Diuretics and Antihypertensives

Diuretics and Antihypertensives Diuretics

Remove sodium and waterRemove extracellular fluid (edema)

AntihypertensivesLower blood pressure

Both diuretics and antihypertensives Used to treat hypertension

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Hypertension

Abnormal rise in arterial blood pressureDiagnosed at 140/90 mmHg or

higher Caused by a variety of disorders

or can have no known cause

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Hypertension Blood pressure dependent on two factors

cardiac output- controlled by kidney

and heart vessels peripheral resistance- mediated by the

resistance vessels Untreated hypertension can cause:

deterioration of cardiac, renal, and

ocular function stroke

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Hypertension (HTN) All forms of drug therapy focus on

one or both of these systems New guidelines for treatment Life style changes first when

appropriate Then drug therapy diuretics non-diuretic antihypertensive agents

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Classifications Thiazide diuretics Loop diuretics Potassium-sparing diuretics Osmotic diuretics Carbonic anhydrase inhibitors Combination potassium-sparing and

hydrochlorothiazide diuretics

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Excess Fluid Removal of excess fluid results in:

Decreased preload Decreased cardiac output Decreased total peripheral

resistance

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Thiazide Diuretics Developed in the 1950’s, safest in current use Inhibits sodium and chloride reabsorption in

the early portion of the distal tubule May block chloride reabsorption in the

ascending loop of Henle Greater than normal sodium/potassium

exchange rakes place Results in hypokalemia May have increased excretion of chloride

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Thiazide Diuretics Selection of drug based on action desired

and cost Some adverse effects

Elevation of blood glucose Elevation of blood uric acid Sensitivity reactions Hypokalemia Low chloride levels

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Potassium and Chloride Replacement

Replacement is essential to avoid electrolyte imbalances

Administered as potassium chloride May be administered orally or IV

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Loop Diuretics Furosemide (Lasix) Works directly on the ascending limb

of the loop of Henle Inhibits sodium and chloride

reabsorption More potent then thiazides

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Loop Diuretics: Side Effects Dry mouth Potassium depletion

(hypokalemia) Hearing loss (ototoxic) Fatigue Dehydration Hypotension

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Potassium-Sparing Diuretics Inhibit aldosterone

Example: Spironolactone Weak action: They competitively

bind to aldosterone receptors and block the reabsorption of sodium and water Conservation of water

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Osmotic Diuretics

Action Produce a profound diuretic

effect Used to treat intracranial

pressure and renal failure Mannitol

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Carbonic Anhydrase Inhibitors Carbonic Anhydrase (enzyme) Promotes reabsorption of sodium

and bicarbonate from the renal nephrons proximal tubule

Maintains alkalinity of the bloodNormal blood pH 7.35-7.45

Very weak diuretic Treats glaucoma

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Nursing Considerations Monitor patients with gout or

diabetes Monitor potassium levels Encourage potassium rich foods Monitor blood pressure and

weight

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Nursing Considerations Record intake and output on

hospitalized patients Give early in the day If you record a hypertensive B/P,

re-check it to rule out error or sympathetic nervous system stimulation

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Antihypertensives Diuretics Central acting antiadrenergics Peripherally acting antiadrenergics Beta-adrenergic blocking agents

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Antihypertensives

(cont’d)

Vasodilators Angiotensin-converting enzyme

inhibitors Angiotensin II antagonists Calcium channel blockers

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Diuretics and Antihypertensives Effective control of blood

pressure Diuretics frequently given in

combination with another class of

antihypertensives

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Angiotensin-Converting Enzyme (ACE) Inhibitors Action: Antagonists to the renin-

angiotensin-aldosterone system ACE inhibitors prevent: Angiotensin I conversion to

angiotensin II produces potent

vasoconstriction and stimulation of

aldosterone

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ACE Inhibitors

Result of vasodilation: decreased blood pressure, decreased systemic vascular resistance, and decreased afterload

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Angiotensin II Antagonist Allow angiotensin I to be concerted to

angiotensin II, but block the receptors that receive angiotensin II

Block vasoconstriction and release of

aldosterone Lower blood pressure

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Calcium Channel Blockers Action:

Dilate peripheral arterioles and reduce peripheral resistance

Reduce arterial blood pressure at rest and during exercise

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Beta-adrenergic Blocking Agents Inhibit beta1and beta 2 receptors in

the heart and both the heart and lung Reduce

Heart rate Force of contraction

Adverse Effect Bronchoconstriction

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Peripherally Acting Antiadrenergic Agents Two main actions:

Deplete norepinephrine Adverse effect: depression,

hypotension Block adrenergic receptors

Prevent sympathetic nervous system stimulation

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Central Acting Antiadrenergics

Action unclear Theory 1: replace norepinephrine in

adrenergic storage sites Theory 2: sympathetic outflow from

the central nervous system is decreased Adverse Effects:

Sedation Orthostatic hypotension

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Patient Teaching Instruct your clients to:

Do not stop taking abruptly Rebound hypertensive crisis Oral forms should be given with meals

so the absorption is more gradual and

effective IV usage should be by pump

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Nursing Considerations

Use appropriate size cuff when measuring blood pressure

If the reading is high, retake in the other arm

Take a thorough patient history Observe for signs of anxiety Ongoing assessment of blood pressure,

weight, diet, alcohol use, smoking and medications

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Nursing Considerations

Assess potassium needs Salt substitutes may contain

potassium Education on the disease process and

medication regiment Teach the patient to report concerns

and side effects Report changes in status to health

care provider

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