12 - Phosphodiesterase inhibitors

Phosphodiesterase inhibitors

are another positive inotropic group of drugs given to treat acute HF.

This drug group inhibits the enzyme phosphodiesterase (PDE), which promotes a positive inotropic response and vasodilation.

milrinone lactate

This drug increases stroke volume and cardiac output and promotes vasodilation

Milrinone

is a high-alert medication that may cause significant harm to a patient when giver inappropriately.

It is administered intravenously for no longer than 48 hours to 72 hours. Severe cardiac dysrhythmias might result from the use of PDE inhibitors, so the patient's electrocardiogram (ECG) and cardiac status should be closely monitored.

Antianginal drugs

are used to treat angina pectoris, a condition of acute cardiac pain caused by inadequate blood flow to the myocardium due to either plaque occlusions within or spasms of the coronary arteries.

increase blood flow either by increasing oxygen supply or by decreasing oxygen demand by the myocardium.

angina pectoris

a condition of acute cardiac pain caused by inadequate blood flow to the myocardium due to either plaque occlusions within or spasms of the coronary arteries.

Anginal pain

is frequently described by the patient as tightness, pressure in the center of the chest. and pain radiating down the left arm. Referred pain felt in the neck and left arm commonly occurs with severe angina pectoris

✓ Classic or (stable angina)

✓ Unstable (pre-infarction) angina

✓ Variant (Prinz-metal, vasospastic)

Types of Angina Pectoris

Classic or (stable angina)

occurs with predictable stress or exertion

Unstable (pre-infarction) angina

occurs frequently with progressive severity unrelated to activity and is unpredictable regarding stress/exertion and intensity.

Variant (Prinz-metal, vasospastic) angina

occurs during rest.

(1 )nitrates

(2) beta blockers

(3) calcium channel blockers

Types of Antianginal Drugs

reduction of venous tone

The major systemic effect of nitrates is a _______________-, which decreases the workload of the heart and promotes vasodilation.

Beta blockers and calcium channel blockers

decrease the workload of the heart and decrease oxygen demands

Nitrates

were the first agents used to relieve angina. They affect coronary arteries and blood vessels in the venous circulation.

cause generalized vascular and coronary vasodilation, which increases blood flow through the coronary arteries to the myocardial cells. This group of drugs reduces myocardial ischemia but can cause hypotension.

Nitroglycerin

acts directly on the smooth muscle of blood vessels, causing relaxation and dilation. It decreases cardiac preload (amount of blood in the ventricle at the end of diastole) and afterload (peripheral vascular resistance) and reduces myocardial O2 demand.

is also available in other forms: topical (ointment, transdermal patch), translingual, oral extended-release capsule and tablet, aerosol spray (inhalation), and IV.

Sublingual nitroglycerin

is the most commonly used nitrate. It is not swallowed, because it undergoes first-pass metabolism by the liver, which decreases its effectiveness. Instead, it is readily absorbed into the circulation through the SL vessels.

The onset of action of nitroglycerin depends on the method of administration. With SL use, the onset of action is rapid (1-3 minutes); it is slower with the transdermal method 

30 to 60 minutes

The effects of SL nitroglycerin last for ___________-. The SL tablets decompose when exposed to heat and light, so they must be kept in their original, airtight glass containers.

After a dose of nitroglycerin, the patient may experience dizziness, faintness, or headache as a result of the peripheral vasodilation. If pain persists, the patient should immediately call for medical assistance.

isosorbide dinitrate

Among the various types of organic nitrates is ________________, which can be administered in an SL tablet form and is also available as a chewable tablet, immediate-release tablet, and sustained- release tablet or capsule.

Isosorbide mononitrate

can be given orally in immediate- and sustained -release tablets.

Beta blockers, calcium channel blockers, vasodilators, and alcohol

can enhance the hypotensive effect of nitrates.

IV nitroglycerin

may antagonize the effects of heparin.

Headaches

are one of the most common side effects of nitroglycerin, but they may become less frequent with continued use.

Side Effects and Adverse Reactions of Nitroglycerin

Other side effects include hypotension, dizziness, weakness, and faintness.

✓ When nitroglycerin ointment or transdermal patches are discontinued, the dose should be tapered over several weeks to prevent the rebound effect of severe pain caused by myocardial ischemia

Beta-adrenergic blockers

block the beta1- and beta2- receptor sites.

decrease the effects of the sympathetic nervous system by blocking the action of the catecholamines, epinephrine and norepinephrine, thereby decreasing the heart rate and blood pressure.

are used as antianginal, antidysrhythmic, and antihypertensive drugs.

These drugs are most useful for classic (stable) angina.

Beta blockers

should not be abruptly discontinued. The dose should be tapered over a specified number of days to avoid reflex tachycardia and recurrence of anginal pain. Patients who have decreased heart rate and blood pressure usually cannot take beta blockers. Patients who have second or third-degree AV block should not take beta blockers

myocardial contraction

Because beta blockers decrease the force of _______________, oxygen demand by the myocardium is reduced. Therefore the patient can tolerate increased exercise with less oxygen requirement. Beta blockers are effective for classic (stable) angina.

30 minutes. 2 to 4 hours

The onset of action of the nonselective beta blocker propranolol is __________, its peak action is reached in_____________, and its duration is 12 to 24 hours

cardio-selective beta blockers

For the ____________________, the onset of action of atenolol is 60 minutes, its peak action occurs in 2 to 4 hours, and its duration of action is 24 hours.

selective metoprolol

The onset of action of _____________- is reached in 30 to 60 minutes, and the duration of action is approximately 3 to 6 hours.

Side Effects of Beta blockers

Both nonselective and selective beta blockers cause a decrease in heart rate and blood pressure.

For the nonselective beta blockers, bronchospasm, behavioral or psychotic response, and impotence (with use of Inderal) are potential adverse reactions

Vital signs need to be closely monitored in the early stages of beta-blocker therapy. When discontinuing use, the dosage should be tapered for 1 or 2 weeks to prevent a rebound effect such as reflex tachycardia or life-threatening cardiac dysrhythmias.

Calcium channel blockers (CCBs),

or calcium blockers, were introduced in 1982 for the treatment of stable and variant angina pectoris, certain dysrhythmias, and hypertension. Calcium activates myocardial contraction, increasing the workload of the heart and the need for more oxygen. CCBs relax coronary artery spasm (variant angina) and relax peripheral arterioles (stable angina), decreasing cardiac oxygen demand.

Bradycardia

is a common problem with the use of verapamil, the first calcium blocker.

Nifedipine

the most potent of the calcium blockers, promotes vasodilation of the coronary and peripheral vessels, and hypotension can result. The onset of action is 10 minutes for verapamil and 30 minutes for nifedipine and diltiazem.

Verapamil

its duration of action is 6 to 8 hours when given orally and 10 to 20 minutes when given intravenously. The duration of action for nifedipine and diltiazem is 6 to 8 hour.

side effects of calcium blockers

include headache, hypotension (more common with nifedipine and less common with diltiazem), dizziness, and flushing of the skin.

Reflex tachycardia

can occur as a result of hypotension.

Peripheral edema

may occur with several CCBs, including nicardipine, nifedipine, and verapamil. CCBs can cause changes in liver and kidney function, and serum liver enzymes should be checked periodically.

1 Nitrates

2 Nitrates plus beta blockers

3 Nitrates plus beta blockers plus calcium blockers

4 Coronary artery bypass graft

Classic angina pectoris

1 Nitrates or calcium blockers

2 Nitrates plus calcium blockers

3 Coronary artery bypass graft

Variant angina pectoris

Nursing Intervention for Calcium Channel Blockers

✓ Monitor vital signs. Hypotension is associated with most antianginal drugs.

✓ Position the patient sitting or lying down when administering a nitrate for the first time. After administration, check vital signs while the patient is lying down and then sitting up. Have the patient rise slowly to a standing position.

✓ Offer sips of water before giving SL nitrates; dryness may inhibit drug absorption. Monitor effects of IV nitroglycerin. Report angina that persists.

✓ Monitor effects of IV nitroglycerin. Report angina that persists.

✓ Apply nitroglycerin ointment to a designated mark on paper. Do not use fingers because drug can be absorbed; use tongue blade or gloves. When using a nitroglycerin patch, do not touch the medication portion.

✓ Administer SL nitroglycerin tablet if chest pain occurs. If pain has not subsided or has worsened in 5 minutes, notify the physician.

cardiac dysrhythmia (arrhythmia)

is defined as any deviation from the normal rate or pattern of the heartbeat. This includes heart rates that are too slow (bradycardia), too fast (tachycardia), or irregular.

The terms dysrhythmia (disturbed heart rhythm) and arrhythmia (absence of heart rhythm) are used interchangeably despite the slight difference in meaning.

Atrial dysrhythmias

 

prevent proper filling of the ventricles and decrease cardiac output by 33%.

Ventricular dysrhythmias

are life threatening because ineffective filling of the ventricle and ineffective pumping results in decreased or absent cardiac output.

With ventricular tachycardia, ventricular fibrillation is likely to occur, followed by death

restore the cardiac rhythm to normal

The desired action of antidysrhythmic (antiarrhythmic) drugs is to

Antidysrhythmic drugs

are high-alert drugs that may cause significant harm to the patient when given inappropriately.

Pharmacodynamics of Antidysrhythmic Drugs

✓ Blocks adrenergic stimulation of the heart

✓ Depresses contractility myocardial excitability and contractility

✓ Decreases conduction velocity in cardiac tissue

✓ Increases recovery time (repolarization) of the myocardium

✓ Suppresses automaticity (spontaneous depolarization to initiate beats)

(1) sodium (fast) channel blockers IA, IB, and IC

(2) beta blockers

(3) drugs that prolong repolarization

(4) calcium (slow) channel blockers

Types of Antidysrhythmic Drugs

Class I: Sodium Channel Blockers

decreases sodium influx into cardiac cells. Responses to the drug are decreased conduction velocity in cardiac tissues; suppression of automaticity, which decreases the likelihood of ectopic foci; and increased recovery time (repolarization or refractory period).

✓ class IA

✓ class IB

✓ class IC

There are three subgroups of sodium channel blockers:

class IA

slow conduction and prolong repolarization (quinidine, disopyramide) procainamide

class IB

slow conduction and shorten repolarization (lidocaine, mexiletine HCl)

class IC

drugs prolong conduction with little to no effect on repolarization (flecainide).

Class II: Beta Blockers

, decrease conduction velocity, automaticity, and recovery time (refractory period).

Examples are propranolol, acebutolol, esmolol, and sotalol.

are more frequently prescribed for dysrhythmias than are sodium channel blockers. This drug class should be gradually reduced in dose upon discontinuation

Class III: Drugs That Prolong Repolarization

are used in emergency treatment of ventricular dysrhythmias when other antidysrhythmic are ineffective.

Amiodarone

increases the refractory period (recovery time) and prolongs the action potential duration (cardiac cell activity).

Class IV: Calcium Channel Blockers

The fourth class consists of the calcium channel blockers verapamil and diltiazem.

Verapamil

is a slow (calcium) channel blocker that blocks calcium influx, thereby decreasing the excitability and (negative inotropic) contractility of the myocardium. It increases the refractory period of the AV node, which decreases ventricular response.

is contraindicated for patients with AV block or HF

Side effects and Adverse Reaction

The side effects of beta blockers are bradycardia and hypotension. Bretylium tosylate and amiodarone can cause nausea, vomiting, hypotension, and neurologic problems. The side effects of calcium blockers include nausea, vomiting, hypotension, and bradycardia.

Quinidine

the first drug used to treat cardiac dysrhythmias, has many side effects that include nausea, vomiting, diarrhea, confusion, and hypotension

High doses of lidocaine

can cause cardiovascular depression, bradycardia, hypotension, seizures, blurred vision, and double vision. Less serious side effects may include dizziness, and confusion.

Nursing Intervention/Consideration

✓ Tell patients to report side effects and adverse reactions to a health care provider, including dizziness, faintness, nausea, and vomiting.

✓ Advise patients to avoid alcohol, caffeine, and tobacco.