injury severity principles

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Injury Severity Principles


Objectives

• Introduction to key injury severity scores / scales

• Overview of key elements that affect these scores

• Provide reference material

• Introduction to the principles of “mapping” for severity

• Introduction to key bench marking principles


Types of Physiologic Scores

• Glasgow Coma Scale (GCS)

• Trauma Score (TS)

• Revised Trauma Score (RTS)Triage (RTS/T)Evaluation (RTS/E)

• Survival Probability (Ps)


Glasgow Coma Scale (GCS)

• Ranges: 3-15

• Composed of 3 parametersBest Eye, Verbal, & Motor (EVM)Response

• What is the purpose of the GCS?• Purpose: Determination of Brain Injury


GCS Important Hints

• Use specifically for Head Injuries and not Spinal Cord Injuries

• Give each component of the GCS

• It does no good to just tell GCS total

• First Recorded GCS*

• GCS Assessment Qualifier*• 1. Patient Chemically Sedated or

Paralyzed• 2. Obstruction to the Patient Eye• 3. Patient Intubated• 4. Valid GCS: Patient was not

sedated, not intubated, and did not have an obstruction to the eye

*Per National Trauma Data Standard, Data Dictionary, 2014 Admissions


GCS Important Hints

Brain Injury Severity:

13-15 – mild

9 - 12 – moderate

3 – 8 - severe


Trauma Score (TS)

• Ranges: 1-16

• Composed of 5 components:Objective Data: Systolic, Respirations, GCSSubjective Data: Capillary Refill, Respiratory Effort

• Purpose – • scoring multiple trauma


Revised Trauma Score (RTS)

• Due to limitations with the subjective data of the TS

• Divided into 2 Categories:1. Triage – Prehospital, unweighted system2. Evaluation – Emergency Department, weighted system

*RTS-E is installed in trauma registry software for the Emergency Department phase of care.


Revised Trauma Score (RTS)

• High inter-rater reliability

• Scored from the first set of data obtained on the patient.

• Range: 0.0000 – 7.8408

• Normal: 7.8408 (weighted formula)

Formula: RTS = 0.9368 (GCS) + 0.7326 (SBP) + 0.2908 (RR)


Injury Severity Score Calculations

• Calculation to reflect the level of severity of the patient’s injuries

• Key Component of the Probability of Survival

• The sum of the squares of the highest AIS from the three most severely injured body regions.

• A² + B² + C² = ISS


ISS ExampleRegion Injury AIS Square

Description Top Three Head &

Neck Cere. Cont. 4 16

Face Mandible Fx 2Chest Flail Chest 4 16

Abdomen Liver Cont. 2 Grade 5 Spleen

injury5 25

Extremity Humerus fx. 3 External Knee Abrasion 1

Injury Severity Score: 57


ISS

• AIS 6 severity is an automatically an ISS of 75 (un-survivable injury)

• example: massive crush destruction of both cranium and brain

• Correlates mortality, morbidity, hospital stay and other measures of severity

• Coding Errors lead to AIS severity errors

• ISS in not weighted and thus many different injury patterns can yield the same score.


New Injury Severity Score (NISS) or Revised ISS

• Drawback of ISS is it does not account for single system injuries

• Purpose: • to reflect severity of multi-organ injury in the same body region

• Has not been validated or accepted as the national norm

• The sum of squares of the highest AIS from the three most severely injured body organs.


NISS ExampleRegion Injury AIS Square

Description Top Three Head & Neck SAH

Open Skull Fx, LOC WRTBL

55

2525

Face No Injury 0 Chest No Injury 0

Abdomen No Injury 0Extremity No Injury 0External No Injury 0 Injury Severity Score = 25 NISS = 50


“MAPPING FOR SEVERITY”

• A computerized conversion table using the ICD-9-CM system into AIS-85 system including body region and severity but not the entire 7 digit AIS number

• This computerized conversion allowed abstractors to enter an ICD-9-CM code which then mapped or linked to an AIS severity score for that injury



• These individual ICD-9-CM codes follow the same rules for calculating ISS (most severe injury in 3 different body regions squared)

• This procedure was redone with AIS 90 was released

• Not aware of a validated, published system for AIS 05.

• Mapping for severity is included in most if not all Trauma Registry Software.



• Many hospitals in the US use AIS, however some use AIS 85, AIS 90, AIS 90 with 98 updates, AIS 05, and now AIS 05 with 09 updates.

• What version do you use?

• Because of this vast difference in methodology, and version, the National Trauma Data Bank requires all hospitals to report ICD-9-CM codes and then applies a single mapping to all records to ensure the same rules (good / bad / ugly) apply to every hospital.


MAPPING EXAMPLE

• Patient with pneumothorax

ICD-9-CM 860.0 Body Region = 4Severity = 3

“Behind the Scenes”

ISS = most severe injury in 3 different body regionhowever this is an isolate injury

ISS = 9


Survival Probability (Ps)

• Also know as TRISS

• Coefficients b0 - b3 are derived the Major Trauma Outcome Study (MTOS) database 1987.

• Ranges: 0.000 – 1.000 (% Survival)


Ps Components• Age

• Mechanism (Blunt vs. Penetrating)

• RTS (Evaluation)

• ISS

• Formula: Ps = 1 / (1 + E –b)


Ps Key Factors

•Age 0-54 or 55 and greater

•Different coefficients for blunt verses penetrating trauma.

• If the patient is less than 15, the blunt coefficients are used regardless of mechanism.


Survival Probability Calculator

• Trauma.org• http://www.trauma.org/index.php/main/article/387

http://www.trauma.org/index.php/main/article/387

http://www.trauma.org/index.php/main/article/387


Benchmarking Scores

• TRISS Chart

• M & Z

• W Score


TRISS Chart

• PRE Chart

• Utilizes a Scatter plot

• Used to demonstrate expected and unexpected outcomes

• Threshold is 0.50 or 50%


TRISS Chart

0 15 30 45 60 75

0

2

4

6

8

ISS

RTS

L

L L

L

D L

L

DD

= Outliers

L = LivedD = Died


M Score

• Characterizes case mix

• Based on ISS compared to the MTOS

• Score Ranges:0.0 – 0.87 = Dissimilarity to MTOS.88 – 1.0 = Similarity to MTOS

* First step in benchmarking: is your patient population Similar or Dissimilar. If Similar – continue on with Z score, if Dissimilar – you can not use Z score as a benchmark


Z Score

• Describes provider’s performance

• Values between -1.96 to + 1.96 allow national comparison

• Score Ranges:Values exceeding +1.96 are significantly betterValues exceeding -1.96 are significantly worse


W Score

• Describes the # of unexpected survivors (+) or deaths (-) per 100 patients

• Formula:W = A – B ÷ C/100

A = Total # of pts with Ps – those that diedB = Sum of the PsC = Total # of pts with Ps


RIPPLE EFFECT

• If any one component is incorrect this causes a ripple effect in the data

• This can be anything from GCS to initial vital signs to under or over coding an injury

Inaccurate mapping for Blunt

VS Penetrating

InaccurateProbabilityOf Survival

PotentialInaccurate

M & ZStatistic

Potential InaccurateW Score

Invalid E-code


Examples:

• A 47 year old male was assaulted to head and back with fists and then slammed into a wall. Found unresponsive in a jail cell.

Initial vital signs HR 76, R 14, BP 127, GCS 8. Injuries: EDH with LOC--AIS=5; eyelid contusion--AIS 1.

ISS 26, RTS 5.967

IF YOU CHOOSE THE WRONG COEFFICIENT FOR BLUNT / PENETRATING• PS (Blunt) = 90.1%• PS (Penetrating) = 84.5%

Inaccurate Injury

Severity Score (ISS)

Inaccurate Probability

Of Survival (PoS)

InaccurateM & Z

Statistic

InaccurateTRISSChart

Incomplete or Inaccurate

Injury Coding


EXAMPLES:

• 65 year old male, fall from ladder, CHI, multiple rib fxs and femur fx.

Initial VS: SBP 110, RR 20, GCS 13 (RTS 7.841)

BASED on this documentationCHI AIS 2Rib Fxs unspecified AIS 2Femur Fx unspecified AIS 3

ISS = 17


EXAMPLE: Clear, detailed documentation

• 65 year old male, fall 12 feet from ladder landing on concrete, positive LOS continuing for 2.5 hours. Initial VS: SBP 110, RR 20, GCS 13 (RTS 7.841)

Injury List includes:Flail chest with unstable chest wall AIS 4Cerebral Contusion (LOC 2.5 hours) AIS 4Intertrochanteric Femur Fx AIS 3

ISS 41


ADVERSE EFFECT

• Based on this example

Age 65RTS 7.841Mechanism BLUNT

ISS 17 = Ps 93.9%ISS 41 = Ps 67.3%


Injury Severity Principles Summary

• Know the Rules:a) GCSb) Initial Vital Signs = RTSc) Accurate ICD-9-CM coding guidelines to ensure

accurate ISSd) ISS and other valid data elements ensures

accurate Ps, M, Z, W scores

• Recite Principles / Components of different scores

• Make no assumptions

injury severity principles

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