Orthostatic Hypotension

from

https://www.aafp.org/pubs/afp/issues/2022/0100/p39.html

Definition

• ↓ SBP ≥20 mmHg or ↓ DBP ≥10 mmHg
• Occurs within 3 minutes of standing from supine
• Or during ≥60° head-up tilt testing
• In supine hypertension, diagnostic threshold is SBP drop ≥30 mmHg

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Epidemiology

• ~5% middle-aged adults
• ~20% adults ≥60 years
• Up to 50–68% in nursing homes/geriatric wards
• ↑ prevalence with diabetes, frailty, polypharmacy

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Clinical Significance

• ↑ risk of:
  • Falls and syncope
  • Coronary heart disease, MI, HF, stroke
  • All-cause mortality ↑ ~50%
• Particularly high risk in:
  • Older adults
  • Diabetes mellitus
  • Neurodegenerative disease

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Pathophysiology

• On standing:
  • 500–1000 mL blood pools in legs/splanchnic bed
  • ↓ venous return → ↓ cardiac output
• Normal compensation:
  • Baroreceptor-mediated ↑ HR, ↑ contractility, vasoconstriction
  • RAAS and vasopressin activation
• OH occurs when:
  • Inadequate volume or
  • Impaired autonomic vasoconstriction

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Symptoms (on standing, relieved supine)

• Cerebral: lightheadedness, syncope, cognitive slowing, vertigo
• Visual: blurred/dim vision
• Cardiac: chest pain, palpitations
• Pulmonary: dyspnoea, fatigue, platypnoea
• Musculoskeletal: neck/shoulder pain (“coat-hanger syndrome”)
• Symptoms not required for diagnosis

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Risk Factors

• Unexplained falls or syncope
• Neurodegenerative disorders (PD, MSA, DLB)
• Peripheral autonomic neuropathies (diabetes, amyloid, HIV)
• Frailty, age ≥70
• Polypharmacy
• Postural dizziness only when standing

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Diagnosis (Key Point)

• Gold standard bedside test:
  • Supine BP/HR after 5 minutes
  • Standing BP/HR at 3 minutes
• Supine → standing is most sensitive
• If high suspicion but normal vitals → tilt table test

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OH Variants

• Classic: within 3 minutes
• Initial: within 15 seconds
• Delayed: after 3 minutes
• Early OH (≤1 min) associated with ↑ falls and mortality

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Classification

Neurogenic OH

• Autonomic failure
• Causes:
  • Parkinson disease
  • Multiple system atrophy
  • Lewy body dementia
  • Pure autonomic failure
  • Diabetic autonomic neuropathy
• Features:
  • Blunted HR response
  • Other autonomic symptoms (urinary, GI, postprandial hypotension)

Non-neurogenic OH

• Secondary to external factors
• Causes:
  • Medications
  • Hypovolaemia
  • Endocrine/metabolic disorders
• Preserved HR compensation

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Heart Rate Response (Very Useful Clinically)

• HR increase ≥0.5 bpm per mmHg SBP drop
  → suggests non-neurogenic OH
• Sensitivity 91%, specificity 88%
• Blunted/absent HR rise → neurogenic OH

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Distinction from POTS

• POTS:
  • HR ↑ ≥30 bpm (≥40 if age 12–19)
  • No hypotension
  • Standing HR often ≥120 bpm
• OH:
  • BP drop is defining feature

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Supine Hypertension

• Present in ~50% of neurogenic OH
• Defined as BP ≥140/90 after 5 min supine
• Screen all neurogenic OH patients
• Consider 24-hr ABPM (esp nocturnal HTN)

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Initial Investigations

• FBC – anaemia
• BMP – electrolytes, renal function, diabetes
• B12 ± MMA
• TSH
• ECG (± cardiology referral if abnormal)
• Supine BP screening

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Management Principles

• Goal: reduce symptoms & improve QoL
  (not BP normalisation)

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Step 1: Address Underlying Causes

• Review & rationalise medications
• Treat:
  • Anaemia
  • Dehydration
  • Endocrine disorders

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Medications That Worsen OH

• Antihypertensives:
  • Diuretics, nitrates
  • ACEi/ARBs
  • Alpha-1 blockers
  • Beta-blockers, non-DHP CCBs
• Anticholinergics
• Antipsychotics, TCAs, sedatives
• Opioids
• Dopaminergic agents

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Non-Pharmacological Management (First-Line)

• Avoid heat, prolonged standing
• Small frequent meals (post-prandial OH)
• Hydration: 2–2.5 L/day
• Sodium intake: 2–3 g/day
• Compression garments (30–40 mmHg waist-high)
• Physical counter-maneuvers (leg crossing, squatting)
• Exercise (avoid sudden posture changes)
• Head-of-bed elevation (limited evidence)

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Pharmacological Management

(Use with non-pharmacologic measures)

First-line

• Midodrine
  • 2.5 mg TDS → up to 10 mg TDS
  • Avoid within 3–5 hrs of bedtime
  • SE: supine HTN, piloerection, urinary retention
• Droxidopa
  • 100 mg TDS → up to 600 mg TDS
  • Avoid near bedtime
  • SE: headache, nausea
  • ↓ falls in PD-related OH

Second-line / Adjunct

• Fludrocortisone (off-label)
  • 0.1–0.2 mg daily
  • Monitor K⁺
  • Long-term risks: LVH, renal failure, HF
• Atomoxetine (off-label)
• Pyridostigmine (off-label)

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Key Practice Recommendations (SORT)

• Supine → standing vitals preferred (C)
• Tilt table if high suspicion despite normal vitals (C)
• Treat symptoms, not BP targets (C)
• Non-pharmacologic measures first (C)
• Midodrine or droxidopa as first-line drugs (B)