McKenna's Pharmacology for Nursing, 2e

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P A R T 8  Drugs acting on the cardiovascular system

CHAPTER SUMMARY ■■ CAD, a leading cause of death in Australia and New Zealand and most Western nations, develops when changes in the intima of coronary vessels lead to the development of atheromas or fatty tumours, accumulation of platelets and debris, and a thickening of arterial muscles, resulting in a loss of elasticity and responsiveness to normal stimuli. ■■ Narrowing of the coronary arteries secondary to the atheroma buildup is called atherosclerosis. ■■ Narrowed coronary arteries eventually become unable to deliver all the blood that is needed by the myocardial cells, causing a problem of supply and demand. ■■ Angina pectoris, or “suffocation of the chest”, occurs when the myocardial demand for oxygen cannot be met by the narrowed vessels. Pain, anxiety and fatigue develop when the supply-and-demand ratio is upset. Types of angina include stable, unstable and variant angina. ■■ MI occurs when a coronary vessel is completely occluded and the cells that depend on that vessel for oxygen become ischaemic, then necrotic and die. ■■ Angina can be treated by drugs that either increase the supply of oxygen or decrease the heart’s workload, which decreases the demand for oxygen. ■■ Nitrates and beta-blockers are used to cause vasodilation and to decrease venous return and arterial resistance—effects that decrease cardiac workload and oxygen consumption. ■■ Glyceryl trinitrate is the drug of choice for treating an acute anginal attack. It is available in various forms. ■■ Beta-blockers prevent the activation of sympathetic receptors, which would normally increase heart rate, increase blood pressure and increase cardiac contraction. All of these actions would increase the demand for oxygen; blocking these actions decreases the demand for oxygen. ■■ Calcium channel blockers block muscle contraction in smooth muscle and decrease the heart’s workload, relax vasospasm in variant angina and possibly block the proliferation of the damaged endothelium in coronary vessels. ■■ The potassium channel opener, nicorandil, promotes arterial dilation and vascular smooth muscle relaxation, reducing both preload and afterload.

■■ Calcium channel blockers block muscle contraction in smooth muscle and decrease the heart’s workload, relax vasospasm in variant angina and possibly block the proliferation of the damaged endothelium in coronary vessels. ■■ Individuals on calcium channel blockers need to be monitored for signs of decreased cardiac output and response, including slow heart rate, hypotension, dizziness and headache. ■■ The potassium channel opener, nicorandil, promotes arterial dilation and vascular smooth muscle relaxation, reducing both preload and afterload. meals to alleviate GI upset ; environmental controls, such as limiting light, maintaining temperature and avoiding excessive noise and interruptions, which could aggravate stress and increase myocardial demand ; and taking safety precautions, such as providing periodic rests and assisting with ambulation if dizziness occurs, to prevent injury. ■ ■ Offer support and encouragement to help the person deal with the diagnosis and the drug regimen. ■ ■ Provide thorough teaching, including the name of the drug and dosage prescribed; measures to avoid adverse effects and prevent anginal attacks; actions to take when an attack occurs; warning signs of problems, and signs and symptoms to report immediately; and the need for periodic monitoring and evaluation to enhance knowledge about drug therapy and to promote compliance. Evaluation ■ ■ Monitor response to the drug (alleviation of signs and symptoms of angina, prevention of angina). ■ ■ Monitor for adverse effects (hypotension, cardiac arrhythmias, GI upset, skin reactions, headache). ■ ■ Monitor the effectiveness of comfort measures and compliance with the regimen. ■ ■ Evaluate the effectiveness of the teaching plan (person can name drug, dosage, proper administration, adverse effects to watch for, specific measures to avoid them and the importance of continued follow-up).

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