Orthostatic hypotension

Orthostatic hypotension (OH) is a condition that occurs in some individuals when they go from lying down, or sitting standing. In persons with OH this positional movement causes a decrease in systolic blood pressure (the top number of a blood pressure reading) of at least 20mmHg and a decrease in diastolic blood pressure (the bottom number of a blood pressure reading) of at least 10mmHg, within three minutes of standing.1,2 The decrease in blood pressure prevents a sufficient amount of blood from getting to the brain (cerebral hypoperfusion) which results in dizziness and fainting. In the general population there is a 6% prevalence in people aged 25-65.3 In elderly patients (above the age of 65), the prevalence has been found to be up to 33% in some populations.3 The higher rates of OH in the elderly may explain higher rates of injuries due to falling in the elderly.

A decrease in blood pressure occurs upon standing in all individuals, but the body has mechanisms that minimize. In healthy individuals, the decline in blood pressure is detected by receptors in some of the blood vessels called baroreceptors. These baroreceptors signal through the autonomic nervous system (the involuntary control system of the periphery) to the brain to limit the decrease in blood pressure by causing constriction of the blood vessels in the body (peripheral vascular resistance), and stimulating heart function.4 If these compensatory mechanisms are not working properly, OH may occur.4 Often, failure of the compensatory mechanisms is a result of a disease that impairs the function of the autonomic nervous system. 36% of patients who have Parkinson’s Disease also have OH because of decreased autonomic function.5 Other conditions associated with OH include multiple system atrophy (severe autonomic dysfunction)6, dementia7,and diabetes8. Many of the diseases are associated with underlying neuropathies (damage of nerves) or other dysfunctions that disrupt autonomic control of blood pressure. Some of the non-disease related causes of OH include decreased blood volume and dilation of blood vessels. These can be caused by alcohol intake, heat, traumatic injury, and heart problems.9,10 The result is the inability to limit a decrease the blood pressure upon standing and therefore individuals experience symptoms associated with hypoperfusion to the brain (inadequate blood flow to the brain).

Signs and Symptoms
Some of the most common symptoms of OH are dizziness, instability and a tendency to fall.1 Additional symptoms may include light-headedness, generalized weakness, fatigue, blurred vision9,10, neck pain (because of reduced blood flow to head and neck)11, and chest pain (because of decreased blood delivered to heart). These symptoms can be exaggerated by exercise, standing for long periods of time, increased room temperature or eating a large meal.9,10,13

There are a variety of treatments used OH. Some non-drug interventions include: standing up slowly and not standing for a long period of time, compression stockings, eating small meals as opposed to large meals, ingesting a greater amount of fluid and salt (to help increase volume of blood), staying in a temperature controlled environment, decreasing alcohol intake and following an individually adapted exercise plan. Most of the drug treatments work to increase blood volume or act as vasoconstrictors (constrict the blood vessels), including Fluorohydrocortisone, Midodrine, Ephedrine and Erythropoietin.3,9,10,12

Written by Magen Brady

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2. Consensus statement on the definition of orthostatic hypotension, pure autonomic failure, and multiple system atrophy. The consensus committee of the American autonomic society and the American academy of neurology. Neurology. 1996;46(5):1470-1470.
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10. Mathias CJ, Kimber JR. Postural hypotension: Causes, clinical features, investigation, and management. Annu Rev Med. 1999;50:317-36.
11. Robertson D, Kincaid DW, Haile V,Robertson RM. The head and neck discomfort of autonomic failure: an unrecognized aetiology of headache. Clin Auton Res 1994:4:99-103.
12. Mathias CJ, Kimber JR. Treatment of postural hypotension. Journal of Neurology, Neurosurgery and Psychiatry. 1998;65(3):285-9.
13. Mathias CJ. Orthostatic hypotension-causes, mechanisms and influencing factors. Neurology. 1995: 45: 5: 6-11.

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