patients in severe hemorrhagic shock.
Acknowledgment Authors’ contributions: J.P., G.V., J.P., G.P., R.R., and D.Y. contributed to the study design. J.P. and D.Y. contributed to
167
the analysis and drafted the manuscript. All authors contributed to the critical review and manuscript revisions.
Disclosure All authors report no conflict of interest or disclosures relevant to this publication.
references
1. Teixeira PGR, Inaba K, Hadjizacharia P, et al. Preventable or potentially preventable mortality at a mature trauma center. J Trauma. 2007;63:1338e1346. discussion 1346-1347. 2. Gutierrez G, Reines HD, Wulf-Gutierrez ME. Clinical review: hemorrhagic shock. Crit Care. 2004;8:373e381. 3. Geeraedts LMG, Kaasjager HaH, van Vugt AB, Fro¨lke JPM. Exsanguination in trauma: a review of diagnostics and treatment options. Injury. 2009;40:11e20. 4. American College of Surgeons, Committee on Trauma. The Advanced Trauma Life Support Student Course Manual. 9th ed. Chicago, IL: American College of Surgeons; 2012. 5. Guly HR, Bouamra O, Little R, et al. Testing the validity of the ATLS classification of hypovolaemic shock. Resuscitation. 2010;81:1142e1147. 6. Mutschler M, Hoffmann M, Wo¨lfl C, et al. Is the ATLS classification of hypovolaemic shock appreciated in daily trauma care? An online-survey among 383 ATLS course directors and instructors. Emerg Med J. 2015;32:134e137. 7. Committee on Trauma, American College of Surgeons. NTDB Version 2014. The content reproduced from the NTDB remains the full and exclusive copyrighted property of the American College of Surgeons. The American College of Surgeons is not responsible for any claims arising from works based on the original data, text, tables, or figures. 2015. Chicago, IL. 8. Mutschler M, Nienaber U, Brockamp T, et al. A critical reappraisal of the ATLS classification of hypovolaemic shock: does it really reflect clinical reality? Resuscitation. 2013;84:309e313. 9. RStudio Team. RStudio; 2016. Boston, MA: Integrated Development for R. RStudio, Inc.; 2016. Available at: http:// www.rstudio.com/. Accessed June 18, 2019. 10. 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;67:1426e1430. 11. Olaussen A, Blackburn T, Mitra B, Fitzgerald M. Review article: shock Index for prediction of critical bleeding posttrauma: a systematic review. Emerg Med Australas. 2014;26:223e228. 12. Davis JW, Shackford SR, Mackersie RC, Hoyt DB. Base deficit as a guide to volume resuscitation. J Trauma. 1988;28:1464e1467. 13. Husain FA, Martin MJ, Mullenix PS, Steele SR, Elliott DC. Serum lactate and base deficit as predictors of mortality and morbidity. Am J Surg. 2003;185:485e491. 14. American College of Surgeons, Committee on Trauma. Advanced Trauma Life Support Student Course Manual. 10th ed. Chicago, IL: American College of Surgeons; 2018.
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.JournalofSurgicalResearch.com
Association for Academic Surgery
Validating the ATLS Shock Classification for Predicting Death, Transfusion, or Urgent Intervention Jonathan Parks, MD,a,* Georgia Vasileiou, MD,a Joshua Parreco, MD,a Gerd D. Pust, MD,a Rishi Rattan, MD,a Tanya Zakrison, MD,b Nicholas Namias, MD, MBA,a and D. Dante Yeh, MDa a b
Ryder Trauma Center, University of Miami, Miami, Florida The University of Chicago Medicine, Section for Trauma and Acute Care Surgery, Chicago, Illinois
article info
abstract
Article history:
Background: The Advanced Trauma Life Support (ATLS) shock classification has been
Received 1 March 2019
accepted as the conceptual framework for clinicians caring for trauma patients. We sought
Received in revised form
to validate its ability to predict mortality, blood transfusion, and urgent intervention.
19 June 2019
Materials and methods: We performed a retrospective review of trauma patients using the
Accepted 16 July 2019
2014 National Trauma Data Bank. Using initial vital signs data, patients were categorized
Available online xxx
into shock class based on the ATLS program. Rates for urgent blood transfusion, urgent operative intervention, and mortality were compared between classes. Results: 630,635 subjects were included for analysis. Classes 1, 2, 3, and 4 included 312,404, 17,133, 31, and 43 patients, respectively. 300,754 patients did not meet criteria for any ATLS shock class. Of the patients in class 1 shock, 2653 died (0.9%), 3123 (1.0%) were transfused blood products, and 7115 (2.3%) underwent an urgent procedure. In class 2, 219 (1.3%) died, 387 (2.3%) were transfused, and 1575 (9.2%) underwent intervention. In class 3, 7 (22.6%) died, 10 (32.3%) were transfused, and 13 (41.9%) underwent intervention. In class 4, 15 (34.9%) died, 19 (44.2%) were transfused, and 23 (53.5%) underwent intervention. For uncategorized patients, 21,356 (7.1%) died, 15,168 (5.0%) were transfused, and 23,844 (7.9%) underwent intervention. Conclusions: Almost half of trauma patients do not meet criteria for any ATLS shock class. Uncategorized patients had a higher mortality (7.1%) than patients in classes 1 and 2 (0.9% and 1.3%, respectively). Classes 3 and 4 only accounted for 0.005% and 0.007%, respectively, of patients. The ATLS classification system does not help identify many patients in severe shock. ª 2019 Elsevier Inc. All rights reserved.
* Corresponding author. Division of Trauma, Emergency Surgery and Surgical Critical Care, Harvard Medical School, 165 Cambridge Street, Suite 810, Boston, MA 02114. Tel: þ1 6176432714; fax: þ1 6176432927. E-mail address: [email protected] (J. Parks). 0022-4804/$ e see front matter ª 2019 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jss.2019.07.041
164
j o u r n a l o f s u r g i c a l r e s e a r c h j a n u a r y 2 0 2 0 ( 2 4 5 ) 1 6 3 e1 6 7
Introduction Hemorrhage is the leading cause of preventable death in trauma patients.1 The identification and early treatment of trauma patients who are in hemorrhagic shock depends on many factors, including mechanism, reports from Emergency Medical Services and law enforcement, testimony from the patient and witnesses if available, and the physical examination. The most important aspect of the initial evaluation is the patient’s vital signs, combined with classic signs and symptoms of severe shock, including mental status, pallor, and diaphoresis.2,3 The Advanced Trauma Life Support (ATLS) program of the American College of Surgeons Committee on Trauma details an algorithmic approach to the initial management of the trauma patient. This program has been accepted internationally as the de facto conceptual framework for most clinicians caring for trauma patients.4 The 9th edition of ATLS classifies shock into four classes of severity based on the patient’s vital signs combined with symptoms of shock, such as mental status changes. A simplified table of the definitions for each class is shown in Table 1.4 Depending on shock class, ATLS then makes treatment recommendations; for example, patients in classes 1 and 2 should be given intravenous crystalloid, whereas patients in classes 3 and 4 should instead be transfused blood products.4 Although the ATLS shock classification system is used primarily as an educational tool, the definitions for ATLS shock class are not evidence based, and the thresholds for each category are somewhat arbitrary.5 In addition, other factors frequently affect the presenting vital signs, including concomitant traumatic brain injury or spinal cord injury, medication or illicit drug use, medical history, and so forth.2,6 Trauma practitioners consider these variables in practice, and among surveyed practitioners, only approximately 10% considered ATLS shock classification a valuable guide for evaluation and management of patients in hemorrhagic shock.6 We hypothesized that the ATLS shock classification is a poor predictor of actual clinical status and outcomes. We sought to validate its usefulness and ability to predict mortality, blood transfusion, and urgent intervention.
Material and methods We performed a retrospective review using the 2014 National Trauma Data Bank (NTDB). The NTDB is supported by the American College of Surgeons and collects detailed data from over 900 trauma centers in the United States.7 The Institutional Review Board of the University of Miami waived the requirement for approval of this study because the NTDB contains deidentified, publicly available data and is not considered human subjects research. Entries were queried for age, sex, presenting vital signs (heart rate [HR], systolic blood pressure [SBP], respiratory rate [RR]) in the emergency department, presenting Glasgow Coma Scale (GCS), and discharge disposition. Patients younger than 18 y, as well as patients with missing values for any of these
variables, were excluded from the analysis. Patients were also excluded if they were transferred to another hospital as final disposition was ultimately unknown. Patients were then classified by ATLS 9th edition shock class according to the values in Table 1. It was necessary to interpret some of the descriptions in Table 1. An SBP “decrease” was taken to indicate values from 90 to 110 mmHg. “Greatly decreased” was taken to indicate values less than 90 mmHg. NTDB does not collect information on “anxiety,” thus anxious was taken as a GCS of 15. Confusion would be indicative of a score of 4 in the GCS verbal component, so “anxious/confused” was interpreted as a GCS of 14. Lethargy indicates decreased score in the eye component of the GCS so “confused/lethargic” was interpreted as a GCS of 13 or less. Similar interpretations were used by Guly et al.5 and Mutschler et al.8 Patients were only included in a classification group if all variables met the definition for the group. Patients who did not fit the definition for any shock classification were classified as “uncategorized.” Outcomes for mortality, urgent intervention, and urgent blood transfusion were then determined for each record. Mortality was defined as in-hospital and determined if hospital or emergency department disposition for the patient was classified as deceased/expired. Urgent intervention was defined as laparotomy, thoracotomy, or embolization procedure within 24 h of admission. Urgent blood transfusion was defined as transfusion of any blood products within 4 h of admission. Median age, sex distribution, and Injury Severity Score were calculated for each group. Median values for vital signs and GCS were reported to validate proper classification of patients into appropriate ATLS shock class. Rates for each outcome were then compared between shock classes. Analysis was performed using RStudio (RStudio 2016, Boston, MA).9
Results After exclusions, 630,635 subjects were included for analysis. Classes 1, 2, 3, and 4 included 312,404 (49.6%), 17,133 (2.7%), 31 (0.005%), and 43 (0.007%) patients, respectively. A total of 300,754 (47.7%) patients did not meet the criteria for any shock class per the ATLS paradigm and were not categorized. Demographic data are shown in Table 2. Of the patients in class 1 shock, 2653 died (0.9%), 3123 (1.0%) were urgently transfused blood products, and 7115 (2.3%) underwent an urgent operative procedure. In class 2, 219 (1.3%) died, 387 (2.3%) were transfused, and 1575 (9.2%) underwent operative intervention. In class 3, 7 (22.6%) died, 10 (32.3%) were transfused, and 13 (41.9%) underwent operative intervention. In class 4, 15 (34.9%) died, 19 (44.2%) were transfused, and 23 (53.5%) underwent operative intervention. For the uncategorized patients, 21,356 (7.1%) died, 15,168 (5.0%) were transfused, and 23,844 (7.9%) underwent operative intervention. Results are shown in Table 3.
Discussion The results of this analysis of over 630,000 trauma patients demonstrates that the shock classification scheme defined by
165
parks et al validating atls shock class
Table 1 e ATLS shock classification (9th edition). Parameter
Class 1
Class 2
Class 3
Class 4
Blood loss (mL)
<750
750-1500
1500-2000
>2000
Blood loss (% volume)
<15
15-30
30-40
>40
<100
100-120
120-140
>140
Normal
Normal
Decreased
Greatly decreased
Heart rate Systolic blood pressure
14-20
20-30
30-40
>35
Slightly anxious
Mildly anxious
Anxious, confused
Confused, lethargic
Respiratory rate Mental status
ATLS 9th edition did not help identify almost half of patients in severe shock nor did it correlate with the clinical outcomes of mortality, urgent procedure, or urgent transfusion. However, for those patients who did fall into the defined class 1 through 4 categories, there was a stepwise increase in urgent transfusion, need for procedure, and mortality, thus validating the construct for a subset of trauma patients. Although patients in ATLS shock classes 3 and 4 had higher rates for mortality, urgent transfusion, and emergency procedures, the number of patients that fits the definition of classes 3 and 4 shock was low, accounting for only 0.01% of all patients. Furthermore, nearly half of all patients (47.7%) were uncategorizable by the ATLS definitions. This uncategorized group had a much higher mortality rate and urgent transfusion rate than both classes 1 and 2, as well as a higher rate of urgent intervention than class 1. This shows that a large number of hemodynamically compromised patients are not captured by the classification scheme. These results demonstrate poor predictive validity for the classification system, as it fails to accurately predict outcomes for a large proportion of patients. Moreover, the ATLS shock definitions lack content validity; that is, the included variables are not sufficient to accurately diagnose hemorrhagic shock or measure actual shock severity in a stepwise fashion. To be clinically useful, the categories should include all patients with shock and also be mutually exclusive, as in the American Association for the Surgery of Trauma Organ Injury scale or the American Joint Committee on Cancer TNM cancer staging system. Several confounders affect hemodynamics, that is, presence of traumatic brain injury or spinal cord injury,
medication or illicit drug use, and the medical history, and so forth. In addition, we know that the compensatory response to hemorrhagic shock is variable in different cohorts of patients, that is, the elderly, athletes, and in pregnancy.2 There may be other factors or clinical signs that should play a greater role in the evaluation of hemorrhagic shock. Considerations about change from baseline for the individual could provide more insight but present a challenge when evaluating a patient with altered mental status in the acute setting. Other measures, such as shock index (HR/SBP), base deficit, or serum lactate level may prove useful in predicting severity of shock and poor outcomes or intervention.10-13 Further analysis may provide insight into what factors should be emphasized. In 2010, Guly et al. performed an analysis of the shock classification from the 8th edition of ATLS. Their study included 107,649 adult trauma patients treated at trauma centers in England and Wales from 1989 to 2007 who were reported to the Trauma Audit and Research Network database. They categorized patients into ATLS shock class by individual vital sign rather than for all vital sign targets as in our analysis. When considering each vital sign, they demonstrated that absence of tachycardia did not rule out hemorrhagic shock. They went on to note that severe hemorrhagic shock can be associated with bradycardia. They concluded that in trauma patients there is an interrelationship between derangements of HR, SBP, RR, and GCS but not to the same degree as that suggested by the ATLS classification of shock.5 In 2013, Mutschler et al. analyzed records from the TraumaRegister DGU of the German Society for Trauma Surgery to perform a similar analysis on German adult trauma patients from 2002 to 2010. Again they used definitions from ATLS 8th
Table 2 e Characteristics by shock class. Parameter
Class 1
Class 2
No. of patients
Class 3
Class 4
Uncategorized 300,754
312,404
17,133
31
43
% of Total
49.6
2.7
0.005
0.007
47.7
% Male
60.4
64.7
51.6
62.8
65.2
Median age
55 (38-72)
40 (25-55)
43 (27-59)
34 (23-45)
47 (30-65)
Median HR
80 (72-89)
107 (103-112)
127 (122-132)
152 (144-160)
96 (81-111)
Median SBP
141 (127-155)
141 (128-155)
98 (93-103)
77 (65-90)
134 (117-151)
Median RR
18 (17-19)
23 (22-25)
33 (31-36)
41 (38-44)
18 (15-21)
Median GCS
15
15
14
10 (6-13)
15 (14-15)
Median ISS
5 (4-10)
8 (4-13)
18 (13-25)
22 (9-34)
9 (4-16)
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j o u r n a l o f s u r g i c a l r e s e a r c h j a n u a r y 2 0 2 0 ( 2 4 5 ) 1 6 3 e1 6 7
Table 3 e Mortality, urgent transfusion, and urgent procedure by ATLS shock class. Parameter
Class 1
Class 2
No. of patients
312,404
17,133
31
43
300,754
2653
219
7
15
21,356
No. of deaths Mortality (%) No. of urgent transfusions % of urgent transfusion No. of urgent procedures % of urgent procedure
0.9
Class 3
1.3
7141
618
2.3
3.6
7115
1575
2.3
9.2
edition to classify patients into shock class, using HR, SBP, and GCS. Of the 36,504 patients included in their analysis, only 3411 (9.3%) could be categorized into ATLS shock class by matching the combination of all three parameters. The vast majority of categorizable patients were allocated to class 1 shock (91%, n ¼ 3411), presenting with normal HR, SBP, and GCS. The authors concluded that the ATLS shock classification does not seem to reflect clinical reality accurately.8 In our study, we analyzed over 630,000 patients. We categorized patients similar to the Mutschler group, requiring the combination of HR, SBP, RR, and GCS to match the ATLS shock class definition. We used the updated ATLS 9th edition definitions for our analysis. This resulted in a much larger proportion of categorizable patients but still left almost half uncategorizable. Although both previous studies compared mortality rates and blood transfusion rates between groups, we also analyzed the need for urgent procedure, an important clinical outcome and one in which the initial assessment of the patient is paramount. In concordance with the studies by Guly and Mutschler, our analysis confirms that the ATLS classification system for hemorrhagic shock does not apply to a large proportion of trauma patients and can be misleading if strictly interpreted. In the summer of 2018, the ACS published the 10th edition of the ATLS course. The new program included an updated version of the hemorrhagic shock classification (Table 4), which replaced the vital sign threshold values with arrows to indicate an increase, decrease, or unchanged value.14 The new changes, however, provide no reference value, and it must be assumed that they reflect a change from the patient’s baseline, which is almost never known during the initial evaluation of trauma patient. These new definitions may only add to the confusion about how to grade the severity of hemorrhagic shock for a given patient.
Class 4
22.6
34.9
10
19
32.3
44.2
13
23
41.9
53.5
Uncategorized
7.1 20,887 6.9 23,844 7.9
To be fair, the shock classification system taught in the ATLS program is not only intended for clinical use but also serves an important role in education, providing a framework to understand the physiologic changes that accompany hemorrhagic shock. In addition, the program is not only taught to advanced trauma practitioners but also to students and other health care providers that may not encounter hemorrhagic shock frequently. The point cannot be emphasized enough, although, that a great proportion of patients will not completely fit in any category and a high degree of suspicion should be maintained when evaluating the trauma patient. The question arises of what to do with the large number of uncategorizable patientsdby our analysis, these patients lie between class 2 and class 3 shock in terms of clinically significant outcomes. Perhaps the point that should be considered is that these patients do not fit into class 1 or class 2 shock for a reason, for example, beta-blockade precluding tachycardia. Thus, if a patient is not categorizable by all strict criteria, a higher index of suspicion should be maintained, as this uncategorizable patient has a higher potential for worse outcome than someone who fits into class 1 or 2. Further study is necessary to delineate if this is true or if there are other criteria that may more clearly indicate the direction the patient is heading. Clinical judgment and expertise are needed here as well.
Limitations The limitations of our study must be acknowledged. First, the quality of our analysis is dependent on the quality of data submitted by trauma centers to the NTDB and is subject to several limitations. The registry process at every hospital differs slightly and may result in some variation on how
Table 4 e ATLS shock classification (10th edition). Parameter
Class 1
Class 2
Class 3
Class 4
<15%
15%-30%
30%-40%
>40%
Heart rate
4
4/[
[
[/[[
Blood pressure
4
4
4/Y
Y
Respiratory rate
4
4
4/[
[
Glasgow Coma Scale score
4
4
Y
Y
Approximate blood loss
parks et al validating atls shock class
records are coded. In addition, the NTDB includes a disproportionate number of large trauma centers with younger and more severely injured patients and may not be representative of the population at large. Furthermore, participation in the NTDB is voluntary, and hospitals submitting data have demonstrated a commitment to monitoring and quality improvement that may not be representative of all hospitals treating injured patients. Because our data rely on vital signs at presentation, we believe it is somewhat protected from this bias, as the ATLS shock classification solely depends on the presenting vital signs. Coding variations would affect patients in all groups. Another potential limitation is that our analysis is based on the ATLS ninth edition, which is no longer the most current edition. However, as stated earlier, the ATLS 10th edition replaces the numeric thresholds with arrows pointing up, down, and sideways. Although more reflective of clinical reality and the difficulties of relying on traditional vital signs to diagnose shock, it is impossible to reliably and accurately classify a patient into a discrete shock severity in this updated framework without knowing the patient’s baseline vital signs. Even if this were possible, the NTDB does not include base deficit or lactate, and therefore, we cannot use this data set to validate the ATLS 10th edition shock severity classification. We acknowledge that nearly half of the subjects in the sample fell into the “uncategorized” cohort. Due to limitations of the data set, we are unable to provide more data on the populations to compare the cohorts to one another. Despite these limitations, we have demonstrated a clear deficit in the ability of the ATLS shock classification definitions to determine which patients are critically ill. Hemorrhagic shock is the most common cause of preventable mortality in trauma patients, and further research is needed to identify additional factors that can help in its expedient and accurate identification. This is a critical step in reducing preventable trauma deaths.
Conclusions Although mortality, urgent transfusion, and urgent procedure rates increased as ATLS hemorrhagic shock class severity increased, almost half of all trauma patients do not meet the criteria for any category of shock according to the ATLS. These uncategorized patients had a higher mortality (7.1%) than the patients in shock classes 1 and 2 (0.85% and 1.28%, respectively). In addition, shock classes 3 and 4 each only accounted for 0.005% and 0.007%, respectively, of the categorizable patients. Given these results, the current classification system defined by ATLS does not help the clinician identify many patients in severe hemorrhagic shock.
Acknowledgment Authors’ contributions: J.P., G.V., J.P., G.P., R.R., and D.Y. contributed to the study design. J.P. and D.Y. contributed to
167
the analysis and drafted the manuscript. All authors contributed to the critical review and manuscript revisions.
Disclosure All authors report no conflict of interest or disclosures relevant to this publication.
references
1. Teixeira PGR, Inaba K, Hadjizacharia P, et al. Preventable or potentially preventable mortality at a mature trauma center. J Trauma. 2007;63:1338e1346. discussion 1346-1347. 2. Gutierrez G, Reines HD, Wulf-Gutierrez ME. Clinical review: hemorrhagic shock. Crit Care. 2004;8:373e381. 3. Geeraedts LMG, Kaasjager HaH, van Vugt AB, Fro¨lke JPM. Exsanguination in trauma: a review of diagnostics and treatment options. Injury. 2009;40:11e20. 4. American College of Surgeons, Committee on Trauma. The Advanced Trauma Life Support Student Course Manual. 9th ed. Chicago, IL: American College of Surgeons; 2012. 5. Guly HR, Bouamra O, Little R, et al. Testing the validity of the ATLS classification of hypovolaemic shock. Resuscitation. 2010;81:1142e1147. 6. Mutschler M, Hoffmann M, Wo¨lfl C, et al. Is the ATLS classification of hypovolaemic shock appreciated in daily trauma care? An online-survey among 383 ATLS course directors and instructors. Emerg Med J. 2015;32:134e137. 7. Committee on Trauma, American College of Surgeons. NTDB Version 2014. The content reproduced from the NTDB remains the full and exclusive copyrighted property of the American College of Surgeons. The American College of Surgeons is not responsible for any claims arising from works based on the original data, text, tables, or figures. 2015. Chicago, IL. 8. Mutschler M, Nienaber U, Brockamp T, et al. A critical reappraisal of the ATLS classification of hypovolaemic shock: does it really reflect clinical reality? Resuscitation. 2013;84:309e313. 9. RStudio Team. RStudio; 2016. Boston, MA: Integrated Development for R. RStudio, Inc.; 2016. Available at: http:// www.rstudio.com/. Accessed June 18, 2019. 10. 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;67:1426e1430. 11. Olaussen A, Blackburn T, Mitra B, Fitzgerald M. Review article: shock Index for prediction of critical bleeding posttrauma: a systematic review. Emerg Med Australas. 2014;26:223e228. 12. Davis JW, Shackford SR, Mackersie RC, Hoyt DB. Base deficit as a guide to volume resuscitation. J Trauma. 1988;28:1464e1467. 13. Husain FA, Martin MJ, Mullenix PS, Steele SR, Elliott DC. Serum lactate and base deficit as predictors of mortality and morbidity. Am J Surg. 2003;185:485e491. 14. American College of Surgeons, Committee on Trauma. Advanced Trauma Life Support Student Course Manual. 10th ed. Chicago, IL: American College of Surgeons; 2018.