Orthostatic Hypotension

OVERVIEW

Orthostatic Hypotension (OH) is defined as a sustained drop in blood pressure occurring within 3 minutes of standing or head-up tilt:

• Systolic BP: Decrease of >= 20 mmHg AND/OR
• Diastolic BP: Decrease of >= 10 mmHg

(In patients with supine hypertension >= 150/90 mmHg, a drop of >= 30 mmHg SBP is required).

Normal Physiological Response to Orthostasis (standing up)

• Standing up from a recline or sitting position results in pooling of 500-1000mL of blood in the lower extremities and splanchnic circulation.
• The physiological response
  • ↓venous return to the heart → ↓ventricular filling → ↓cardiac output → baroreceptor reflex
  • Baroreceptor reflex
    • → stimulation of the vasomotor center → peripheral vasoconstriction → ↑BP → ↑venous return + ↑cardiac output
    • → stimulation of the cardiovascular center  → ↑HR → ↑cardiac output +↑venous return
  • Overall clinically  there is a small reduction in systolic BP (<10mmHg), increase in diastolic BP and an increase in HR

APPROACH

Step 1: Diagnostic Confirmation (Active Stand Test / Bedside Orthostatics)

• Measurement Protocol: Measure HR and BP after 5 minutes resting supine, then at 1 minute and 3 minutes post-standing.

Step 2: Emergency Triage & Red Flags

• Syncope with Trauma or Head Injury: Rule out intracranial hemorrhage/cervical spine injury.
• Acute Volume Loss / Hemorrhage: Tachycardia + severe orthostasis -> GI bleed, ruptured ectopic pregnancy, ruptured AAA.
• Acute Cardiac Signs: Chest pain, dyspnea, irregular pulse -> Arrhythmia, ACS, aortic stenosis, PE.
• Neurological Red Flags: Rapidly progressive parkinsonism, ataxia, early autonomic failure, vertical gaze palsy -> Central neurodegenerative etiologies (e.g., Multiple System Atrophy).

Step 3: Branching Logic (Heart Rate Response Analysis)

• Neurogenic Orthostatic Hypotension (nOH): Blunted HR increase (< 15 bpm upon standing despite significant BP drop). Indicates baroreflex arc failure or sympathetic denervation.
• Non-Neurogenic Orthostatic Hypotension: Compensatory reflex tachycardia (> 15 bpm HR increase upon standing). Indicates hypovolemia, vasodilation, or drug-induced etiology.
• POTS Differential: HR increase >= 30 bpm (or >= 40 bpm if age 12–19) within 10 minutes of standing WITHOUT a drop in SBP >= 20 mmHg.

DIFFERENTIAL DIAGNOSIS

Non-Neurogenic Causes (Intact Baroreflex, Compensatory Tachycardia):

• Volume Depletion / Hypovolemia:
  • Distinguishing features: Dehydration, vomiting/diarrhea, overt GI bleeding, excessive diuresis, elevated BUN/creatinine ratio (> 20:1), dry mucous membranes.
• Medication-Induced (Most common overall cause in elderly):
  • Distinguishing features: Antihypertensives (alpha-blockers e.g., tamsulosin/doxazosin, vasodilators, diuretics), psychotropics (TCAs, antipsychotics), SGLT2 inhibitors, nitrates.
• Cardiovascular Deconditioning / Prolonged Bedrest:
  • Distinguishing features: Recent prolonged hospitalization, frailty, muscle wasting; intact autonomic reflexes.
• Adrenal Insufficiency (Addison’s Disease):
  • Distinguishing features: Hyperpigmentation, hyponatremia, hyperkalemia, weight loss, fatigue, hypoglycemia.

Neurogenic Causes (nOH – Impaired Baroreflex, Blunted HR Response):

• Central Synucleinopathies (Primary Autonomic Failure):
  • Parkinson’s Disease (PD): Resting tremor, rigidity, bradykinesia + orthostasis.
  • Multiple System Atrophy (MSA): Orthostatic hypotension + prominent ataxia (MSA-C) or early severe autonomic failure with erectile dysfunction and urinary retention (MSA-P/Shy-Drager).
  • Dementia with Lewy Bodies (DLB): Visual hallucinations, fluctuating cognition, parkinsonism + early orthostasis.
  • Pure Autonomic Failure (PAF): Isolated autonomic failure without central neurological signs.
• Peripheral Neuropathies (Secondary Autonomic Failure):
  • Diabetic Autonomic Neuropathy: Longstanding diabetes, stocking-glove sensory loss, gastroparesis, resting tachycardia.
  • AL Amyloidosis: Nephrotic syndrome, macroglossia, periorbital purpura (“raccoon eyes”), sensorimotor neuropathy + severe orthostasis.
  • Autoimmune Autonomic Ganglionopathy (AAG): Acute/subacute severe pan-autonomic failure (fixed pupils, dry mouth, severe orthostasis; anti-gAChR antibodies).
  • Other Neuropathies: Sjögren’s syndrome, HIV, Vitamin B12 deficiency, Guillain-Barré / Miller Fisher variant.

INVESTIGATIONS

First-Line / Bedside & Basic Diagnostic Tests:

• Active Stand Test (Bedside Orthostatics): Standard 3-minute test quantifying SBP, DBP, and HR changes.
• 12-Lead ECG: Assess for arrhythmia, ischemic changes, conduction delay, or prolonged QTc.
• Full Blood Count (FBC): Screen for anemia (occult bleeding/hemolysis).
• Urea, Electrolytes, Creatinine: Screen for dehydration (elevated BUN/Cr), renal dysfunction, or Addisonian electrolyte shifts (low Na+, high K+).
• Fasting Glucose & HbA1c: Rule out diabetic neuropathy / metabolic causes.
• Morning Cortisol (8 AM): Screen for adrenal insufficiency.

Targeted / Specialized Autonomic Investigations:

• Head-Up Tilt Table Testing (HUTT): Indicated if active stand test is inconclusive, or to differentiate nOH from POTS or vasovagal syncope.
• Autonomic Function Tests:
  • Ewing Battery: Heart rate variability with deep breathing (30:15 ratio), Valsalva maneuver phase IV overshoot, cold pressor test.
• Serum Free Light Chains, SPEP/UPEP: Screen for AL Amyloidosis / Plasma cell dyscrasia.
• Serum Anti-Neuronal Ganglionic Acetylcholine Receptor (gAChR) Antibodies: Confirm Autoimmune Autonomic Ganglionopathy.
• Supine and Standing Plasma Norepinephrine Levels:
  • Normal: Norepinephrine doubles upon standing.
  • nOH (Central/PAF): Low supine norepinephrine (< 100 pg/mL) with minimal rise upon standing (< 100% increase).

CRITICAL MANAGEMENT

Immediate Stabilization (Symptomatic Acute / Severe Drops):

• Positioning: Place patient supine with legs elevated (Trendelenburg position) to optimize venous return and cerebral perfusion.
• Acute Fluid Bolus: If hypovolemic or acutely symptomatic without heart failure -> Rapid infusion of 500 mL normal saline IV (or rapid ingestion of 500 mL cold water orally, which triggers a sympathetically mediated pressor response lasting 30–60 min).
• Drug Re-evaluation: Hold or depressurize non-essential antihypertensives, diuretics, and alpha-blockers immediately.

First-Line Non-Pharmacological Measures (Core Long-Term Strategy):

• Physical Counterpressure Maneuvers (PCM): Leg crossing, muscle squeezing, squatting, or toe-raising at onset of symptoms.
• Dietary Sodium & Fluid Intake: 2–3 L fluid/day + 6–10 g salt/day (unless contraindicated by severe heart failure).
• Abdominal Binder & Waist-High Compression Stockings: Abdominal compression (15–20 mmHg) is more effective than lower leg compression alone due to splanchnic venous pooling.