Measuring%20Injury%20Severity

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Measuring Injury Severity
A brief introduction
Thomas Songer, PhD University of
Pittsburgh tjs_at_pitt.edu
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Degrees of Injury Severity
Injury Deaths
Hospitalization
Emergency Dept.
Physician Visit
Households
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EMS
Police
Self-Treat
Emergency Dept.
doctor
Injury
Hospital
Morgue
Trauma Center
Rehab Center
Robertson, 1992
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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 improvement in the care of
injured patients?
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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

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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
Physiological Measurements
Anatomical Injury
Age Blunt/Penetrating
Probability of survival of individual patients
Comparisons between groups
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INJURY SEVERITY Alphabet Soup
ASCOT
APS
IIS
CRAMS
ICISS
TRISS
ISS
APACHE
AIS
RTS
GCS
AP
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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
MINOR MODERATE SERIOUS SEVERE CRITICAL MAXIMUM
INJURY, VIRTUALLY UNSURVIVABLE
1 2 3 4 5 6
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Severity scores are subjective assessments
assigned by expertsImplicitly based on four
criteria

• Threat to life
• Permanent Impairment
• Treatment Period
• Energy Dissipation

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Addressing Multiple Injuriesfor 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

AIS Score Region

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
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Anatomic Profile
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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 components injuries
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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 gt 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

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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
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
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Revised 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
Category
Score
Clinical Parameter
x weight
10-29
4
gt29
3
Respiratory rate
(Breaths per minute)
0.2908
6-9
2
1-5
1
0
0
gt89
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
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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)