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Blood pressure = CO x SVR
- cardiact output
- systemic vascular resistance
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Hypertension is
High blood pressure
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Four stages, based on BP measurements
- -Normal
- -Prehypertension
- -Stage 1 hypertension
- -Stage 2 hypertension
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Classification and management of blood pressure
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Classification of BP
- Hypertension can also be defined by its cause
- -Unknown cause-Essential, idiopathic, or primary hypertension, 90% of the cases
- -Known cause- Secondary hypertension, 10% of the cases
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Compelling indications
- -Post-MI
- -High cardiovascular risk
- -Heart failure
- -Diabetes mellitus
- -Chronic kidney disease
- -cerebrovascular disease
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JNC-7: Significant changes
- -High diastolic BP (DBP) is no longer considered to be more dangerous than high systolic BP (SBP)
- -Studies have shown that elevated SBP is strongly associated with heart failure, stroke, and renal failure.
- -For those older than age 50, SBP is a more important risk factor for cardiovascular disease (CVD) than DBP
- -"Prehypertensive" BPs are no longer considered "high normal" and require lifestyle modifications to prevent CVD.
- -Thiazide-type diuretics should be the initial drug therapy for most patients with hypertension (alone or with other drug classes)
- -The previous labels of "mild", "moderate", and "severe" have been dropped.
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Cultural Considerations
- -Beta-blockers and ACE inhibitors have been found to be more effective in Caucasians patients than African American patients.
- -CCBs and diuretics have been shown to be more effective in geriatric and African American patients than in Caucasian patients.
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Non-Pharmacologic Treatment
- -Diet and Exercise
- -Limit alcohol consumption
- -Reduce sodium intake
- -Smoking cessation
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Antihypertensive Agents: Categories
- -Adrenergic agents
- -Angiotensin converting enzyme (ACE) inhibitors
- -Angiotensin II receptor blockers (ARBs)
- -Calcium channel blockers (CCBs)
- -Diuretics
- -Vasodilators
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Site and mechanism of action for various antihypertensive agents.
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Adrenergic Agents
- -Centrally and peripherally acting adrenergic neuron blockers
- -Centrally acting alpha2-receptor agonists
- -Peripherally acting alpha1-receptor antagonists
- -Peripherally acting beta-receptor blockers (beta blockers)-both cardioselective (beta1-receptors) and nonselective (noth beta1 and beta2-receptors)
- -Peripherally acting dual alpha1-and beta receptor blockers
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Location of the nicotinic receptors within the parasympathetic and sympathetic nervous systems.
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Adrenergic agents: Mechanism of action
- -Centrally and peripherally stores in neurotransmitters storage vesicles
- -SNS is not stimulated (beta-receptors in the heart and alpha1-receptors in blood vessels)
- -Result: decreased blood pressure.
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Centrally and peripherally action neuron blocker
- -Resperine
- -The only centrally and peripherally acting neuron blocker still available in the U.S.
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Adrenergic Agents: Mechanism of action
- -Centraly acting alpha2-receptor agonists
- -stimulate alpha2-adrenergic receptors in the brain
- -Sympathetic outflow from the CNS is decreased
- -Norepinephrine production is decreased
- -Result: decreased blood pressure
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Adrenergic Agents: Centrally acting alpha2-receptor agonists
- -clonidine (catapres)
- clonidine patch (catapres-TTS)
- -guanfacine (Tenex)
- -methyldopa (aldomet) -drug of choice for hypertension in pregnancy
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Adrenergic Agents: Mechanism of Action
- -Preipherally acting alpha1-receptor antagonists.
- -Block the alpha1-adrenergic receptors
- -The SNS is not stimulated
- -Result: decreased blood pressure
- -stimulation of alpha1-adrenergic receptors cause hypertension
- -Blocking alpha1-adrenergic receptors causes decreased blood pressure
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Adrenergic Agents: Peripherally acting alpha1-receptor antagonists
- -Doxazosin (cardura)
- -Prazosin (minipress)
- -Terazosin (hytrin)
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Adrenergic Agents Indications
- -Adrenergic neuronal blockers (centrally and peripherally acting neuron blocker)
- -Treatment of hypertension, either alone or with other agents.
- -seldom used because of frequent side effects
- -Centrally acting alpha2-receptor agonists
- -Treatment of hypertension, either alone or with other agents
- -Usually used after other agents have failed due to side effects.
- -Centally acting alpha2-receptor agonists
- -Also may be used for treatment of severe dysmenorrhea, menopausal flushing, glaucoma
- -Clonidine is useful in the management of withdrawal symptoms in opioid- or nicotine- dependent persons.
- -Peripherally acting alpha1-receptor antagonists
- -Treatment of hypertension
- -Relief of symptoms of BPH
- -Management of severe HF when used with cardiac glycosides and diuretics
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Adrenergic Agents Side effects
- Most common: dry mouth, drowsiness, sedation, constipation
- Other: Headaches, sleep disturbances, nausea, rash, cardiac disturbances (palpations)
- HIGH INCIDENCE OF ORTHOSTATIC HYPOTENSION
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Adrenergic Agents- Beta Blockers
- -Act in the periphery
- -Reduce heart rate due to beta1-blockade
- -Examples: Propranolol (inderal), atenolol (tenormin), metoprolol (Lopressor), metoprolol-extended release (Toprol XL)
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Adrenergic Agents -Dual alpha1-and beta-receptor blockers
- -Act in the periphery at heart and blood vessels
- -Reduce heart rate (beta1-receptor blockade)
- -Cause vasodilation (alpha1-receptor blockade)
- -Excamples: labetalol (Normodyne,Tandate),carvdilol(Coreg)
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Angiotensin Converting Enzyme Inihibitors (ACE inhibitors, or ACEIs)
- -Large group of safe and effective drugs
- -Often used as first-line agents for HF and hypertension
- -May be combined with a thiazide diuretic or calcium channel blocker
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Ace inhibitors: Mechanism of Action
- RAAS: renin angiotensin-aldosterone system
- -When the enzyme angiotensin I is converted to angiotensin II, the result is potent vasconstriction and stimulation of aldosteron.
- -Result of vasoconstriction: increased systemic vascular resistance and increased afterload
- result: increased BP
- -Aldosteron stimulates water and sodium resorption
- -Result: increased blood volume, increased preload, and increased BP
- -ACE inhibitors block the angiotensin converting enzyme, thus preventing the formation of angiotensin II
- -Also prevent the breakdown of the vasodilating substance, bradykinin
- -Result: decreased systemis vascular resistance (afterload), vasodilation, and therefore decreased blood pressure.
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ACE inhibitors: Indications
- -Hypertension
- -HF (either alone or in cobination of diuretics or other agents)
- -Slows progression of left ventricular hypertrophy after an MI
- -Renal protective effects in patients with diabetes
- -Drugs of choice in hypertensive patients with HF
- -captopril (Capoten)- very short half life
- -enalapril (Vasotec)- Available in oral and parenteral forms
- -lisinopril (Prinivil and Zestril) and quinapril (Accupril)- Newer agents, long half-lives, once a day dosing
- -Several other agents available
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ACE Inhibitors : Side efftects
- -Fatigue, headache, impaired taste, dizziness, mood changes, possible hyperkalemia, dry, nonproductive cough, which reverses when therapy is stopped
- NOTE: First-dose hypotensive effect may occur!!
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Angiotensin II Receptor Blockers
- -( A II blockers, or ARBs)
- -Newer class
- -Well tolerated
- -Do not cause a dry cough
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Angiotensin II Receptor Blockers: Mechanism of Action
- -Allow angiotensin I to be converted to angiotensin II, but block the receptors that receive angiotensin II
- -Block vasconstriction and release of aldosterone
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Angiotensin II Receptor Blockers
- -Isartan (Cozaar, Hyzaar)
- -valsartan, (Diovan)
- -candesartan (Atacand)
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Angiotensin II Receptor Blockers: Indications
- -Hypertension
- -Adjunctive agents for the treatment of HF
- -May be used alone or with other agents such as diuretics
- -Used primarily in patients who cannot tolerate ACE inhibitors
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Angiotensin II Receptor Blockers: Side Effects
- -Upper respiratory infections
- -Headache
- -May cause occasional dizziness, inability to sleep, diarrhea, dyspnea, heartburn, nasal congestion, back pain, fatigue
- -Hyperkalemia much less likely to occur
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Calcium Channel Blockers: Mechanism of Action
- -Cause smooth muscle relaxation by blocking the binding of calcium to its receptors, preventing muscle contraction
- -This causes decreased peripheral smooth muscle tone and decreased systemic vascular resistance
- -Result: decreased blood pressure
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Calcium Channel Blockers
-Benzothiazepines - diltiazem (Cardizem, Dilacor)
-Phenylalkamines- verapamil (Calan, Isoptin)
-Dihydropyridines- amlodipine (Norvasc), nicardipine (Cardene) nifedipine (Procardia), nimodipine (Nimotop)
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Calcium Channel Blockers : Indications
- -Angina
- -Hypertension
- -Dysrhythmias
- -Migraine headaches
- -Raynaud's disease
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Calcium Channel Blockers: Side Effects
- -Cardiovascular- Hypotension, palpitations, tachycardia
- -Gastrointestinal- Constipation, nausea
- -Other- Rash, flushing, peripheral edema, dermatitis
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DIURETICS
- -Decrease the plasma and extracellular fluid volumes
- -Results: Decreased preload, decreased cardiac output, decreased total peripheral resistance
- -Overall effect: Decreased worload of the heart, and decreased blood pressure.
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Vasodilators: Mechanisms of Action
- -Directly relax arteriolar smooth muscle
- -Result: decreased systemic vascular response, decreased afterload, and peripheral vasodilation
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Antihypertensive Agents Vasodilators
- -diazoxide (Hyperstat)
- -hydralazine HCl (Apresoline)
- -minoxidil (Loniten,Rogaine)
- -sodium nitroprusside (Nipride, Nitropress)
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Vasodilators: Indications
- -Treatment of hypertension
- -May be used in combination with other agents
- -Intravenous sodium nitroprusside and diazoxide are reserved for the management of hypertensive emergencies.
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Vasodilators: Side Effects
-Hydralazine-Dizziness, headache, anxiety, tachycardia, nausea, and vomiting, diarrhea, anemia, dyspnea, edema, nasal congestion
-Sodium nitroprusside- Bradycardia, hypotension, possible cyanide toxicity.
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Nursing Implications
- -Before beginning therapy, obtain a thorough health history and head to toe physical examination
- -Assess for contraindications to specific antihypertensive agents
- -Assess for conditions that require cautious use of these agents
- -Educate patients about the importance of not missing a dose and taking the medications exactly as prescribed
- -Patients should never double up on doses if a dose is missed; check with the physician for instruction on what to do if a dose is missed
- -Monitor BP during therapy; instruct patients to keep a journal of regular BP checks
- -Instruct patients that these drugs should be stopped abruptly because this may cause a rebound hypertensive crisis, and perhaps lead to a stroke
- -Oral forms should be given with meals so that absorption is more gradual and effective.
- -Administer IV forms with extreme caution and use an IV pump
- -Remind patients that medication is only part of therapy. Encourage patients to watch their diet, stress level, weight, and alcohol intake.
- -Patients should avoid smoking and eating food high in sodium
- -Encourage supervised exercise
- -Instruct patients to change positions slowly to avoid syncope from postural hypotension
- -Patients should report unsual shortness of breath; difficulty breathing; swelling of the feet, ankles, face, or around the eyes; weight gain or loss; chest pain; palpitations; or excessive fatigue
- -Men takign theses agents may not be aware that impotence is an expected effect. This may influence compliance with the drug therapy
- -If patients are experincing serious side effects, or believe that t he dose or medication needs to be changed, they should contact their physician immediately
- -Hot tubs, showers, or baths; hot weather; prolonged sitting or standing; physical exercise; and alcohol ingestion may aggravate low blood pressure, leading to fainting and injury. Patients should sit or lie down until symptoms subside.
- -Patients should not take any other medications, including OTC drugs, without frist getting the approval of their physician.
- -Educate about lifestyle change that may be needed
- -Weight loss
- -Stress management
- -supervised exercise
- -Monitor for side/adverse effects (dizziness,orthostatic hypotension, fatigue) and for toxic effects
- -Monitor for therapeutic effects - BP should be maintained at less than 140/90mm hg
- -If a patient with hypertension also has diabetes or renal disease, the BP goal is <130/80 mm hg
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