The Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS) are used in polytrauma. The ISS is calculated from the three most severely injured body regions. If AIS scores are: Head/neck = 4, Chest = 3, Abdomen = 3, the ISS is:
- A 34 ✓
- B 28
- C 22
- D 16
Correct answer: A. 34
Explanation
ISS = sum of squares of the three highest AIS scores from different body regions: 4² + 3² + 3² = 16 + 9 + 9 = 34. An ISS ≥16 defines major trauma; ≥25 is associated with high mortality. The ISS cannot exceed 75 (3 × 5²), and an AIS of 6 (unsurvivable injury) in any region automatically gives ISS = 75.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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