Orthostatic Hypotension Jan 2022 Flashcards
Summary Abstract
Orthostatic hypotension is defined as a decrease in blood pressure of 20 mm Hg or more systolic or 10 mm Hg or more diastolic within three minutes of standing from the supine position or on assuming a head-up position of at least 60 degrees during tilt table testing. Symptoms are due to inadequate physiologic compensation and organ hypoperfusion and include headache, lightheadedness, shoulder and neck pain (coat hanger syndrome), visual disturbances, dyspnea, and chest pain. Prevalence of orthostatic hypotension in the community setting is 20% in older adults and 5% in middle-aged adults. Risk factors such as diabetes mellitus increase the prevalence of orthostatic hypotension in all age groups. Orthostatic hypotension is associated with a significant increase in cardiovascular risk and falls, and up to a 50% increase in relative risk of all-cause mortality. Diagnosis is confirmed by measuring blood pressure and heart rate after five minutes in the supine position and three minutes after moving to a standing position. [corrected] If the patient is unable to stand safely or the clinical suspicion for orthostatic hypotension is high despite normal findings on the bedside test, head-up tilt table testing is recommended. Orthostatic hypotension is classified as neurogenic or nonneurogenic, depending on etiology and heart rate response. Treatment goals for orthostatic hypotension are reducing symptoms and improving quality of life. Initial treatment focuses on the underlying cause and adjusting potentially causative medications. Nonpharmacologic strategies include dietary modifications, compression garments, physical maneuvers, and avoiding environments that exacerbate symptoms. First-line medications include midodrine and droxidopa. Although fludrocortisone improves symptoms, it has concerning long-term effects.
KEY RECOMMENDATIONS FOR PRACTICE
- The test for the diagnosis of orthostatic hypotension should consist of blood pressure and heart rate measurement in the supine position for five minutes followed by standing position for three minutes, instead of sitting to standing position.24,26–28 [corrected]
- If clinical suspicion for orthostatic hypotension is high, head-up tilt table testing should be performed even with normal bedside orthostatic vital signs.24,28,33,43,44
- Patients with neurogenic orthostatic hypotension and supine hypertension should be evaluated with a 24-hour ambulatory blood pressure monitor.45
- Treatment of orthostatic hypotension should be aimed at reducing symptoms to improve quality of life, rather than normalizing blood pressure.2,22,24,46
- Nonpharmacologic management strategies should be attempted before prescribing a medication. If nonpharmacologic management is insufficient alone, it should be used in combination with medications.2,22,24,33,66
- First-line pharmacologic therapy should include midodrine or droxidopa (Northera) titrated to relieve symptoms.2,22,24,56–61,66
General Summary
With increasing age, there is a normal decline in baroreceptor sensitivity and increase in autonomic neurodegenerative disease.2 Orthostatic hypotension occurs in only 5% of middle-aged adults but affects approximately 20% of those 60 years and older.3–5 Prevalence in nursing homes and geriatric wards is as high as 50% and 68%, respectively.1,6
Orthostatic hypotension is associated with significant morbidity and mortality, with the greatest risk in those who have comorbidities. Several large meta-analyses reported that orthostatic hypotension is associated with up to a 50% increase in relative risk of all-cause mortality (relative risk [RR] = 1.50; 95% CI, 1.24 to 1.81).7–9 In middle-aged, community-dwelling patients, it is associated with an increased risk of death (hazard ratio = 1.19 [95% CI, 1.09 to 1.30] to 1.70 [95% CI, 1.40 to 2.00]) after adjustment for other risk factors.10,11
Orthostatic hypotension is also associated with increased rates of coronary heart disease, myocardial infarction, heart failure, stroke, and falls.3,8–10 Older people especially are at risk of myocardial infarction and recurrent falls.12,13 Patients with diabetes mellitus are more likely to develop orthostatic hypotension and have an increased risk of mortality, microvascular and macrovascular complications, and cardiovascular events.14–18 In the United States, the rate of hospitalizations related to orthostatic hypotension is 36 per 100,000 adults and increases to 233 per 100,000 adults for those 75 years and older.19
Pathophysiology
Approximately 500 to 1,000 mL of blood pools in the splanchnic circulation and lower extremities when a person stands, causing a decrease in venous return and cardiac output.2,20–22 Baroreceptors detect decreased stretch and activate the sympathetic nervous system, which elevates the heart rate, bolsters contractility, and increases peripheral resistance through vasoconstriction.2,21 Baroreceptors also sense decreased blood volume, prompting upregulation of renin release, sodium reabsorption, and vasopressin activity, resulting in enhanced water retention.2,21 Orthostatic hypotension occurs when there is inadequate intravascular volume or when sympathetic nervous system–mediated vasoconstriction is unable to compensate for gravitational pooling, leading to decreased organ perfusion and associated symptoms 20,23
Clinical Presentation and Evaluation
Symptoms of orthostatic hypotension appear while assuming a standing or upright position and are relieved by returning to a supine position (Table 1).2,22,24 These symptoms are due to organ hypoperfusion compensation, but they do not have to be present for a diagnosis.2,5 A history and physical examination aimed at identifying underlying causes of orthostatic hypotension should be performed. Risk factors for orthostatic hypertension are outlined in Table 2.19,24,25
Orthostatic hypotension is diagnosed by measuring blood pressure and heart rate after five minutes in the supine position and three minutes after moving to a standing position.26 [corrected] There is no standard timing of measurements (e.g., one-minute intervals, one-minute and three-minute intervals) or positioning (e.g., supine to sitting, supine to standing, sitting to standing, all three).19,24,26,27 Supine to standing measurements evoke the greatest hemodynamic changes and are more sensitive.27,28 A sustained decrease in blood pressure of 20 mm Hg or more systolic or 10 mm Hg or more diastolic within three minutes of standing is diagnostic of orthostatic hypotension.1,26
Variations in the time it takes for blood pressure to fall allow orthostatic hypotension to be classified as classic (within three minutes), initial (within 15 seconds), and delayed (after three minutes).2,22,26 Although the clinical significance of these variants is not completely understood, it suggests that orthostatic hypotension is a spectrum of disordered physiology.1,29–31 A large prospective study reported an association with adverse events (e.g., fall, fracture, syncope, death) in patients 45 to 64 years of age if orthostatic hypotension occurred within one minute of standing.32
Orthostatic hypotension is further classified as neurogenic or nonneurogenic2,4,6,22,24,33 (Table 32,4,6,20–22,24,33). Neurogenic orthostatic hypotension is caused by an intrinsic failure of the autonomic nervous system to create a normal physiologic response (baroreflex dysfunction). The differential diagnosis includes neurodegenerative disorders, pure autonomic failure, small fiber neuropathies, and acquired disorders.2,4,6,22,24 Nonneurogenic orthostatic hypotension is secondary to external factors (often medication use) inhibiting the body’s normal compensatory pattern.
Measuring heart rate with each position change can help detect baroreflex dysfunction.2,22,24,27 The compensatory rise in heart rate is maintained in nonneurogenic orthostatic hypotension, whereas the heart rate response is markedly reduced or absent in neurogenic orthostatic hypotension.2,26 An increase in heart rate of 0.5 beats per minute or more for every mm Hg decrease in systolic blood pressure has a high sensitivity (91%) and specificity (88%) for nonneurogenic orthostatic hypotension.34,35 Additional features that differentiate the two are outlined in Table 4.2,22,34,35
Supine hypertension is defined as blood pressure of 140 mm Hg or higher systolic or 90 mm Hg or higher diastolic after five minutes in the supine position and affects about 50% of patients with neurogenic orthostatic hypotension.2,21,22,25,45 Anti-hypotensive medications may worsen supine hypertension; therefore, screening for supine hypertension is recommended for all patients with neurogenic orthostatic hypotension.22,45 Because of a higher baseline blood pressure in patients with supine hypertension, orthostatic hypotension is diagnosed with a decrease in systolic blood pressure of 30 mm Hg or more.1,45 If supine hypertension is suspected, 24-hour ambulatory blood pressure monitoring can be used to assess severity (particularly nocturnal hypertension) and tailor therapies based on activities throughout the day.45
Additional evaluation is focused on ruling out nonneurogenic orthostatic hypotension.24 Table 7 includes initial testing for patients presenting with orthostatic hypotension.24,33,45 The overall approach to the diagnosis and management of orthostatic hypotension is summarized in Figure 2.
Management
Treatment goals for orthostatic hypotension are reducing symptoms and improving quality of life, rather than normalizing blood pressure.2,22,24,46 Management begins with identifying and treating the underlying cause. The patient’s current medications should be evaluated and potentially causative agents adjusted if safe to do so (Table 8).2,20,22,24,46,47
The discontinuation or tapering of opioid, psychoactive, dopaminergic, and anticholinergic medications should be considered.2,20,22,24 A retrospective study demonstrated a 23% increased prevalence of orthostatic hypotension in older patients taking even one of these medications.48
Antihypertensives can exacerbate orthostatic hypotension symptoms because they reduce intravascular volume, trigger vasodilation, and have negative chronotropic effects.22,24 Nighttime dosing of antihypertensives should be considered to reduce orthostatic hypotension symptoms.22,24,49 Use of a 24-hour ambulatory blood pressure monitor may be helpful in guiding this decision.22,45,49
Anemia can exacerbate orthostatic hypotension by reducing blood viscosity and increasing nitric oxide–mediated vasodilation. Therefore, treatment for anemia should be optimized as part of the patient’s comprehensive management.2,22
Non-pharmacologic Management
Initiating lifestyle-based treatments, such as avoiding or modifying exacerbating activities, is the first-line approach for the management of neurogenic orthostatic hypotension.2,22,24,46 Although there is conflicting evidence of their effectiveness, expert consensus guidelines advocate the use of nonpharmacologic treatments because of minimal risk of harm.2,22,24,33
Hot and humid conditions can exacerbate symptoms via vasodilatory cooling. Patients should be vigilant in avoiding environmental exposures and exacerbating activities.2,22,24 Postprandial hypotension is common in neurogenic orthostatic hypotension because of redistribution of blood volume to the splanchnic circulation. Diets should include frequent small meals to minimize this effect.2,22,24,50 Physical fitness should be encouraged because bed rest can further exacerbate orthostatic hypotension.2 Exercise regimens in older people have been shown to improve head-up tilt table testing results.51 Modifications should be made as needed to alleviate symptoms during exercise, such as avoiding frequent position changes.2,24
Appropriate volume status is maintained by adequate hydration and sodium intake. Physicians should assess the risks of increased water and sodium intake in patients with comorbid conditions such as heart failure, cirrhosis, or chronic kidney disease. Consumption of 2 to 2.5 L of fluids per day is recommended to counteract expected urinary losses.2,20,22,24 Increased salt intake has been shown to provide short-term symptom improvement.52 Patients should aim for at least 2 to 3 g of sodium intake per day through dietary sources or salt tablets. A urinary sodium excretion of more than 170 mEq per L (170 mmol per L) every 24 hours and a urinary volume of more than 1,500 mL indicate adequate fluid and sodium intake.2,20
Physical counter maneuvers, including leg-crossing or squatting, in addition to wearing waist-high compression garments with graded pressures of 30 to 40 mm Hg, may be used to reduce venous pooling in the legs and splanchnic circulation.53,54,46 However, the use of compression garments is limited by poor compliance.22,53,54
Elevating the head of the bed by 30 to 45 degrees at night can theoretically prevent supine hypertension, which exacerbates morning orthostatic hypotension by promoting nocturnal diuresis and natriuresis. One trial demonstrated that this did not change 24-hour ambulatory blood pressure values or urinary volume.55
Pharmacologic Management
Two medication strategies can be used to augment nonpharmacologic management if it is insufficient alone. Midodrine and droxidopa (Northera) act to increase peripheral vascular resistance, whereas fludrocortisone expands intravascular volume.2,22 The choice of medication is guided by underlying etiology, patient preference, adverse effects, cost, and therapeutic response.22 Specific medication dosages and considerations in the management of orthostatic hypotension are summarized in Table 9.2,21,22,24,56–65
Midodrine, a short-acting alpha-1 adrenergic agonist that acts via vasoconstriction, has been shown to alleviate symptoms of orthostatic hypotension and elevate blood pressure in multiple randomized placebo-controlled trials.22,24,56–58,64,66 It is approved by the U.S. Food and Drug Administration for the treatment of orthostatic hypotension and is a recommended first-line medication.2,22,24,56–58,64,66 A double-blind, multicenter, randomized controlled trial of 171 patients demonstrated significant improvement in global symptom scores and standing systolic blood pressure in patients treated with midodrine, 10 mg, three times per day.56 Midodrine can cause supine hypertension and should be avoided within three to five hours of bedtime.2,22,24,66 Other common adverse effects include piloerection, scalp itching, and urinary retention.2,22,24,64,66
Droxidopa, a short-acting norepinephrine precursor, is another first-line medication approved by the U.S. Food and Drug administration for the treatment of orthostatic hypotension. Based on validated symptom scores, this medication increases standing systolic blood pressure and alleviates orthostatic hypotension symptoms.2,24,59,66 Droxidopa should also be avoided before bedtime because it can cause supine hypertension.2,24,59 The most common adverse effects are headaches and nausea. Falls, dizziness, and urinary tract infections have also been reported.65 Patients with neurogenic orthostatic hypotension secondary to Parkinson disease who are treated with droxidopa have a reduced risk of falls.67
Fludrocortisone is a synthetic mineralocorticoid that promotes renal sodium reabsorption, thereby increasing intravascular volume.2,24 Additionally, it increases vascular alpha-adrenergic receptor sensitivity, promoting vasoconstriction.2,24 Expert consensus recommends the off-label use of fludrocortisone in the treatment of orthostatic hypotension.2,22,24 One small (n = 17), short-term (three weeks) study demonstrated an improvement in symptom scores with the use of this medication.60 There are significant adverse effects,2,22,24,66 and its use is cautioned in patients with heart failure. Fludrocortisone has long-term risks, including left ventricular hypertrophy, renal failure, and hospitalization.22,68
Off-label use of atomoxetine (Strattera) and pyridostigmine (Mestinon) can be considered as adjunctive therapy.63,69 Atomoxetine has been shown to reduce symptoms of orthostatic hypotension compared with placebo and is comparable with midodrine in improving standing blood pressure.61,62
Referral
There are limited evidence-based referral criteria for orthostatic hypotension. Symptoms that are incapacitating or severely impact activities of daily living and a 30 mm Hg or more drop in systolic blood pressure may warrant a specialist evaluation.24 Cardiology referral may be considered for known heart disease or abnormal electrocardiogram findings.33,70 Other reasons for referral include treatment failure, significant gastrointestinal impairment, or physician discomfort in treatment.24,46
