Ppt chapter 31

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Chapter 31

Drugs Affecting Cardiac Rhythm

Chapter 31

Drugs Affecting Cardiac Rhythm


Physiology Physiology

• Contractions of the heart are dependent on the unique electrical conduction system of the cardiac muscle.

• The conduction system connects to highly specialized cardiac cells that allow the heart to beat predictably and rhythmically.

• The system is composed of the sinoatrial (SA) node, the atrioventricular (AV) node, the bundle of His, the bundle branches, and the Purkinje fibers.


Physiology (cont.)Physiology (cont.)

• The SA node, influenced by both the sympathetic and the parasympathetic nervous systems, is known as the pacemaker of the heart.

• It is important to understand how potassium, sodium, and calcium ions bring about electrical changes in the cardiac cells that stimulate contraction of the cardiac cells.


Travel of Electrical Current Travel of Electrical Current


ElectrocardiogramElectrocardiogram


Movement of ElectrolytesMovement of Electrolytes


Pathophysiology Pathophysiology

• Arrhythmias, also called dysrhythmias, are a disturbance in the electrical activity of the heart.

• Some arrhythmias are insignificant and do not create any problems for the patient.

• Others disrupt the function of the heart, increase the oxygen demand of the heart, and interfere with cardiac output.

• Changes in the ionic currents through ion channels of the myocardial cell membrane are the main cause of cardiac arrhythmia.

• Ionic changes allow arrhythmias to develop in one of the three ways: through a disorder with impulse formation, through a disorder of the impulse conduction system, or through a combination of both.


Drugs and Other Therapies to Treat Arrhythmias Drugs and Other Therapies to Treat Arrhythmias • Drug therapy previously was the mainstay for treating

arrhythmias; now ICDs are added to that treatment.

• ICDs have an established and definitive role in preventing sudden cardiac death.

• Arrhythmias can be treated by catheter ablation.

• Antiarrhythmics are agents used to prevent, suppress, or treat a disturbance in cardiac rhythm.

• The primary outcomes are to decrease automaticity, decrease speed of conduction, and decrease reentry.

• When antiarrhythmic drugs were developed, a system of classification was sought in an attempt to organize the complex information into a conceptually meaningful fashion.


Class I Antiarrhythmic Drugs Class I Antiarrhythmic Drugs

• Class I antiarrhythmics are local anesthetics or membrane-stabilizing agents that depress phase 0 in depolarization.

• The drugs in subgroups of A, B, and C are not interchangeable because they have different pharmacotherapeutics.

• Class IB antiarrhythmics prototype drug: lidocaine (Xylocaine)


Lidocaine: Core Drug Knowledge Lidocaine: Core Drug Knowledge

• Pharmacotherapeutics

– Treat all acute ventricular arrhythmias.

• Pharmacokinetics

– Administered: IV. Metabolism: liver. Excreted: kidneys. T1/2: 1.5 to 2 hours

• Pharmacodynamics

– Decreases automaticity, excitability and membrane responsiveness. Decreases action potential duration and effective refractory period of Purkinje fibers and ventricular muscle


Lidocaine: Core Drug Knowledge (cont.)Lidocaine: Core Drug Knowledge (cont.)

• Contraindications and precautions

– Hypersensitivity, several cardiac conditions, digitalis toxicity, hypovolemia, shock

• Adverse effects

– Cardiac arrhythmias, hypotension, dizziness, lightheadedness, fatigue, drowsiness

• Drug interactions

– Many classes of drugs


Lidocaine: Core Patient Variables Lidocaine: Core Patient Variables

• Health status

– Determine whether the patient has a type of ventricular arrhythmia that is an indication for therapy.

• Life span and gender

– Pregnancy category B

• Environment

– Should be given in hospital or emergency setting with continuous ECG monitoring


Lidocaine: Nursing Diagnoses and Outcomes Lidocaine: Nursing Diagnoses and Outcomes

• Decreased Cardiac Output related to cardiac changes secondary to adverse effects of drug therapy

– Desired outcome: The patient will not develop deleterious cardiac changes that alter cardiac output.

• Risk for Injury, such as hepatic toxicity, related to adverse effects of drug therapy

– Desired outcome: The patient will not incur hepatic toxicity while on drug therapy.

• Change in level of consciousness related to CNS changes secondary to adverse effects of drug therapy

– Desired outcome: The patient will not experience dangerous CNS changes while on therapy.


Lidocaine: Planning and InterventionsLidocaine: Planning and Interventions

• Maximizing therapeutic effects

– After initial (or several) IV push dose of 50 to 100 mg, continuous drip of 1 to 4 mg/minute may be started.

• Minimizing adverse effects

– Monitor rhythm continuously with ECG.

– Notify prescriber immediately of arrhythmias, CNS depression or irritability.

– Monitor liver and kidney function tests.


Lidocaine: Teaching, Assessment, and EvaluationsLidocaine: Teaching, Assessment, and Evaluations

• Patient and family education

– Explain the purpose of the drug and the potential adverse effects.

– Explain the rationale for ECG monitoring and frequent blood testing.

• Ongoing assessment and evaluation

– Monitor the patient’s ECG and pulse throughout therapy.

– Check lidocaine blood levels, liver enzymes, renal function, and complete blood counts.


QuestionQuestion

• Serum levels of lidocaine above ______ are considered toxic.

– A. 2 mcg/mL

– B. 4 mcg/mL

– C. 6 mcg/mL

– D. 8 mcg/mL


AnswerAnswer

• C. 6 mcg/mL

• Rationale: When serum levels of lidocaine are greater than 6 mcg/mL, toxicity is present and the patient is at risk for developing seizures and loss of consciousness.


Class IA Antiarrhythmics Class IA Antiarrhythmics

• The class IA drugs are similar to lidocaine (class IB) and class IC drugs because they depress phase 0 (although not as much).

• These drugs also may cause arrhythmias in addition to treating them.

• Unlike lidocaine, their use in treating life-threatening ventricular arrhythmias has not been shown to improve survival.


Class IC Antiarrhythmics Class IC Antiarrhythmics

• Class IC drugs are flecainide (Tambocor), propafenone (Rythmol), and moricizine.

• These drugs depress phase 0 considerably.

• They have a slight effect on repolarization and decrease conduction substantially.

• Flecainide and propafenone have proarrhythmic effects.

• Both of these class IC drugs can be given orally.

• Their use has been limited to patients with life-threatening arrhythmias.


Class II Antiarrhythmic Drugs Class II Antiarrhythmic Drugs

• Antiarrhythmic class II drugs (beta blockers) depress phase 4 depolarization. Beta blockers slow heart rate by suppressing the SA node, slow the speed of conduction through the AV node, and decrease the force of contraction.

• They effectively reduce mortality in patients who have had a recent MI, those with symptomatic heart failure, and those with congenital long QT syndrome.

• Researchers have found that beta blockers are the most effective drugs for controlling the ventricular rate in AFib.

• It is important to keep in mind that only some of the beta blockers are approved for use as antiarrhythmics.


Class III Antiarrhythmic Drugs Class III Antiarrhythmic Drugs

• Class III antiarrhythmics produce a prolongation of phase 3 (repolarization).

• Action potential duration and refractory periods are prolonged, leading to reduction in membrane excitability of all myocardial tissue.

• Prototype drug: amiodarone (Cordarone, Pacerone)


Amiodarone: Core Drug Knowledge Amiodarone: Core Drug Knowledge


– Approved for use only in life-threatening arrhythmias


– Absorbed slowly; bioavailability of a single dose of the drug is about 50%. Highly lipid soluble.


– Prolongation of the refractory period, and noncompetitive alpha- and beta-adrenergic inhibition


Amiodarone: Core Drug Knowledge (cont.)Amiodarone: Core Drug Knowledge (cont.)• Contraindications and precautions

– Severe sinus-node dysfunction, 2nd and 3rd degree AV block

• Adverse effects

– Pulmonary toxicity, exacerbation of the arrhythmia, and liver disease


– Digoxin, flecainide, and warfarin


Amiodarone: Core Patient Variables Amiodarone: Core Patient Variables

• Health status

– Determine cardiac status.


– Safety has not been established in children.

• Environment

– Assess environment where drug will be given.

• Culture and inherited traits

– May be genetically related, however, little is known yet about this variation


Amiodarone: Nursing Diagnoses and Outcomes Amiodarone: Nursing Diagnoses and Outcomes

• Decreased Cardiac Output related to cardiac arrhythmia.

– Desired outcome: cardiac rhythm will return to normal, allowing for normal cardiac output.

• Risk for Injury related to adverse effects of drug therapy

– Desired outcome: The patient will not suffer permanent injury or death as a result of drug therapy.


Amiodarone: Planning and InterventionsAmiodarone: Planning and Interventions


– Administer the prescribed loading doses.

– Mix the drug in glass bottles or polyolefin bags.

– Use a volumetric infusion pump to prevent underdosage.


– It is important to correct electrolyte disturbances before beginning therapy.

– Use pulse oximetry or arterial blood gases to assess for changes in respiratory function.

– Assess for symptoms of visual impairment.


Amiodarone: Teaching, Assessment, and EvaluationsAmiodarone: Teaching, Assessment, and Evaluations


– Explain the purpose of the drug and possible adverse effects of the drug.

– Emphasize the importance of returning for follow-up blood work and ECGs.

– Teach patients to use appropriate protection when out in the sun and to limit sun exposure.


– The patient’s ECG should be monitored intermittently throughout therapy.


QuestionQuestion

• The most serious side effect of amiodarone is

– A. Pulmonary toxicity

– B. Other arrhythmias

– C. Liver disease

– D. Seizures


AnswerAnswer

• A. Pulmonary toxicity

• Rationale: Amiodarone can cause pulmonary toxicity. It is important to monitor lung function during therapy.


Class IV Antiarrhythmic Drugs Class IV Antiarrhythmic Drugs

• Class IV antiarrhythmics depress phase 4 depolarization and lengthen phases 1 and 2 of repolarization.

• Prototype drug: verapamil (Calan)


Verapamil: Core Drug Knowledge Verapamil: Core Drug Knowledge


– Antiarrhythmic for chronic atrial flutter or fibrillation


– Well absorbed after oral administration. Metabolized: liver. Excreted: kidneys


– Inhibits the movement of calcium ions across the cardiac and arterial muscle cell membrane


Verapamil: Core Drug Knowledge (cont.)Verapamil: Core Drug Knowledge (cont.)

• Contraindications and precautions

– Sick sinus syndrome, 2nd or 3rd degree heart block, and hypotension

• Adverse effects

– Constipation, dizziness, headache, nausea, hypotension, and peripheral edema


– Several drugs interact with verapamil


Verapamil: Core Patient Variables Verapamil: Core Patient Variables • Health status

– Determine type of arrhythmia the patient has.


– Pregnancy category C

• Lifestyle, diet, and habits

– Assess alcohol use.

• Environment

– Assess environment where drug will be given.


Verapamil: Nursing Diagnoses and Outcomes Verapamil: Nursing Diagnoses and Outcomes • Risk for Constipation related to adverse effects of the

drug

– Desired outcome: The patient will prevent or minimize constipation by increasing fluid intake and adding fruit and fiber to the diet.

• Decreased Cardiac Output related to decreased rate and force of contraction and return to normal rhythm related to therapeutic effects of drug

– Desired outcome: The patient’s decreased cardiac output will reduce symptoms of cardiac alterations without developing adverse cardiac effects from drug therapy.


Verapamil: Planning and InterventionsVerapamil: Planning and Interventions


– Verify that the IV line is patent before IV administration.

– Digoxin may be given with verapamil to achieve the additive effect of slowing at the AV node.


– IV route; do not dilute it with a sodium lactate.

– Do not administer IV verapamil simultaneously with (or within a few hours of) IV beta blockers.


Verapamil: Teaching, Assessment, and EvaluationsVerapamil: Teaching, Assessment, and Evaluations


– Explain the purpose of the drug and its adverse effects.

– Stress the importance of adequate fluid intake and dietary fruit and fiber to help prevent constipation.


– Monitor the patient’s ECG and blood pressure throughout therapy with verapamil.

– It is important to monitor liver function periodically to detect elevated serum drug levels.


QuestionQuestion

• Verapamil is a pregnancy category ____ drug.

– A. A

– B. B

– C. C

– D. D

– E. X


AnswerAnswer

• C. C

• Rationale: Verapamil is a pregnancy category C.


Potassium-Removing Resins Potassium-Removing Resins

• Because hyperkalemia may lead to cardiac arrhythmias, potassium-removing resins are drugs used to prevent arrhythmias from occurring.

• These resins bind with potassium and allow it to be excreted.

• Prototype drug: sodium polystyrene sulfonate (Kayexalate)


Sodium Polystyrene Sulfonate: Core Drug Knowledge Sodium Polystyrene Sulfonate: Core Drug Knowledge


– Potassium-removing resin used in treating hyperkalemia.


– The drug is not absorbed systemically and is excreted through the GI tract.


– Releases sodium ions that are replaced with potassium ions.


Sodium Polystyrene Sulfonate: Core Drug Knowledge (cont.)Sodium Polystyrene Sulfonate: Core Drug Knowledge (cont.)• Contraindications and precautions

– Use caution when giving this drug to anyone who cannot tolerate a small increase in sodium intake.

• Adverse effects

– Hypokalemia, other electrolyte imbalances, gastric irritation, anorexia, nausea, vomiting, and constipation


– When administered with nonabsorbable cation-donating antacids and laxatives, such as magnesium hydroxide and aluminum carbonate, systemic alkalosis can occur.


Sodium Polystyrene Sulfonate: Core Patient Variables Sodium Polystyrene Sulfonate: Core Patient Variables

• Health status

– Monitor the patient’s serum potassium level.


– Note the patient’s age.

• Lifestyle, diet, and habits

– Assess dietary history.

• Environment

– Be aware that sodium polystyrene sulfonate is administered in the hospital.


Sodium Polystyrene Sulfonate: Nursing Diagnoses and Outcomes Sodium Polystyrene Sulfonate: Nursing Diagnoses and Outcomes

• Risk for Constipation related to adverse effects of drug therapy

– Desired outcome: constipation will be prevented by administering sorbitol, orally or rectally, if warranted.

• Potential complication: hypokalemia.

– Desired outcome: The patient’s potassium level will be lowered only to the normal range.


Sodium Polystyrene Sulfonate: Planning and InterventionsSodium Polystyrene Sulfonate: Planning and Interventions


– Clear the GI tract with a cleansing enema before administering the drug by enema.

– When the drug is administered orally, create a suspension of the powdered formula with water or syrup for greater palatability.


– If the potassium serum level is severely elevated, use other methods to reduce potassium.


Sodium Polystyrene Sulfonate: Teaching, Assessment, and EvaluationsSodium Polystyrene Sulfonate: Teaching, Assessment, and Evaluations• Patient and family education

– Explain the therapeutic and possible adverse effects of the drug.

– Emphasize the importance of repeated blood work to monitor blood electrolyte concentrations.


– Monitor serum electrolytes throughout therapy.


QuestionQuestion

• Sodium polystyrene sulfonate may be administered

– A. Enema

– B. PO

– C. SC

– D. IV

– E. Both A and B

– F. All of the above


AnswerAnswer

• E. Both A and B

• Rationale: Sodium polystyrene sulfonate may be given either orally or as an enema.

Ppt chapter 31

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