Bradycardia

Bradycardia: Excerpt from Signs & Symptoms: A 2-in-1 Reference for Nurses

Bradycardia refers to a heart rate of less than 60 beats/minute. It occurs normally in young adults, trained athletes, and elderly people as well as during sleep. It’s also a normal response to vagal stimulation caused by coughing, vomiting, or straining during defecation. When bradycardia results from these causes, the heart rate rarely drops below 40 beats/minute. However, when it results from pathologic causes (such as cardiovascular disorders), the heart rate may be slower. (See Managing severe bradycardia, page 102.)

History

After detecting bradycardia, check for related signs of life-threatening disorders. If the patient’s bradycardia isn’t accompanied by unfavorable signs, ask the patient if he or a family member has a history of a slow pulse rate because this may be inherited. Also, find out if he has an underlying metabolic disorder such as hypothyroidism which can precipitate bradycardia. Ask which medications he’s taking and if he’s complying with the prescribed schedule and dosage.

Physical assessment

Monitor vital signs, temperature, pulse, respirations, blood pressure, and oxygen saturation. Then perform a complete cardiac assessment.

Medical causes

Cardiac arrhythmia

Depending on the type of cardiac arrhythmia and the patient’s tolerance of it, bradycardia may be transient or sustained, benign, or life-threatening. Related findings result from reduced cardiac output and include hypotension, palpitations, dizziness, weakness, dyspnea, chest pain, decreased urine output, altered level of consciousness (LOC), syncope, and fatigue.

Cardiomyopathy

Cardiomyopathy, a potentially life-threatening disorder, may cause transient or sustained bradycardia. Other findings include dizziness, syncope, edema, fatigue, jugular vein distention, orthopnea, dyspnea, and peripheral cyanosis.

Cervical spinal injury

Bradycardia associated with a cervical spinal injury may be transient or sustained, depending on the severity of the injury. Its onset coincides with sympathetic denervation. Associated signs and symptoms of cervical spinal injury include hypotension, decreased body temperature, slowed peristalsis, leg paralysis, and partial arm and respiratory muscle paralysis.

Hypothermia

When core body temperature drops below 89.6° F (32° C), causing hypothermia, bradycardia usually appears. It’s accompanied by shivering, peripheral cyanosis, muscle rigidity, bradypnea, and confusion leading to stupor. If the core temperature drops below 86° F (30° C), the patient may appear dead (in a state of rigor mortis) with no palpable pulse or audible heart sounds.

Hypothyroidism

Hypothyroidism causes severe bradycardia in addition to fatigue, constipation, unexplained weight gain, and sensitivity to cold. Related signs include cool, dry, thick skin; sparse, dry hair; facial swelling; periorbital edema; thick, brittle nails; and confusion leading to stupor.

Myocardial infarction

Sinus bradycardia is the arrhythmia most commonly associated with acute myocardial infarction (MI). Accompanying signs and symptoms of an MI include an aching, burning, or viselike pressure in the chest that may radiate to the jaw, shoulder, arm, back, or epigastric area; nausea and vomiting; cool, clammy, and pale or cyanotic skin; anxiety; and dyspnea. Blood pressure may be elevated or depressed. Auscultation may reveal abnormal heart sounds.

Other causes

Diagnostic tests

Cardiac catheterization and electrophysiologic studies can induce temporary bradycardia.

Drugs

Beta-adrenergic blockers and some calcium channel blockers, cardiac glycosides, topical miotics (such as pilocarpine), protamine, quinidine and other antiarrhythmics, and sympatholytics may cause transient bradycardia. Failure to take thyroid replacements may cause bradycardia.

Invasive treatments

Suctioning can induce hypoxia and vagal stimulation, causing bradycardia. Cardiac surgery can cause edema or damage to conduction tissues, causing bradycardia.

Special considerations

Continue to monitor vital signs frequently. Be especially alert for changes in cardiac rhythm, respiratory rate, and LOC.

Prepare the patient for laboratory tests, which can include complete blood count; cardiac enzyme, serum electrolyte, blood glucose, blood urea nitrogen, arterial blood gas, and blood drug levels; thyroid function tests; and a 12-lead electrocardiogram. If appropriate, prepare the patient for 24-hour Holter monitoring.

Pediatric pointers

Heart rates are normally higher in children than in adults. Fetal bradycardia — a heart rate of less than 120 beats/minute — may occur during prolonged labor or complications of delivery, such as compression of the umbilical cord, partial abruptio placentae, and placenta previa. Intermittent bradycardia, sometimes accompanied by apnea, commonly occurs in premature infants. Bradycardia rarely occurs in full-term infants or children. However, it can result from congenital heart defects, acute glomerulonephritis, and transient or complete heart block associated with cardiac catheterization or cardiac surgery.

Geriatric pointers

Sinus node dysfunction is the most common bradyarrhythmia encountered among  elderly patients. Patients with this disorder may have as their chief complaint fatigue, exercise intolerance, dizziness, or syncope. If the patient is asymptomatic, no intervention is necessary. Symptomatic patients, however, require careful scrutiny of their drug therapy. Beta-adrenergic blockers, verapamil, diazepam, sympatholytics, antihypertensives, and some antiarrhythmics have been implicated; symptoms may clear when these drugs are discontinued. Pacing is usually indicated in patients with symptomatic bradycardia lacking a correctable cause.

Patient counseling

Discuss signs and symptoms to report, such as light-headedness or syncope. Teach the patient to take his pulse and make sure he knows parameters for calling the physician and seeking emergency care. If the patient had a pacemaker inserted, provide instructions for its use.

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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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Signs & Symptoms: A 2-in-1 Reference for Nurses Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-58255-318-1

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