General MedicineTier 1Approach to a presentation

Undifferentiated presentations - reduced level of consciousness

Red flags

GCS <=8 - airway protection required
Asymmetric pupils or focal neurological signs - structural cause
Hypoglycaemia - immediately reversible, check first
Fever + reduced consciousness - meningoencephalitis/sepsis
Signs of trauma - intracranial haemorrhage until excluded
Rapid fluctuation - non-convulsive status epilepticus

Differential by mechanism

Structural

Stroke (ischaemic/haemorrhagic), subdural/extradural haematoma, mass lesion, raised ICP, herniation

Metabolic/toxic

Hypoglycaemia, hyperglycaemia (DKA/HHS), hyponatraemia, uraemia, hepatic encephalopathy, hypoxia/hypercapnia, hypothyroidism (myxoedema coma), Addisonian crisis
Drug/toxin effect - sedatives, opioids, alcohol (see pharm-tox coma note for toxidrome detail)

Infective

Meningitis, encephalitis, sepsis-associated encephalopathy

Seizure-related

Post-ictal state, non-convulsive status epilepticus (persistent reduced consciousness without obvious convulsive activity)

Psychiatric/functional

Catatonia, pseudo-coma (rare, diagnosis of exclusion)

Focused history

Collateral history - onset speed, preceding symptoms (headache, fever, trauma), known medical conditions, medications
Time last seen well/normal (critical for stroke thrombolysis eligibility)
Substance use history, psychiatric history

Focused examination

GCS (or AVPU if rapid triage needed), pupils (size, symmetry, reactivity), posturing (decorticate/decerebrate)
Signs of trauma, meningism, focal neurological deficit
Glucose at the bedside immediately
Signs of chronic disease (liver, renal, thyroid) or toxidrome features

Investigation strategy

Glucose, VBG/ABG, UEC, LFT, calcium, ammonia if hepatic cause suspected, TSH if myxoedema considered
Paracetamol/salicylate levels in any unexplained presentation
CT brain - first-line if any focal signs, trauma, or unclear cause
Lumbar puncture if CNS infection suspected (after CT if any concern for raised ICP)
EEG if non-convulsive status epilepticus suspected

Management

1. Airway, breathing, circulation

Protect airway if GCS <=8

2. Treat reversible causes immediately

Glucose if hypoglycaemic or unknown, naloxone if opioid toxidrome suspected, thiamine before/with glucose if alcohol/malnutrition risk

3. Cause-specific

Stroke pathway (thrombolysis/thrombectomy window) if ischaemic and within time window
Neurosurgical referral for structural lesion/haemorrhage with mass effect
Treat sepsis/meningoencephalitis per standard protocols
Levothyroxine + corticosteroids for suspected myxoedema coma (treat empirically - high mortality if delayed)

4. Supportive care and monitoring

ICU-level care if airway/ventilatory support needed, serial neurological observations

Traps

A normal-looking initial exam does not exclude an evolving structural lesion - reassess serially
Flumazenil is not routine in undifferentiated reduced consciousness - seizure risk in mixed overdose/chronic benzodiazepine use
Myxoedema coma is rare but has high mortality if the diagnosis (and empirical treatment) is delayed awaiting TFT results
Always check glucose before attributing reduced consciousness to any other single cause

Talk track

"Glucose and pupils first - two observations that change management before any test result comes back."
"I reassess serially rather than trust a single snapshot exam in anyone with reduced consciousness."

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