ppt chapter 26

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Chapter 26

Drugs Affecting Blood Pressure

Chapter 26

Drugs Affecting Blood Pressure


Physiology Physiology

• The heart is composed of four chambers: the left atrium, the right atrium, the left ventricle, and the right ventricle.

• Blood is circulated throughout the body by a coordinated sequence of chamber contractions and valve openings and closings known as the cardiac cycle.

• The two phases of the cardiac cycle are systole and diastole.

• Contractions of the heart propel blood through the vascular system.


Physiology (cont.)Physiology (cont.)

• Blood pressure is measured in millimeters of mercury (mm Hg) and is calculated by measuring the amount of blood leaving the heart multiplied by the amount of resistance in the peripheral vessels.

• The formula for measuring blood pressure is:

blood pressure = cardiac output peripheral resistance

or BP = CO PR.


Regulation of Blood PressureRegulation of Blood Pressure


Role of Adrenergic Receptors Role of Adrenergic Receptors • Adrenergic receptors in the nervous system have a role in

blood pressure management.

• When alpha-1 receptors are stimulated, they cause peripheral constriction and blood pressure increases as a result.

• This effect, which is similar to stimulation of the sympathetic nerves, is called a sympathomimetic effect (one that mimics the effect of the sympathetic system).

• Alpha-2 receptor sites are located within the brain.

• Beta-1 receptor sites are located primarily in the heart.

• Beta-2 receptor sites are located primarily in the bronchial and vascular musculature.


Role of Renin-Angiotensin-Aldosterone System Role of Renin-Angiotensin-Aldosterone System

• Another mechanism involved in blood pressure regulation is the renin-angiotensin-aldosterone system.

• Renin, which is synthesized by the kidneys, produces angiotensin I.

• Angiotensin I is a basically inactive substance until it is converted to the active angiotensin II.

• Angiotensin II is a potent vasoconstrictor.

• It also stimulates secretion of aldosterone from the adrenal medulla.


Pathophysiology Pathophysiology

• In the United States, hypertension is a chronic disorder that affects all age groups.

• Hypertension is common in all racial groups, although some groups are more prone to hypertension than others.

• The American Heart Association defines adult hypertension as persistent elevation of systolic pressure ≥ 140 mm Hg or diastolic pressure ≥ 90 mm Hg.

• Therefore, a definitive diagnosis of hypertension is not made until the average of two or more readings, each recorded at two or more visits.

• Two types of hypertension are primary and secondary.


Classification of HypertensionClassification of Hypertension


Lifestyle Modification and Hypertension Lifestyle Modification and Hypertension

• In prehypertension, therapy usually consists of lifestyle changes, which include reducing weight and adopting the Dietary Approaches to Stop Hypertension (DASH).

• DASH recommends a diet rich in fruits, vegetables, and nonfat dairy, along with reduced intake of saturated and total fat but higher potassium and calcium intake.

• Lifestyle modifications also include limit alcohol intake, regular exercise, and stop smoking.

• Lifestyle changes also are believed to be essential in preventing hypertension.

• Lifestyle modification remains an important aspect of therapy for patients in stage 1 or stage 2 hypertension. Lifestyle modifications may decrease the required drug therapy dosage.


Drug Therapy and Hypertension Drug Therapy and Hypertension

• Drug therapy is now recommended to be started with every patient who has been diagnosed as having hypertension, whether it is stage 1 or stage 2.

• Drug therapy is also recommended in prehypertension if the patient has compelling indications.

• Drugs used to manage blood pressure primarily include those classified as diuretics, beta blockers, calcium channel blockers, ACE inhibitors, and angiotensin II receptor blockers.


Drug Therapy and Hypertension (cont.)Drug Therapy and Hypertension (cont.)

• Combination therapy is common.

• A thiazide diuretic should be used in drug treatment for most patients with uncomplicated hypertension.

• Combination therapy is indicated for stage 2 hypertension.


Drug Therapy for Hypertension (cont.)Drug Therapy for Hypertension (cont.)


First Line of Drugs Used to Treat HypertensionFirst Line of Drugs Used to Treat Hypertension

• Diuretics

– Promotes excretion of sodium and water, decrease blood volume

• Beta blockers

– Several mechanisms of action have been proposed to explain how they work

• Calcium channel blockers

– Inhibit the movement of calcium ions across cell membranes, decreases mechanical contraction of heart, lessens conduction velocity


Angiotensin-Converting Enzyme Inhibitors Angiotensin-Converting Enzyme Inhibitors

• In the renin-angiotensin-aldosterone sequence, a special enzyme is needed to convert the inactive angiotensin I to the active angiotensin II.

• Angiotensin II is a potent vasoconstrictor. Its presence increases the secretion of aldosterone.

• The ACE inhibitors prevent the conversion of angiotensin I to angiotensin II.

• ACE inhibitors are used as first-line antihypertensives if the patient has comorbidities.

• Prototype drug: captopril (Capoten)


Captopril: Core Drug Knowledge Captopril: Core Drug Knowledge

• Pharmacotherapeutics

– HTN, CHF, diabetic nephropathy, and left ventricular dysfunction

• Pharmacokinetics

– Administered: Oral. Metabolism: liver. Excreted: kidneys. T½: 2 hours

• Pharmacodynamics

– Inhibits the ACE needed to change the inactive angiotensin I to the active form angiotensin II


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

• Contraindications and precautions

– Second and third trimester of pregnancy and hypersensitivity

• Adverse effects

– Persistent nonproductive cough, angioedema, rash, hypotension, neutropenia, and dyspnea

• Drug interactions

– Several drugs


Captopril: Core Patient Variables Captopril: Core Patient Variables • Health status

– Assess blood pressure before starting therapy.

• Life span and gender

– Determine pregnancy status.

• Lifestyle, diet, and habits

– Assess normal dietary habits.

• Environment

– Assess environment where drug will be given.

• Culture and inherited traits

– Assess patient’s ethnic and cultural background.


Captopril: Nursing Diagnoses and Outcomes Captopril: Nursing Diagnoses and Outcomes

• Risk for Injury from first-dose hypotension related to effect of drug therapy and from drug-induced neutropenia

– Desired outcome: The patient will not sustain injury from hypotensive event or neutropenia.

• Ineffective Therapeutic Regimen Management, Nonadherence, related to persistent dry cough secondary to drug therapy

– Desired outcome: adherence to drug therapy will be unaffected by chronic cough.


Captopril: Nursing Diagnoses and Outcomes (cont.)Captopril: Nursing Diagnoses and Outcomes (cont.)

• Disturbed Sensory Perception related to possible electrolyte imbalance, hyperkalemia, and hyponatremia, related to effects of captopril

– Desired outcome: The patient’s electrolyte levels will remain within normal ranges.

• Risk for Impaired Skin Integrity related to drug induced urticaria and pruritus

– Desired outcome: skin integrity will not be impaired.


Captopril: Planning and InterventionsCaptopril: Planning and Interventions

• Maximizing therapeutic effects

– Administer captopril 1 hour before meals because food decreases absorption.

• Minimizing adverse effects

– Monitor the patient for at least 2 hours after the initial dose and until blood pressure stabilizes.

– Assess blood reports for hyperkalemia, hyponatremia, and neutropenia, and assess urine for proteinuria.


Captopril: Teaching, Assessment, and EvaluationsCaptopril: Teaching, Assessment, and Evaluations

• Patient and family education

– Teach purpose of drug therapy and any adverse reactions.

– Teach signs and symptoms to report.

• Ongoing assessment and evaluation

– Monitor blood pressure throughout captopril therapy.

– Blood pressure that decreases to a normal range is indicative of successful drug therapy.


QuestionQuestion

• What condition(s) besides hypertension is captopril used to treat?

– A. Congestive heart failure

– B. Left ventricular dysfunction

– C. Proteinuria

– D. All of the above


AnswerAnswer

• D. All of the above

• Rationale: Captopril is used to treat heart failure, asymptomatic left ventricular dysfunction, history of ST elevation MI, history of non-ST elevation MI with an anterior infarct, diabetes, systolic dysfunction, or proteinuric chronic renal failure.


Angiotensin II Receptor Blockers Angiotensin II Receptor Blockers

• Angiotensin II receptor blockers (ARBs) block the action of angiotensin II from all the different pathways where it is formed.

• These drugs are effective in lowering blood pressure.

• In addition, they seem to block deleterious effects from angiotensin II at the end-organ stage, which is where serious complications of sustained hypertension occur.

• The indications for ARBs and their efficacy are similar to those of ACE inhibitors.

• ARBs is the first-line treatment for severe hypertension with ECG evidence of left ventricular hypertrophy.

• Prototype drug: losartan (Cozaar)


Losartan: Core Drug Knowledge Losartan: Core Drug Knowledge


– HTN, diabetic nephropathy, left ventricle dysfunction


– First pass metabolism. Peak: 1 hour. T½: 2 hours. Excretion: urine and stool


– Selectively blocking the binding of angiotensin II to the angiotensin I receptors in many tissues


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


– Hypersensitivity

• Adverse effects

– Hypotension, diarrhea, asthenia, dizziness, and fatigue


– Lithium, fluconazole, indomethacin, rifampin, and grapefruit juice


Losartan: Core Patient Variables Losartan: Core Patient Variables

• Health status

– Assess patient’s health status and chronic conditions.


– Assess pregnancy and lactation status.


– Assess usual lifestyle.

• Environment

– Can be given in any environment


– Assess racial background before administration.


Losartan: Nursing Diagnoses and Outcomes Losartan: Nursing Diagnoses and Outcomes • Risk for Injury related to adverse effects on the fetus and the

neonate

– Desired outcome: The patient receiving losartan will report pregnancy to prescriber as soon as possible.

• Risk for Injury related to fall secondary to adverse effect of dizziness

– Desired outcome: the patient will not fall.

• Risk for Infection (upper respiratory) related to adverse effects of drug therapy

– Desired outcome: The patient will not develop an upper respiratory infection, or if one develops, it will be managed appropriately to minimize complications.


Losartan: Planning and InterventionsLosartan: Planning and Interventions


– Should be accompanied by the recommended lifestyle changes

– Avoid giving losartan with grapefruit juice.


– Monitor creatinine, BUN, hemoglobin, and hematocrit levels.

– If taking a potassium supplement, contact prescribing provider.


Losartan: Teaching, Assessment, and EvaluationsLosartan: Teaching, Assessment, and Evaluations


– Teach about adverse effects on the fetus and the neonate.

– Teach about lifestyle modification.

– Teach about signs and symptoms to report.


– Monitor blood pressure throughout losartan therapy and determine whether the desired blood pressure goal has been achieved.


QuestionQuestion

• What is the effect of administering losartan with grapefruit juice?

– A. Increased metabolism

– B. Decreased metabolism

– C. There is no effect on metabolism


AnswerAnswer

• B. Decreased metabolism

• Rationale: Grapefruit juice will slow the metabolism of losartan to its active form, so it may decrease the effectiveness of losartan.


Selective Aldosterone Blockers Selective Aldosterone Blockers

• Selective aldosterone blockers are approved for use in treating hypertension.

• These drugs block the mineralocorticoid receptors while having little interaction with androgen and progesterone receptors.

• Blockade of these selective aldosterone receptors lowers blood pressure and reduces the end-organ damage that occurs with hypertension.


Selective Aldosterone Blockers (cont.)Selective Aldosterone Blockers (cont.)

• The use of ACE inhibitors and ARBs alone does not protect organs from damage completely because the body uses renin-angiotensin-aldosterone system escape mechanisms.

• Aldosterone blockers, when added to either ACE inhibitor therapy or ARB therapy, provide added benefit

• Prototype drug: eplerenone (Inspra)


Eplerenone: Core Drug Knowledge Eplerenone: Core Drug Knowledge


– Used to treat hypertension


– Administered: oral. Metabolism: liver. Excreted: urine and stool. Peak: 1.5 hour


– Binds selectively to the mineralocorticoid receptors, thereby blocking aldosterone from binding to these receptors


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


– Potassium level >5.5 mEq/L, creatinine >2 mg/dL

• Adverse effects

– Hyperkalemia, diarrhea, albuminuria, gynecomastia, abnormal vaginal bleeding, and hypercholesterolemia


– ACE inhibitors, ARBs, or CYP3A4 potent inhibitors


Eplerenone: Core Patient Variables Eplerenone: Core Patient Variables

• Health status

– Assess blood pressure and laboratory studies.


– Pregnancy effects are unknown; assess life span status


– Assess use of OTC potassium supplement.

• Environment

– Assess environment where drug will be given.


Eplerenone: Nursing Diagnoses and Outcomes Eplerenone: Nursing Diagnoses and Outcomes

• Risk for Injury related to the adverse effect of dizziness

– Desired outcome: The patient will not become injured from a fall caused by dizziness while on eplerenone therapy.

• Potential complication: Hyperkalemia related to eplerenone therapy

– Desired outcome: The patient will maintain normal potassium levels while taking eplerenone therapy.


Eplerenone: Nursing Diagnoses and Outcomes (cont.)Eplerenone: Nursing Diagnoses and Outcomes (cont.)

• Deficient Knowledge related to avoiding potassium supplements and potassium-based salt substitutes

– Desired outcome: patient will have adequate knowledge to make informed decisions when choosing OTC supplements and salt substitutes while taking eplerenone.


Eplerenone: Planning and InterventionsEplerenone: Planning and Interventions


– Provide patient education prior to and during therapy.


– Monitor the patient’s serum potassium level periodically

– Monthly assessments throughout therapy are indicated for those at risk for hyperkalemia.


Eplerenone: Teaching, Assessment, and EvaluationsEplerenone: Teaching, Assessment, and Evaluations


– Teach patient how to take medication.

– Teach about avoiding potassium supplements.

– Teach about the need for periodic lab evaluation.


– Potassium levels and renal function should be assessed throughout therapy.


Second Line of Drugs Used to Treat AntihypertensionSecond Line of Drugs Used to Treat Antihypertension

• Selective aldosterone blockers

• Direct acting vasodilators

• Centrally acting alpha-2 agonists

• Peripherally acting alpha-1 blockers

• Peripherally acting antiadrenergics


Drugs Used in Hypertensive CrisisDrugs Used in Hypertensive Crisis

• Prototype drug: nitroprusside (Nitropress)


Nitroprusside: Core Drug Knowledge Nitroprusside: Core Drug Knowledge


– Indicated in hypertensive crisis


– Administered: IV. Onset: 2 minutes. T½: 2 minutes


– Directly relaxes vascular smooth muscle, allowing dilation of peripheral arteries and veins


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


– Aortic coarctation or arteriovenous shunting

• Adverse effects

– Cyanide toxicity


– No drug interactions are associated with nitroprusside.


Nitroprusside: Core Patient Variables Nitroprusside: Core Patient Variables

• Health status

– Assess blood pressure and any contraindications to therapy.


– Pregnancy category C

• Environment

– Assess setting where medication will be given.


– Nitroprusside has a prompt hypotensive effect on all populations.


Nitroprusside: Nursing Diagnoses and Outcomes Nitroprusside: Nursing Diagnoses and Outcomes

• Decreased Cardiac Output related to venous dilation, diminished preload, and severe hypotension secondary to therapeutic and adverse effects of drug therapy

– Desired outcome: Hypotension will not occur to an extent that cardiac output cannot meet the perfusion needs of the vital organs.

• Acute Pain related to decreased comfort from rapid blood pressure reduction secondary to too rapid drug infusion

– Desired outcome: The patient’s blood pressure will not drop so quickly that adverse effects result.


Nitroprusside: Nursing Diagnoses and Outcomes (cont.)Nitroprusside: Nursing Diagnoses and Outcomes (cont.)

• Risk for Injury related to increased intracranial pressure, cyanide poisoning, or thiocyanate toxicity secondary to adverse effects of drug therapy

– Desired outcome: The patient will not suffer injury while on drug therapy.


Nitroprusside: Planning and InterventionsNitroprusside: Planning and Interventions


– Infusion rate for nitroprusside must be titrated to reduce blood pressure without compromising organ perfusion.


– To avoid extreme hypotensive effect, start nitroprusside at a low infusion rate (0.3 mcg/kg/minute) and increase it gradually until the desired effect has been achieved or the maximum infusion rate (10 mcg/kg/minute) is attained.


Nitroprusside: Teaching, Assessment, and EvaluationsNitroprusside: Teaching, Assessment, and Evaluations


– Explain to patient and families that the drug is being given to lower blood pressure quickly and that blood pressure will be monitored constantly to prevent it from dropping too low.


– Monitor blood pressure throughout nitroprusside therapy so that it is reduced without sacrifice to vital organs.


QuestionQuestion

• An unusual adverse effect to watch for with nitroprusside infusion is

– A. Anuria

– B. Seizures

– C. Cyanide toxicity

– D. Hyperthermia


AnswerAnswer

• C. Cyanide toxicity

• Rationale: Cyanide toxicity can occur with the nitroprusside infusion rate exceeds the rate of cyanide excretion.

ppt chapter 26

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