What is the approach to a patient with loss of consciousness, considering potential causes such as head trauma, stroke, seizure, hypoglycemia, or opioid overdose, and taking into account their medical history, including pre-existing conditions like epilepsy, diabetes, or heart disease?

Approach to Patient with Loss of Consciousness

Immediately stabilize airway, breathing, and circulation (ABCs) while simultaneously assessing for life-threatening causes—this takes absolute priority over diagnostic workup. 1, 2

Initial Emergency Stabilization (First 0-2 Minutes)

Secure the airway first—without this, resuscitation is hopeless. 3 The initial evaluation mirrors management of any critically ill patient:

• Assess and secure airway patency in all unconscious patients, as altered consciousness is associated with potentially life-threatening airway compromise 2, 3
• Ensure adequate breathing and oxygenation through rescue breathing or bag-mask ventilation if needed 1, 3
• Verify circulation with pulse check and blood pressure assessment 1
• Check fingerstick glucose immediately—hypoglycemia is a rapidly reversible cause that mimics stroke and other serious conditions 1, 4

Critical Point on Airway Management

Not all unconscious patients require immediate intubation. In non-trauma unconscious patients, 85% regain consciousness before hospital transport when appropriately managed, and only 19% of those remaining unconscious ultimately require intubation. 5 However, maintain readiness to intubate if airway protection becomes necessary.

Rapid Diagnostic Assessment (Minutes 2-5)

Essential Historical Information

The single most important piece of information is time of symptom onset—defined as when the patient was last at baseline or symptom-free. 1 For patients who cannot provide this or who awoke with symptoms, the onset time is when they were last known to be normal. 1

Obtain focused history addressing:

• Precipitating events: emotional stress, prolonged standing, pain, instrumentation, specific situations (urination, defecation, cough, swallowing) 1
• Prodromal symptoms: preceding aura, nausea, diaphoresis, visual changes 1
• Witnessed seizure activity versus brief seizure-like movements (the latter commonly occurs during syncope and should NOT be regarded as indicating epilepsy) 1, 6
• Medical history: diabetes, cardiac disease, epilepsy, medication use (especially antiepileptics, psychiatric medications, opioids) 1

Physical Examination Priorities

• Orthostatic vital signs: Measure blood pressure after 5 minutes supine, then each minute for 3 minutes standing. A decrease in systolic BP ≥20 mmHg or to <90 mmHg defines orthostatic hypotension. 1
• Cardiovascular examination: Check for arrhythmias, murmurs suggesting structural heart disease, signs of heart failure 1
• Neurological examination: Assess for focal deficits, cranial nerve abnormalities, inconsistent findings suggesting psychogenic causes 1
• 12-lead ECG immediately: Look for ischemia, arrhythmias, prolonged QT, Brugada pattern, heart block 1

Differential Diagnosis Framework

Syncope (True Loss of Consciousness from Cerebral Hypoperfusion)

Neurally-Mediated (Reflex) Syncope 1, 6

• Vasovagal syncope is diagnosed when precipitating events (fear, severe pain, emotional distress, prolonged standing) are associated with typical prodromal symptoms 1
• Situational syncope is diagnosed when loss of consciousness occurs during or immediately after urination, defecation, cough, or swallowing 1
• These patients with uncomplicated presentations require ECG but do NOT need immediate specialist referral 1

Orthostatic Hypotension 1, 6

• Primary autonomic failure (pure autonomic failure, multiple system atrophy, Parkinson's disease) 6
• Secondary causes: diabetic neuropathy, amyloid neuropathy, drug-induced, volume depletion 6

Cardiac Causes (MOST LETHAL—Require Immediate Cardiovascular Specialist Assessment) 1, 6

• Arrhythmias: sinus node dysfunction, AV block, ventricular tachycardia, inherited syndromes (long QT, Brugada) 1, 6
• Structural disease: valvular obstruction, acute MI/ischemia, hypertrophic cardiomyopathy, atrial myxoma, aortic dissection, pulmonary embolism 1, 6

Non-Syncopal Causes of True Loss of Consciousness

Metabolic Disorders 1

• Hypoglycemia: Most common in diabetic patients; generalized tonic-clonic seizures occur only when glucose drops below 2.0 mM (36 mg/dL), though focal seizures can occur at higher levels 7
• Hypoxia, hyperventilation with hypocapnia 1

Seizure/Epilepsy 1

• History of prior seizures, witnessed seizure activity, postictal period 1
• Approximately 25% of diabetic patients experience seizures, particularly with DKA episodes 8

Stroke/TIA 1

• Vertebrobasilar TIA can cause loss of consciousness (carotid TIA does NOT) 1
• Acute ischemic stroke with ECG evidence of ischemia 1

Intoxications 1

• Opioid overdose: CNS and respiratory depression progressing to respiratory then cardiac arrest 1
• Drug toxicity: lithium, phenytoin, carbamazepine 1

Conditions Mimicking Loss of Consciousness (No True LOC)

• Psychogenic pseudo-syncope, cataplexy, drop attacks 1, 6
• Carotid TIA (no actual loss of consciousness) 1

Specific Management Algorithms

If Opioid Overdose Suspected

For respiratory arrest (pulse present, no normal breathing): 1

1. Provide rescue breathing or bag-mask ventilation immediately 1
2. Administer naloxone (it is reasonable to give) 1
3. Continue ventilation until spontaneous breathing returns 1

For cardiac arrest (no pulse): 1

1. High-quality CPR takes absolute priority over naloxone—standard resuscitative measures should NOT be delayed 1
2. Naloxone can be administered alongside CPR if it does not delay compressions 1
3. Activate emergency response immediately; do NOT wait for response to naloxone 1

If Hypoglycemia Confirmed

• Administer IV dextrose immediately if glucose <70 mg/dL with altered consciousness 4
• Monitor for hyperglycemia complications during treatment, especially in patients with underlying CNS disease 4

If Stroke Suspected

• Triage with same priority as acute MI or serious trauma regardless of deficit severity 1
• Activate stroke team/pathway immediately 1
• Transport to facility capable of acute stroke treatment; bypass hospitals without stroke resources 1
• Obtain brain imaging emergently 1

Disposition and Referral Guidelines

Immediate Specialist Cardiovascular Assessment Required: 1, 6

• Suspected cardiac cause of loss of consciousness 1
• Unexplained loss of consciousness after initial assessment 1
• ECG abnormalities suggesting arrhythmia or structural disease 1

Neurological Referral Indicated: 1

• Loss of consciousness that CANNOT be attributed to syncope 1
• Features suggesting epilepsy (but NOT brief seizure-like movements during syncope) 1, 6
• Suspected autonomic failure or cerebrovascular steal syndrome 1

Psychiatric Evaluation Recommended: 1

• Symptoms suggesting psychogenic pseudo-syncope 1
• Known psychiatric disorder with medication that may need adjustment 1

No Immediate Specialist Referral Needed: 1

• Uncomplicated vasovagal syncope with typical features 1
• Situational syncope with clear trigger 1
• Orthostatic hypotension documented with typical presentation 1
• These patients still require ECG but can be managed in primary care 1

Common Pitfalls to Avoid

• Do NOT assume brief tonic-clonic movements indicate epilepsy—these commonly occur during syncope from cerebral hypoperfusion 1, 6
• Do NOT routinely order neurological investigations for clear syncope cases 1
• Do NOT delay emergency response while awaiting naloxone response in suspected opioid overdose 1
• Do NOT miss cardiac causes—these are the most lethal and require immediate specialist assessment 1, 6
• Do NOT forget to check glucose—hypoglycemia mimics stroke and other serious conditions 1, 4