Download Lecture 8 - Harper College

Lecture 8
Chapters 37 & 38
Cardiac Disorders
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Cardiac Disorders
System = heart, blood vessels (arteries & veins), Blood
Blood rich w/ O2 & nutrients moves through vessels called arteries to narrower
arteriols to capillaries where the rich blood is absorbed by bodies cells & waste
products are absorbed (CO2, urea, Cr, ammonia)
deoxygenated blood returned to
circulation via venules to veins for elimination through lungs & kidneys
Cardiac disorders
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Heart =
* 4 chambers - R & L atria, R & L ventricles
* Blood from circulation to R atrium to R ventricle to pulmonary artery to lungs for gas
exchange (CO2 & O2) to L atrium to L ventricle to aorta to systemic circulation
• Heart muscle = myocardium & surrounds the atria & ventricles
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Cardiac Disorders
Pericardium = fibrous covering around the heart that protects it from injury &
infection
Endocardium = 3-layered membrane that lines the inner part of the heart chambers
Valves = 4 - two atrioventricular (tricuspid & mitral) & 2 semilunar (pulmonic &
aortic) - control blood. flow between atria & ventricles & pulmonary artery & the aorta
Cardiac disorders
• Conduction = Generated & conducted by the myocardium - usually
* Originates in sinoatrial (SA) node - pacemaker
atrioventricular (AV) node
bundle of HIS
purkinje fibers
ventricular muscle tissue
contraction from apex upward forcing blood to lungs & circulatory system
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Blood flow & Heart Rate (HR)
* Ave. HR = 60 - 80 beats/min. (adult)
* Ave. BP = 120/80 mm/Hg - resistance to blood flow through systemic arterial
circulation
• Arterial BP determined by Cardiac Output (CO) = the volume of bld. expelled form
the heart in 1 min. - calculated by mult. HR by stroke volume - Ave. CO = 4 - 8 l/min.
Cardiac Disorders
• Stroke Volume (SV) = amt. of bld ejected from the L vent. w/ each heart beat - Ave. =
70ml/beat
- SV determined by 3 factors:
-Preload - blood flow force that stretches the ventricle
- Contractility - force of ventricular contraction
- Afterload - Resistance to vent. ejection of blood caused by opposing pressures in aorta
& systemic circulation
• Specific drugs can or preload & afterload, affecting both SV & CO - most
vasodilators dec. preload & afterload
a dec. in arterial pressure & CO
Cardiac Disorders
Cardiac Glycosides
• Digitalis - One of the oldest drugs (1200 AD)
- Effective in treating congestive heart failure (CHF)
- CHF = when the heart muscle weakens & enlarges loss of ability to pump blood
through the heart & into the systemic circulation = heart failure (or pump failure)
- peripheral & lung tissues become congested = CHF
Cardiac Disorders
Cardiac Glycosides
• CHF can be left sided or right sided
• Cardiac glycosides = digitalis glycosides
- inhibits the Na - K pump
inc. intracellular Ca
cardiac muscle fibers contract more efficiently
- Digitalis = 3 effects on the heart 1) + inotropic action (inc. myocard. contraction) 2) chronotropic action (dec. HR) #) - dromotropic action (dec. conduction of the heart
cells
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Cardiac Disorders
Cardiac Glycosides
The inc. in myocardial contractility = inc. card., peripheral, & kidney function by inc.
CO, dec. preload, improving bld flow to periphery & kidneys, dec. edema, & inc. fluid
excretion fluid retention in lung & extremities is decreased
Digitals also used to correct atrial fibrillation & atrial flutter (cardiac dysrhythmias)
Cardiac Disorders
Cardiac Glycosides
• Digoxin (Lanoxin) - Protein binding - low, t1/2 = 36 hrs - drug accumulation can
occur
- monitor SE & serum levels closely
- metabolized by liver & excreted by kidneys - kidney dysfunction can affect excretion
of dig.
- Do not confuse digoxin & digitoxin
- digitoxin = highly protein bound w/ a long t1/2 - seldom prescribed
Cardiac Disorders
Digoxin (Lanoxin)
• Action = inc. myocardial contraction (+ inotrophy),
and slows HR (- chronotropy), therefore regulating the rate & rhythm of the heart
- Therapeutic serum levels = 0.5 - 2.0 ng/ml
• Use = moderate/severe systolic CHF, arrythmias
• SE = Dig. toxicity - bradycardia (pulse < 60), anorexia, diarrhea, N&V, blurred vision,
lethargy - older adults more prone to toxicity
• DI - Other heart meds
Cardiac Disorders
Heart Failure
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Other drugs =
* Vasodilators - dec. venous blood return to the heart & dec. cardiac filling, ventricular
stretching & O2 demand
* Angiotensin-converting enzyme (ACE) inhibitors - dilate venules & arterioles &
improves renal bld flow & dec. bld fluid volume
* Diruetics - first-line = reduces fluid volume
Cardiac Disorders
Antianginal Drugs
• Used to treat angina pectoris ( acute cardiac pain caused by inadequate bld flow
resulting from plaque occlusion in the coronary arteries of the myocardium or from
spasms of the coronary arteries) - described as tightness, pressure in center of chest,
pain radiating down L arm - attacks may lead to an MI
• 3 Types of angina pectoris
1. Classic (stable) - stress or exercise
2. Unstable (preinfarction) - frequently over day, severity
3. Variant (Prinzmetal, vasospastic) - during rest
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Antianginal Drugs
Action - Inc. blood flow by inc. O2 supply, or by dec. O2 demand by the myocardium
Nitrates, beta-blockers, calcium channel blockers
Nitrates & calcium channel blockers effective in treating variant or vasospastic angina
(not beta blockers)
beta blockers effective in treating stable angina
Non-pharm Rx = avoid heavy meals, smoking, extremes in weather changes, strenuous
exercise, stress - Proper nutrition, moderate exercise, adequate rest & relaxation
techniques
Cardiac Disorders
Antianginals
• Nitrates - First agents used - Nitroglycerine (NTG)
- Action - acts directly on the smooth muscle of blood vessels = relaxation & dilation.
- Dec. cardiac preload & afterload & reduces O2 demand
- dilation of veins = less blood return to the heart
- dilation of arteries = less vasoconstriction & resistance
- Onset of Action
- sublingual (under the tongue) & IV = 1 - 3 min.
- transderm nitro patch = 30 - 60 min
Cardiac Disorders
Antianginals
• SE = Headaches - less frequent w/ continued use, hypotension, dizziness, weakness,
faintness
• Beta Blockers - Block the beta receptor site
Atenolol (Tenormin), Metoprolol tartrate (Lopressor), Nadolol (Corgard),
Propranolol HCL (Inderal)
- Action - Dec. the effects of the sympathetic nervous system by blocking release of epi.
& norepi
dec. HR & BP reduce the need for O2 & the pain of angina
- Nonselective (beta-1 & beta-2) - Inderal, Corgard, Visken
- Selective (beta -1) - Tenormin, Lopressor
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Antianginals
• SE - Dec. in HR & BP
- Closely monitor vital signs
• Calcium Channel Blockers (Calcium Blockers) - Newest
Amlodipine (Norvasc), Diltiazem HCL (Cardizem), Nifedipine (Procardia,
Adalat), Verapamil (Calan, Isoptin)
- Action - Ca activates myocard. contraction; inc. workload of heart. Calcium blockers
dec. cardiac contractility (- inotropic) & the workload of the heart = dec. O2 need
Cardiac Disorders
Calcium Blockers
• Use - long - term Rx of angina
• SE - Headache, Hypotension, dizziness, flushing of the skin
- Bradycardia w/ verapamil (Calan)
- Hypotension esp. w/ Nifedipine (most potent) - promotes vasodilation of coronary &
peripheral arteries
• Calcium blockers can cause changes in liver & kidney function - Check liver enzymes
periodically
• Can be given w/ nitrates to prevent angina
Cardiac Disorders
Antidysrhythmics
• Cardiac dysrhythmia (arrhythmia) = any deviation from the normal rate or pattern of
the heartbeat. HR’s too slow (bradycardia), fast (tachycardia), or irregular
• Electrocardiogram (ECG) identifies the type of dysrhythmia
- P wave = atrial activation
- QRS complex = ventricular depolarization
- T wave = ventricular repolarization
- PR interval = atrioventricular conduction time
- QT interval = ventricular action potential duration
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Antidysrhythmics
Atrial dysrhythmias = prevent proper filling of the ventricles & dec. CO by 1/3
Ventricular dysrhythmias = life threatening d/t ineffective filling of the ventricle = dec.
or absent CO
Dysrhythmias can occur - after an MI, from hypoxia (lack of O2 to body tissue),
hypercapnia (inc. CO2 in the bld.), excess catecholamines (epi, norepi), or electrolyte
imbalance
Cardiac Disorders
Antidysrhythmic Drugs
• 2 major classifications of dysrhythmias
* Above bundle of HIS = supraventricular - A-flutter, a-fib., PAC’s
* Below bundle of HIS = Ventricular - PVC’s, Vent. tachycardia, V-fib.
• Desired action = restoration of normal cardiac rhythm
• 4 Classes:
• 1. Fast (sodium) Channel Blockers - dec. the fast Na influx to the cardiac cells, so dec. conduction time of cardiac tissue, dec. likelihood of ectopic foci, inc.
repolarization
- 3 subgroups of fast channel blockers
Cardiac Disorders
Antidysrhythmics
• Class 1A - Procainamide (Pronestyl, Procan), Quinidine Sulfate (Quinidex) slows conduction & prolongs repolarization
- Use = Control PVC’s, vent. tachycardia
- SE = Anorexia, headache, dizziness, weakness
• Class 1B - Lidocaine (Xylocaine), Mexiletine (Mexitil) Slows conduction & shortens repolarization
- Use = Ventricular arrythmias associated w/ acute MI’s
- IM & IV - IV bolus then a drip started (1 - 4 mg/min.)
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Antidysrhythmics
• Class 1C - Flecainide (Tambocor) - Prolongs conduction w/ little to no effect on
repolarization
- Use - Life-threatening vent. dysrhythmias, supraventricular tachycardia, a-fib or
flutter
• Beta Blockers - dec. conduction velocity
• Prolong Repolarization - Amiodarone (Cordarone) - emergency Rx of ventricular
dysrhythmias. Inc. refractory perios & prolong action potential duration
• Calcium Channel Blockers - inc. refractory period of the AV node, dec. vent. response
Diuretics
• Used for 2 main purposed: decrease hypertension (lower BP), & decrease edema
(peripheral & pulmonary) in CHF and renal or liver disorders
* Other uses = Dec. cerebral edema (Mannitol), dec. intraocular eye pressure
(glaucoma), dec. ascities (liver disease)
• Used either singly or in combo to dec. BP & dec. edema
• Diuretics produce inc. urine flow (diuresis) by inhibiting Na & H2O reabsorption from
the kidney tubules. Act on the kidneys in diff. locations to enhance excretion of Na
(pg. 678)
Diuretics
• Every 11/2 hr. the total vol. of the body’s extracellular fluid (ECF) goes through the
kidneys (glomeruli) for cleansing = 1st process for urine formation - sm. particles
(electrolytes, drugs, glucose & waste) filtered in the glomeruli
• Normally 99% of filtered Na passing through glomeruli reabsorbed. 50 - 55% Na
reabsorbtion in proximal tubules, 35 - 40% in loop of Henle, 5 - 10% in distal tubules,
<3% in collecting tubules
• Diuretics that act on tubules closest to glomerule have greatest effect in causing
natriuresis (Na loss in urine) - Mannitol
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Diuretics
Diuretics have an antihypertensive effect by promoting Na & H2O loss by blocking
Na/Cl reabsorption = a dec. in fluid vol. & a dec. of BP
With fluid loss - edema should decrease. When Na is retained, H2O also retained &
BP increases
Many diuretics cause loss of other electrolytes (K, Mg, Cl, bicarb)
5 categories of diuretics:
Action of Diuretics on Different Segments of Renal Tubules
Diuretics
Thiazides/Thiazide-like Diuretics
• Hydrochlorothiazide (Hydrodiuril, HCTZ), Metolazone (Zaroxolyn)
* Action - Distal tubules of the kidney to promote Na, Cl, & H2O excretion; acts
directly on arterioles, causing vasodilation & BP; preload & CO = dec. vascular
fluid & dec. in BP
* Use - Rx of hypertension & peripheral edema
* SE - Electrolyte imbalance (hypokalemia), hyperglycemia (inc. bld sugar),
hyperlipidemia (inc. bld lipid level), dizziness, headaches, N&V
Diuretics
Thiazides
* CI - renal failure
* DI - Digoxin - if hypokalemia occurs, the action of digoxin is enhanced & dig. toxicity
can occur
* Considered potassium - wasting - K supplements are frequently prescribed & serum K
levels are monitored
Loop Diuretics - Act on the ascending loop of Henle by inhibiting Cl transport of Na into
the circulation (inhibits passive reabsorbtion of Na)
- Potent & cause marked depletion of H2O & electrolytes
- Effect = dose related - dose & response
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Diuretics
Loop diuretics
More potent than thiazides as diuretics, but less effective as antihypertensive agents
Can renal bld flow up to 40%
Have a great saluretic (Na-loosing) effect & can cause rapid diuresis
vascular fluid
vol. dec. in CO & BP
Bumetanide (Bumex), Furosemide (Lasix) - derivatives of sulfonamides
Furosemide (Lasix) * Use - Rx fluid retention/overload due to CHF, renal dysfunction, cirrhosis;
hypertension; pulmonary edema
Diruetics
Loop Diuretics
• Lasix (con’t) - used when other conservative measures fail (Na restriction & less
potent diuretics)
* May be given IV or PO
* SE - Electrolyte imbalance ( esp. hypokalemia K < 3.5) & dehydration, orthostatic
hypotension
* DI - digitalis preparations - dig. toxicity can result
* Nursing - Strict I & O, daily weights, vital signs, hydration status of client
 Clients should be on K supplements, monitor serum K levels closely
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Diuretics
Potassium-Sparing Diuretics
Weaker than thiazides & loop diuretics
Action - act primarily in the collecting distal duct renal tubules to promote Na & H2O
excretion & K retention
Use - mild diuretics or in combo w/ antihypertensive drugs
K supplements not used - serum potassium excess (hyperkalemia) results if K
supplement taken w/ potassium - sparing diuretics
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Diuretics
Potassium - Sparing
Spironolactone (Aldactone), Triamterene (Dyrenium)
Aldactone (an aldosterone antagonist) - Aldosterone = a mineralocorticoid hormone
that promotes Na retention & K excretion; Aldosterone antagonsits inhibit the Na-K
pump (K retained & Na excreted)
Amiloride (Midamor) - antihypertensive agent
Triamterene - Rx of edema caused by CHF or cirrhosis
K - sparing diuretics used alone = less effective than when combined with reducing
body fluid & Na
- Usually combine w/ a potassium wasting diuretic
Diuretics
Combination
Combine a potassium sparing & potassium wasting diuretic = intensifies the diuretic
effect & prevents K loss
spironolactone & hydrochlorothiazide (Aldactazide)
amiloride & hydrochlorothiazide (Moduretic)
triamterene & hydrochlorothiazide (Dyazide, Maxide)
When diuretic combinations are used, either combined in one tablet or as separate
tablets, the dose of each is usually less than the dose of any single drug
SE = hyperkalemia - caution w/ clients having poor renal function; do NOT use K
supplements (unless K low)