CH.54

EY POINTS

▪ Anginal pain occurs when cardiac oxygen supply is insufficient to meet cardiac oxygen demand.

▪ Cardiac oxygen demand is determined by heart rate, contractility, preload, and afterload. Drugs that reduce these factors can help relieve anginal pain.

▪ Cardiac oxygen supply is determined by myocardial blood flow. Drugs that increase oxygen supply will reduce anginal pain.

▪ Angina pectoris has three forms: chronic stable angina, variant (vasospastic) angina, and unstable angina.

▪ The underlying cause of stable angina is coronary artery atherosclerosis.

▪ The underlying cause of variant angina is coronary artery spasm.

▪ Drugs relieve pain of stable angina by decreasing cardiac oxygen demand. They do not increase oxygen supply.

▪ Drugs relieve pain of variant angina by increasing cardiac oxygen supply. They do not decrease oxygen demand.

▪ Nitroglycerin and other organic nitrates are vasodilators.

▪ To cause vasodilation, nitroglycerin must first be converted to nitric oxide, its active form. This reaction requires a sulfhydryl source.

▪ Nitroglycerin relieves pain of stable angina by dilating veins, which decreases venous return, which decreases preload, which decreases oxygen demand.

▪ Nitroglycerin relieves pain of variant angina by relaxing coronary vasospasm, which increases oxygen supply.

▪ Nitroglycerin is highly lipid soluble and therefore is readily absorbed through the skin and oral mucosa.

▪ Nitroglycerin undergoes very rapid inactivation in the liver. Hence, when the drug is administered orally, most of each dose is destroyed before reaching the systemic circulation.

▪ When nitroglycerin is administered sublingually, it is absorbed directly into the systemic circulation and therefore temporarily bypasses the liver. Hence, to produce equivalent effects, sublingual doses can be much smaller than oral doses.

▪ Nitroglycerin causes three characteristic side effects: headache, orthostatic hypotension, and reflex tachycardia. All three occur secondary to vasodilation.

▪ Reflex tachycardia from nitroglycerin can be prevented with a β-blocker, verapamil, or diltiazem.

▪ Continuous use of nitroglycerin can produce tolerance within 24 hours. The mechanism may be depletion of sulfhydryl groups.

▪ To prevent tolerance, nitroglycerin should be used in the lowest effective dosage, and long-acting formulations should be used on an intermittent schedule that allows at least 8 drug-free hours every day, usually during the night.

▪ Nitroglycerin preparations that have a rapid onset (e.g., sublingual nitroglycerin) are used to abort an ongoing anginal attack and to provide acute prophylaxis when exertion is expected. Administration is as needed (PRN).

▪ Nitroglycerin preparations that have a long duration (e.g., patches, sustained-release oral capsules) are used for extended protection against anginal attacks. Administration is on a fixed schedule (but one that allows at least 8 drug-free hours a day).

▪ Nitroglycerin should be used cautiously with most vasodilators and must not be used at all with sildenafil (Viagra) and other PDE5 inhibitors.

▪ β-blockers prevent pain of stable angina primarily by decreasing heart rate and contractility, which reduces cardiac oxygen demand.

▪ β-blockers are administered on a fixed schedule, not PRN.

▪ β-blockers are not used for variant angina.

▪ CCBs relieve the pain of stable angina by reducing cardiac oxygen demand. Two mechanisms are involved. First, all CCBs relax peripheral arterioles and decrease afterload. Second, verapamil and diltiazem reduce heart rate and contractility (in addition to decreasing afterload).

▪ CCBs relieve pain of variant angina by increasing cardiac oxygen supply. The mechanism is relaxation of coronary artery spasm.

▪ When a CCB is combined with a β-blocker, a dihydropyridine (e.g., nifedipine) is preferred to verapamil or diltiazem. Verapamil and diltiazem will intensify the cardiosuppression caused by the β-blocker, whereas a dihydropyridine will not.

▪ Ranolazine appears to reduce anginal pain by helping the heart generate energy more efficiently.

▪ Ranolazine should not be used alone. Rather, it should be combined with a nitrate, a β-blocker, or amlodipine (a CCB).

▪ Ranolazine increases the QT interval and may pose a risk for torsades de pointes, a serious ventricular dysrhythmia.

▪ In patients with chronic stable angina, treatment has two objectives: (1) prevention of MI and death and (2) prevention of anginal pain.

▪ The risk for MI and death can be decreased with two types of drugs: (1) antiplatelet agents (e.g., aspirin, clopidogrel) and (2) cholesterol-lowering drugs.

▪ Anginal pain is prevented with one or more long-acting antianginal drugs (β-blocker, CCB, long-acting nitrate) supplemented with sublingual nitroglycerin when breakthrough pain occurs.

▪ As a rule, revascularization with CABG surgery or PCI is indicated only after treatment with two or three antianginal drugs has failed.

Summary of Major Nursing Implicationsa

NITROGLYCERIN

Therapeutic Goal

Reduction of the frequency and intensity of anginal attacks.

Recognize Cues

Obtain baseline data on the frequency and intensity of anginal attacks, the location of anginal pain, and the factors that precipitate the attacks.

The patient interview and physical examination should identify risk factors for angina pectoris, including treatable contributing pathophysiologic conditions (e.g., hypertension, hyperlipidemia).

Analyze Cues and Prioritize Hypotheses

Identifying High-Risk Patients

Use with caution in hypotensive patients and in patients taking drugs that can lower blood pressure, including alcohol and antihypertensive medications. Use with sildenafil (Viagra) and other PDE5 inhibitors is contraindicated.

Generate Solutions

Minimize Risks for Headache

Advise patients that headache can be relieved with aspirin, acetaminophen, or some other mild analgesic.

Minimize Risks for Orthostatic Hypotension

Inform patients about symptoms of hypotension (e.g., dizziness, lightheadedness), and advise them to sit or lie down if these occur. Inform patients that hypotension can be minimized by moving slowly when changing from a sitting or supine position to an upright posture.

Advise patients to avoid alcohol. Exercise caution when nitroglycerin is used in combination with β-blockers, CCBs, diuretics, and all other drugs that can lower blood pressure.

Warn patients not to combine nitroglycerin with a PDE5 inhibitor (e.g., sildenafil [Viagra]) because life-threatening hypotension can result.

Minimize Risks for Reflex Tachycardia

This reaction can be suppressed by concurrent treatment with a β-blocker, verapamil, or diltiazem.

Take Actions

Routes

Sublingual Tablets or Powder

Administration

Instruct patients to place the tablet or empty the powder under the tongue and leave it there until fully dissolved; these medications should not be swallowed.

Instruct patients to call 911 or go to an emergency department if pain is not relieved in 5 minutes. While awaiting emergency care, they can take one more dose and then a third 5 minutes later.

Instruct patients to store tablets in a dry place at room temperature in their original container, which should be closed tightly after each use. Under these conditions, the tablets should remain effective until the expiration date on the container.

Instruct patients to swallow sustained-release oral capsules intact, without chewing or crushing.

Instruct patients to apply transdermal patches to a hairless area of skin, using a new patch and a different site each day.

Instruct patients to remove the patch after 12 to 14 hours, allowing 10 to 12 “patch-free” hours each day. This will prevent tolerance.

Instruct patients to direct the spray against the oral mucosa. Warn patients not to inhale the spray.

Instruct patients to remove any remaining topical ointment before applying a new dose.

Technique of Administration for transdermal cream

(1) Squeeze a ribbon of ointment of prescribed length onto the applicator paper provided; (2) using the applicator paper, spread the ointment over an area at least 2.5 inches by 3.5 inches (application may be made to the chest, back, abdomen, upper arm, or anterior thigh); and (3) cover the ointment with plastic wrap. Avoid touching the ointment.

Instruct patients to rotate the application site to minimize local irritation.

Evaluate Outcomes

Instruct patients to keep a record of the frequency and intensity of anginal attacks, the location of anginal pain, and the factors that precipitate attacks.

Isosorbide Mononitrate and Isosorbide Dinitrate

Both drugs have pharmacologic actions identical to those of nitroglycerin. Differences relate only to dosage forms, routes of administration, and time course of action. Therefore, the implications presented for nitroglycerin apply to these drugs as well.