What are the leading differentials for hypotension?

Leading Differential Diagnoses for Hypotension

The leading differentials for hypotension are organized into four primary categories: distributive shock (sepsis, anaphylaxis, neurogenic), cardiogenic shock (acute myocardial infarction, heart failure, arrhythmias, valvular emergencies), obstructive shock (pulmonary embolism, cardiac tamponade, tension pneumothorax, aortic dissection), and hypovolemic shock (hemorrhage, dehydration), with orthostatic hypotension representing a distinct non-shock category requiring separate consideration. 1

Shock States (Acute Hypotension)

Distributive Shock

• Septic shock is characterized by inappropriate vasodilation with warm extremities initially, requiring early vasopressor support (norepinephrine as first-line agent) 2
• Anaphylactic shock presents with acute onset, urticaria, bronchospasm, and angioedema requiring immediate epinephrine 2
• Neurogenic shock occurs after spinal cord injury with loss of sympathetic tone, presenting with hypotension and paradoxical bradycardia 2

Cardiogenic Shock

• Acute coronary syndrome/myocardial infarction should be evaluated with bedside cardiac ultrasound (BCU) to assess for regional wall motion abnormalities, left ventricular dysfunction, and mechanical complications (ventricular septal defect, papillary muscle rupture) 1
• Acute decompensated heart failure with reduced ejection fraction presents with pulmonary edema and requires BCU to distinguish from other causes 1
• Acute valvular regurgitation or prosthetic valve dysfunction can cause sudden hemodynamic collapse and should be identified with emergency echocardiography 1
• Arrhythmias including ventricular tachycardia or bradyarrhythmias with hemodynamic compromise 1

Obstructive Shock

• Cardiac tamponade presents with jugular venous distention, muffled heart sounds, and pulsus paradoxus, though classic findings are frequently absent; BCU should be performed immediately to identify pericardial effusion with chamber collapse 1
• Massive pulmonary embolism causes acute right ventricular dysfunction visible on echocardiography showing right ventricular dilation and dysfunction; this is a category I indication for emergency echocardiography in hemodynamically unstable patients 1
• Tension pneumothorax causes mediastinal shift and cardiovascular collapse, identifiable with point-of-care ultrasound 1
• Aortic dissection should be considered in patients with chest pain and hypotension, with echocardiography serving as an initial imaging modality in the emergency setting 1

Hypovolemic Shock

• Hemorrhagic shock from trauma, gastrointestinal bleeding, or ruptured aortic aneurysm presents with tachycardia and evidence of volume depletion 2
• Severe dehydration from gastrointestinal losses, inadequate intake, or osmotic diuresis 2

Orthostatic Hypotension (Non-Shock Hypotension)

Classical Orthostatic Hypotension

• Neurogenic orthostatic hypotension is defined by sustained decrease in systolic BP ≥20 mmHg or diastolic BP ≥10 mmHg within 3 minutes of standing, with blunted heart rate increase (usually <10 bpm) indicating autonomic dysfunction 3, 4
• Medication-induced orthostatic hypotension is extremely common in elderly patients, with cardiovascular medications responsible for almost half of syncope episodes; antihypertensive drugs, diuretics, and vasodilators are primary culprits 1, 5
• Autonomic failure (primary or secondary to Parkinson's disease, diabetes with dysautonomia, or other neurodegenerative disorders) presents with impaired compensatory heart rate response 4, 5, 6

Delayed Orthostatic Hypotension

• Age-related delayed orthostatic hypotension occurs beyond 3 minutes of standing with progressive BP decrease and variable heart rate compensation, particularly common in elderly patients 1, 3, 5

Initial Orthostatic Hypotension

• Initial orthostatic hypotension is characterized by BP decrease >40 mmHg systolic and/or >20 mmHg diastolic within 15 seconds of standing, with spontaneous recovery within 40 seconds 3

Endocrine Causes

• Adrenal insufficiency (primary or secondary) presents with chronic hypotension, hyponatremia, and hyperkalemia in primary adrenal failure; acute adrenal crisis causes severe hypotension requiring immediate hydrocortisone 6
• Isolated hypoaldosteronism (primary with hyperreninism or secondary with hyporeninism from diabetes, renal failure, or medications) causes hypotension with hyperkalemia 6
• Hypothyroidism can cause chronic hypotension through reduced cardiac output and vascular tone 6

Critical Diagnostic Approach

For undifferentiated hypotension, perform bedside cardiac ultrasound immediately to differentiate cardiogenic shock (left ventricular dysfunction) from other shock types, as this fundamentally changes management. 1, 7

Key Ultrasound Findings

• Left ventricular dysfunction on focused cardiac ultrasound has 94% specificity for cardiogenic shock, with positive likelihood ratio of 10.62 7
• Right ventricular dilation and dysfunction suggests massive pulmonary embolism 1
• Pericardial effusion with chamber collapse confirms tamponade 1
• Hyperdynamic left ventricle ("kissing walls") suggests distributive or hypovolemic shock 7

Common Pitfalls

• Failing to measure orthostatic vital signs properly: BP must be measured after 5 minutes supine rest, then at 1 and 3 minutes standing with arm at heart level 3
• Assuming tachycardia always accompanies hypotension: Neurogenic orthostatic hypotension and neurogenic shock present with blunted or absent heart rate response 4, 2
• Overlooking medication effects in elderly patients: Review all cardiovascular medications, as they cause nearly 50% of hypotensive episodes in this population 5
• Missing adrenal insufficiency: Consider in patients with chronic hypotension, hyponatremia, and hyperkalemia, especially those on chronic steroids 6
• Delaying vasopressors in distributive shock: Early norepinephrine administration may improve outcomes; peripheral administration is safe and facilitates early use 2
• Using vasopressors as primary treatment for hypovolemic shock: Volume resuscitation is the definitive treatment; vasopressors only temporize 2