measuring injury severity a brief introduction thomas songer, phd university of pittsburgh...
TRANSCRIPT
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Measuring Injury Severity
A brief introduction
Thomas Songer, PhDUniversity of Pittsburgh
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Degrees of Injury Severity
Households
Emergency Dept.
Hospitalization
Injury Deaths
Physician Visit
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Injury
Police
Hospital
Self-Treat
Robertson, 1992
doctor
EMS
Rehab CenterTrauma Center
Morgue
Emergency Dept.
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Major Areas of Application on Injury Severity Indices
Triage Prognostic Evaluation Research and Evaluation
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Is there potential for Is there potential for improvement in the care of improvement in the care of
injured patients?injured patients?
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Improvements in outcomes related Improvements in outcomes related to injury may be achieved by:to injury may be achieved by:
• Enhancing pre-hospital care
• Adopting ATLS principles
• Integrating trauma care within and between hospitals
• Investing in rehabilitation services
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Measuring the Burden of Injuries
• 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
Segui-Gomez
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Injury Severity Scales
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Impact of the Injury will depend on...
Extent of tissue damage Physiological response to the injury Host factors that mediate the
response
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Aspects of Injury Severity
Anatomical Injury
Physiological Measurements
AgeBlunt/Penetrating
Probability of survival of individual patientsProbability of survival of individual patients
Comparisons between groupsComparisons between groups
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INJURY SEVERITYINJURY SEVERITY
Alphabet SoupAlphabet Soup
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Abbreviated Injury Scale (AIS)
Anatomical measure that addresses the extent of tissue damage
ICD-based classifications
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AIS Severity Component
MINORMINORMODERATEMODERATESERIOUSSERIOUSSEVERESEVERECRITICALCRITICALMAXIMUM INJURY,MAXIMUM INJURY,VIRTUALLY VIRTUALLY UNSURVIVABLEUNSURVIVABLE
1 1 22 33 44 5 5 66
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Severity scores are subjective assessments assigned by experts
Implicitly based on four criteria:
Threat to life Permanent Impairment Treatment Period Energy Dissipation
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Addressing Multiple Injuries
for predicting survival
Injury Severity Score (ISS)The New Injury Severity Score (NISS)The Anatomic Profile (AP)
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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
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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
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Criticisms of the ISS
Does not take into account multiple injuries within a body system
Equal weights across body regions; underscores severe head injuries
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The New Injury Severity Score (NISS)
Sums of squares of the 3 highest AIS scores regardless of body region
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ISS vs. NISS - an Example
Multiple abrasionsDeep laceration tongueSubarachnoid hemorrhageMajor kidney lacerationMajor liver laceration
1 2344
External Face Head/Neck Abdomen Abdomen
ISS = (4)ISS = (4)22 + (3) + (3)22 + (2) + (2)22 = 29 = 29NISS = (4)NISS = (4)22 + (4) + (4)22 + (3) + (3)22 = 41 = 41
AIS Score Region
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Anatomic Profile
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Anatomic ProfileDefinition of Components
AIS Region AIS Region
AIS SeverityAIS SeverityAA
BB
CCDD
Head/BrainHead/BrainSpinal cordSpinal cordThoraxThoraxFront of NeckFront of NeckAll other body regionsAll other body regionsAll othersAll others
3-63-63-63-63-63-63-63-63-63-61-21-2
The square root of the sum of squares of AIS scores The square root of the sum of squares of AIS scores is used to summarize a component’s injuriesis used to summarize a component’s injuries
Component Component
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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
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Injury Severity Scales
In Use
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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
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Percent of ISS > = 16 Patients Getting to Trauma Centers:
Metro Area A 55%Metro Area B59%Metro Area C66%Metro Area D 68%Metro Area E73%Metro Area F78%Metro Area G 85%
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Physiologic Response
Glasgow Coma Score Revised Trauma Score
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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
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Glasgow Coma Scale
Parameter Response ScoreNil 1To pain 2To speech 3
Eye opening
Spontaneously 4Nil 1Extensor 2Flexor 3Withdrawal 4Localising 5
Motor response
Obeys command 6Nil 1Groans 2Words 3Confused 4
Verbal response
Orientated 5
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Revised Trauma ScoreRevised Trauma Score
- a physiological measurement
- based on data at arrival to hospital
considers: Respiratory rate
Systolic blood pressure
Glasgow Coma Scale
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Revised Trauma Score
Clinical Parameter Category Score x weight10-29 4>29 36-9 21-5 1
Respiratory rate(Breaths per minute)
0 0
0.2908
>89 476-89 350-75 21-49 1
Systolic bloodPressure
0 0
0.7326
13-15 49-12 36-8 24-5 1
Glasgow ComaScale
3 0
0.9368
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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
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Host Factors
Age Pre-existing conditions Other
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Combining information on …
Tissue damage
Physiologic response
Host factors
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Probability of Survival Models
TRISS ASCOT
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Further Improvements
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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
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AIS BASED MEASURES of IMPAIRMENT
Injury Impairment Scale (IIS) Functional Capacity Score (FCI)