McKenna's Pharmacology for Nursing, 2e

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P A R T 8  Drugs acting on the cardiovascular system

drugs ; pregnancy or breastfeeding because of the potential adverse effects on the fetus or neonate ; cardiovascular dysfunction; visual problems; urinary retention; and phaeochromocytoma, which could be exacerbated by the effects of the drugs. ■ ■ Assess baseline status before beginning therapy to determine any potential adverse effects ; this includes body temperature and weight; skin colour, lesions and temperature; pulse, blood pressure, orthostatic blood pressure and perfusion; respiration and adventitious sounds; bowel sounds and abdominal examination; and renal and liver function tests. Implementation with rationale ■ ■ Monitor blood pressure carefully to monitor effectiveness and blood pressure changes. ■ ■ Do not administer the drug to people who are bedridden, but only to people who are up and mobile, to ensure therapeutic effects and decrease the risk of severe hypertension. ■ ■ Monitor heart rate regularly when beginning therapy to monitor for bradycardia, which commonly occurs at the beginning of therapy; if bradycardia persists, it may indicate a need to discontinue the drug. ■ ■ Monitor the person with known visual problems carefully to ensure that the drug is discontinued if visual fields change. ■ ■ Encourage the person to void before taking a dose of the drug to decrease the risk of urinary retention problems. ■ ■ Provide comfort measures to help the person tolerate drug effects, including small, frequent meals; access to bathroom facilities; safety precautions if CNS effects occur; environmental controls; appropriate skin care as needed; and analgesics as needed. ■ ■ Provide thorough teaching, including the name of the drug, dosage prescribed, measures to avoid adverse effects, warning signs of problems and the need for periodic monitoring and evaluation, to enhance knowledge about drug therapy and to promote compliance. ■ ■ Offer support and encouragement to help the person deal with the diagnosis and the drug regimen. Evaluation ■ ■ Monitor response to the drug (maintenance of blood pressure within normal limits). ■ ■ Monitor for adverse effects (hypertension, dizziness, visual changes, piloerection, chills, urinary problems).

■ ■ Evaluate the effectiveness of the teaching plan (person can name drug, dosage, adverse effects to watch for, specific measures to avoid them and the importance of continued follow-up). ■ ■ Monitor the effectiveness of comfort measures and compliance with the regimen.

KEY POINTS

■■ Severe hypotension, or shock, is treated with sympathomimetic drugs that stimulate the sympathetic system to increase blood pressure. ■■ Midodrine, an alpha-specific adrenergic stimulant, is an oral drug used to treat people with orthostatic hypotension whose lives are considerably impaired by the fall in blood pressure when they stand. CHAPTER SUMMARY ■■ The cardiovascular system is a closed system that depends on pressure differences to ensure the delivery of blood to the tissues and the return of that blood to the heart. ■■ Blood pressure is related to heart rate, stroke volume and the total peripheral resistance against which the heart has to push the blood. ■■ Control of blood pressure involves baroreceptor (pressure receptor) stimulation of the medulla to activate the sympathetic nervous system, which causes vasoconstriction and increased fluid retention when pressure is low in the aorta and carotid arteries, and vasodilation and loss of fluid when pressure is too high. ■■ The kidneys activate the renin–angiotensin– aldosterone system when blood flow to the kidneys is decreased. ■■ Renin activates the conversion of angiotensinogen to angiotensin I in the liver; angiotensin I is converted by angiotensin-converting enzyme (ACE) to angiotensin II in the lungs; angiotensin II then reacts with specific receptor sites on blood vessels to cause vasoconstriction to raise blood pressure and in the adrenal gland to cause the release of aldosterone, which leads to the retention of fluid and increased blood volume. ■■ Hypertension is a sustained state of higher-than- normal blood pressure that can lead to damage to blood vessels, increased risk of atherosclerosis and damage to small vessels in end organs. Because ■■ Peripheral resistance is primarily controlled by constriction or relaxation of the arterioles. Constricted arterioles raise pressure; dilated arterioles lower pressure.