A multicenter validation of the prehospital index

ORIGINAL CONTRIBUTION scoring, injury severity; trauma, prehospital index; trauma, severity scoring

A Multicenter Validation of the Prehospital Index The prehospital index (PHI) is a triage-oriented trauma severity scoring system. This prospective multicenter validation of the PHI was undertaken in response to a favorable pilot studyd We applied the PHI to 3,581 patients from 14 different institutions during the period from January 1985 to February I986. The PHI was accurate in predicting the need for emergency lifesaving surgery within four hours (P < .0001) and mortality within 72 hours (P < .0001) following traumatic injury. The curves were generated for PHI versus emergency surgery, mortality, surgery and mortality, injury severity score, and ICU admission rate. These data compare favorably with those from previously published, prospectively tested, triage-oriented trauma severity scoring systems. [Koehler JJ, Malafa SA, Hillesland J, Baer LJ, Rogers RN, Navitskas NR, Briggs D, Simpson D, Roller B, Lilleboe P, Morton T Jr, Meador SA, Harris M, Meindertsma MS, Czarnecki M, Bjerke G: A multicenter validation of the prehospital index. Ann Emerg Med April 1987;16: 380-385.]

John J Koehler, MD~ Stuart A MaJafa, MD~ Jeffrey Hillesland, MD~ Lawrence J Baer, PhD~ Ralph N Rogers, MD 1 Nancy R Navitskas~ Deborah Briggs, CRN2 Donna Simpson, CRN2 Benedict Roller, MD3 Polly Lilleboe, MD4 Terrence Morton, Jr, MD5 Steven A Meador, MD6 Martin Harris, MD7 Michael S Meindertsma 7 Mark Czarnecki, DO8 Greg Bjerke, MD9

INTRODUCTION

From the Department of Emergency Medicine, Butterworth Hospital, Grand Rapids, Michigan;~ Borgess InFlight, Borgess Medical Center, Kalamazoo, Michigan; 2 Department of Emergency Medicine, Dakota Hospital, Fargo, North Dakota;3 Department of Emergency Medicine, Edward W Sparrow Hospital, Lansing, Michigan; '~ Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota;5 Department of Emergency Medicine, Hershey Medical Center, Hershey, Pennsylvania;6 Department of Emergency Medicine, Mt Carmel Hospital, Detroit, Michigan;7 Muskegon General Hospital, Muskegon, Michigan; 8 and the Department of Emergency Medicine, St Luke's Hospital, Fargo, North Dakota.9

The concept of prehospital trauma scoring, along with other recent advances in the care of trauma patients, has been developed out of the need to use prehospital data more effectively for appropriate triage, prehospital management, and emergency department preparation. The prehospital index (PHI) was developed and prospectively field tested in 1985.1 The PHI (Figure 1) includes four components: systolic blood pressure, pulse, respiratory status, and level of consciousness, each rated 0 to 5 on a nonlinear scale. The PHI is the sum of the values for each of the four components, producing a range of 0 to 24 (those patients sustaining penetrating abdominal or penetrating thoracic injuries were given an additional four points). Our prospective field trial] revealed that those patients with PHIs of 0 to 3 had a very low emergency surgical rate relative to those scoring 4 to 24 (P < .001). In addition, mortality in the 0 to 3 group was 0, compared to 27% in the 4 to 24 group (P < .001). Based on these data, those patients scoring 0 to 3 are considered minor trauma, and those scoring 4 to 24 are considered major trauma. The results of the pilot study were very encouraging but included only 388 patients. In an effort to not only increase the study population but to test its applicability and reliability in other emergency medical services (EMS) systems, we conducted this multicenter trial.

METHODS The PHI was applied prospectively to 3,581 patients from 14 institutions during the period from January 1985 through February 1986. Not all institutions participated for the full study period. The mean participation time was seven months. Participants consisted of both inner-city and community hospitals that varied in both size and volume. Only trauma patients transported to the ED by ambulance were included in the study. Of the 14 participating hospitals only Hennepin County Medical Center and Mt Carmel Hospital are designated Level I trauma centers. Patients were transported to all institutions without regard to the data gathered for the study. With the exception of two institutions, radio contact with the emergency medical technicians (EMTs) was the exclusive source of 16:4 April 1987

Annals of Emergency Medicine

Received for publication May 14, 1986. Revision received September 8, 1986. Accepted for publication December 23, 1986. Presented at the University Association for Emergency Medicine Annual Meeting in Portland, Oregon, May 1986. Address for reprints: John J Koehler, MD, Department of Emergency Medicine, Swedish American Hospital, 1400 Charles Street, Rockford, Illinois 61108.

380/17

PREHOSPITAL INDEX Koehler et al

FIGURE 1. Prehospital index. Prehospital Index PHI data. At Hennepin County Medical Center in Minneapolis and Mt Carmel Hospital in Detroit, where transport times can be less than two minutes, radio contact was not always feasible. In these few cases, the PHI was generated on arrival, prior to any definitive treatment. T h e o n l y m e t h o d o l o g i c a l change made compared to the pilot study 1 was to decrease the time limitation for general surgery (abdominal, thoracic, or major vascular) or neurosurgery from 24 to four hours. This change was instituted at the beginning of this study as we believed that the fourhour time limitation more accurately reflects the concept of emergency, lifesaving surgery. We did not calculate the emergency operative rate using the 24-hour cutoff nor did we separately analyze penetrating versus blunt trauma or age categorization.

Component Systolic blood pressure

>100 86-100 75-85 <75 >120 51-120 <50 Normal Labored/shallow <10, needs intubation

Pulse rate

Respiratory status

Level of consciousness

Normal Confused/combative No intelligible words

*Total PHI score 0 to 3 denotes minor trauma. 4 to 24 denotes major trauma. *Penetrating abdominal or penetrating chest injuries - - add additional four points.

1

RESULTS Of t h e 3,120 p a t i e n t s scored as minor trauma in the field (PHI 0 to 3), there was a 0% m o r t a l i t y rate and only a 0.6% emergency operative rate. The combined surgical and mortality incidence, therefore, was also only 0.6%. Those scored as major trauma in the field (PHI 4 to 24) had a mortality of 23.0% (PHI 4 to 7, 4.4%; 8 to 24, 41.0%) and an e m e r g e n c y operative rate of 47.3% (PHI 4 to 7, 3t.3%; 8 to 24, 62.8%). Combined surgical and mortality rates had an incidence of 52.1% (PHI 4 to 7, 31.7%; 8 to 24, 71.8%) (Table 1). Of the 3,120 patients categorized as minor trauma by the PHI, 19 required emergency surgery. However, no patient categorized as m i n o r t r a u m a died. The false negative rate then was 7.3%, and the negative predictive value was 99.4%. Of the 461 patients categorized by the PHI as major trauma, 221 did not require emergency surgery or die. Therefore, the false positive rate was 6.7% and the positive predictive value was 52.1% (Table 2). The ability of the PHI to predict mortality (P < .0001) and the need for emergency surgery (P < .0001) were demonstrated using chi-square analysis. Curves describing the relationships among PHI and surgery, mortality, and surgery plus mortality, were produced. They illustrate a consistent relation18/381

TABLE 1. PHI versus surgery and mortality Minor Trauma

Major Trauma

PHI total Surgery

0 to 3 19/3,120

% 0.6

4 to 7 71/227

% 31.3

8 to 24 147/234

% 62.8

Mortality

0/3,120

0.0

10/227

4.4

96/234

41.0

19/3,120

0.6

72/227

31,7

168/234

71.8

Surgery or mortality

ship in both outcome parameters from a PHI of 0 to 24 (Figures 2, 3, 4). In addition, curves were generated comparing the PHI with the ISS {Figure 5)¢-4 and the ICU admission rate (Figure 6}. These were reported to illustrate the PHI's close correlation with less specific yet very significant measures of overall trauma severity (P < .001).

DISCUSSION Of the m a n y prehospital t r a u m a scoring systems reported in the literature, it is important to note that only the C R A M S ScaleS, 6 and the Prehospital Index have undergone prospective trials in the US. Although the Trauma Score7, 8 is probably the most familiar of the trauma scoring systems available, it has never been validated prospectively. Morris et al 9 recently completed a 1,106-patient trial of the Annals of Emergency Medicine

Trauma Score at San Francisco General Hospital. Although considered by the authors to be a prospective trial, the patients' trauma scores were calculated by the investigators retrospectively from EMS run forms. Thus, the paramedics were not required to calculate and t r a n s m i t the Trauma Score in the prehospital setting. The authors themselves admit that the acc u r a t e c a l c u l a t i o n of t h e T r a u m a Score by prehospital personnel is an assumption. It is our view that the Trauma Score is too complex for field use. This is further supported by the fact that only 5,130 of 18,925 trauma cases in a retrospective trauma registry review had sufficient information to be scored using this system, lo Recently, Champion et al u have stated their intentions to simplify the Trauma Score in order to make it more applicable to field use. 16:4 April 1987

100 90 80 Surgical Rate (%)

70

~S v

60 50

Q

•

•

40 30 20 10 0 ~.<2:~,.~

0

1 2 3 4

5 6 7 8 9 10 11 12

13

14

15

16

17

18 19

20

21

22

23 24

PHI Total

2 FIGURE 2. Surgical rates versus PHI total.

TABLE 2. PHI versus surgery or mortality Surgery or Mortality PHI Oto3 4 to 24

Yes

No

19

3,101

240

221

False negative rate

19/240 + 19 = 7.3%

False positive rate

221/3,101 + 221 = 6.7%

Sensitivity

240/240 + 19 = 92.7%

Specificity

3,101/3,101 + 221 = 93.3%

Positive predictive value

240/240 + 221 = 52.1%

Negative predictive value

3,101/3,101 ÷ 19 = 99.4%

Reinforcing this need for simplicity, we see that despite specific training for multivariable data collection, only 57% of all eligible cases collected by Kane et al I2 were used for their study, In our opinion, an effective prehospital trauma scoring system should d e m o n s t r a t e the following: Simplicity It should be simple enough to be rapidly and easily calculated at the scene of a trauma by prehospital personnel with no extensive in-service training required. Acceptability The system m u s t be widely accepted by prehospital personnel. They may tend to reject a more complicated system or a s y s t e m that requires t h e m to spend valuable time measuring pa16:4 April 1987

rameters they do not already routinely measure. Validity The system should have the ability to accurately differentiate m i n o r t r a u m a victims from major trauma victims using widely accepted follow-up criteria applied to a large number of patients. Versatility It should be shown to be both applicable and valid in multiple EMS systems in different geographic and demographic areas. In order to adequately demonstrate w h e t h e r these characteristics apply to a particular scoring system, it is necessary that the system undergo a prospective field trial. In terms of simplicity, the PHI (Figure 1) has four components and the CRAMS Scale s has five. Two of the Annals of Emergency Medicine

four PHI components are objective vital signs, systolic blood pressure and pulse; and the other two are subjective observations, respiratory status and level of consciousness. The CRAMS Scale uses systolic blood pressure as its only objective vital sign, while respiratory status and speech are subjective observations. Significantly, however, the third and fourth components of the CRAMS Scale require the performance of abdominal and motor examinations. Although most EMTs are well trained and experienced in both examinations, to have 40% of a scoring system dependent on these two findings may introduce substantial inaccuracies, particularly considering the less than optimal circumstances so often found at the scene of a trauma. It has also been shown that there is a significant discrepancy between EMT and paramedic subjective patient evaluation, especially so for patients in critical condition. 9 Both the CRAMS Scale 6 and the PHI have proven validity in prospective multicenter field trials. Clemmer et al 6 p r o s p e c t i v e l y a p p l i e d t h e C R A M S Scale to 2,110 p a t i e n t s at eight community hospitals in the Salt Lake City area. In the minor trauma group they reported one ED death and two late deaths (0.I5%), 125 ICU ad382/19'

PREHOSPITAL INDEX Koehler et al

100 9O 80 70 Mortality Rate (%)

60 5O 4O -

30 2O 10 0

0 1 2 3 4

5 6 7 8 9 10 11 12 13

14

15

16

17 18

19 20

21

22

23

24

d' PHI Total

3

9,

100

~"

90 80 Surgical and Mortality Rate (%)

70 60 50 40 30 20 10

"

,

0 ~-,

0 1 2 3 4

5 6 7 8

9 10

11 12 13

14

15

16 17

18 19

20

21

22

23

24

- - " : ~ ' 4"~ " o PHI Total

FIGURE 3. Mortality rates versus PHI total. F I G U R E 4. C o m b i n e d surgical and m o r t a l i t y rates versus PHI total. m i s s i o n s (6.3%), and 124 admissions to surgery (6.3%)(the type of surgery performed was not reported). The statistical significance was P < .0002. 20/383

In contrast, the PHI m i n o r trauma category missed no mortalities, had only a 3.4% ICU admission rate and a 0.6% surgical rate (limited to general and neurosurgical). When tested against the ISS as a more global measure of trauma severity, we found the PHI was again q u i t e a c c u r a t e (P < .001) (Figure 5). In fact, the PHI is actually a better predictor of the need for Annals of Emergency Medicine

emergency operative intervention and injury severity than is the ISS. The ISS was d e s i g n e d u s i n g d a t a c o l l e c t e d from 2,128 t r a u m a cases related only to highway incidents. 2 These data and the ISS thus are skewed in that blunt trauma usually involves more than one body system, and therefore, high ISS v a l u e s in a m a j o r i t y of cases. Using the US Vital Statistics classifi16:4 April 1987

60 50

..j-

40 ISS Total

|

30

20

10

J"

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

20

21 22

23

24

PHI Total

5

100 w

9O

-"

--

m

m

.

.

.

.

I

8O 7O

ICU

6O

Admit Rate (%)

5O 40 3O 2O 10

~,. o~

0 1 2 3 4 5 6 7 8

910

11 12

13 14 15 16

17 18 19

20

21

22

23

24

q,, PHI Total

cation la definition of trauma that includes m o t o r vehicle, water, air, and space transportation; industrial accidents; accidents caused by firearms, explosives, and fire; as well as suicide and h o m i c i d e , we have a m o r e inclusive l i s t of w h a t t r a u m a t r u l y entails, which allows for lethal focal injuries. 16:4 April 1987

T h e C R A M S Scale a n d t h e PHI have demonstrated versatility in their prospective trials. Although the C R A M S Scale trial6 was l i m i t e d to one city and EMS system, it did use eight c o m m u n i t y hospitals of varying sizes. T h e PHI was t e s t e d in four states and nine cities, and in 14 hospitals that ranged from small c o m m u n i Annals of Emergency Medicine

FIGURE 5. M e a n i n j u r y s e v e r i t y score versus PHL

FIGURE 6. S u r v i v o r I C U a d m i t rate versus PHI.

ty hospitals to urban university traum a centers. Based on the data presented, we be384/21

PREHOSPITAL INDEX Koehler et al

]ieve t h a t t h e PHI c a n b e a n i n t e g r a l p a r t of a n y EMS s y s t e m i n t h e following .ways. Patient triage. T h e PHI's u t i l i t y i n t h i s area is o b v i o u s , b u t d u e to t h e v a r i a t i o n a n d c o m p l e x i t y i n EMS syst e m s i t w o u l d b e i m p o s s i b l e to d i c t a t e a specific PHI level t h a t w o u l d necess i t a t e triage to a Level I t r a u m a center. For e x a m p l e , i n G r a n d Rapids, M i c h i gan, t h e r e are four h o s p i t a l s , n o n e of w h i c h is a Level I t r a u m a center. W h a t we r e c o m m e n d is for e a c h EMS syst e m to c o n s i d e r its o w n t r a u m a care availability and set triage criteria b a s e d o n t h e PHI. C o n s i d e r a t i o n m u s t b e g i v e n n o t o n l y to t h e p r e s e n c e of a Level I t r a u m a center, b u t its availability v e r s u s t h e Level II t r a u m a center. Generally, w e r e c o m m e n d t h a t all patients with PHIs above 3 be transported to the highest level trauma c e n t e r available. Prehospital m a n a g e m e n t . T h o s e pat i e n t s w i t h PHIs of m o r e t h a n 3 repres e n t a group i n n e e d of aggressive preh o s p i t a l r e s u s c i t a t i o n . P r o t o c o l s for EMT treatment may be established a n d g u i d e d b y t h e PHI prior to c o n t a c t with medical control. Rapid patient r e m o v a l 14 a n d l o a d - a n d - g o p r o t o c o l s are a d d i t i o n a l m o d a l i t i e s t h a t c a n b e activated automatically through the u s e of t h e PHI. ED preparation. T h e PHI c a n s u p p l y t h e o b j e c t i v e c r i t e r i a n e c e s s a r y for staff a c c e p t a n c e of t r a u m a a l e r t protocols. S u c h p r o t o c o l s c a n b e i n i t i a t e d l o n g before t h e p a t i e n t arrives a n d c a n provide much needed uniformity and e f f e c t i v e n e s s i n t h e m o b i l i z a t i o n of

22/385

a n c i l l a r y services, b l o o d p r o d u c t s , a n d e s p e c i a l l y t h e t r a u m a s u r g e o n a n d operating room personnel. Disaster planning. A l l EMS s y s t e m s should have disaster plans. The PHI can be a useful tool in the developm e n t a n d i m p l e m e n t a t i o n of d i s a s t e r p l a n s for r e a s o n s t h a t are self-evident. CONCLUSION O u r m u l t i c e n t e r trial of t h e PHI is t h e largest of its k i n d to d a t e a n d h a s d e m o n s t r a t e d w h a t w e b e l i e v e t o be t h e n e c e s s a r y r e q u i r e m e n t s of a n eff e c t i v e p r e h o s p i t a l t r a u m a s c o r i n g syst e m . We h a v e r e p o r t e d its a c c u r a c y i n p r e d i c t i n g t h e n e e d for e m e r g e n c y lifes a v i n g s u r g e r y w i t h i n four h o u r s (P < .0001) a n d m o r t a l i t y w i t h i n 72 h o u r s (P < .0001}. C u r v e s w e r e g e n e r a t e d for e a c h of t h e a b o v e o u t c o m e p a r a m e t e r s v e r s u s PHI i n order t o i l l u s t r a t e t r e n d s a n d t o p r o v i d e a m o r t a l i t y a n d surgical r a t e for e a c h PHI v a l u e f r o m 0 to 24. We s t r o n g l y r e c o m m e n d t h e PHI to all E M S s y s t e m s for u s e i n g u i d i n g triage, p r e h o s p i t a l t r e a t m e n t , a n d E D p r e p a r a t i o n . It is h o p e d t h a t its u t i l i z a t i o n u l t i m a t e l y w i l l i m p r o v e o u r preh o s p i t a l m a n a g e m e n t of t r a u m a pat i e n t s a n d h e n c e save lives.

T h e a u t h o r s e x t e n d special t h a n k s to Amanda K Stressman for her assistance in the preparation of this manuscript.

REFERENCES 1. Koehler JJ, Baer LJ, Malafa SA, et ah Prehospital index: A scoring system for field triage of trauma victims. Ann Emerg Med 1986;15:

Annals of Emergency Medicine

178-182. 2. Committee on Medical Aspects of Automotive Safety: Rating the severity of tissue damage. I. The abbreviated scale. JAMA I971; 215:277-280. 3. Baker SP, O'Neill B, Haddon W, et al: The injury severity score: A method for describing patients with multiple injuries and evaluating emergency care. J Trauma 1974;14:187-196. 4. Greenspan L, McLellan BA, Greig H: Abbreviated injury scale and injury severity score: A scoring chart. J Trauma 1985;25:60-64. 5. Gormican SP: CRAMS scale: Field triage of trauma victims. Ann Emerg Mecl 1982;11: 132-135. 6. Clemmer TP, Orme JF, Thomas F, et al: Prospective evaluation of the CRAMS scale for triaging major trauma. J Trauma 1985;25:188-19L 7. Champion HR, Sacco WJ, Camazzo AJ, et al: The trauma score. Crit Care Med 1981;9: 672-676. 8. Sacco WJ, Champion HR, Gainer PS, et al: The trauma score as applied to penetrating trauma. Ann Emerg Med 1984;13:415-418. 9. Morris JA, Auerbach PS, Marshall GA, et al: The trauma score as a triage tool in the prehospital setting. JAMA 1986;256:1319-1325. 10. Ornato JP, Mlinek EJ, Craren EJ, et al: Ineffectiveness of the trauma score and the CRAMS scale for accurately triaging patients to trauma centers. Ann Emerg Med 1985;14:1061-I064. 11. Moreau M, Gainer ?S, Champion H, et al: Application of the trauma score in the prehospital setting. Ann Emerg Med 1985;14:10491054. 12. Kane G, Engelhardt R, Celentano J, et al: Empirical development and evaluation of prehospital trauma triage instrument. J Trauma 1985;25:482-488. 13. Vital Statistics for the United States, 1977, Mortality, Part A. Washington, DC, Center for Health Statistics. 14. Butman AM, McSwain NE: Emergency patient removal. J Pre-Hospital Care 1984;July-August: 23-45.

16:4 April 1987