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Low blood pressure

Medicine > Cardiovascular

Differential Diagnosis Schema 🧠

Cardiovascular Causes

  • Cardiogenic shock: Often due to myocardial infarction, arrhythmias, or severe heart failure; presents with chest pain, breathlessness, and signs of poor perfusion.
  • Aortic stenosis: Narrowing of the aortic valve leading to reduced cardiac output; presents with exertional syncope, chest pain, and a slow-rising pulse.
  • Pericarditis and cardiac tamponade: Inflammation of the pericardium or accumulation of fluid causing compression; presents with chest pain, pulsus paradoxus, and muffled heart sounds.

Endocrine Causes

  • Adrenal insufficiency (Addison’s disease): Lack of cortisol and aldosterone; presents with fatigue, hyperpigmentation, and hyponatraemia.
  • Hypothyroidism: Reduced thyroid hormone levels; presents with fatigue, weight gain, cold intolerance, and bradycardia.
  • Diabetic autonomic neuropathy: A complication of diabetes causing dysregulation of blood pressure; presents with postural hypotension, gastroparesis, and erectile dysfunction.

Neurological Causes

  • Autonomic neuropathy: Damage to the autonomic nervous system, often seen in diabetes or Parkinson’s disease; presents with postural hypotension and other autonomic dysfunctions.
  • Vasovagal syncope: A common cause of fainting due to reflexive vasodilation and bradycardia; often triggered by stress, pain, or prolonged standing.
  • Intracranial haemorrhage: Increased intracranial pressure can cause Cushing’s triad (hypertension, bradycardia, irregular respirations), but initial stages may present with hypotension.

Infectious Causes

  • Sepsis: A systemic response to infection leading to widespread vasodilation and hypotension; presents with fever, tachycardia, and signs of infection.
  • Toxic shock syndrome: Caused by bacterial toxins, leading to hypotension, fever, rash, and multiorgan failure.
  • Meningitis: Infection of the meninges causing inflammation and potential shock; presents with headache, neck stiffness, photophobia, and altered mental status.

Hypovolemic Causes

  • Haemorrhage: Acute blood loss from trauma, gastrointestinal bleeding, or ruptured aneurysm; presents with tachycardia, pallor, and cold extremities.
  • Dehydration: Excessive loss of fluids from vomiting, diarrhoea, or inadequate intake; presents with dry mucous membranes, reduced skin turgor, and oliguria.
  • Third-space losses: Fluid shifts into the interstitial space as seen in burns or pancreatitis; presents with tachycardia, hypotension, and signs of underlying cause.

Key Points in History 🥼

Symptom Onset and Duration

  • Acute vs chronic : Acute onset may suggest shock, haemorrhage, or cardiac causes while chronic symptoms might indicate endocrine issues or autonomic dysfunction.

Positional Changes

  • Postural hypotension indicates autonomic dysfunction, dehydration, or drug effects, whereas consistent hypotension regardless of position suggests cardiac or endocrine causes.

Associated Symptoms

  • Chest pain: Suggests myocardial infarction, aortic stenosis, or pulmonary embolism.
  • Fever: Points towards sepsis, toxic shock syndrome, or an infectious cause.
  • Syncope: Could be due to vasovagal syncope, orthostatic hypotension, or cardiac arrhythmias.
  • Weight loss and fatigue: May suggest adrenal insufficiency or chronic illness.

Background

  • Past medical history: Important to identify previous episodes of hypotension, cardiovascular disease, endocrine disorders, or chronic illnesses.
  • Drug history: Includes antihypertensives, diuretics, and medications that can cause vasodilation or affect autonomic function.
  • Family history: Look for a history of cardiovascular disease, endocrine disorders, or genetic conditions like Marfan syndrome.
  • Social history: Consider alcohol use, recreational drug use, and occupation (e.g., exposure to toxins) that may contribute to hypotension.

Possible Investigations 🌡️

Blood Tests

  • Full blood count: To identify anaemia or infection.
  • Urea and electrolytes: To assess renal function and electrolyte imbalances.
  • Cortisol levels: To check for adrenal insufficiency.
  • Thyroid function tests: To identify hypothyroidism.
  • Blood cultures: If sepsis is suspected.

Imaging

  • Chest X-ray: To assess for cardiac size, pulmonary oedema, or aortic dissection.
  • Echocardiogram: To evaluate cardiac function and structural abnormalities like valve disease or pericardial effusion.
  • CT or MRI scan: If there is a concern for intracranial pathology or aortic dissection.

Special Tests

  • Tilt table test: To diagnose postural hypotension and autonomic dysfunction.
  • 24-hour blood pressure monitoring: To assess for patterns of hypotension, especially in autonomic dysfunction or medication-related cases.
  • Electrocardiogram (ECG): To identify arrhythmias or signs of ischaemia.

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Cardiovascular