Orthostatic hypotension
In orthostatic hypotension, also called postural hypertension, the patient’s blood pressure drops 15 to 20 mm Hg or more — with or without an increase in the heart rate of at least 20 beats/minute — when he rises from a supine to a sitting or standing position. (Blood pressure should be measured 5 minutes after the patient has changed his position.) This common sign indicates failure of compensatory vasomotor responses to adjust to position changes. It’s typically associated with light-headedness, syncope, or blurred vision and may occur in a hypotensive, normotensive, or hypertensive patient. Although commonly a nonpathologic sign in elderly patients, orthostatic hypotension may result from prolonged bed rest, fluid and electrolyte imbalance, endocrine or systemic disorders, and the effects of drugs.
To detect orthostatic hypotension, take and compare blood pressure readings with the patient supine, sitting, and then standing.
Emergency Actions
If you detect orthostatic hypotension, quickly check for tachycardia, altered level of consciousness (LOC), and pale, clammy skin. If these signs are present, suspect hypovolemic shock. Insert a large-bore I.V. line for fluid or blood replacement. Take the patient’s vital signs every 15 minutes, and monitor his intake and output.
History
If the patient is in no danger, obtain a history. Ask the patient if he frequently experiences dizziness, weakness, or fainting when he stands. Also ask about associated symptoms, particularly fatigue, orthopnea, impotence, nausea, headache, abdominal or chest discomfort, and GI bleeding. Then obtain a complete drug history.
Physical assessment
Begin the physical assessment by checking the patient’s skin turgor. Palpate peripheral pulses, and auscultate the heart and lungs. Finally, test muscle strength and observe the patient’s gait for unsteadiness.
Medical causes
Adrenal insufficiency
In adrenal insufficiency, orthostatic hypotension may be accompanied by fatigue, muscle weakness, poor coordination, anorexia, nausea and vomiting, fasting hypoglycemia, weight loss, abdominal pain, irritability, and a weak, irregular pulse. Another common feature is hyperpigmentation — bronze coloring of the skin — which is especially prominent on the face, lips, gums, tongue, buccal mucosa, elbows, palms, knuckles, waist, and knees. Diarrhea, constipation, decreased libido, amenorrhea, and syncope may also occur along with enhanced taste, smell, and hearing, and cravings for salty food.
Amyloidosis
Orthostatic hypotension is commonly associated with amyloid infiltration of the autonomic nerves. Associated signs and symptoms vary widely and include angina, tachycardia, dyspnea, orthopnea, fatigue, and cough.
Diabetic autonomic neuropathy
Orthostatic hypotension may be accompanied by syncope, dysphagia, constipation or diarrhea, painless bladder distention with overflow incontinence, impotence, and retrograde ejaculation.
Hyperaldosteronism
Hyperaldosteronism typically produces orthostatic hypotension with sustained elevated blood pressure. Most other clinical effects of hyperaldosteronism result from hypokalemia, which increases neuromuscular irritability and produces muscle weakness, intermittent flaccid paralysis, fatigue, headache, paresthesia and, possibly, tetany with positive Trousseau’s and Chvostek’s signs. The patient may also exhibit vision disturbance, nocturia, polydipsia, and personality changes. Diabetes mellitus is a common finding.
Hyponatremia
In hyponatremia, orthostatic hypotension is typically accompanied by headache, profound thirst, tachycardia, nausea and vomiting, abdominal cramps, muscle twitching and weakness, fatigue, oliguria or anuria, cold clammy skin, poor skin turgor, irritability, seizures, and decreased LOC. Cyanosis, thready pulse, and eventually vasomotor collapse may occur in severe sodium deficit. Common causes include adrenal insufficiency, hypothyroidism, syndrome of inappropriate antidiuretic hormone secretion, and use of thiazide diuretics.
Hypovolemia
Mild to moderate hypovolemia may cause orthostatic hypotension associated with apathy, fatigue, muscle weakness, anorexia, nausea, and profound thirst. The patient may also develop dizziness, oliguria, sunken eyeballs, poor skin turgor, and dry mucous membranes.
Other causes
Drugs
Certain drugs may cause orthostatic hypotension by reducing circulating blood volume, causing blood vessel dilation, or by depressing the sympathetic nervous system. These drugs include antihypertensives (especially guanethidine and the initial dosage of prazosin), tricyclic antidepressants, phenothiazines, levodopa, nitrates, monoamine oxidase inhibitors, morphine, bretylium, and spinal anesthesia. Large doses of diuretics can also cause orthostatic hypotension.
Treatments
Orthostatic hypotension is commonly associated with prolonged bed rest (24 hours or longer). It may also result from sympathectomy, which disrupts normal vasoconstrictive mechanisms.
Special considerations
Monitor the patient’s fluid balance by carefully recording his intake and output and weighing him daily. To help minimize orthostatic hypotension, advise the patient to change his position gradually. Elevate the head of the patient’s bed, and help him to a sitting position with his feet dangling over the side of the bed. If he can tolerate this position, have him sit in a chair for brief periods. Immediately return him to bed if he becomes dizzy or pale or displays other signs of hypotension. Never leave the patient unattended while he’s sitting or walking; evaluate his need for assistive devices, such as a cane or walker.
Prepare the patient for diagnostic tests, such as hematocrit, serum electrolyte and drug levels, urinalysis, 12-lead electrocardiogram, and chest X-ray.
Pediatric pointers
Because normal blood pressure is lower in children than in adults, familiarize yourself with normal age-specific values to detect orthostatic hypotension. From birth to age 3 months, normal systolic pressure is 40 to 80 mm Hg; from age 3 months to 1 year, 80 to 100 mm Hg; and from ages 1 to 12, 100 mm Hg plus 2 mm Hg for every year over age 1. Diastolic blood pressure is first heard at about age 4; it’s normally 60 mm Hg at this age and gradually increases to 70 mm Hg by age 12.
The causes of orthostatic hypotension in children may be the same as those in adults.
Geriatric pointers
Elderly patients commonly experience autonomic dysfunction, which can present as orthostatic hypotension. Postprandial hypotension occurs 45 to 60 minutes after a meal and has been documented in up to one-third of nursing home residents.
Patient counseling
Patients with conditions that can lead to autonomic dysfunction should be made aware of the acute drop in blood pressure that can occur with positional changes. This is particularly important in patients with diabetes. When the problem appears, such patients need to avoid volume depletion and perform positional changes gradually instead of suddenly.
Pictures
Book Source Details
- Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 Lippincott Williams & Wilkins.
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Read excerpts from these other book chapters related to Low blood pressure:
Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2008 Williams & Wilkins.
More About Causes of Low blood pressure
» Next page: Pulse pressure, narrowed (Nursing: Interpreting Signs and Symptoms)
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