Trauma score versus revised trauma score in TRISS to predict outcome in children with blunt trauma

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References: Please call 1-800-526-8785 for reprints and further information. 1. Bergfeld JA, Cox JS, Drez D, Raemy H, Weiker GG: Symposium: Management of acute ankle sprains. ContempOrthoped 1986: 13. 2. Stover CN: Air-Stirrup management of ankle injuries in the athlete. AmJ ...... Sports Med 1980;,8:560-565. 3. Kimura IF, et al: Effect of the Air-Stirrup in controlling ankle inversion stress. J Ortho Sports Phgs Therstudy 1987; 9:33-39. " . . . . . . - - ~: 4. Stuessi E, et al: A biomechanical of the stabilization effect of the AIRCAST Ankle Brace, in Biomechanics. Champaign, IL: /,~ Human Kinetics Publishers, pp 159-164, 1987. 5. Raemy H, Jakob RP: Functional treatment of fresh fibula]igarnent lesions using the AIRCAST Ankle Brace. SwissJ Sports Mad 1983; 31:53-57. 6. Hamilton WG: Sprained ankles in ballet dancers. Foot and Ankle . 1982; 3:99-102. 7. Stayer CN, York JM: AIRCAST/Air-Stirrup system for graduated management of lower extremity injuries. Scientific exhibit paper, AAOS, San Francisco, 1979. -~

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TRAUMA SCORE Eichelberger et al

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FIGURE 1. TRISS analysis: prechart. TABLE 1. Revised Trauma Score variables

FIGURE 2. R-TRISS analysis: prechart. The TS is the sum of five coded variables: respirations (R), respiratory expansion (RE), systolic blood pressure (SBP), capillary refill (CR), and Glasgow Coma Scale (GCS). A TS of 16 represents no physiologic derangement, while a TS of 1 indicates severe physiologic derangement. The RTS evolved in response to the finding that severity of injury for some head-injured patients was underestimated by the TS. s The RTS is the weighted sum of three variables: RR, SBP, and GCS. Coded values of these variables (Table 1) are used to calculate RTS as follows: RTS = 0.936 (coded GCS) + 0.732 (coded SBP) + 0.290 (coded R) The numerical weights for the coded variables were determined from the MTOS data. 4,s With this modification, RTS predicted survival-death outcome better than TS for the adult MTOS data despite the elimination of CR and respiratory effort. The TS and RTS were computed at admission to the emergency department. The ISS is based on the Abbreviated Injury Scale (AIS)-85, which divides the body into six regions head-neck, face, chest, abdomen, extremity, and external.,The ISS is the sum of the squares of the highest AIS code in each of the three most severely injured body regions. If the patient has any AIS level 6 injury, his ISS is 75 by definition. ISS scores were computed following discharge 74/940

Systolic Blood Pressure (mm Hg)

Respirations

13 - 15

> 89

10 - 29

4

9-12

76 - 89

> 29

3

Glasgow Coma Scale

6-

8

50 - 75

6 -

9

4-

5

1-49

1-

5

3

0

0

Coded Value

2 1 0

From Reference 5.

TABLE 2. Trauma Score distribution Trauma Score

Count

%

Cumulative %

1

13

0.83

0.83

2

1

0.06

3

1

0.06

4

3

0.19

0.89 0.95 1.14

5

8

0.51

1.65

6

8

0.51

2.16

7

24

1.54

3.70

8

13

0.83

4.53

9

5

0.32

4.85

10

5

0.32

5.17

11

8

0.5t

5.68

12

25

1.60

7.28

13

66

4.22

11.50

14

292

18.69

30.19

15

391

25.03

55.22

699

44.78

100.00

1,562

100.00

100.00

16 Total

Annals of Emergency Medicine

18:9 September 1989

TABLE 3. Revised Trauma Score distribution

Revised Trauma Score

Count

0

%

Cumulative %

the survival probabilities over the entire population), and S is a scale factor that accounts for the variance of the survival probability estimates. A z score of more than 1.96 or less than -1.96 indicates a significant difference (P < .05) between the populations being compared.

15

0,96

0.96

0.01 - 1,00

1

0.06

1.02

1.01 - 2.00

3

0.19

1.21

RESULTS

2.01 - 3.00

31

1.98

3.19

3.01 - 4.00

10

0.64

3.83

4.01 - 5.00

19

1.22

5.05

5.01 - 6.00

41

2.62

7.67

6.01 - 7.00

99

6.33

14.00

The 1,562 injured children in our study were predominantly boys who had been involved in a motor vehicle crash or a fall: There were 1,519 survivors (97.2%) and 43 deaths (2.8%). Most came to CHNMC directly from the scene {66.4%). Transport of the injured children occurred by ambulance (48.7%), helicopter (26.4%), or private automobile (24.9%). Distributions of injury severity, as measured by TS and RTS, are shown (Tables 2 and 3). Triage using a TS of 14 or less has been shown to capture most of the severely injured patients requiring a trauma center. 11 Approximately 30% of our patients fall into this category. The ISS distribution of our data base (Table 4) shows that nearly one fourth (25.6%) of the patients have ISS values of 10 or more and 12.5% have ISS values of more than 15. The TRISS and R-TRISS analyses are represented graphically (Figures 1 and 2). The diagonal lines in these figures represent 50% chance of survival isobars for MTOS patients (ages 15 to 54 years). Patients depicted on the lines have a 50% chance of survival. Patients depicted above the isobar are not expected to survive (less than 50% chance of survival). Those depicted below the isobar are less severely injured and are expected to survive (more t h a n 50% chance of survival). Both figures show excellent demarcation of survivors and nonsurvivors. Survivors above the isobar and nonsurvivors below the isobar are " u n e x p e c t e d " o u t c o m e s w h o merit quality of care review. TRISS and R-TRISS analyses are summarized (Table 5). The predicted number of survivors using TRISS was 1,506.86. The predicted number of survivors using R-TRISS was 1,505.55. The z scores for TRISS and R-TRISS were 2.67 and 2.93; both scores indicate a statistically significant survival-death outcome difference between children from CHNMC and adults from the MTOS controls for TRISS and R-TRISS pop-

7.01 - 7.83

435

27.85

41.85

7.84

908

58.15

100.00

Total

1,562

100.00

100.00

TABLE 4. Injury Severity Score distribution

Injury Severity Score 75 41 - 74

Count

%

Cumulative %

3

0.19

0.19

19

1.21

1.40

36 - 40

3

0.19

1.59

31 - 35

10

0.64

2.23

26 - 30

48

3.07

5.30

21 - 25

39

2.50

7.80

16 - 20

73

4.67

12.47

11 - 15

79

5.06

17.53

464

29.71

47.24

824

52.76

100.00

1,562

100.00

100.00

6-

10

1-

5

Total

TABLE 5. TRISS analysis

Trauma Score

Revised Trauma Score

Total no.

1,562

1,562

Actual s u r v i v o r s

1,519

1,51 9

Expected survivors

1,506.86

1,505.55

Scale factor

4.56

4,59

z score

2.67

2.93

and AIS-859 coding. Outcome evaluation by TRISS and R-TRISS involves the computation of z scores,4,6,7,1° defined by the following equation: 18:9 September 1989

z = (A - E) / S where A is the actual number of survivors, E is the expected number of survivors (calculated by s u m m i n g

Annals of Emergency Medicine

941/75

TRAUMA SCORE Eichelberger et al

ulations. T h e TRISS a n a l y s i s h a d 13 m i s classifications; six were u n e x p e c t e d d e a t h s and s e v e n were u n e x p e c t e d s u r v i v a l s . In the R-TRISS m o d e l , there were six unexpected deaths and n i n e unexpected survivals, for a total of 15 m i s c l a s s i f i c a t i o n s . M i s c l a s s i fications are patients who die despite a n ED a d m i s s i o n TRISS s u r v i v a l probability of more than .50 or Who s u r v i v e d e s p i t e a n ED a d m i s s i o n TRISS s u r v i v a l p r o b a b i l i t y of less t h a n .50. E i g h t m i s c l a s s i f i c a t i o n s were c o m m o n to both groups, leaving only 12 children out of 1,562 (five from TRISS and seven from R-TRISS} for w h o m the two m e t h o d s do n o t agree o n s u r v i v a l - d e a t h c l a s s i f i c a tion. T h e m i s c l a s s i f i c a t i o n rates for TRISS and R-TRISS were 0.83% and 0.96%, respectively. DISCUSSION To analyze the consequences of injury to children, objective m e t h o d s to c h a r a c t e r i z e s e v e r i t y a n d docum e n t o u t c o m e are essential. Impressions persist that children have imp r o v e d o u t c o m e f r o m t r a u m a because they are resilient and tolerate head injury well. Statistically significant data to support this c o n t e n t i o n have n o t been published. TRISS and R-TRISS provide the opportunity for an objective comparison; each m e t h o d provides an excellent repres e n t a t i o n of the i n j u r e d p a t i e n t by a c c o u n t i n g for b o t h physiologic response and a n a t o m i c injury, an approach lacking in previous o u t c o m e studies c o m p a r i n g adults w i t h children.12-16 TRISS, originally described in 1981, provides an accurate and reproducible m e a s u r e of i n j u r y s e v e r i t y i n a d u l t p o p u l a t i o n s . Over the years, TRISS and, m o r e recently, R-TRISS have b e c o m e t h e standard tools for quality of care and o u t c o m e analyses for a d u l t t r a u m a centers. TRISS67 and R-TRISS have been s h o w n to be valid predictors of o u t c o m e for pediatric populations as well. T h e f i r s t p u b l i s h e d u s e of t h e TRISS m e t h o d i n a pediatric populat i o n showed no sta{istically significant difference (z = 1.32) i n expected o u t c o m e s b e t w e e n 594 C H N M C children and the adult population of the MTOS; the misclassification rate for survival-death was 0.8%. 6 S i n c e that time, a second TRISS analysis for i n j u r e d c h i l d r e n was published, 76/942

W h i c h y i e l d e d s i m i l a r r e s u l t s (z score, 1.95; m i s c l a s s i f i c a t i o n rate, 0.7%). 7 T h e c u r r e n t a n a l y s i s u s i n g TRISS showed a statistically significant difference in predicted outcomes in 1,562 children from C H N M C and the adult population of the MTOS using both TRISS (z score, 2.67) and R-TRISS (z score, 2.93). The increase i n the TRISS z score from 1.32 to 2.67 reflects t h e s u s t a i n e d b e t t e r C H N M C o u t c o m e t h a n the MTOS p o p u l a t i o n for an a d d i t i o n a l 968 p a t i e n t s treated since the first study. Clinically, these data indicate that the C H N M C care resulted i n nearly one more survivor per 100 p a t i e n t s treated t h a n expected by MTOS adult norms. From these findings, there are several p o s s i b l e c o n c l u s i o n s : children are more resilient to injury t h a n adults, C H N M C provides better t h a n average t r a u m a care to children, or a c o m b i n a t i o n of the first two conclus i o n s a c c o u n t s for these b e t t e r results. The first conclusion is confounded by the o b s e r v a t i o n that some adult t r a u m a c e n t e r s also a t t a i n s t a t i s t i c a l l y and c l i n i c a l l y s i g n i f i c a n t z values, s Thus, it is possible that either c h i l d r e n are n o t m o r e r e s i l i e n t than adults or they are b u t adult centers provide better care. C o n s i s t e n t l y high z scores from o t h e r p e d i a t r i c t r a u m a centers, or the lack thereof, m a y shed some light on this issue. It is n o t p o s s i b l e to d e t e r m i n e t h e source of the elevated z score findings. As w e h a v e s h o w n , TRISS a n d R-TRISS c h a r a c t e r i z e s u r v i v a l a n d death well i n i n j u r e d children. T h e misclassification rates for TRISS and R-TRISS were 0.83% and 0.96%, respectively; these low misclassification rates m a y be due in part to the small percentage of severely injured children (ISS of more t h a n 15, 12.5%; TS of 14 or less, 30.2%) i n our data base. This is an i m p o r t a n t observation because it is the care of the severely injured children that influences the z score and misclassificat i o n rate the m o s t . However, this p e r c e n t a g e is c o m p a r a b l e to o t h e r pediatric t r a u m a centers that serve as a primary and secondary referral center. CONCLUSION Both the TS and RTS have the cap a b i l i t y to q u a n t i f y survival probaAnnals of Emergency Medicine

b i l i t y w i t h the TRISS m e t h o d . The simplified RTS w i t h increased statistical weight for head injury is a useful score for quality-care assessment of the injured child. Also, the TS and RTS, u s e d i n t h e c u r r e n t MTOS TRISS model, d e m o n s t r a t e a statistically significant difference (P < .05) i n the predicted outcomes of children in our population compared w i t h the MTOS. T h e TRISS model, whether using the TS or the RTS, is a highly useful and accurate tool for charact e r i z i n g s u r v i v a l - d e a t h o u t c o m e in injured children.

REFERENCES

1. ChampionHR, Sacco WJ, Camazzo AJ, et ah Trauma Score. Grit Care Med 1981;9:672-676. 2. Baker SP, O'Neill B, Haddon W Jr, et at: The Injury Severity Score: A method for describing patients with multiple injuries and evaluating emergency care. ] Trauma 1974;14:187-196. 3. Baker SP, O'Neill B: The Injury Severity Score: An update. J Trauma 1976;16:882-885. 4. BoydCR, Tolson MA, Copes WS: Evaluating trauma care: The TRISS method. J Trauma 1987;27:370-378. 5. AmericanCollegeof SurgeonsCommittee on Trauma: Major Outcome Study Bulletin. Washington, DC, May 2, 1986. 6. EichelbergerMR, MangubatEA, SaccoWJ, et ah Comparative outcomes of children and adults suffering blunt trauma. J Trauma 1988; 28:430-434. 7. EichetbergerMR, MangubatEA, Sacco WJ, et at: Outcome analysis of blunt injury to children. J Trauma 1988;28:1109-1117. 8. FloraJD: A method for comparingsurvivalof burn patients to a standard survival curve. J Trauma 1978;18:701-705. 9. Association for the Advancement of Automotive Medicine: The Abbreviated Injury Scale, 1985 Revision. Des Plaines, Illinois, AAAM, 1985. 10. Walker SH, Duncan DB: Estimation of the probability of an event as a function of several independent variables. Biometrika 1967;54: 167-179. 11. Morris JA, AuerbachPS, GregoryAM, et al: The Trauma Score as a triage tool in the prehospital setting. JAMA 1986;256:1319-1325. 12. Haller JA, Shorter N, Miller D, et al: Organization and function of a regional pediatric trauma center: Does a system of management improve outcome? J Trauma 1983;23:691-696. 13. Jennett B, Teasdale G, Halbraith S, et ah Severe head injuries in three countries. J Neurol Neurosurg Psychol 1977;40:291-298.

14. Mayor T, Matlak M, Johnson D, et at: The Modified Injury SeverityScale in pediatric multiple trauma patients. J Pediatr Surg 1980;15: 719-726.

15. Smyth BT: Chest trauma in children J Pediatr Surg 1979;14:41-47.

16. Bruce DA, Schut L, Bruno LA, et at: Outcome followingsevere head injury in children J Neurosurg 1978;48:679-688.

18:9 September 198•