Flashcard: Postural Hypotension
What is orthostatic hypotension, and how is it clinically defined?
Orthostatic hypotension, also known as postural hypotension, is defined as a drop in systolic blood pressure of ≥20 mmHg or diastolic blood pressure of ≥10 mmHg within three minutes of standing. It results from the failure of the autonomic nervous system to compensate for changes in posture.
What are the primary causes and risk factors for developing orthostatic hypotension?
Primary causes include age-related changes in blood pressure regulation, dehydration, medications (e.g., antihypertensives, diuretics), autonomic dysfunction (e.g., Parkinson's disease, diabetes), and prolonged bed rest. Risk factors include advanced age, chronic diseases, and certain medications.
Explain the pathophysiology of orthostatic hypotension. How does the condition develop?
Orthostatic hypotension occurs due to the failure of compensatory mechanisms, such as baroreceptor reflexes, to maintain blood pressure upon standing. This leads to insufficient vasoconstriction, resulting in decreased venous return, reduced cardiac output, and subsequent hypotension.
What are the common symptoms of orthostatic hypotension, and how do they impact daily life?
Common symptoms include dizziness, light-headedness, blurred vision, weakness, fatigue, and syncope (fainting). These symptoms can significantly impact daily life, increasing the risk of falls, limiting mobility, and reducing quality of life, particularly in older adults.
How is orthostatic hypotension diagnosed according to NICE guidelines?
Diagnosis involves measuring blood pressure and heart rate in two positions: lying down and standing. A significant drop in systolic or diastolic blood pressure upon standing confirms the diagnosis. Additional tests may be performed to identify underlying causes.
What non-pharmacological strategies are recommended for managing orthostatic hypotension?
Non-pharmacological strategies include increasing fluid and salt intake, using compression stockings, performing physical counter-manoeuvres (e.g., leg crossing), elevating the head of the bed, and educating patients to rise slowly from a seated or lying position.
What pharmacological treatments are available for orthostatic hypotension, and when are they indicated?
Pharmacological treatments include fludrocortisone, which increases blood volume, and midodrine, a vasoconstrictor. These are indicated when non-pharmacological measures are insufficient and symptoms are significantly impacting the patient's quality of life.
Discuss the importance of reviewing medications in patients with orthostatic hypotension.
Reviewing medications is crucial as certain drugs (e.g., antihypertensives, diuretics, antidepressants) can exacerbate orthostatic hypotension. Adjusting dosages, changing medications, or discontinuing them can help manage the condition and reduce symptoms.
What are the potential complications of untreated orthostatic hypotension?
Complications include increased risk of falls, fractures, and other injuries due to syncope. It can also lead to reduced mobility, social isolation, and diminished quality of life, particularly in older adults.
How should patients with orthostatic hypotension be monitored and followed up?
Patients should be regularly monitored for blood pressure changes, symptom severity, and response to treatment. Follow-up should include assessing the effectiveness of lifestyle changes and medication adjustments, with periodic reviews to prevent complications.
Orthostatic Hypotension (Postural Hypotension)
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Diagnosis | Management
Definition
Orthostatic hypotension (OH), also known as postural hypotension, is defined as a significant drop in blood pressure upon standing up from a sitting or lying position. Clinically, it is characterised by a decrease in systolic blood pressure of at least 20 mmHg or a decrease in diastolic blood pressure of at least 10 mmHg within three minutes of standing. This can lead to symptoms such as dizziness, lightheadedness, and in some cases, syncope (fainting). While these episodes are usually transient, persistent orthostatic hypotension may indicate underlying health issues.
Aetiology
Orthostatic hypotension can result from various conditions or external factors, including:
- Dehydration: Caused by fever, vomiting, inadequate fluid intake, severe diarrhoea, or excessive sweating from physical activity, leading to reduced blood volume.
- Anaemia: Reduced oxygen-carrying capacity of the blood can exacerbate symptoms of hypotension.
- Prolonged Bed Rest: Extended periods of immobility can lead to deconditioning of the cardiovascular system, increasing the risk of orthostatic hypotension.
- Medications: Certain medications, including diuretics, beta-blockers, antidepressants, and antihypertensives (e.g., ACE inhibitors, calcium channel blockers, and alpha-blockers), can contribute to orthostatic hypotension.
- Endocrine Disorders: Conditions like adrenal insufficiency, thyroid disorders, and diabetes can disrupt the body’s ability to regulate blood pressure.
- Neurodegenerative Diseases: Conditions such as Parkinson’s disease, Lewy body dementia, and amyloidosis can impair autonomic regulation of blood pressure.
Pathophysiology
Orthostatic hypotension occurs when the body fails to adequately respond to changes in posture. The normal physiological response involves:
- Blood Pooling: Upon standing, gravity causes blood to pool in the lower extremities and abdomen, reducing venous return to the heart.
- Baroreceptor Activation: Baroreceptors, located in the aortic arch and carotid sinuses, detect the drop in blood pressure and signal the brain to initiate compensatory mechanisms.
- Compensatory Mechanisms: The brain responds by increasing heart rate (tachycardia) and constricting blood vessels (vasoconstriction) to maintain blood pressure.
- Failure of Compensation: Orthostatic hypotension occurs when these compensatory mechanisms are inadequate, leading to reduced cerebral perfusion and the associated symptoms.
Risk Factors
Several factors increase the likelihood of developing orthostatic hypotension, including:
- Age: The condition is more common in individuals aged 65 and older due to decreased baroreceptor sensitivity and vascular stiffness.
- Medications: Use of antihypertensive medications, particularly diuretics, beta-blockers, and alpha-blockers, can increase the risk.
- Prolonged Bed Rest: Extended immobility due to illness or injury can predispose individuals to orthostatic hypotension.
- Alcohol Consumption: Alcohol can exacerbate hypotension by dilating blood vessels and reducing blood pressure.
Signs and Symptoms
The clinical presentation of orthostatic hypotension includes:
- Dizziness or Lightheadedness: Particularly upon standing.
- Weakness: Generalised weakness due to reduced cerebral perfusion.
- Visual Disturbances: Blurred or tunnel vision may occur during hypotensive episodes.
- Syncope: Episodes of fainting or near-fainting, particularly when standing up quickly.
- Falls: Resulting from sudden loss of consciousness or balance.
Investigations
Diagnostic investigations for orthostatic hypotension include:
- Full Blood Count (FBC): To assess for anaemia, which may contribute to hypotension.
- Urea & Electrolytes (U&E): To evaluate kidney function and detect electrolyte imbalances.
- HbA1c: To screen for diabetes, which may be a contributing factor.
- Pregnancy Test: In women of childbearing age, to rule out pregnancy-related hypotension.
- Electrocardiogram (ECG): To assess for arrhythmias or other cardiac conditions that may contribute to hypotension.
- Echocardiogram: If structural heart disease is suspected, to evaluate cardiac function and structure.
Diagnosis
The diagnosis of orthostatic hypotension is confirmed by measuring blood pressure changes upon standing:
- A fall in systolic blood pressure of at least 20 mmHg or a fall in diastolic blood pressure of at least 10 mmHg within three minutes of standing is diagnostic of orthostatic hypotension.
- Further assessment should include evaluating the patient’s history, medication use, and potential contributing conditions.
Management
The primary goal of managing orthostatic hypotension is to improve quality of life, prevent falls, and manage underlying causes:
1. Conservative Management
- Lifestyle Modifications: Encourage patients to rise slowly from a sitting or lying position, avoid prolonged standing, and elevate the head of the bed during sleep.
- Fluid and Salt Intake: Adequate hydration and increased salt intake (unless contraindicated) can help maintain blood pressure.
- Eliminate Triggers: Review and adjust medications that may contribute to orthostatic hypotension, such as antidepressants, diuretics, and other antihypertensives.
2. Medication Management
- Fludrocortisone: An off-label use to increase renal sodium reabsorption, thereby increasing blood volume and blood pressure.
- Midodrine: A vasoconstrictor that increases blood pressure by constricting blood vessels.
References
- National Institute for Health and Care Excellence (NICE) (2024) Management of Orthostatic Hypotension. Available at: https://www.nice.org.uk/guidance/ng207 (Accessed: 26 August 2024).
- British Heart Foundation (2024) Orthostatic Hypotension: Diagnosis and Management. Available at: https://www.bhf.org.uk (Accessed: 26 August 2024).
- British National Formulary (BNF) (2024) Medications for Hypotension. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).
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