Severity of Illness Scoring

First Things First

  • Combines clinical observations and statistical theory to create a single metric of the patient’s condition and associated outcome (e.g., mortality, length of hospital stay, etc.)

History and Physical (assess for the following)

  • Scoring systems are calibrated based on a logistic regression analysis of variables from large observational studies.
    • Regression analysis results must be considered in light of the facilities and inclusion criteria of the original study and may not apply to all institutions.
  • Epidemiological tools that cannot be used to determine an individual patient’s outcome
  • Can be subdivided to particular condition and population studied, such as:
    • Trauma vs. non-trauma surgical vs. medical vs. cardiac populations, etc.
    • Can evaluate multiple aspects of the patient’s condition (e.g., APACHE II) or can be organ-specific (e.g., Glasgow Coma Scale [GCS])
    • Performed at the time of admission or at intervals throughout hospital stay

Diagnostic Tests

  • Have to be individualized to the particular scoring system employed

General Management Principles

  • Scoring systems typically incorporate elements of:
    • Anatomic injury (mainly in trauma-specific scoring systems)
    • Physiological derangement
    • Effects of comorbidities
  • Allow for between-facility comparison in the quality and efficacy of intensive care
  • Increasingly used to determine risk/benefit of applying particular therapies (e.g., drotrecogin alpha)

Specific Treatment

General severity of illness scoring methods for adult ICU admissions

Acute Physiology and Chronic Health Evaluation (APACHE II; 1985)

  • Incorporates 2/3 scoring elements of physiologic derangement, and comorbid diseases
  • Score is based on the initial data collection at the time of admission and includes:
    • 12 physiological measurements
    • Age
    • Previous health status
  • Score ranges from 0-71 points
  • Benefits
    • Drotrecogin alpha may be considered for the treatment of sepsis based on the presence of both:
      • Sepsis-induced multiple organ failure, septic shock, or sepsis-induced acute respiratory distress syndrome [ARDS]) and,
      • An APACHE II score >25
    • Allows for adjustment in scores based upon a multitude of comorbidity modifiers
  • Limitations
    • Lacks anatomic injury component and therefore less useful in trauma patients
    • APACHE III (1992) is intended to rectify trauma limitation but the system is proprietary
    • More complex than other commonly available ICU admission scoring systems

Simplified Acute Physiology Score (SAPS II; 1993)

  • Similar to APACHE II
    • 12 routine physiological measurements during the first 24 hours, age, and prior health status
    • Score ranges from 0-24
  • Benefits
    • Most commonly used severity of illness scoring system
  • Limitations
    • Also lacks an anatomic injury component
    • Uses only 3 chronic health conditions in scoring (metastatic or hematologic malignancy, AIDS)

Sequential Organ Failure Assessment (SOFA; 1996)

  • Uses only 6 physiologic measurements and no chronic health or age-related modifiers
  • Score ranges from 0-24
  • Benefits
    • Ease of use
    • Uses common and readily available variables
    • Can be performed on a daily basis
  • Limitations:
    • Also lacks an anatomic injury component
    • Fails to take into account preexisting comorbidity modifiers

MODS (Multiple Organ Dysfunction Score)

  • Similar criteria and scoring system as SAPS II, with the same benefits/limitations

Severity of illness scoring methods for adult trauma admissions

Abbreviated Injury Scale (AIS)

  • Measures anatomic injury only
    • Originally intended for documentation of motor vehicle accidents
    • Comprises a lexicon of six-digit coded injuries (>2,000 listed) based on:
      • Region
      • Type of anatomic structure
      • Specific structure
      • Level of injury
    • Injuries are assigned a severity value of 1 (minor) to 6 (fatal)
    • Uses maximum AIS score based on the highest AIS severity among a set of injuries
  • Benefits
    • Most advanced and comprehensive trauma-specific coding system
  • Limitations
    • Uses only the single worst injury for a single area to provide the maximum AIS
    • Ineffective in the multiply injured patient
    • Proprietary system that requires specially trained coding personnel
    • Assigned values are subjective
    • Does not include comorbidities or physiological variables

Injury Severity Score (ISS; 1974)

  • Summation of AIS scores from the squared values of the three most severely injured body areas
  • Scores range from 0-75
  • Benefits: includes more injuries in its score derivation
  • Limitations
    • Same as AIS scoring, with the exception of number of injuries scored
    • Recognizes only the 3 most severe injuries
    • Includes only 1 injury from each area

Trauma-Related Injury Scoring System (TRISS; 1987)

  • Overcomes the lack of comorbid conditions and physiologic variables missing from AIS/ISS
    • Incorporates ISS, age, and 3 physiological variables
    • Final modifying equation is applied depending on whether the trauma was blunt or penetrating
  • Benefits
    • Has become the most accepted means of estimating trauma-related survival probabilities
    • Overcomes the ISS limitations of lack of physiological and comorbid disease data
  • Limitations
    • Same as AIS scoring
    • Only 3 physiological variables included

Revised Trauma Score (RTS)

  • Measures physiologic derangement
  • Combines coded values for systolic BP (SBP), respiratory rate (RR) & GCS
  • Coded values are given for each GCS, SBP, RR
  • GCS
    • 13-15 = 4
    • 9-12 = 3
    • 6-8 = 2
    • 4-5 = 1
    • 3 = 0
  • SBP
    • >89mmHg=4
    • 76-89 mmHg = 3
    • 50-75 mmHg = 2
    • 1-49 mmHg = 1
    • 0 mmHg = 0
  • RR
    • 10-29 bpm = 4
    • >29bpm=3
    • 6-9 bpm = 2
    • 1-5 bpm = 1
    • 0 bpm = 0
  • Coded values can be added for score of 0-12 for use in pre-hospital triage.
    • RTS value < 11 suggests need for transfer to trauma center.
  • Values are weighted for in-hospital use as follows:
    • RTS = 0.9368 (GCScoded) + 0.7326 (SBPcoded) + 0.2908 (RRcoded)
    • Range of values 0-7.84
    • RTS >5, >90% survival
    • RTS < 3, < 20 % survival
    • Used primarily as research tool for outcome assessment & quality assurance

Severity of illness scoring methods for pediatric ICU admissions

Pediatric Risk of Mortality (PRISM; 1988)

  • Uses 12 physiologic measurements, papillary response and GCS assessment – similar to APACHE II
  • Benefit: comprehensive scoring tool
  • Limitation: does not include comorbid disease assessments

Severity of illness scoring methods for pediatric trauma admissions

Pediatric Trauma Score (PTS)

  • Combines aspects of anatomic injury, physiologic derangement & physiologic reserve
  • Components include pt size, airway, consciousness, SBP, fracture, cutaneous injury
  • Used for pre-hospital triage
  • Each category is scored -1, +1 or +2.
  • Size
    • Child >20 kg = +2
    • Toddler 11-20 kg = +1
    • Infant < 10 kg = -1
  • Airway
    • Normal = +2
    • Assisted w/ oxygen = +1
    • Intubated = -1
  • Consciousness
    • Awake = +2
    • Obtunded/lost consciousness = +1
    • Unresponsive = -1
  • SBP
    • >90mmHg=+2
    • 51-90 mmHg = +1
    • < 50 mmHg = -1
  • Fracture
    • No fracture = +2
    • Single closed fracture = +1
    • Multiple or open fracture = -1
  • Cutaneous
    • No visible injury = +2
    • Contusion/abrasion or laceration not through fascia = +1
    • Tissue loss, gunshot or stab through fascia = -1
  • Total score ranges from -6 to +12
  • PTS >8, 0% mortality; PTS < 0, 100% mortality
  • PTS < 9 indicates need for transfer to a pediatric trauma center.

Ongoing Assessment

Commonly used organ specific scoring methods

  • GCS (1974)
    • Easily applied and reproducible assessment of level of consciousness
    • Based on combined scores for visual, motor, and verbal interaction
    • Eye Opening
      • Spontaneous = 4
      • To Voice = 3
      • To Pain = 2
      • None = 1
    • Verbal Response
      • Oriented = 5
      • Confused = 4
      • Inappropriate words = 3
      • Incomprehensible sounds = 2
      • None = 1
    • Motor Response
      • Obeys commands = 6
      • Localizes pain = 5
      • Withdraws from pain = 4
      • Flexor posturing to pain = 3
      • Extensor posturing to pain = 2
      • None = 1
    • Benefits:
      • GCS < 9 suggests inability to protect airway
      • Can be performed throughout the patient’s hospital course
  • Killip classification (1967) of heart failure after acute myocardial infarction
    • Stratified according to physiological variables and thoracic auscultation
      • Killip class I - no clinical signs of heart failure; 6% mortality
      • Killip class II - rales or crackles in the lungs, S3 gallop, and elevated jugular venous pressure; 17% mortality
      • Killip class III describes individuals with frank acute pulmonary edema; 38% mortality
      • Killip class IV - cardiogenic shock evidence of peripheral vasoconstriction; 81% mortality
    • Predictor of all-cause mortality for the following:
      • ST and non-ST segment elevation myocardial infarction
      • Unstable angina
      • Those undergoing percutaneous coronary intervention
  • Risk of acute renal failure, Injury to the kidney, Failure of kidney function,Loss of kidney function and End-stage kidney disease (RIFLE; 2007)
    • Uses the duration and extent of decline in urine output and creatinine levels or glomerular filtration rate to define the extent of acute kidney injury
    • Stratified injury among:
      • 3 grades of increasing severity of kidney injury: Risk, Injury, and Failure and
      • 2 outcome classes: Loss and End-stage
      • Particular stratification predicts mortality across multiple patient populations
      • Easily applied and reproducible scoring system

Complications

  • Avoid extrapolation of mortality prediction model results to individual patients.
  • Scoring systems are largely used in the research and quality assurance settings.
  • SOFA score and GCS are easily applied and reproducible and can be repeated daily.

Author

  • Written by James B. Sampson, MD, and Jeffrey D. Kerby, MD, PhD
  • Revised by Patrick F. Allan, MD

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Last updated: May 3, 2010

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