Primary Injury
- The initial trauma load causes injury to the brain and other organs, bony skeleton and vascular architecture (i.e. major haemorrhage)
- There may be death from raised ICP or exsanguination
- This initial injury leads to:
- Shock, and hyperlactataemia
- Microvascular flow abnormalities
- Primary coagulopathy
Secondary Injury
- Secondary injury, at the cellular level, is mediated by:
- Complement activation
- Damage-associated molecular patterns
- The primary mediators are neutrophils, who undergo adhesion, transmigration and degranulation with release of reactive oxygen species
- There is consequent:
- Ischaemia-reperfusion injury
- Cellular apoptosis
- Tissue necrosis
Injury Severity Score
- The most reliable indicator of injury load is the Injury Severity Score (ISS)
- An ISS >15 indicates major/severe traumatic injury
- It was initially derived from blunt, traumatic injury from motor vehicle collisions
- It measures the most severe injury in each of six organ systems
- Each organ system is given an abbreviated injury scale from 0 - 6, where 0 is no injury and 6 is unsurvivable
- The organ systems with the three highest scores (A, B and C) are used, and ISS = A2 + B2 + C2