Makindo Medical Notes

Note: A symptomatic fall in blood pressure (BP) on standing is common in the elderly. Always check for medication as a potential cause. Orthostatic hypotension is typically defined as a drop of >20 mmHg systolic or >10 mmHg diastolic, but the clinical significance can vary based on the starting BP. For example, a drop from 200 mmHg to 180 mmHg is different from a drop from 100 mmHg to 80 mmHg.

About

• Orthostatic hypotension is common in the elderly, and often the exact cause is not found.
• It increases the risk of falls, cognitive impairment, and even death.
• One in five community-dwelling older adults experience orthostatic hypotension.

Physiology of Standing

• When standing, approximately 1 liter of blood pools in the veins of the legs.
• This causes a transient reduction in venous return, leading to decreased cardiac output (CO) and BP.
• The baroreceptors in the aortic arch trigger an autonomic reflex, increasing sympathetic tone.
• This leads to increased heart rate (HR) and contractility, and greater tone in capacitance vessels to restore blood pressure.
• Parasympathetic inhibition also helps by increasing HR.
• Standing activates the renin-angiotensin-aldosterone (RAA) system and antidiuretic hormone (ADH) release, leading to salt and water retention.

Causes

• Peripheral/Autonomic Causes: Diabetes, amyloidosis, nutritional deficiencies.
• Neurological Disorders: Parkinson’s disease, multiple system atrophy (MSA).
• Medications: Antihypertensives, nitrates (GTN), diuretics, levodopa, antidepressants, and sildenafil (Viagra).
• Other Causes: Dehydration, Addison’s disease, overdiuresis, post-dialysis, or idiopathic.

Another Suggested Division of OH

• Neurogenic OH:
  • α-synucleinopathies such as multiple system atrophy, Parkinson's disease, or dementia with Lewy bodies.
  • Autonomic degeneration due to diabetes or other causes.
  • Failure to release adequate peripheral norepinephrine, leading to impaired vascular tone.
• Cardiogenic OH:
  • Low cardiac output due to reduced preload (e.g., volume loss, impaired venous return), left ventricular stiffness, or pulmonary hypertension.
  • Decreased contractility due to left ventricular dysfunction or amyloidosis.
• Mixed OH: A combination of both neurogenic and cardiogenic factors.

Clinical Features

• Lightheadedness, weakness, and blurred vision.
• Syncope, presyncope, and an increased risk of falls.

Investigations

• Blood Tests: Full blood count (FBC), electrolytes (U&E), and calcium levels (Ca).
• 24-hour Holter Monitor: To rule out bradycardia, tachyarrhythmias, or postural orthostatic tachycardia syndrome (POTS).
• Implantable Loop Recorder: May be used in select cases to assess for arrhythmias.
• Short Synacthen Test: Considered in cases with suspected adrenal insufficiency.
• Echocardiography (Echo): To exclude obstructive heart diseases such as aortic stenosis (AS) or hypertrophic obstructive cardiomyopathy (HOCM).
• Tilt Table Test: May be necessary to assess syncope or transient loss of consciousness (TLOC).

Management

• Review Medications: Stop or reduce any drugs that contribute to orthostatic hypotension, particularly in the elderly, who have decreased baroreceptor sensitivity.
• Reduce or stop diuretics, calcium channel blockers (CCB), alpha-blockers, beta-blockers, vasodilators, and anti-Parkinsonian drugs.
• Supportive Measures:
  • Consider TED (compression) stockings and head-up tilt at night.
  • Increase salt intake, and consider fludrocortisone (100-200 mcg at night) to increase blood volume, though this may cause low potassium and fluid retention.
  • Midodrine (2.5-10 mg three times daily) can also be used, but avoid dosing near bedtime to prevent nighttime hypertension.
• Falls Prevention: Consider providing the patient with a pendant alarm for assistance in case of a fall. In severe cases, limited walking or the use of a wheelchair may be needed.
• Each patient requires an individualized treatment plan depending on the underlying cause and severity of symptoms.

References

• The Prevalence of Orthostatic Hypotension: A Systematic Review and Meta-Analysis
• Orthostatic Hypotension: Management of a Complex, but Common, Medical Problem