Treat the greatest threat to life first: catastrophic haemorrhage and airway, then breathing, circulation, disability and exposure — and grade blood loss from the vitals.
How it's asked: A trauma vignette with vital signs: you pick the class of shock, or the very first step (airway with C-spine protection).
Why this is true
The primary survey is ordered by how fast each failure kills. An obstructed airway kills in minutes, a tension pneumothorax in minutes to an hour, haemorrhage over the first hour. Haemorrhagic shock follows a predictable compensation curve: early loss is hidden by tachycardia and vasoconstriction, so blood pressure is preserved until roughly 30% of volume is gone. A falling systolic pressure is therefore a late sign, and a narrowing pulse pressure with rising heart rate is the earlier warning.
Key points
Primary survey, in order
- 1Catastrophic external bleedingDirect pressure, tourniquet
ATLS classes of haemorrhagic shock (70 kg adult)
| Class | Blood loss | Heart rate | Systolic BP | Urine output | Mental state |
|---|---|---|---|---|---|
| I | <15% (<750 mL) | <100 | Normal | >30 mL/h | Slightly anxious |
| II | 15–30% | 100–120 | Normal (pulse pressure ↓) | 20–30 mL/h | Anxious |
| III | 30–40% | 120–140 | Decreased | 5–15 mL/h | Confused |
| IV | >40% (>2 L) | >140 | Markedly decreased | Negligible | Lethargic |
Common traps
- Hypotension is not an early sign — Class II shock has a normal systolic pressure. Don't call a tachycardic, normotensive trauma patient 'stable'.
- Elderly patients on beta-blockers and young athletes may not mount a tachycardia, so shock is under-graded in both.
Clinical case
A 28-year-old is brought after a road traffic accident. HR 128/min, BP 96/70 mmHg, RR 28/min, confused, urine output 10 mL/h after catheterisation.
High-yield
First step in any trauma: airway with cervical-spine protection. Systolic BP only falls once ~30% of blood volume is lost (Class III).
Quick check
Q1.A trauma patient has HR 110/min, normal systolic BP and a narrowed pulse pressure. Estimated blood loss?
Q2.Best immediate management of suspected tension pneumothorax in a crashing trauma patient?