25.2 Prehospital Care and Intra- and Inter-Hospital Transport of the Critically Ill
Key Takeaways
Prehospital care follows a structured approach such as cABCDE, in which catastrophic external haemorrhage is controlled first with direct pressure, haemostatic dressings or tourniquets.
Prehospital emergency anaesthesia uses a standard operating procedure and checklist, with the same monitoring standards as in hospital, including continuous waveform capnography.
Patients should be stabilised before transfer: secure the airway if it may deteriorate, ensure adequate venous access, control haemorrhage where possible, and secure all lines and tubes.
At altitude, gas-filled spaces expand (Boyle's law) and falls, so pneumothoraces must be drained, tracheal cuffs checked or filled with saline, and inspired oxygen increased; aircraft cabins are typically pressurised to an altitude of about 1,800-2,400 m.
Transfer equipment must be battery-powered, secured, and checked, with oxygen supplies calculated to cover at least the expected journey time plus a reserve (commonly at least an extra hour or double the expected requirement).
25.2 Prehospital Care and Intra- and Inter-Hospital Transport of the Critically Ill
Prehospital Care
Structured Approach
Prehospital and trauma care uses a modified primary survey:
c Catastrophic haemorrhage: direct pressure, haemostatic dressings, tourniquets
A Airway with cervical spine protection where indicated
B Breathing: oxygen, decompress tension pneumothorax (finger thoracostomy if ventilated)
C Circulation: haemorrhage control, pelvic binder, IV or IO access, blood products if carried
D Disability: GCS, pupils, glucose
E Exposure and environment: prevent hypothermia
Triage at major incidents sorts casualties by priority (for example P1 immediate, P2 urgent, P3 delayed, and expectant or dead) using tools based on walking ability, breathing, respiratory rate, pulse or capillary refill. Trauma networks direct severely injured patients to major trauma centres, even if this bypasses a nearer hospital, when the transfer time is acceptable.
Prehospital Haemorrhage Management
- Tourniquets for life-threatening limb bleeding; note the time of application.
- Pelvic binders for suspected pelvic fractures in unstable patients.
- Permissive hypotension in penetrating trauma without head injury (radial pulse or systolic pressure of about 80-90 mmHg) until haemorrhage control.
- Tranexamic acid 1 g within 3 hours of injury.
- Some services carry red cells and plasma for prehospital transfusion.
Prehospital Emergency Anaesthesia (PHEA)
Indications include airway compromise, ventilatory failure, unconsciousness with loss of airway reflexes, and the need to control a combative patient with a severe head injury for safe transport.
- Performed by trained teams using a standard operating procedure and a challenge-response checklist.
- Minimum monitoring standards are the same as in hospital: ECG, non-invasive blood pressure, pulse oximetry and continuous waveform capnography.
- Common drug choices are ketamine (cardiovascular stability) or reduced doses of other agents, with fentanyl and rocuronium in a fixed-dose or weight-based protocol.
- Videolaryngoscopy and a bougie improve first-pass success; plans for failed intubation include supraglottic airways and surgical cricothyroidotomy.
- Positioning the patient for access around the head (for example, moving the patient out of a vehicle or onto a trolley) improves success.
Indications and Types of Transfer
| Type | Examples |
|---|---|
| Primary | From scene to hospital |
| Intra-hospital | Emergency department to CT, theatre or ICU |
| Secondary (inter-hospital) | For specialist care (neurosurgery, cardiothoracic surgery, burns, ECMO), for capacity reasons, or repatriation |
Inter-hospital transfers should be undertaken by trained and experienced staff (an anaesthetist or intensivist plus a trained assistant for critically ill ventilated patients, or a specialist retrieval team).
Planning and Stabilisation
"Stabilise before transfer" applies except when the transfer itself is the definitive treatment (for example a patient with an expanding extradural haematoma who needs immediate surgery).
Checklist Before Departure
| Area | Checks |
|---|---|
| Airway | Secure the airway if there is any risk of deterioration; check tube position and fixation; capnography |
| Breathing | Ventilation on the transport ventilator for a period before leaving; blood gas check; drain pneumothoraces |
| Circulation | Two reliable venous accesses; arterial line for invasive pressure; vasoactive drugs in syringe drivers with spare syringes |
| Disability | Sedation, analgesia and paralysis plan; glucose; spinal immobilisation if needed |
| Exposure | Temperature control, warming |
| Documentation | Notes, imaging, blood results, referral details, consent and communication with family |
| Logistics | Destination bed confirmed, receiving team informed, route and vehicle arranged, staff insured and wearing appropriate clothing |
Equipment
- Battery-powered monitors, ventilators and infusion pumps with sufficient battery life and spare batteries.
- Equipment must be secured so that it cannot become a projectile in an accident.
- Suction, airway equipment for failed intubation, defibrillator, drugs for resuscitation.
Oxygen Calculation
For example, a 90-minute transfer at a minute ventilation of 8 L/min with an of 0.5 uses about L of oxygen for ventilation alone, plus any driving gas used by a pneumatic ventilator (which may be about 1 L/min or more). Carry at least double the calculated amount or enough for an extra hour. A size E cylinder holds about 680 L, and a CD cylinder about 460 L.
Physiological Hazards of Transport
Acceleration and Deceleration
Rapid acceleration displaces blood towards the feet (hypotension in hypovolaemic patients); deceleration towards the head (raised intracranial pressure). Loading the patient head-first in an ambulance means acceleration causes the greatest problems. Smooth driving matters more than speed.
Vibration, Noise and Temperature
Vibration and noise interfere with monitoring (non-invasive blood pressure, auscultation) and cause discomfort; hypothermia develops quickly.
Air Transport
| Effect | Mechanism | Precaution |
|---|---|---|
| Hypoxia | Falling barometric pressure lowers (Dalton's law); cabins are usually pressurised to about 1,800-2,400 m (6,000-8,000 ft), where is about 14-16 kPa | Increase inspired oxygen; consider sea-level cabin pressure for severe hypoxaemia |
| Gas expansion | Boyle's law: gas volume increases by about 30-35% at 2,400 m | Drain pneumothoraces before flight; fill tracheal tube cuffs with saline or monitor pressure; vent nasogastric tubes; avoid flying after recent air in the eye, intracranial air or bowel obstruction where possible |
| Reduced humidity | Dry cabin air | Humidify ventilated patients |
| Space and access | Limited room in helicopters and aircraft | Complete interventions before take-off |
Helicopters are useful for distances that would take a long time by road or where roads are inaccessible, but they are noisy, cramped and weather-dependent; fixed-wing aircraft are used for longer distances.
Intra-Hospital Transfer
Transfers to CT or other departments carry similar risks to inter-hospital transfers: accidental extubation, line disconnection, equipment failure, hypotension and hypoxaemia. The same monitoring standards (including capnography for ventilated patients), staff competence and checklists apply. Critical incidents occur in a substantial proportion of intra-hospital transfers.
Handover
Use a structured handover (for example ATMIST in trauma: Age, Time of incident, Mechanism, Injuries, Signs, Treatment; or SBAR) and ensure that the receiving team has the documentation, imaging and a clear account of events during transfer.
A ventilated patient with a small traumatic pneumothorax, not drained, is to be flown to a specialist centre in an aircraft pressurised to the equivalent of 2,400 m. What is the most important intervention before departure?
Reduce the inspired oxygen concentration, because oxygen requirements fall at altitude
Insert a chest drain before departure, as the pneumothorax will expand
Remove the tracheal tube cuff air entirely so that the cuff does not expand
No intervention is needed, because a pressurised cabin prevents gas expansion
Which statement about inter-hospital transfer of a critically ill ventilated patient is correct?
Monitoring can be reduced to pulse oximetry alone because transfers are short
Equipment should be placed loosely on the patient's bed for easy access
Use ICU-standard monitoring including capnography, with secured battery-powered equipment
The patient should be transferred before resuscitation is complete, because the receiving hospital can stabilise them
A ventilated patient will be transferred for about 2 hours with a minute ventilation of 10 L/min, an of 0.6 and a ventilator that consumes an extra 1 L/min of driving gas. Approximately how much oxygen should be carried?
About 1,700 L or more (double the calculated 840 L)
About 120 L, because the transport ventilator recycles exhaled oxygen
About 420 L, the requirement for 1 hour
About 7,000 L, because each breath uses a full cylinder
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