Syncope
ABCs
- A–B–C, lay flat, check glucose immediately, IV access, full vitals + monitor
- if still unresponsive → treat as reduced GCS, not simple syncope (airway, call for help)
define what you’re dealing with
- syncope = transient LOC from global cerebral hypoperfusion, with rapid onset and full spontaneous recovery
- not everything that drops a patient is syncope: separate out seizure, hypoglycaemia, stroke, intoxication, arrhythmia
three buckets of true syncope
| type | clues |
|---|---|
| reflex (vasovagal) | prodrome (nausea, warmth, tunnel vision); triggers (pain, standing, micturition) |
| orthostatic | on standing; drugs (antihypertensives, diuretics), dehydration, autonomic failure |
| cardiac | the dangerous one: see red flags |
red flags
cardiac syncope until proven otherwise
- syncope on exertion or while supine
- no prodrome (“found on the floor”), or palpitations just before
- family history of sudden cardiac death
- known structural heart disease
- abnormal ECG
workup
- ECG on everyone: long QT, Brugada, pre-excitation (WPW), bifascicular block, pauses, ischaemia, AV block
- lying & standing BP: drop ≥ 20 systolic / 10 diastolic = orthostatic
- glucose, FBC (anaemia / bleed), U&E
- telemetry if cardiac cause suspected; echo if structural concern
calculator Canadian Syncope Risk · MDCalc ↗︎
syncope vs seizure
- lateral tongue bite, prolonged post-ictal confusion, incontinence → seizure
- brief jerks after collapse, rapid recovery → likely convulsive syncope
management
- treat the cause; hold the offending drug (antihypertensives, QT-prolongers)
- cardiac suspicion, injury, or abnormal ECG → admit / monitor + escalate
- reflex / orthostatic with a clear benign story → reassure, optimise meds, safety-net
MOC+ Volume 2 · Cardiopulmonary covers syncope & collapse. order here.
studying for the IM exam? the IM Rapid Review covers syncope in the same format. see the sample chapter.
Last reviewed · June 2026