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Chapter 28Drugs Affecting Blood Pressure
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Physiology The heart is composed of four chambers: the left
atrium, the right atrium, the left ventricle, and theright ventricle.
The two phases of the cardiac cycle are:systole and diastole.
Contractions of the heart propel blood through thevessels
The formula for measuring blood pressure is:Blood pressure = cardiac output peripheralresistance
BP = CO PR:
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Regulation of Blood Pressure
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Role of Adrenergic Receptors
Adrenergic receptors affect blood pressure causing aSympathomimetic effect
Sympathomimetic effect (one that mimics the effect of thesympathetic system).
Alpha-1 receptors :
Stimulated peripheral constriction
(blood pressure increases)
Blocked dilates arterioles and veins
( blood pressure drops)
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Role of Adrenergic Receptors
Alpha-2receptor sites are located within the brain
Stimulation inhibits sympathetic system
(sympathetic outflow from the CNS)
Results in : heart rate, vasoconstriction
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Role of Adrenergic Receptors
Beta-1 receptor sites located in the heart
Stimulation- heart rate
speed of conduction
force of contraction
Blockingcauses the opposite effect,
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Role of Adrenergic Receptors
Beta 2 receptors are in the:
bronchial and vascular musculatue
Stimulation causes :
bronchial and peripheral dilation
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Role of Renin-Angiotensin-AldosteroneSystem
Another mechanism involved in blood pressure regulationis the renin-angiotensin-aldosterone system.
Renin,which is synthesized by the kidneys, producesangiotensin I.
Angiotensin I is an inactive substance until it isconverted to the active angiotensin II
Angiotensin II is a potent vasoconstrictor.
{It also stimulates secretion of aldosterone from theadrenal medulla}
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Pathophysiology
In the United States, hypertension is a chronic disorderthat affects all age groups.
Hypertension is common in all racial groups, {althoughsome groups are more prone to hypertension thanothers}.
The American Heart Association defines adult
hypertension as :persistent elevation of 140/90 mm Hg.
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Classification of Hypertension
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Lifestyle Modification and Hypertension
In prehypertension, therapy usually consists of lifestylechanges,which include reducing weight and adopting theDietary Approaches to Stop Hypertension (DASH).
DASH recommends a diet rich in fruits, vegetables, and nonfatdairy, along with reduced intake of saturated and total fat, buthigher potassium and calcium intake.
Lifestyle modifications also include: limiting alcohol intake,regular exercise, and stopping smoking.
Lifestyle changes also are believed to be essential inpreventing hypertension.
Lifestyle modification remains an important aspect of therapyfor patients in stage 1 or stage 2 hypertension. Lifestylemodifications may decrease the required drug therapy dosage.
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Angiotensin-Converting EnzymeInhibitors (ACE inhibitors)
In the renin-angiotensin-aldosterone sequence, a specialenzyme is needed to convert the inactive angiotensin I to theactive angiotensin II.
Angiotensin II is a potent vasoconstrictor. Its presenceincreases secretion of aldosterone.
The ACE inhibitors prevent the conversion of angiotensin I toangiotensin II.
ACE inhibitors are used as first-line antihypertensives if thepatient has comorbidities.
Prototype drug: captopril (Capoten)
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Captopril: Core Drug Knowledge Pharmacotherapeutics
Hypertension, Congestive Heart failure, diabeticnephropathy, and left ventricular dysfunction.
Pharmacokinetics
Administered: Oral ( rapid onset of action)
Metabolism: liver. Excreted: kidneys.
Pharmacodynamics Inhibits the ACE(enzyme) needed to change the
inactive angiotensin I to the active form angiotensinII.
Decreasing Angiotensin II decreases aldosteronesecretion {which prevents Na and H2O retention}
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Captopril: Core Drug Knowledge (cont.)
Contraindications and precautions
2nd and 3rd trimester of pregnancy (cause injury tothe fetus) {Black Box Warning category D }
- Hypersensitivity and cross sensitivity with other ACEinhibitors
Adverse effects
Persistent nonproductive cough, rash, hypotension
Hyperkalemia ; Hyponatremia
Drug interactions
Several drugs
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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 patients ethnic and cultural background.
{smaller antihypertensive response in African Americans than
Caucasions}
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Captopril: Planning & Interventions
Maximizing therapeutic effects
Administer captopril 1 hour before mealsbecause food decreases absorption.
Minimizing adverse effects
Monitor the patient for at least 2 hours afterthe initial dose and until blood pressurestabilizes.
Assess lab values for:
hyperkalemia, hyponatremia, neutropenia, proteinuria.
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Captopril: Teaching, Assessment &Evaluations
Patient and family education
Teach purpose of drug therapy and any adversereactions.
Teach signs and symptoms to report.
Ongoing assessment and evaluation
Monitor blood pressure throughout captopril therapy.
Blood pressure that decreases to a normal range isindicative of successful drug therapy.
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Angiotensin II Receptor Blocker
Losartanis the prototype drug ( a monopotassium salt)
Pharmacotherapeutics used to treat hypertension
Pharmacokinetics- has a high first pass metabolism
converted in liver to an active metabolite
highly protein bound
Pharmacodynamics- inhibits the pressor effect of
Angiotensin II by preventing binding to receptor sites
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Angiotensin II Blocker
Contraindications - hypersensitivity to the drug
Pregnancy Category C 1sttrimester
Pregnancy Category D 2nd, 3rdtrimester
{ Black Box warning for this}
Maximimize Therapeutic Effect-
does not cause the cough that ACE inhibitors do
Adverse effects hypotension, dizzyness, fatigue,diarrhea, upper respiratory infections
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Angiotensin II Blocker
Drug Interactions lithium, rifampin and indomethacin
{ if taken with K or K sparing medications can cause
increased K levels}
Food Interactions grapefruit juice may drugeffectiveness
Core Patient Variables- not for use in patients with
severe congestive heart failure
Increases in BUN / creatinine in the elderly
If hepatic disease; give lower starting dose
Safety and efficacy in children < 18 yrs of age unknown
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Angiotensin II Receptor Blocker
Minimize adverse effects help the patient out of bed
Nursing diagnosis :
Risk for injury related to fall, secondary to adverseeffect of dizzyness
Desired outcome :patient will not fall
Provide Patient and Family Education related to :
dizzyness pregnancy category
caution with OTC drugs upper respiratory infection
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Alpha-Beta Blockers
Alpha Beta Blocker:
slow heart rate
decrease cardiac output
lower blood pressure.
Prototype drug: labetalol (Normodyne)
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Labetalol: Core Drug Knowledge
Pharmacotherapeutics
Treatment of hypertension.
Pharmacokinetics
Administered: oral.
Peak: 2-4 hours. Crosses the bloodbrain barrier.
Pharmacodynamics Adrenergic non specific blocking agent at:
the beta-1 and beta-2 receptor sites
selective alpha-1 blocking action.
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Labetalol: Core Patient Variables
Health status
Assess for the underlying pathology of the hypertension.
Life span and gender
Assess age; safety has not been established inchildren.
Lifestyle, diet, and habits
Assess lifestyle changes.
Environment
Assess environment where drug will be given.
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Labetalol: Nursing Diagnoses andOutcomes
Decreased Cardiac Output related to effect of drugtherapy
Desired outcome:the patient will not developdecreased cardiac output substantial enough to altercardiac perfusion.
Risk for Injury related to orthostatic hypotension
secondary to adverse effects of drug therapy Desired outcome:the patient will not sustain injury
if transient orthostatic hypotension develops.
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Labetalol: Planning & Interventions
Maximizing therapeutic effects
Administer oral labetalol with food to increaseabsolute bioavailability.
Minimizing adverse effects
Prepare IV infusions of labetalol carefully.
Observe the patient closely for signs of heart failure.
Monitor closely the blood pressure of patientsreceiving IV infusions of labetalol.
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Labetalol: Teaching, Assessment &Evaluations
Patient and family education
Explain the purpose of the drug.
Explain the importance of not stopping drug therapyabruptly.
Ongoing assessment and evaluation
Monitor blood pressure throughout labetalol therapy.
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Question
Labetalol is contraindicated for the treatment ofhypertension in which of the following patients?
A. 23 y/o male with diabetes mellitus type I
B. 55 y/o female how just had her third heart attack
C. 34 y/o male with history of bronchial asthma
D. 75 y/o female with congestive heart failure
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Rationale
Labetalol is contraindicated for the treatment ofhypertension in which of the following patients?
C. 34 y/o male with history of bronchial asthma
Labetalol blocks both beta-1 and beta-2 stimulation.The result of blocking beta-2 stimulation isbronchoconstriction. For that reason, labetalol would
not be given to a patient with asthma.
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Hydralazine: Core Drug Knowledge
Direct acting vasodilators Hydralazine(prototype)
Pharmacotherapeutics
Adjunct to other antihypertensives.
Pharmacokinetics
Absorbed: orally. Peak: 1 to 2 hours. Metabolized:liver. Excreted: kidneys.
Pharmacodynamics
Produces direct smooth muscle relaxation of thearterioles peripheral resistance BP
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Hydralazine: Core Drug Knowledge (cont.)
Contraindications and precautions
Hypersensitivity, CAD, and mitral valvular disease
Adverse effects
Arthralgia, dermatoses, fever, splenomegaly, andglomerular nephritis
Drug interactions
Metoprolol, propranolol, furosemide, andindomethacin
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Hydralazine: Core Patient Variables
Health status
Blood pressure and drug history.
Life span and gender Pregnancy category C.
Lifestyle, diet, and habits
Explore lifestyle modification.
Environment Assess environment where drug will be given.
Culture and inherited traits
Assess genetic background.
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Hydralazine: Nursing Diagnoses andOutcomes
Ineffective Therapeutic Regimen Management related toadverse effects of drugs
Desired outcome:the patient will not experienceadverse effects severe enough to stop drug therapy.
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Hydralazine: Planning & Interventions
Maximizing therapeutic effects
Administering hydralazine with food promotes
bioavailability.
Minimizing adverse effects
Administer hydralazine with a beta blocker(preferably) or clonidine to decrease reflex
tachycardia and with a diuretic to offset fluidretention.