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Measuring Injury Severity

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  1. Measuring Injury Severity A brief introduction Thomas Songer, PhD University of Pittsburgh tjs@pitt.edu

  2. Degrees of Injury Severity Injury Deaths Hospitalization Emergency Dept. Physician Visit Households

  3. EMS Police Self-Treat Emergency Dept. doctor Injury Hospital Morgue Trauma Center Rehab Center Robertson, 1992

  4. Major Areas of Application on Injury Severity Indices • Triage • Prognostic Evaluation • Research and Evaluation

  5. Is there potential for improvement in the care of injured patients?

  6. Improvements in outcomes related to injury may be achieved by: • Enhancing pre-hospital care • Adopting ATLS principles • Integrating trauma care within and between hospitals • Investing in rehabilitation services

  7. Fatal Counts and rates Years of Potential Life Lost Non-fatal Short term Health care use Hospitalization rates Functional limitations Severity AIS RTS, etc Pathology Measuring the Burden of Injuries Segui-Gomez

  8. Injury Severity Scales

  9. Impact of the Injury will depend on... • Extent of tissue damage • Physiological response to the injury • Host factors that mediate the response

  10. Aspects of Injury Severity Physiological Measurements Anatomical Injury Age Blunt/Penetrating Probability of survival of individual patients Comparisons between groups

  11. INJURY SEVERITY Alphabet Soup ASCOT APS IIS CRAMS ICISS TRISS ISS APACHE AIS RTS GCS AP

  12. Abbreviated Injury Scale (AIS) • Anatomical measure that addresses the extent of tissue damage • ICD-based classifications

  13. AIS Severity Component 1 2 3 4 5 6 MINOR MODERATE SERIOUS SEVERE CRITICAL MAXIMUM INJURY, VIRTUALLY UNSURVIVABLE

  14. Severity scores are subjective assessments assigned by expertsImplicitly based on four criteria: • Threat to life • Permanent Impairment • Treatment Period • Energy Dissipation

  15. Addressing Multiple Injuriesfor predicting survival • Injury Severity Score (ISS) • The New Injury Severity Score (NISS) • The Anatomic Profile (AP)

  16. The Injury Severity Score (ISS) • Sum of squares of the highest AIS in each of 3 most severely injured body regions • ISS Body Regions: • Head or neck - Face • Abdominal - Chest • Extremities - External

  17. INJURY SEVERITY SCORE Example AIS Score Small subdural haematoma 4 Parietal lobe swelling 3 Major liver laceration 4 Upper tibial fracture (displaced) 3 ISS = 42 + 42 + 32 = 41

  18. Criticisms of the ISS • Does not take into account multiple injuries within a body system • Equal weights across body regions; underscores severe head injuries

  19. The New Injury Severity Score (NISS) Sums of squares of the 3 highest AIS scores regardless of body region

  20. ISS vs. NISS - an Example AIS ScoreRegion Multiple abrasions Deep laceration tongue Subarachnoid hemorrhage Major kidney laceration Major liver laceration 1 2 3 4 4 External Face Head/Neck Abdomen Abdomen ISS = (4)2 + (3)2 + (2)2 = 29 NISS = (4)2 + (4)2 + (3)2 = 41

  21. Anatomic Profile

  22. Anatomic ProfileDefinition of Components Component AIS Region AIS Severity A B C D 3-6 3-6 3-6 3-6 3-6 1-2 Head/Brain Spinal cord Thorax Front of Neck All other body regions All others The square root of the sum of squares of AIS scores is used to summarize a component’s injuries

  23. ICD to AIS Conversion(ICDMAP) • Converts ICD-9CM coded discharge diagnoses into AIS scores and computes ISS, NISS, APS • Conservative measure of injury severity - refer to as ICD/AIS scores

  24. Injury Severity Scales In Use

  25. Evaluating System Performance Using hospital discharge data, classify patients according to where they should have been treated (based on AIS severity) Compare where they should have been treated to where they actually were treated

  26. Percent of ISS > = 16 Patients Getting to Trauma Centers: Metro Area A 55% Metro Area B 59% Metro Area C 66% Metro Area D 68% Metro Area E 73% Metro Area F 78% Metro Area G 85%

  27. Physiologic Response • Glasgow Coma Score • Revised Trauma Score

  28. Glasgow Coma Scale • Head injuries vary as to severity ranging from mild, moderate, to severe • The Glasgow Coma Scale is a measure of this severity • The GCS is assessed immediately following the injury and during the initial recovery

  29. Glasgow Coma Scale Parameter Response Score Nil 1 Eye opening To pain 2 To speech 3 Spontaneously 4 Nil 1 Extensor 2 Motor response Flexor 3 Withdrawal 4 Localising 5 Obeys command 6 Nil 1 Groans 2 Verbal response Words 3 Confused 4 Orientated 5

  30. Revised Trauma Score -a physiological measurement - based on data at arrival to hospital considers: Respiratory rate Systolic blood pressure Glasgow Coma Scale

  31. Revised Trauma Score Category Score Clinical Parameter x weight 10-29 4 Respiratory rate >29 3 (Breaths per minute) 0.2908 6-9 2 1-5 1 0 0 >89 4 Systolic blood 76-89 3 Pressure 0.7326 50-75 2 1-49 1 0 0 13-15 4 Glasgow Coma 9-12 3 Scale 0.9368 6-8 2 4-5 1 3 0

  32. Assessing RTS may be problematic Accurate GCS and RR difficult when the patient is intubated, chemically paralyzed or under the influence of drugs or alcohol

  33. Host Factors • Age • Pre-existing conditions • Other

  34. Combining information on … Tissue damage Physiologic response Host factors

  35. Probability of Survival Models • TRISS • ASCOT

  36. Further Improvements

  37. Refining the State of the Art 1. Further refine the AIS and RTS 2. Revisit Probability of Survival Models -- especially for population based data 3. Better delineate role of host factors

  38. AIS BASED MEASURES of IMPAIRMENT Injury Impairment Scale (IIS) Functional Capacity Score (FCI)