What is orthostatic hypotension?

Orthostatic Hypotension: Definition, Classification, and Management

Orthostatic hypotension (OH) is defined as a sustained decrease in systolic blood pressure ≥20 mmHg and/or diastolic blood pressure ≥10 mmHg within 3 minutes of standing or during head-up tilt testing of at least 60 degrees. 1

Types of Orthostatic Hypotension

There are several distinct types of orthostatic hypotension, each with different characteristics:

1. Classical OH:

   • Sustained decrease in systolic BP ≥20 mmHg, diastolic BP ≥10 mmHg, or a decrease in systolic BP to <90 mmHg within 3 minutes of standing
   • In patients with supine hypertension, a systolic BP drop ≥30 mmHg should be considered significant 1
   • Typically presents with a "concave" curve pattern of BP decrease 1

2. Initial OH:

   • BP decrease on standing of >40 mmHg for systolic BP and/or >20 mmHg for diastolic BP within 15 seconds of standing
   • BP spontaneously and rapidly returns to normal, with symptoms lasting <40 seconds 1

3. Delayed OH:

   • Occurs beyond 3 minutes of standing
   • Characterized by a slow, progressive decrease in BP 1
   • May be missed if monitoring is terminated too early

4. Neurogenic OH:

   • Due to dysfunction of the autonomic nervous system
   • Not solely due to environmental triggers (e.g., dehydration or drugs)
   • Associated with primary autonomic failure (e.g., pure autonomic failure, multiple system atrophy, Parkinson's disease) or secondary autonomic failure (e.g., diabetes, amyloidosis, spinal cord injuries) 1

Clinical Presentation

Common symptoms of orthostatic hypotension include:

• Dizziness and lightheadedness
• Visual disturbances (blurring, enhanced brightness, tunnel vision)
• Weakness, fatigue, lethargy
• Palpitations and sweating
• Hearing disturbances (impaired hearing, crackles, tinnitus)
• Pain in neck (occipital/paracervical and shoulder region), low back pain, or precordial pain 1
• Syncope in severe cases

Pathophysiology

Orthostatic hypotension occurs when there is inadequate physiologic compensation to postural changes:

• A decrease in systolic blood pressure to 60 mmHg is associated with syncope 2
• Sudden cessation of cerebral blood flow for 6-8 seconds is sufficient to cause complete loss of consciousness 2
• As little as a 20% drop in cerebral oxygen delivery can cause loss of consciousness 2
• The absolute BP level, rather than just the magnitude of BP drop, is important in determining syncope risk 2

Diagnosis

Diagnosis is confirmed by measuring blood pressure and heart rate:

1. After 5 minutes in the supine position
2. At 1 minute and 3 minutes after standing

For patients unable to stand safely or when clinical suspicion remains high despite normal bedside testing, head-up tilt table testing is recommended 3.

Key diagnostic pitfalls to avoid:

• Not monitoring long enough to detect delayed OH (extend beyond 3 minutes when suspected) 2
• Failing to account for supine hypertension when assessing for OH 2
• Not considering the absolute BP level in addition to the magnitude of drop 2
• Overlooking pseudohypertension in elderly patients, which can lead to overtreatment and OH 2

Management

Treatment goals are to reduce symptoms, improve quality of life, and prevent complications such as falls and syncope. The approach should follow these steps:

1. Identify and address reversible causes:

   • Review and adjust medications that may cause OH (antihypertensives, especially alpha-blockers, psychoactive medications) 2, 4
   • Correct volume depletion if present

2. Non-pharmacologic interventions:

   • Patient education about postural changes and symptom recognition
   • Dietary modifications (adequate salt and fluid intake)
   • Compression garments for lower extremities
   • Physical counter-maneuvers (leg crossing, squatting)
   • Avoiding precipitating factors (hot environments, large meals, alcohol)

3. Pharmacologic treatment (when non-pharmacologic measures are insufficient):

   • First-line medications: midodrine and droxidopa 3
   • Fludrocortisone may improve symptoms but has concerning long-term effects 3
   • Pyridostigmine may be beneficial in some cases 5

Prognosis and Complications

Orthostatic hypotension is associated with:

• Increased risk of falls
• Syncope
• Cognitive impairment
• Up to 50% increase in relative risk of all-cause mortality 3
• Increased cardiovascular risk 3

Proper diagnosis and management are essential to reduce these risks and improve quality of life for affected individuals.