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 parameters Best 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: – mild – moderate 3 – 8 - severe

Trauma Score (TS) Ranges: 1-16 Composed of 5 components: Objective Data: Systolic, Respirations, GCS Subjective 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 system 2. 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: – Normal: (weighted formula) Formula: RTS = (GCS) (SBP) (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 Example RegionInjuryAISSquare DescriptionTop Three Head & Neck Cere. Cont.416 FaceMandible Fx2 ChestFlail Chest416 AbdomenLiver Cont.2 Grade 5 Spleen injury 525 ExtremityHumerus fx.3 ExternalKnee Abrasion1 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 Example RegionInjuryAISSquare DescriptionTop Three Head & NeckSAH Open Skull Fx, LOC WRTBL FaceNo Injury0 ChestNo Injury0 AbdomenNo Injury0 ExtremityNo Injury0 ExternalNo Injury0 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

“MAPPING FOR SEVERITY” 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.

“MAPPING FOR SEVERITY” 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 Body Region = 4 Severity = 3 “Behind the Scenes” ISS = most severe injury in 3 different body region however 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 Ranges: – (% 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

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 L L L L D L L D D = Outliers L = Lived D = 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 to allow national comparison Score Ranges: Values exceeding are significantly better Values exceeding 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 died B = Sum of the Ps C = 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 Inaccurate Probability Of Survival Potential Inaccurate M & Z Statistic Potential Inaccurate W 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 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) Inaccurate M & Z Statistic Inaccurate TRISS Chart 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 documentation CHIAIS 2 Rib Fxs unspecifiedAIS 2 Femur Fx unspecifiedAIS 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 wallAIS 4 Cerebral Contusion (LOC 2.5 hours)AIS 4 Intertrochanteric Femur FxAIS 3 ISS 41

ADVERSE EFFECT Based on this example Age 65 RTS Mechanism BLUNT ISS 17 = Ps 93.9% ISS 41 = Ps 67.3%

Injury Severity Principles Summary Know the Rules: a) GCS b) Initial Vital Signs = RTS c) Accurate ICD-9-CM coding guidelines to ensure accurate ISS d) ISS and other valid data elements ensures accurate Ps, M, Z, W scores Recite Principles / Components of different scores Make no assumptions