Crush injury is the one emergency where the danger is not the crushing but the release, and where the person can look and feel entirely well while trapped.
What is actually happening. Compressed muscle dies and its contents leak into
the tissue — potassium, which can stop the heart, and myoglobin,
which blocks the kidneys. While the limb is compressed, none of it can circulate. Release opens
the tap. That is why someone chatting to you under a wall can arrest within minutes of being
freed, and it is called crush syndrome.
1. The decision, and what it actually means for a bystander
| Time trapped | What to do |
|---|---|
| Under about 15 minutes | If you can free them safely, do it now. The syndrome needs time to develop and early release is the right call. The 15 minutes is a working threshold rather than a sharp line, so if the timing is genuinely unknown, treat it as prolonged |
| Longer, or unknown | 999 first, and say clearly that someone is trapped and for how long — that sentence changes what the ambulance brings and who is dispatched. Ideally release happens with intravenous fluids running and a monitor attached |
| The chest or abdomen is compressed | Release immediately, whatever the duration. This is the exception that overrides the rest of the table. A load on the chest stops them breathing — traumatic asphyxia — and no amount of preparation for crush syndrome helps someone who is being suffocated while you wait. The face and neck may look dark red or purple with pinpoint bleeding into the skin and the eyes, which is the sign of it. Airway and breathing outrank everything in this chapter |
| Immediate danger — fire, water, collapsing structure | Get them out. Crush syndrome is a risk; a fire is a certainty. The calculation is not close |
What this does not mean
- It does not mean leaving someone trapped and doing nothing. If you are alone with someone under a fallen object and help is minutes away, waiting for a crew with fluids is preferable — but a bystander who lifts a wall off a trapped person has not done something reckless, and should not be left thinking they have.
- What matters most is that you say how long they were trapped. That single number changes the treatment more than anything you can do with your hands, and only you have it.
- Never put yourself under an unstable load. A second casualty ends the rescue for both.
- If release has already happened and they deteriorate — collapse, irregular pulse, cardiac arrest — that is crush syndrome. Start CPR and say on the phone that they have just been released from a crush. It changes the drugs that are given.
2. What you can always do, whatever the timing
- Call 999 and say “trapped, for about X minutes”.
- Keep them warm. Trapped people get cold fast, on cold ground, often wet, often for a long time — and hypothermia makes everything that follows worse. Insulate above and below.
- Keep talking to them and stay where they can see you. Not sentiment: an entrapment is frightening and prolonged, and a deteriorating conscious level is something you will only notice if you have been talking to them throughout.
- Nothing by mouth. They may need an anaesthetic, and vomiting while trapped and unable to turn is a serious hazard.
- Control any external bleeding you can reach — see catastrophic bleeding.
- Look at the whole scene once, then keep looking. How stable is the load, is there fuel or gas, is there anyone else under it, is the ground moving.
- Do not apply a tourniquet in an attempt to prevent crush syndrome. It was once taught and it is not recommended — it adds ischaemic injury without preventing the metabolic one. A tourniquet is for uncontrollable bleeding, and nothing else.
3. What the team will do, so it does not look like delay
It can appear that nobody is rushing. They are not waiting; they are doing the thing that makes release survivable.
| Step | Why |
|---|---|
| Intravenous fluid before release, often in large volumes | Dilutes the potassium load, protects the kidneys from myoglobin, and fills a circulation that is about to expand into a reperfused limb |
| Cardiac monitoring through the release | The dangerous rhythm changes happen in the first minutes after the load comes off |
| Treatment for high potassium, ready in advance | Given at the first electrical sign rather than after a blood result |
| Analgesia and sometimes anaesthesia | Release is extremely painful, and a still patient is a safer extrication |
| Fire and rescue stabilising the load | Lifting the wrong part first can crush further or collapse the space |
| Deliberate sequencing of the lift | Sometimes releasing one limb at a time, so the metabolic hit arrives in stages |
4. Afterwards, because the injury continues for days
- Kidney injury is the main long-run problem, and it is driven by muscle breakdown rather than by the wound. It needs fluids, monitoring and sometimes dialysis, and it can develop over a day or two.
- Dark brown or cola-coloured urine after any crush — or after prolonged immobility, an electrical injury, or extreme exertion — means muscle breakdown and is a same-day medical problem, not something to watch.
- Compartment syndrome in the released limb: pain out of proportion, tightness, numbness, a limb that becomes hard to move. Surgical release is time-critical.
- The same physiology applies without any wall involved — an older person who has lain on a floor for many hours after a fall, or someone unconscious on a limb after an overdose, develops the same muscle breakdown and kidney injury. It is regularly missed because there is nothing to see and no dramatic mechanism. “Found on the floor, unknown down time” is a crush presentation.