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Decreased/loss of consciousness

Medicine > Endocrine & metabolic

Differential Diagnosis Schema 🧠

Neurological Causes

  • Epilepsy: Recurrent seizures with postictal confusion or amnesia.
  • Stroke: Sudden onset focal neurological deficits, possible loss of consciousness in hemorrhagic stroke.
  • Transient ischemic attack (TIA): Brief episodes of neurological deficit, usually without loss of consciousness, but may cause confusion.
  • Head injury: History of trauma, potential for intracranial hemorrhage, confusion, or loss of consciousness.
  • Brain tumor: Gradual onset of headaches, focal neurological signs, and possible seizures or confusion.
  • Subarachnoid hemorrhage: Sudden, severe headache (“thunderclap headache”), loss of consciousness, neck stiffness.
  • Meningitis/encephalitis: Fever, headache, neck stiffness, altered mental status, and possible seizures.
  • Hypoglycemia: Confusion, sweating, tremors, and possible loss of consciousness, often in diabetic patients.
  • Hyponatremia: Nausea, vomiting, confusion, seizures, and possible loss of consciousness.
  • Wernicke’s encephalopathy: Confusion, ataxia, nystagmus, typically in patients with alcohol misuse or malnutrition.
  • Toxic/metabolic encephalopathy: Confusion, altered consciousness due to renal or hepatic failure, toxins, or drugs.
  • Dementia: Progressive memory loss and confusion, but may lead to decreased consciousness in advanced stages or during acute illness.
  • Delirium: Acute confusion, fluctuating consciousness, often triggered by infection, surgery, or medications.
  • Non-convulsive status epilepticus: Prolonged altered consciousness without obvious convulsions, typically diagnosed with EEG.

Cardiovascular Causes

  • Syncope: Brief loss of consciousness due to transient cerebral hypoperfusion, often vasovagal or orthostatic
  • Cardiac arrhythmias: Sudden loss of consciousness, often without warning, may be associated with palpitations
  • Myocardial infarction: Chest pain, sweating, nausea, and possible loss of consciousness due to cardiac arrest or severe ischemia
  • Aortic stenosis: Exertional syncope, chest pain, and dyspnea, typically in older adults with a history of heart disease
  • Pulmonary embolism: Sudden onset dyspnea, pleuritic chest pain, and possible syncope or shock
  • Hypertrophic cardiomyopathy: Exertional syncope, palpitations, family history of sudden death
  • Aortic dissection: Severe tearing chest or back pain, possible syncope due to shock
  • Heart failure: Reduced cardiac output leading to fatigue, dyspnea, and possible episodes of syncope
  • Orthostatic hypotension: Dizziness and possible syncope upon standing, often in elderly or those on antihypertensive medications
  • Cardiogenic shock: Severe hypotension, cold extremities, and altered mental status due to cardiac failure
  • Carotid sinus hypersensitivity: Syncope triggered by pressure on the carotid sinus, often during shaving or head movement

Respiratory Causes

  • Hypoxia: Confusion, agitation, and possible loss of consciousness due to severe respiratory failure (e.g., COPD exacerbation, severe asthma)
  • Hypercapnia: Headache, confusion, drowsiness, and possible loss of consciousness, often in COPD or severe respiratory depression
  • Pulmonary embolism: Acute onset dyspnea, pleuritic chest pain, and syncope, often with hypoxia and tachycardia
  • Carbon monoxide poisoning: Confusion, headache, dizziness, and possible loss of consciousness, often with normal oxygen saturation but elevated carboxyhemoglobin
  • Sleep apnea: Episodes of decreased consciousness or confusion upon waking, often with snoring and daytime sleepiness
  • Aspiration: Coughing, choking, and possible loss of consciousness in severe cases, often in patients with impaired swallowing
  • Pneumonia: Fever, cough, dyspnea, and possible confusion or decreased consciousness in severe cases, particularly in elderly or immunocompromised patients
  • Pneumothorax: Sudden onset chest pain, dyspnea, and possible syncope or respiratory distress, often with reduced breath sounds on the affected side
  • Near-drowning: Hypoxia and possible loss of consciousness following submersion in water
  • Asthma exacerbation: Severe dyspnea, wheezing, hypoxia, and possible loss of consciousness in poorly controlled asthma
  • Acute respiratory distress syndrome (ARDS): Rapid onset of respiratory failure with hypoxia, dyspnea, and possible decreased consciousness

Metabolic and Toxic Causes

  • Hypoglycemia: Confusion, sweating, tremor, seizures, and possible loss of consciousness, particularly in diabetic patients
  • Diabetic ketoacidosis (DKA): Polyuria, polydipsia, vomiting, dehydration, and possible decreased consciousness in poorly controlled diabetes
  • Hyperosmolar hyperglycemic state (HHS): Severe dehydration, hyperglycemia, and altered mental status in elderly patients with type 2 diabetes
  • Hypernatremia/hyponatremia: Confusion, seizures, and possible loss of consciousness due to electrolyte imbalances
  • Hypercalcemia: Lethargy, confusion, and decreased consciousness, often associated with malignancy or hyperparathyroidism
  • Liver failure: Jaundice, confusion, and altered mental status due to hepatic encephalopathy
  • Renal failure: Uremia leading to confusion, seizures, and decreased consciousness, particularly in end-stage renal disease
  • Toxins/poisons: Confusion, seizures, and possible loss of consciousness due to ingestion of toxic substances (e.g., alcohol, drugs, CO poisoning)
  • Overdose: Decreased consciousness, respiratory depression, and hypotension following overdose of sedatives, opioids, or other CNS depressants
  • Sepsis: Fever, hypotension, and altered mental status due to systemic infection, leading to septic shock and possible organ failure
  • Hypothyroidism (myxedema coma): Hypothermia, bradycardia, hypotension, and decreased consciousness in severe untreated hypothyroidism
  • Alcohol intoxication: Confusion, ataxia, nystagmus, and possible loss of consciousness due to acute alcohol intoxication
  • Withdrawal syndromes: Delirium tremens or benzodiazepine withdrawal presenting with agitation, confusion, seizures, and decreased consciousness
  • Addisonian crisis: Severe hypotension, abdominal pain, vomiting, and decreased consciousness due to acute adrenal insufficiency
  • Heat stroke: Hyperthermia, confusion, and decreased consciousness due to prolonged exposure to high temperatures
  • Hypothermia: Shivering, confusion, and decreased consciousness due to prolonged exposure to cold temperatures

Key Points in History 🥼

Onset and Duration

  • Sudden vs. gradual onset: Sudden onset suggests a vascular, cardiac, or seizure-related cause, while gradual onset may suggest metabolic, toxic, or infectious causes
  • Duration of unconsciousness: Brief episodes suggest syncope, while prolonged unconsciousness may indicate severe metabolic disturbances, intoxication, or CNS pathology
  • Associated triggers: Identify any precipitating factors such as exertion (cardiac causes), stress (vasovagal syncope), or ingestion of substances (toxins, drugs)
  • Warning symptoms: Palpitations, chest pain, or aura before loss of consciousness may suggest arrhythmias, myocardial infarction, or epilepsy
  • Post-event symptoms: Confusion, weakness, or incontinence post-event may suggest a seizure or stroke
  • Frequency of episodes: Recurrent episodes may suggest a chronic underlying condition, such as epilepsy or cardiac arrhythmia

Background

  • Past medical history: History of cardiovascular disease, epilepsy, diabetes, or psychiatric illness may provide clues to the underlying cause
  • Drug history: Medications such as antihypertensives, insulin, oral hypoglycemics, antiepileptics, or recreational drugs may contribute to altered consciousness
  • Family history: Family history of sudden cardiac death, epilepsy, or inherited metabolic disorders may indicate a hereditary cause
  • Social history: Alcohol or substance misuse, recent travel, or occupational exposure may suggest toxic or infectious causes
  • Lifestyle factors: Physical activity levels, diet, and stress levels may provide insight into cardiac risk factors or triggers for syncope
  • Psychosocial stressors: Recent life events, work-related stress, or personal conflicts may contribute to functional or psychogenic causes
  • Recent illnesses: Recent infections, fever, or dehydration may indicate an infectious or metabolic cause of altered consciousness
  • Immunization history: Particularly relevant in cases of possible meningitis or encephalitis
  • Sleep history: Poor sleep patterns or sleep apnea may contribute to daytime somnolence and decreased consciousness
  • Previous similar episodes: A history of previous episodes may suggest a recurrent or chronic condition, such as epilepsy or recurrent syncope
  • Occupational history: Exposure to chemicals or physical stressors may indicate occupational causes of decreased consciousness

Possible Investigations 🌡️

Bedside Tests

  • Glasgow Coma Scale (GCS): To assess the level of consciousness and guide further management
  • Capillary blood glucose: To quickly assess for hypoglycemia in patients with altered consciousness
  • Pulse oximetry: To assess oxygen saturation, particularly in patients with respiratory distress or suspected hypoxia
  • ECG: To assess for arrhythmias, myocardial infarction, or signs of structural heart disease
  • Urinalysis: To assess for signs of infection, ketones (DKA), or toxic substances
  • Temperature: To assess for fever or hypothermia, which may indicate an infectious or metabolic cause
  • Neurological examination: To assess for focal neurological deficits, which may indicate stroke, TIA, or other CNS pathology
  • Postural blood pressure: To assess for orthostatic hypotension, particularly in elderly or those on antihypertensive medications
  • Peak flow measurement: To assess for asthma or COPD exacerbation in patients with respiratory distress
  • EEG: To assess for seizure activity or non-convulsive status epilepticus in patients with unexplained altered consciousness
  • ABG (Arterial blood gas): To assess for hypoxia, hypercapnia, or metabolic acidosis in critically ill patients
  • Carboxyhemoglobin levels: To assess for carbon monoxide poisoning in patients with normal oxygen saturation but suspected exposure
  • Toxicology screen: To assess for drugs or toxins in patients with suspected overdose or poisoning
  • Cardiac monitor: Continuous monitoring of heart rate and rhythm in patients with suspected arrhythmias
  • Urine drug screen: To assess for substances that may cause altered consciousness, particularly in cases of suspected overdose
  • Lactate levels: Elevated in sepsis, shock, or hypoperfusion states, often associated with metabolic acidosis
  • Nasal cannula/face mask: Immediate oxygen therapy for patients with hypoxia
  • Intravenous access: For administration of fluids, medications, or blood products as required
  • External pacing/defibrillation: Immediate intervention for life-threatening arrhythmias

Laboratory Tests

  • Full blood count (FBC): To assess for anemia, infection, or malignancy
  • Urea and electrolytes (U&E): To assess renal function and electrolyte imbalances
  • Liver function tests (LFTs): To assess for hepatic encephalopathy or liver dysfunction
  • Thyroid function tests: To assess for hypo- or hyperthyroidism
  • C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR): To assess for inflammation or infection
  • Glucose levels: To assess for hypoglycemia or hyperglycemia
  • Arterial blood gas (ABG): To assess for hypoxia, hypercapnia, or acid-base disturbances
  • Serum calcium: To assess for hypercalcemia or hypocalcemia
  • Serum osmolality: To assess for hyperosmolar states such as HHS
  • Coagulation profile: To assess for coagulopathy, particularly in patients with suspected stroke or hemorrhage
  • Blood cultures: If sepsis is suspected
  • Toxicology screen: To assess for toxic substances, particularly in cases of suspected overdose or poisoning
  • Ammonia levels: To assess for hepatic encephalopathy
  • Cortisol levels: To assess for adrenal insufficiency, particularly in patients with shock or Addisonian crisis
  • Autoimmune screen: To assess for conditions such as lupus or vasculitis
  • Serum ketones: To assess for DKA, particularly in diabetic patients with altered consciousness
  • Lumbar puncture: To assess for meningitis or encephalitis in patients with fever and neurological signs
  • CSF analysis: To assess for infections, malignancy, or autoimmune conditions in the central nervous system
  • Echocardiogram: To assess for structural heart disease in patients with syncope or cardiac symptoms
  • Imaging studies: To assess for brain injury, hemorrhage, or tumor in patients with neurological symptoms
  • Serum electrolytes: To assess for imbalances that may cause altered consciousness
  • Blood glucose monitoring: Regular monitoring in diabetic patients with altered consciousness
  • Serum lactate: Elevated in sepsis, shock, or severe hypoperfusion
  • Serum ammonia: Elevated in hepatic encephalopathy
  • Serum paracetamol/salicylate levels: To assess for overdose
  • CSF culture and sensitivity: To identify pathogens in cases of suspected meningitis

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Endocrine & metabolic