Emergency Medicine: Triage, systems, prehospital care and major incidents

• The department: The Emergency Department — Overview | Triage | Streaming and Alternatives to Admission | The ED Consultation — Assess, Decide, Disposition | Time-critical Pathways
• Before hospital: Prehospital Care and Ambulance Services | Handover and Crowding
• Major incidents: Major Incidents | Major Incident Triage | Chemical, Biological, Radiological and Nuclear Incidents
• Safety, law and vulnerable patients: Patient Safety and Diagnostic Error in the ED | Safeguarding in the ED | Capacity, Leaving, Restraint and the Police | Frequent Attenders, Alcohol and Health Inequalities
• Revision: The ED at a Glance | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

🚑 The emergency department — triage, systems, prehospital care and major incidents. Emergency medicine is the specialty of the undifferentiated patient: anyone, with anything, at any time. Its skills are rapid prioritisation, recognising the few dangerous diagnoses among many minor ones, deciding who needs admission and who can go home safely, and running a department that copes with surges and major incidents. Clinical emergencies by system are covered in the Acute Medicine, Major Trauma, Poisoning and Psychiatric Emergencies chapters.
Your four questions for every ED patient: How sick are they, and how quickly do they need to be seen? What is the most dangerous diagnosis I must not miss? Do they need admission, same-day care, or can they go home safely? Is anyone vulnerable here — the patient, a child, or someone else?

The Emergency Department — Overview

• Types of urgent and emergency care (England):
  • Type 1 — consultant-led 24-hour emergency departments with full resuscitation facilities.
  • Type 2 — single-specialty emergency services (e.g. eye casualty, paediatric ED).
  • Type 3 — urgent treatment centres and minor injury units (minor injuries and illness, often nurse- or GP-led).
• Access — walk-in, ambulance, GP referral, NHS 111 (booked slots).
• Areas of a typical ED — resuscitation ("resus"), majors, minors (or "see and treat"), paediatric ED, ambulatory care, mental health assessment rooms, observation (clinical decision unit).
• Performance standards:
  • Four-hour standard — patients admitted, transferred or discharged within 4 hours of arrival (constitutional standard 95%; interim NHS England targets have been lower).
  • 12-hour waits from arrival (or decision to admit) — associated with excess deaths — reported and reviewed.
  • Ambulance handover within 15 minutes (and never over 60).
• Crowding is mainly caused by exit block (lack of inpatient beds) rather than inappropriate attendances — it causes harm (delayed antibiotics, corridor care, deaths) and staff burnout (RCEM).
• The ED team — emergency physicians, emergency nurse practitioners and advanced clinical practitioners, nurses, healthcare assistants, physician associates, pharmacists, physiotherapists, mental health liaison, alcohol care teams, frailty and social care teams, play specialists.
• Data — the Emergency Care Data Set (ECDS) records every attendance (diagnosis, acuity, outcome).

Triage

• Triage — rapid assessment (within about 15 minutes of arrival) to prioritise patients by clinical urgency rather than arrival time.
• Manchester Triage System (widely used in the UK) — chooses a presentation flowchart, then discriminators (life threat, pain, haemorrhage, conscious level, temperature, acuity) assign a category:

  Category	Name and colour	Target time to clinician	Examples
  1	Immediate — red	0 minutes	Cardiac arrest, airway compromise, shock, unresponsive child, active seizure
  2	Very urgent — orange	10 minutes	Cardiac chest pain, severe pain, altered conscious level, suspected sepsis, stroke
  3	Urgent — yellow	60 minutes	Moderate pain, persistent vomiting, uncomplicated fracture with deformity
  4	Standard — green	120 minutes	Minor injuries, mild pain
  5	Non-urgent — blue	240 minutes	Minor problems of long duration

• Physiological scores — NEWS2 in adults; paediatric early warning scores (PEWS — national system being introduced); sepsis screening tools.
• Triage limitations — under-triage of older people (atypical presentations), patients with learning disabilities or language barriers, and those who look well but have time-critical conditions (aortic dissection, ectopic pregnancy) — re-triage if waiting or deteriorating.
• Rapid assessment and treatment ("RAT") — a senior clinician at the front door starts investigations and treatment early.
• Waiting room safety — regular observations and re-assessment; escalation if NEWS2 rises.

Streaming and Alternatives to Admission

• Streaming — directing patients at the front door to the best place: urgent treatment centre, primary care, ED majors, paediatrics, specialty (eyes, early pregnancy, surgical assessment), same day emergency care (SDEC), frailty unit, mental health.
• Same day emergency care — investigation and treatment without an overnight stay (see Acute Medicine chapter).
• Clinical decision units (observation wards) — short stays (up to about 24 hours) for patients needing a period of observation or a test before discharge — e.g. head injury, alcohol intoxication, low-risk chest pain, overdose awaiting levels and psychosocial assessment.
• Hospital at home and virtual wards; urgent community response (2-hour crisis teams) for older people.
• Direct access pathways — fracture clinic ("virtual fracture clinic" — many injuries managed by phone review and advice), DVT, early pregnancy, ophthalmology, ENT.
• Frailty at the front door — Clinical Frailty Scale, early comprehensive geriatric assessment, therapy assessment, avoiding unnecessary admission.
• Benefits — patients avoid harms of hospital stays (delirium, infection, deconditioning) and departments decongest.

The ED Consultation — Assess, Decide, Disposition

• Primary assessment — ABCDE for unwell patients; resuscitate first, diagnose later.
• Focused history and examination — presenting complaint, timeline, red flags, past history, drugs (anticoagulants!), allergies, social situation and baseline function; collateral history (family, carers, ambulance crew, GP record).
• Worst-first thinking — for every complaint, list and actively exclude the dangerous diagnoses:

  Presentation	Don't miss
  Chest pain	ACS, aortic dissection, PE, tension pneumothorax, oesophageal rupture
  Headache	SAH, meningitis, CVST, temporal arteritis, carbon monoxide, raised ICP
  Abdominal pain	Ruptured AAA, ectopic pregnancy, mesenteric ischaemia, perforation, DKA, testicular or ovarian torsion
  Back pain	AAA, cauda equina, spinal infection, cord compression, aortic dissection
  Collapse	Arrhythmia, PE, GI bleed, AAA, ectopic, aortic stenosis
  Dizziness	Posterior circulation stroke, arrhythmia, bleeding
  Limp in a child	Septic arthritis, SUFE, NAI, malignancy
  Sore throat	Epiglottitis, quinsy, deep neck infection

• Investigations — targeted; know the limits (a normal ECG or troponin doesn't exclude everything; a normal CT at 8 hours doesn't exclude SAH).
• Disposition — admit (which specialty?), refer to SDEC or clinic, observe, or discharge.
• Safe discharge:
  • Clear diagnosis or working diagnosis explained to the patient.
  • Safety-netting — specific symptoms to watch for, when and how to return (verbal and written).
  • Follow-up arranged (GP, clinic, results), medication, fit note.
  • Check the patient can cope at home; communicate with GP (discharge letter).
  • "Would I be happy for this patient to be my relative going home?"
• Seek senior review before discharging high-risk groups (RCEM) — e.g. adults with non-traumatic chest pain over 30, febrile infants under 1, patients returning within 72 hours with the same complaint, abdominal pain in over-70s.

Time-critical Pathways

• Pre-alerts from ambulance services allow teams to be ready (resus, stroke, STEMI, trauma, paediatric).
• Bypass pathways — ambulances take STEMI patients directly to heart attack centres, stroke to hyperacute stroke units, major trauma to major trauma centres.

Prehospital Care and Ambulance Services

• NHS 111 — telephone and online triage for urgent but not life-threatening problems — books ED or UTC slots, GP appointments, clinician call-backs.
• 999 ambulance response categories (England — Ambulance Response Programme):

  Category	Examples	Target response
  1	Life-threatening — cardiac arrest, airway obstruction, not breathing	Mean 7 minutes (90% within 15)
  2	Emergency — stroke, chest pain, major burns, sepsis	Mean 18 minutes (90% within 40)
  3	Urgent — falls, abdominal pain, minor burns	90% within 2 hours
  4	Less urgent — may be managed by telephone advice	90% within 3 hours

• Paramedics — assessment, treatment (including drugs, airway, defibrillation), "see and treat" or "hear and treat" (avoiding conveyance), referral to community services.
• Advanced resources — critical care paramedics, helicopter emergency medical services (HEMS) and air ambulances (doctor–paramedic teams — prehospital anaesthesia, blood transfusion, resuscitative thoracotomy), hazardous area response teams (HART).
• Community first responders and public-access defibrillators — bystander CPR and early defibrillation are the strongest predictors of survival from out-of-hospital cardiac arrest; The Circuit registers defibrillator locations for 999 call handlers.
• Advance care plans — ReSPECT forms and DNACPR decisions guide prehospital treatment (in the patient's home).
• Prehospital trauma care — catastrophic haemorrhage control (tourniquets, haemostatic dressings), pelvic binders, splints, analgesia, prehospital blood products and tranexamic acid, triage to major trauma centres.

Handover and Crowding

• Ambulance handover — structured (e.g. ATMIST for trauma: Age, Time of injury, Mechanism, Injuries, Signs and symptoms, Treatment given) or SBAR for medical patients — the team listens without interrupting ("hands off, eyes on").
• Handover delays — ambulances queuing outside EDs leave crews unavailable for new 999 calls — harm both in the ED and in the community; "release to respond" protocols.
• Corridor care — care in non-clinical spaces during crowding — risks to dignity, privacy, infection control, monitoring and safety — should be exceptional and time-limited (RCEM, RCN).
• Escalation — OPEL (Operational Pressures Escalation Levels) and full capacity protocols move admitted patients to wards to free the ED.
• Handover between shifts — board rounds, SBAR, flagging sick and outstanding patients; never hand over unresolved critical results.
• Handover to inpatient teams — clear question, results, treatment given, ceiling of care.

Major Incidents

• Major incident — any event whose impact can't be handled within routine arrangements and needs special arrangements (e.g. mass casualties from transport crashes, terrorist attacks, fires, chemical releases, pandemic surges, internal hospital failures — loss of power, IT, water, or fire).
• Declaration — by the ambulance service, police or hospital — "major incident standby" then "major incident declared"; "cancelled" or "stand down".
• METHANE report (scene information from the first responder):
  • M — Major incident declared (or standby).
  • E — Exact location.
  • T — Type of incident.
  • H — Hazards (present and potential).
  • A — Access and egress routes.
  • N — Number and type of casualties.
  • E — Emergency services present and required.
• Joint working — JESIP principles (co-locate, communicate, co-ordinate, jointly understand risk, shared situational awareness); command levels — gold (strategic), silver (tactical), bronze (operational).
• Hospital major incident plan:
  • Action cards for each role; switchboard cascade; the ED becomes the receiving area; elective activity cancelled; wards discharge suitable patients; theatres and ICU prepared.
  • Key roles — ED consultant in charge (clinical lead), senior nurse, hospital co-ordination team (incident control room), triage officer at the door.
  • Major incident documentation — pre-labelled numbered records, identification of unknown patients.
  • Families' information centre, media handling, staff welfare.
• Training and exercises — tabletop and live exercises; lessons from previous incidents (e.g. Manchester Arena 2017).

Major Incident Triage

• Aim — do the most good for the most people with limited resources — not the same as everyday triage.
• Primary triage at the scene — quick, physiology-based (NHS Ambulance Service — triage sieve / ten-second triage):
  1. Catastrophic haemorrhage? → control it → T1 (immediate).
  2. Walking? → T3 (delayed).
  3. Not breathing after opening the airway? → dead (in a mass casualty setting).
  4. Respiratory rate under 10 or 30 or more? → T1.
  5. Pulse over 120 (or capillary refill over 2 seconds)? → T1.
  6. Otherwise → T2 (urgent).
• Priority categories:

  Category	Colour	Meaning
  T1 / P1 — Immediate	Red	Life-saving intervention needed now
  T2 / P2 — Urgent	Yellow	Needs treatment within a few hours
  T3 / P3 — Delayed	Green	Walking wounded — can wait
  Expectant (only when declared by command)	Blue	Unlikely to survive given resources — comfort care
  Dead	White or black	—

• Secondary triage (at the casualty clearing station or hospital) — more detailed assessment (e.g. Triage Sort using physiological scores).
• Triage is dynamic — repeat as patients improve or deteriorate.
• Blast and ballistic injuries — primary blast (lungs — "blast lung", ears — tympanic rupture, bowel), penetrating fragments, crush, burns, amputations; tourniquets and haemostatic dressings save lives; delayed presentations.

Chemical, Biological, Radiological and Nuclear Incidents

• Recognise — several casualties with similar unexplained symptoms, unusual smells, vapours or liquids, collapsed people without obvious cause ("STEP 1-2-3": one casualty — approach normally; two — caution; three or more — don't approach, suspect hazardous materials).
• Protect yourself — don't become a casualty; isolate the scene and the patients; report.
• Decontamination — "Remove, Remove, Remove" (initial operational response):
  1. Remove yourself from the area (fresh air).
  2. Remove outer clothing — removes most of the contamination; bag it.
  3. Remove the substance from the skin — dry decontamination (blot and rub with absorbent material) for most chemicals; wet decontamination (shower) for caustic substances.
• Chemical agents:
  • Nerve agents and organophosphates — cholinergic crisis (SLUDGE — salivation, lacrimation, urination, defecation, GI upset, emesis; miosis, bronchorrhoea, bradycardia, fasciculations, weakness, seizures) — atropine (to dry secretions), pralidoxime, benzodiazepines.
  • Irritant gases (chlorine, ammonia) — eye and airway irritation, pulmonary oedema (may be delayed).
  • Cyanide (fires, industrial) — collapse, seizures, high lactate — hydroxocobalamin.
  • Carbon monoxide — high-flow oxygen.
• Biological — clusters of unusual infections (anthrax, plague, smallpox) — infection control, public health (UKHSA).
• Radiological — external contamination (remove clothing, wash), internal contamination, acute radiation syndrome (nausea and vomiting timing predicts dose; lymphocyte count falls) — treat life-threatening injuries before decontamination; radiation protection advisers; potassium iodate tablets for radioactive iodine exposure (public health decision).
• Hospital response — decontamination area outside the ED, personal protective equipment, staff training, poisons advice (TOXBASE, National Poisons Information Service).

Patient Safety and Diagnostic Error in the ED

• Why errors happen in the ED — high workload, interruptions, undifferentiated patients, incomplete information, shift handovers, crowding, fatigue, night shifts.
• Commonly missed diagnoses:
  • ACS (atypical presentations — women, diabetics, older people), aortic dissection, PE, SAH, AAA (mistaken for renal colic), ectopic pregnancy, sepsis (in older people), stroke mimics and chameleons (posterior circulation stroke labelled "vertigo"), cauda equina, spinal epidural abscess, testicular torsion, compartment syndrome.
  • Injuries — scaphoid fractures, posterior shoulder dislocation, Lisfranc injuries, cervical spine fractures in older people, tendon injuries in hand wounds, retained foreign bodies (glass), Maisonneuve fractures.
• Cognitive biases:
  • Anchoring — sticking with the first impression.
  • Premature closure — stopping thinking once a diagnosis is made.
  • Diagnostic momentum — accepting a label from triage or another clinician ("anxiety", "drunk", "frequent attender").
  • Availability bias, search satisficing (stopping after finding one abnormality).
  • Attribution bias — attributing symptoms to mental illness, alcohol, learning disability or frailty (diagnostic overshadowing).
• Safeguards — checklists, "what else could this be?", senior review of high-risk groups, re-assessment before discharge, written safety-netting, results review systems (ED X-ray discrepancies recalled), learning from incidents (Patient Safety Incident Response Framework).
• Returns within 72 hours — a warning sign of missed diagnosis — senior review.

💡 Clinical Pearl: "Drunk" is a description, not a diagnosis. An intoxicated patient with a head injury, low glucose, hypothermia, a GI bleed or a subdural can look exactly the same as one who is simply drunk — assess, observe and re-examine before anyone leaves or is labelled.

Safeguarding in the ED

• The ED is often the first place harm is seen — every clinician has a duty to recognise and act.
• Children:
  • Injuries inconsistent with history or development, delayed presentation, bruising in non-mobile babies ("those who don't cruise rarely bruise"), frequent attendances, burns with clear margins, neglect.
  • Think of the child behind the adult — ask about children at home when adults present with domestic abuse, substance misuse, mental illness, overdose.
  • Check the child protection information system (CP-IS); involve the paediatric team and safeguarding leads.
• Adults at risk — older people (neglect, financial and physical abuse), people with learning disabilities or dementia — Care Act 2014 safeguarding referrals.
• Domestic abuse — ask directly and privately (no partners or family members present, professional interpreters); risk assessment (DASH); refer high-risk cases to a MARAC (independent domestic violence advisers in many EDs); non-fatal strangulation is a major risk factor for homicide.
• Female genital mutilation — mandatory reporting to police of known FGM in girls under 18 by regulated professionals.
• Modern slavery and human trafficking, county lines and child criminal exploitation (stab wounds, drug-related injuries in teenagers), child sexual exploitation.
• Knife and gunshot wounds — GMC guidance — inform the police when a patient has a gunshot wound or a knife wound from an assault (usually without identifying details at first) — protects the public.
• Self-harm in young people — psychosocial assessment (see Psychiatric Emergencies).

Capacity, Leaving, Restraint and the Police

• Capacity (Mental Capacity Act 2005) — assume capacity; assess decision-specifically (understand, retain, weigh, communicate); acts in the best interests of those lacking capacity; document.
• Patients wanting to leave:
  • With capacity — they can refuse treatment and leave, even unwisely; explain risks, offer alternatives, document, safety-net, inform GP; "self-discharge" forms are optional.
  • Without capacity (e.g. head injury, delirium, intoxication with risk) — can be prevented from leaving in their best interests using the least restrictive option (MCA sections 5 and 6); proportionate restraint if needed.
  • Mental disorder with risk — Mental Health Act — doctors' holding powers (section 5(2)) apply to inpatients, not to ED patients; police may use section 136 in public places; in the ED, use the MCA or arrange urgent MHA assessment.
• Restraint and rapid tranquillisation — last resort, proportionate, by trained staff; monitoring after sedation; NICE NG10.
• The police in the ED:
  • Confidentiality still applies — disclosure only with consent, a court order, or in the public interest (serious crime, risk of serious harm) — consult senior colleagues and the Caldicott guardian.
  • Blood samples for alcohol and drug testing in drivers — with consent; if the patient lacks capacity, the police surgeon can take a sample, but it can't be tested without later consent; the treating doctor must not be compromised.
  • Patients in custody — remain your patient — clinical needs first.
• Fitness to drive — tell patients about DVLA notification duties (seizures, syncope, stroke and TIA, visual problems); if they won't stop driving and risk is serious, GMC allows disclosure to the DVLA after informing them.
• Death in the ED — verification, breaking bad news, organ and tissue donation referral, medical examiner review, coroner referral (unnatural, sudden unexplained, within 24 hours of admission in some circumstances).

Frequent Attenders, Alcohol and Health Inequalities

• Frequent attenders (e.g. 5 or more attendances a year) — often have unmet needs: mental illness, alcohol or drug dependence, homelessness, loneliness, chronic pain, long-term conditions, social crisis — high mortality.
  • Multidisciplinary case management, personalised care plans, high-intensity user services.
  • Each attendance still needs a fresh, open-minded assessment — serious illness happens in frequent attenders too.
• Alcohol — a major cause of ED attendances (intoxication, injuries, assaults, withdrawal, pancreatitis, GI bleeding, liver disease):
  • Screen (AUDIT-C); brief interventions reduce harmful drinking.
  • Alcohol care teams — specialist nurses for withdrawal management, detoxification and community follow-up.
  • Thiamine (IV Pabrinex) for anyone at risk of Wernicke's encephalopathy.
• Health inequalities — deprived communities, homeless people, migrants, Gypsy, Roma and Traveller communities, people with learning disabilities and severe mental illness use EDs more and have worse outcomes — the ED is an opportunity for screening (HIV and hepatitis opt-out testing in high-prevalence EDs), vaccination, smoking cessation and social referral.
• Homeless patients — discharge planning (duty to refer to the local housing authority — Homelessness Reduction Act 2017), avoiding discharge to the street.
• Violence reduction — youth workers in EDs, sharing anonymised assault data with community safety partnerships (Cardiff Model).

The ED at a Glance

Spot the Diagnosis

Exam-style Scenarios

1. A 72-year-old man arrives by ambulance with left loin pain radiating to the groin. He has never had kidney stones. HR 110, BP 98/60. Triage has put him in the "renal colic" stream.
Answer: Suspected ruptured or leaking AAA.

• Move to resus; senior review; two large-bore cannulas; crossmatch; permissive hypotension.
• Bedside ultrasound of the aorta; urgent vascular surgical referral.
• CT angiography only if stable; unstable — straight to theatre or EVAR.