Unclassified Antidysrhythmic Therapy

Digoxin absorption

Rapidly absorbed following oral administration

Digoxin gastrointestinal system (GI)

Document any changes in appetite and/or complaints of nausea, diarrhea, or vomiting.

A patient is being treated with digoxin for atrial fibrillation. Which finding would concern the nurse?

Development of second-degree block

There are also common foods and herbal supplements that interact with digoxin.

Ephedra may increase the risk of dysrhythmias. Licorice and ginseng can increase digoxin toxicity. St. John's wort can lead to subtherapeutic effects of digoxin. Large amounts of high-fiber foods (bran, pectin) can decrease the absorption of oral digoxin. Digoxin should be administered 1 hour before or 2 hours after a high-fiber meal.

Due to the extremely short half-life and duration of action, the adverse effects of adenosine resolve very quickly. Patients should be instructed as follows:

They may experience brief chest pressure, nausea, lightheadedness, head or neck pain, or shortness of breath. These symptoms will resolve quickly. Flushing/headache may occur temporarily after administration. Continued chest pain, lightheadedness, head or neck pain, or difficulty breathing should be reported immediately.

Adenosine distribution

Unknown

Adenosine excretion

Unknown

Evaluate the effectiveness of the antidysrhythmic drugs by comparing

heart rate and rhythm with the baseline. Note any troublesome side effects. Also note any adverse drug effects and report them to the health care provider.

Digoxin toxicity can occur with

hypokalemia, which can worsen cardiac dysrhythmias.

Which statement by Mr. Torres indicates an understanding of the possible side effects of adenosine?

"I might feel some chest pressure, but it will not last long." The patient might experience brief chest pressure with adenosine. Other symptoms the patient may feel include nausea, lightheadedness, head or neck pain, or shortness of breath because of the brief periods of asystole. Because the half-life is less than 10 seconds, these symptoms should resolve quickly.

A nurse is preparing to administer adenosine through an established intravenous site with intravenous fluids infusing. Which intravenous fluids would the nurse accept as compatible with adenosine?

0.9% NaCl D5W Ringer's lactate

Teach the patient to check weight daily and to report weight gain of

2 lb in 24 hours or 5 lb or more in 1 week to the health care provider.

A nurse is preparing to administer digoxin to a patient who is complaining of nausea. Which action is the nurse's priority?

Assess for bradycardia.

Digoxin neurologic system

Assess for history of headaches, fatigue, confusion, or convulsions. Assess level of alertness and orientation.

Before administering digoxin, which action will the nurse take?

Assess the apical pulse.

Digoxin is prescribed to a patient who has been taking verapamil for hypertension. Which dosing change would the nurse anticipate seeing in the prescription?

A reduction in digoxin dose by 50%

The nurse is preparing to administer a loading dose of digoxin to a patient in atrial fibrillation with a heart rate of 130 beats/minute. Which statement describes the rationale for the loading dose?

Achieve therapeutic effect of digoxin more quickly.

IV Incompatibilities of adenosine

Adenosine is incompatible with all drugs. It is incompatible with all solutions, except the following: 0.9% NaCl, D5W, Ringer's lactate, or abciximab.

Adenosine

Adenosine is the drug of choice for treating paroxysmal supraventricular tachycardia (PSVT). PSVT begins in an area above the ventricles with the heart rate often exceeding 150 beats/min.

A patient remains in supraventricular tachycardia after administration of adenosine 6 mg. Which action would the nurse anticipate taking?

Administer adenosine 12 mg in 1 to 2 minutes after the previous dose.

diet for digoxin

Advise the patient to eat foods high in potassium, such as fresh and dried fruits, fruit juices, and vegetables, including potatoes.

A nurse would anticipate that which dysrhythmia will likely develop when adenosine is administered?

Asystole

The most common adverse effects include the following: of adenosine

Atrial tachydysrhythmias AV block Cardiac arrest Ventricular dysrhythmias Atrial fibrillation Bronchospasm Adenosine frequently causes asystole for a few seconds. No treatment is required due to the short half-life of the drug.

Storage of adenosine

Any portion of the drug not used should be discarded because the drug does not contain preservatives. The drug should be stored at room temperature. Solution should appear clear. Do NOT refrigerate, as cold will cause crystallization. If crystallization occurs, warm to room temperature, and the crystals will dissolve.

Digoxin baseline rhythm and pulse rate

Apical pulse rate should be taken for a full minute. If pulse is 60 beats/min or less, contact the health care provider.

Adenosine stimulates the

adenosine-sensitive potassium channels in the sinoatrial (SA) node and internodal tracts. The use of adenosine results in specific effects on the heart and the electrocardiogram (ECG). The nurse must be aware of these effects and understand how adenosine is used therapeutically.

Methylxanthines, such as aminophylline, theophylline, and caffeine, block receptors for

adenosine. Patients who are taking aminophylline, theophylline, or caffeine need larger doses of adenosine, and even then adenosine may not be effective. Dipyridamole, an antiplatelet drug, blocks cellular uptake of adenosine and can thereby intensify its effects.

Which products can increase the risk for digoxin toxicity?

Quinidine Dronedarone Ginseng

Adenosine interaction with dipyridamole, nicotine

may increase effect

Digoxin

Digoxin is primarily used for heart failure. Digoxin can also be used for atrial fibrillation/flutter and PSVT. Digoxin is not effective against ventricular dysrhythmias, such as supraventricular tachycardia/fibrillation.

Subsequent Dosing Assessment for digoxin

Digoxin levels must be closely monitored due to the narrow range between therapeutic and toxic levels. Assess apical pulse for 1 minute. If 60 beats/min or less, withhold drug and contact health care provider. Digoxin levels should be evaluated 6 to 8 hours after administration or just before the next dose. Therapeutic serum level: 0.8 to 2 ng/mL; toxic serum level: greater than 2 ng/mL.

Digoxin distribution

Distributed throughout the body with highest concentration in the heart, kidneys, intestine, liver, stomach, and skeletal muscle. It is 20%-30% protein bound.

Digoxin visual and sensory system

Document baseline vision and changes in vision, such as green, yellow, or purple halos surrounding peripheral field of vision.

The nurse should be on heightened alert for the signs and symptoms of digoxin toxicity.

During the first 1 to 2 hours after administration, assess apical pulse for bradycardia and ECG or cardiac monitor for dysrhythmias (excessive slowing of pulse may be first clinical sign of toxicity). During loading dose, assess for signs of toxicity (GI disturbances and neurologic abnormalities). Monitor serum potassium, magnesium, calcium, and renal function. Assess for signs and symptoms of digitalis toxicity (anorexia, nausea, vomiting, bradycardia, cardiac dysrhythmias, and visual disturbances). Report symptoms immediately to the health care provider.

A patient who has been taking digoxin for several months is now complaining about changes to vision. Which action would the nurse take?

Further inquire about the vision changes.

A nurse is reviewing laboratory results on a patient who is taking oral digoxin. Which electrolyte imbalance would the nurse associate with digoxin toxicity?

Hypokalemia

Digoxin serum electrolytes

Hypokalemia and hypomagnesemia may precipitate digitalis toxicity.

Administration of adenosine

IV push should be administered undiluted and rapidly (over 1 to 2 sec). Before administering adenosine, flush the IV line with 0.9% NaCl to prevent precipitation of particulate matter. Flush with 20 mL 0.9% NaCl after the rapid IV bolus.

Before administering adenosine, the nurse should do the following:

Identify the dysrhythmia. Assess apical pulse and blood pressure. Determine whether specific symptoms are present and whether the symptoms are related to tachydysrhythmias.Assess the patient's symptoms.Determine whether the patient is stable.Determine whether the rhythm is regular or irregular.Assess whether the QRS complex is narrow or wide.Determine whether the patient is in sinus tachycardia, supraventricular tachycardia, or atrial fibrillation with rapid ventricular response (RVR). Assess for altered mental status, continuing chest pain, hypotension, or other signs of shock.

Adenosine absorption

Immediately taken up by red blood cells (RBCs) and tissues after intravenous (IV) administration

Digoxin excretion

In urine (50%-80%)

Side effects for digoxin

Instruct the patient to report side effects: nausea, vomiting, headache, diarrhea, and visual disturbances, including diplopia.

Before administering digoxin, the nurse would conduct a thorough assessment, knowing that digoxin accumulates the highest in which areas of the body?

Kidney Intestine Heart Skeletal muscle

The nurse will anticipate administering a second dose of adenosine shortly after the first dose because the drug is effective for which time frame?

Less than 10 seconds

Digoxin interacts with beta blockers

Mechanism: Block beta receptors in the heart Result: Enhanced bradycardic effect of digoxin May have additive effect on slowing AV nodal conduction

Digoxin interacts with calcium channel blockers

Mechanism: Block calcium channels in the myocardium Result: Enhanced bradycardic and negative inotropic effects of digoxin May have additive effect on slowing AV nodal conduction

Digoxin interaction with verapamil, quinidine, amiodarone, dronedarone , cyclosporine, azole antifungals

Mechanism: Decrease clearance Result: Digoxin levels increased by 50%; digoxin dose should be reduced by 50%Amiodarone may increase concentration/toxicity

Digoxin interacts with cholestyramine colestipol sucralfate

Mechanism: Decrease oral absorption Result: Reduced therapeutic effect

Digoxin interaction with potassium- depleting diuretics

Mechanism: Excrete fluid and electrolytes in urine Result: Increased digoxin toxicity

Digoxin interacts with antidysrhythmic calcium (IV)

Mechanism: Increase cardiac irritability Result: Increased digoxin toxicity

A patient's rhythm is now asystole after receiving adenosine. Which action would the nurse take?

Monitor the patient

Digoxin cardiac system

Note history of dysrhythmias, hypotension, abnormal heart sounds, or abnormal ECG findings.

Pharmacodynamic Profile adenosine

Onset: 20 to 30 sec Peak: Immediate Duration: Less than 10 sec Half-Life: Less than 10 sec

Pharmacodynamic Profile of digoxin

Onset: 30 to 120 min for PO Peak: 1 to 3 hr for PO and IV Duration: 3 to 4 days for PO and IV Half-Life: 1 to 3 days for PO and IV

Adenosine is a common medication to treat

PSVT. However, contraindications do exist. There are few drug interactions. Nurses must be aware of medications patients are taking along with their comorbidities.

The nurse will prepare to administer adenosine to a patient with which dysrhythmia?

Paroxysmal supraventricular tachycardia Adenosine is indicated for paroxysmal supraventricular tachycardia. It is not effective in atrial or ventricular dysrhythmias.

Which therapeutic effect does digoxin have on the heart?

Positive inotropic Negative dromotropic Negative chronotropic

Which channels along the cell's membrane do adenosine affect?

Potassium Adenosine stimulates the adenosine-sensitive potassium channels in the sinoatrial node and internodal tracts.

A patient with a history of heart failure is taking both a diuretic and digoxin. Which substance would the nurse anticipate administering to this patient?

Potassium supplement

Digoxin drug/herbal history

Potassium-wasting diuretic or cortisone drug may cause hypokalemia. Low potassium levels enhance action of digoxin, increasing risk of digitalis toxicity. Potassium supplements may be needed.

The nurse monitors the electrical activities of the heart while administering intravenous digoxin because of which potential effects to the heart?

Shortening of QR intervals Depression of ST segments Inversion of T waves

Digoxin metabolism

Some by liver

General drug adherence for digoxin

Stress the importance of taking the medication exactly as prescribed. A nurse may visit to ensure that medications are properly taken. Inform the patient of possible food/herbal drug interactions. Due to the many drug interactions that could occur, over-the-counter (OTC) medications should not be taken without approval from the health care provider. Keep drugs out of reach of small children. Childproof bottles should be requested. Take the medication at the same time every day. Take a missed dose if no more than 12 hours have passed from the time the drug was to have been taken. Do not double up on next dose. Contact the health care provider for further instructions. Never abruptly stop taking the medication.

PO Administration for digoxin

Tablets can be crushed. It can be administered with or without meals.

Which parameter would the nurse follow when administering adenosine to a patient to treat supraventricular tachycardia?

Undiluted and rapidly over 1 to 2 seconds as close to the heart as possible Adenosine should be administered undiluted as rapidly as possible over 1 to 2 seconds as close to the heart as possible, such as the antecubital fossa. It is then followed immediately with 20 mL of normal saline flush.

Adenosine metabolism

Unknown

IV Administration for digoxin

Use digoxin immediately. Should give IV slowly over a minimum of 5 minutes. May administer undiluted or diluted with a minimum of fourfold volume of sterile water for injection or D5W. Using less than four times dilution may result in drug precipitation.

Patient may experience short duration of asystole. Have the crash cart by the patient before administering

adenosine

Asystole can occur with

amiodarone. The patient must be on a continuous cardiac monitor, and the nurse should be prepared to administer cardiopulmonary resuscitation if asystole does not spontaneously convert.

Adenosine interaction with food

avoid caffeine ( may decrease effect)

The electrical conduction system of the heart is also noticeably affected

by digoxin, as is cardiac automaticity. Digoxin reduces dysrhythmias by its effects on the SA and AV node (negative chronotropic and dromotropic effects). Digoxin also decreases conduction through the AV node by acting as a direct depressant on the AV node.

After administration, adenosine significantly

decreases the automaticity of the SA node and slows conduction through the AV node. It also interrupts AV reentry pathways. After adenosine administration, brief asystole is usually apparent on the ECG. Rarely is asystole sustained.

Caution is advised in patients with acute myocardial infarction, acute myocarditis, and severe pulmonary disease for what

digoxin

Teach the patient how to check pulse rate before taking

digoxin and to notify the health care provider if pulse rate is ≤60 beats/min, >100 beats/min, or irregular.

Cardiotoxicity is the major adverse drug effect of

digoxin. Hypokalemia, usually resulting from concurrent therapy with diuretics, enhances the risk of cardiotoxicity. Potassium levels must be monitored closely and kept within normal range (3.5 to 5 mEq/L). Other adverse effects include GI disturbances and central nervous system (CNS) changes. GI disturbances include anorexia, nausea, vomiting, and diarrhea. Changes to the CNS include depression, delirium, and hallucinations. These unwanted effects may signify impending toxicity and should be reported to the health care provider. Changes to vision, such as blurred vision or seeing yellow, can also occur with digoxin toxicity.

A known drug allergy is a contraindication for

digoxin. Other contraindications to consider include heart failure resulting from diastolic dysfunction, ventricular tachycardia/fibrillation, and SA blocks, such as second- or third-degree heart block. Digoxin can promote or worsen bradycardia.

The PR interval on an ECG is prolonged due to the slowed AV conduction produced by

digoxin. The ventricles are also affected, resulting in accelerated repolarization, which causes the QR interval to possibly shorten. ST segment depression also occurs frequently, and the T wave may be inverted or depressed. The QRS complex experiences little change.

Adenosine is used as the

drug of choice for PSVT. Adenosine is not effective in ventricular dysrhythmias, atrial fibrillation, or atrial flutter.

Digoxin can also cause

dysrhythmias because digoxin can increase automaticity in the Purkinje fibers

Adenosine reduces the time for

electrical conduction through the atrioventricular (AV) node. As a result of this action, it is indicated for converting PSVT to sinus rhythm.

Side effects and adverse drug effects of adenosine are

few because of its extremely short half-life and duration of action. If unwanted effects occur, they usually last less than 1 minute. The most common side effects include facial flushing, nausea, dyspnea, and chest pressure.

Common side effects of digoxin include

headache and hypotension.

A desired effect on the heart from the use of digoxin is

increased myocardial contractility without increasing demands for oxygen (positive inotropic effect).

Many drugs interact with digoxin. Drugs that

lower serum potassium or magnesium levels can predispose patients to digoxin toxicity. The most significant drug-drug interactions occur with amiodarone, quinidine, and verapamil. These drugs can increase serum levels of digoxin by 50%, thus greatly increasing the risk of digoxin toxicity.

Adenosine interaction with methylxanthines (ex: theophylline)

may decrease effect

Adenosine interaction with carbamazepine

may increase degree of heart block caused by adenosine

Adenosine interaction with herbal

none significant

The preference for digoxin administration is the

oral route. The patient should receive a total of 1 to 1.5 mg orally over the first 24 hours divided into three or four doses. Afterward, the oral maintenance dose should be between 0.125 to 0.5 mg/day. In patients experiencing renal dysfunction or deficiency, the dose should be decreased.

For digoxin given intravenously, patient safety should be

priority. Proper rate of administration is imperative. Some institutions may require cardiac monitoring during administration of IV digoxin.

Adenosine is contraindicated in patients who have

second- or third-degree heart block, atrial flutter or fibrillation, sick sinus syndrome, or ventricular tachycardia, as well as in those with a known allergy.

The nurse must be aware of the proper preparation, dosage, and administration when handling adenosine. Adenosine is available in a

solution (3 mg/mL) to be used for IV bolus administration. It should be injected IV as close to the heart as possible (e.g., antecubital fossa), followed immediately by a saline flush. The first dose is 6 mg, given over 1 to 2 seconds. If no response is noted in 1 to 2 minutes, a dose of 12 mg may be administered and repeated one time 1 to 2 minutes after the most recent dose. If the patient is going to respond, it should occur as soon as adenosine reaches the AV node.