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Calculate trauma injury severity using the Abbreviated Injury Scale (AIS) for 6 body regions
ISS = (Highest AIS)² + (2nd Highest AIS)² + (3rd Highest AIS)²
Note: If any region has AIS = 6, ISS automatically = 75
Estimated Mortality:
| Body Region | AIS 1 Example | AIS 3 Example | AIS 5 Example |
|---|---|---|---|
| Head/Neck | Headache, dizziness | Unconscious <1 hr | Depressed skull fracture |
| Face | Superficial laceration | Multiple facial fractures | Massive facial crushing |
| Chest | Chest wall contusion | Unilateral pneumothorax | Aortic laceration |
| Abdomen | Abdominal wall contusion | Spleen laceration | Liver rupture with shock |
| Extremity | Simple fracture | Femur fracture | Crushed pelvis |
| External | Minor contusions | Second-degree burns 10-19% | Second-degree burns >65% |
ISS is an anatomical scoring system that provides an overall score for patients with multiple injuries. It ranges from 0 to 75, with higher scores indicating more severe injury. An ISS of 16 or greater is typically used to define major trauma.
ISS is calculated by summing the squares of the highest Abbreviated Injury Scale (AIS) scores in the three most severely injured body regions. The six body regions are: head/neck, face, chest, abdomen, extremities, and external. If any region has an AIS of 6, the ISS is automatically assigned 75.
An ISS of 16 or greater indicates major trauma and is associated with significantly increased mortality risk. These patients typically require trauma center care and may need specialized surgical interventions. The threshold of 16 is commonly used for trauma center triage.
ISS has several limitations: it only uses the three most severe injuries (ignoring multiple injuries in one region), it treats all body regions equally (head injury may be more critical than limb injury), and it's an anatomical score that doesn't account for patient age or physiological response.
ISS is used for trauma triage, research, and quality improvement. It helps predict mortality, guide resource allocation, and compare outcomes across trauma centers. However, it should be used alongside clinical judgment and physiological parameters like vital signs.
Mortality increases exponentially with ISS. Minor injuries (ISS <9) have mortality <1%, moderate injuries (ISS 9-15) have 1-3% mortality, serious injuries (ISS 16-24) have 5-10% mortality, severe injuries (ISS 25-40) have 10-30% mortality, and critical injuries (ISS >40) have mortality exceeding 50%.
This ISS calculator is for educational purposes and clinical decision support only. It should not replace professional medical judgment. ISS is one component of trauma assessment and should be used alongside vital signs, clinical examination, and other scoring systems. Always follow your institution's trauma protocols and consult appropriate specialists for patient care.