Orthostatic hypotension (OH) is common in older people and is encountered daily by emergency and general physicians, neurologists, and cardiologists. It is defined by a drop of >20 mm Hg in systolic blood pressure (BP) or >10 mm Hg in diastolic BP after standing for three minutes. It is seen in almost a quarter of emergency department presentations with syncope, one-fifth of older trauma inpatients, and 68% of older general medicine inpatients. It is associated with a higher risk of coronary artery disease, myocardial infarction, stroke, falls, fracture, road accidents, and death. Hence, it is important that it is identified early so that we can prevent the aforesaid consequences.
Pathophysiology
Normally, standing causes approximately 500-1000 mL of blood to pool transiently in the lower limbs and splanchnic circulation. This reduces venous return, stroke volume, and cardiac output. The resulting reduction in arterial pressure is rapidly sensed by the carotid and aortic baroreceptors, which activate the sympathetic nervous system. This produces peripheral vasoconstriction, increased heart rate, and contractility, thereby maintaining cerebral perfusion.
With ageing, several mechanisms make this response less effective:
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Impaired Baroreflex Sensitivity
Ageing reduces the sensitivity and responsiveness of the arterial baroreceptors. The compensatory increase in heart rate and sympathetic vasoconstriction after standing is therefore blunted.
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Reduced Vascular Compliance and Impaired Vasoconstriction
Arterial stiffness reduces the ability of the peripheral vessels to constrict rapidly and appropriately.
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Reduced Cardiac Reserve
Older adults may have a reduced ability to increase heart rate and cardiac output in response to the fall in venous return.
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Impaired Autonomic Nervous System: Neurogenic OH
This results from impairment at multiple levels of the autonomic nervous system, from the brain and spinal cord to the pre- and post-ganglionic sympathetic and parasympathetic nervous systems, down to the peripheral autonomic nerves. It is commonly seen in central causes like Parkinson’s disease (PD), dementia with Lewy bodies (DLB), multi-system atrophy (MSA), and diseases of the peripheral nervous system like diabetes, HIV, amyloidosis, and autoimmune and paraneoplastic processes.
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Reduced Thirst and Impaired Renal Water Conservation
Older adults are more susceptible to dehydration because thirst perception may decline with age and the kidney’s ability to conserve water becomes less efficient. Even modest volume depletion can therefore exaggerate orthostatic BP falls.
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Increased Medication Burden: Most Common Contributor
Antihypertensives, diuretics, vasodilators, α-blockers, and several other commonly used medications can further impair the compensatory mechanisms.
Symptoms
- Light-headedness on standing
- Giddiness or blackouts on standing/walking
- Sense of imbalance
- Gait instability
- Recurrent falls
- Recurrent syncopal episodes
A simple bedside test can detect this!
Measure the patient’s pulse rate and blood pressure first in the supine position. Then, ask the patient to stand and repeat the measurements at 0, 1, and 3 minutes after standing.
Management
Dietary Adjustments
- Less restricted salt consumption if permissible
- Increase water intake (up to 2.5 L/day)
- Reduce/avoid alcohol consumption
- Eat smaller meals more frequently rather than large meals
Activities
- Use an electric bed or mattress to sleep with the head of the bed raised up to 45 degrees
- Partake in recumbent exercises (e.g., stationary bicycle, rowing machine)
- Practice physical countermaneuvers (e.g., standing up slowly, leg crossing, buttock clenching)
- Avoid strenuous or frequent straining or other Valsalva maneuvers
- Limit exposure to hot environments (e.g., hot/humid weather, overheating, saunas/hot showers)
- Slow transitions are important: sit at the edge of the bed before standing and change position gradually.
Clothing
- Wear an abdominal binder
Wear waist-high (not knee- or thigh-high) compression stockings producing at least 15 to 20 mm Hg pressure.
Pharmacotherapy
Drugs like fludrocortisone (volume expanders) and sympathomimetics like midodrine, droxidopa, and atomoxetine may be given by the treating physician based on individualised decisions.
Conclusion
A simple bedside test can go a long way in the prevention of falls and fractures in the elderly. Orthostatic hypotension is a common problem which can be addressed and should not be missed.
Dr Harini Radhakrishnan
Consultant – Neurologist
Kauvery Hospital, Chennai
