Reasoning GP · Algorithm · 1-page summary
Transient loss of consciousness (TLoC)
For: people over 16 after a blackout, faint or collapse with loss of consciousness. Not for: children (use paediatric pathways), a fall without loss of consciousness. Known epilepsy: see the epilepsy protocol.
Core rule: a 12-lead ECG and a witness account in everyone, with lying and standing BP where appropriate. TLoC on exertion, lying down or without warning is cardiac until proven otherwise; no single feature separates a faint from a seizure.
0Stop — call 999 now — emergency assessment
- Acutely unwell: chest pain, sustained arrhythmia, severe breathlessness, serious injury, ongoing altered consciousness → 999 / ED
- Exertional TLoC with acute symptoms, or suspected PE, aortic dissection, ACS or subarachnoid haemorrhage (thunderclap headache) → 999
- New focal neurological deficit on recovery (neurological emergency), or TLoC or fitting lasting >5 minutes → 999
- Meanwhile: 12-lead ECG immediately; capillary glucose (hypoglycaemia mimics TLoC); neurological examination before calling it a faint. Advise not to drive.
1Triage — after ECG and examination
| Situation | Action |
|---|---|
| Not recovered or acutely unwell | Block 0 → 999 |
| Any CG109 red flag (block 2) | ≤24 h cardiovascular assessment |
| Aged over 65, no prodrome | Consider the same ≤24 h referral |
| Suspected first seizure | ≤2 weeks first-seizure clinic |
| Firm faint, situational or postural | Normal ECG → primary care |
2Screen — CG109 red flags: one is enough
- Abnormal ECG: complete RBBB or LBBB, any heart block, any ST or T-wave change, long or short QT, delta wave, Brugada → ≤24 h
- TLoC during exertion (HCM, aortic stenosis) → ≤24 h; avoid exertion until assessed
- Family history of sudden cardiac death <40 or inherited cardiac disease → ≤24 h
- Heart failure, heart murmur, new or unexplained breathlessness → ≤24 h
- QTc ≥500 ms on repeat ECG → Same-day expert advice; check K, Mg, Ca and QT drugs
3Assess — once blocks 0–2 are answered
☐ True TLoC, not a fall, intoxication or hypoglycaemia ☐ Before, during, after: posture, trigger, prodrome, movements, colour, tongue, recovery ☐ Lying BP, then at 1 and 3 min standing: fall ≥20 systolic or ≥10 diastolic ☐ Pulse, murmur, neurology, injuries ☐ Medicines ☐ Targeted only: glucose, FBC, U&E, pregnancy test
Not in primary care: carotid sinus massage, routine bloods, EEG, CT/MRI brain, prolactin.
4Classify — only if the screen is negative
- Vasovagal / situational — standing, heat, pain, emotion, micturition or cough; nausea, pallor, sweating; recovers flat → primary care.
- Orthostatic — on standing; drugs, dehydration, autonomic failure → medication review.
- Cardiac — no warning, exertion or lying down, palpitations before → cardiovascular assessment.
- Epileptic seizure — aura, lateral tongue bite, confusion >5 min; incontinence and injury are not specific → ≤2 weeks neurology.
- Carotid sinus (aged ≥60, neck turning, tight collar) → syncope clinic. Functional seizures → neurology; never diagnose from a normal EEG.
- Uncertain — no firm diagnosis and not strongly epilepsy → cardiovascular assessment. Refer rather than label.
5Treat today — only these
- Vasovagal: explain and reassure; avoid triggers; teach leg-crossing and hand-grip counter-pressure if a reliable prodrome; lie flat at prodrome.
- Orthostatic: reduce alpha-blockers, diuretics, TCAs, antipsychotics, nitrates; individualised fluid and salt (care in heart failure, CKD, frailty); rise slowly.
- QT: add no QT-prolonging drug; domperidone is contraindicated. Fludrocortisone and midodrine are specialist-led.
- Driving: no driving while awaiting specialist assessment unless a clear uncomplicated faint or situational syncope; check the DVLA chapter; document. Note occupation (heights, machinery).
6Refer routinely
- Recurrent vasovagal despite conservative measures; orthostatic hypotension despite medication changes → specialist.
- Recurrent unexplained TLoC → cardiology for ambulatory ECG chosen by frequency; implantable loop recorder if less than every 2 weeks.
7Never reassure by
- Jerking, incontinence or injury — these occur in syncope; never label epilepsy on movements alone.
- Fast recovery when the onset was exertional, supine or without warning.
- A normal EEG — it neither excludes epilepsy nor diagnoses functional seizures.
- A "faint" with no ECG and no lying/standing BP.
- The patient's account alone — ask for the witness (or a phone video).
- A simple faint diagnosed without a post-episode neurological examination.
8Safety-net — say it, then document it
999 “Call 999 for a blackout with chest pain, palpitations that won't stop or severe breathlessness, a blackout during exercise, a blackout or fit lasting over 5 minutes, fits that keep coming or not waking up fully, new weakness, speech or vision problems even if they go away, or a serious injury.” Same-day “Another blackout while we investigate, a blackout at the wheel, or more fits on epilepsy medicine — contact us today.”
Until seen: no driving, heights or machinery; document DVLA and occupation advice. Review once the ECG and any tests are back.
✓Safe to leave primary care only if — all five, documented
Fully recovered; no block 0–2 row applies
12-lead ECG done and normal
Witness account and lying/standing BP recorded
Firm faint, situational or postural diagnosis, or referral made
Driving, occupation and safety-net advice given
Summary of the full Reasoning GP transient loss of consciousness algorithm, which holds the history, ECG detail, investigations, DVLA documentation and epilepsy follow-up. Sources: NICE CG109, NG217; ESC syncope guideline 2018; DVLA Assessing fitness to drive; MHRA domperidone and valproate safety; CoSRH. Clinical reference — follow local syncope and first-seizure pathways and check doses: NICE/SPC, BNF, local formulary.