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Cardiac System Chapter 47
The Heart • Heart This organ is the driving force of the entire system. It rhythmically contracts at a self-generated pace, although heart rate can be modified by numerous external effects. The contractions propel blood through the vascular system to allow delivery of oxygen, carbon dioxide, and food to individual tissues.
Conduction System • Heart contains cells that carry electrical impulses more rapidly that ordinary muscle fibers. • Autonomic nervous system and the heart • Sympathetic nerves increase heart rate through release of epinephrine and norepinephrine • Parasympathetic nerves, by way of vagus nerve, decrease heart rate.
Cardiac Disorders • Most vascular disease result from the malfunction of endothelial cells or smooth muscle cells. • Dysfunctional endothelium is considered a major factor in atherosclerosis, acute coronary syndrome, myocardial infarction MI, hypertension and thromboembolic disorders.
Drug Therapy • Drugs can be used to manage atherosclerosis, heart failure, cardiac dysrhythmias, ischemia, myocardial infarct, hypertension, hypotension and shock
Goals of Drug Therapy • Restore homeostasis or physiologic balance • Increase or decrease cardiac output • Manage blood pressure and heart rate • Alter heart rhythm • Increase or decrease blood clotting • Alter the quality of blood • Decrease chest pain
Drug Therapy for Heart Failure Chapter 48
Causes of Heart Failure • HF stem from dysfunction of contractile myocardial cells and endothelial cells that line the heart and blood vessels • Endothelial dysfunction allows blood vessels to narrow due to plaque formation, overgrowth of cells or inflammation • Clot formation at the site and vasoconstriction further narrow the blood vessel lumen
Signs and Symptoms of Heart Failure or HF • Often no symptoms at rest • Dyspnea (difficulty breathing) and fatigue occur with increased activity • Edema of ankle and distention of jugular veins • In acute cases pulmonary edema – cough and shortness of breath
Drug Therapy for Heart Failure • Diuretics • Angiotensin-converting enzyme (ACE) Inhibitor • Angiotension II receptor blocker (ARB) • Beta-adrenergic blocking agent or Digoxin
Cardiac Glycosides or Digoxin • Digoxin or Lanoxin is the only commonly used digitalis glycoside
Actions • Digoxin improves the pumping ability of the heart • Increases the force of myocardial contraction by inhibiting the Na, K-adenosine triphosphatase, an enzyme in cardiac cell membrane that decreases the movement of sodium out of myocardial cell after contraction. • Calcium enter the cell in exchange for sodium. • The calcium activates the contractile proteins and increased myocardial contractility.
Administration • Can be given orally or IV • Onset of action occurs in 30 minutes to 2 hours • IV peaks within 10 to 30 minutes • PO peaks within 1 to 2 hours
Serum Blood Levels • Maximum drug action occurs when steady tissue concentration has been achieved – takes about 1 week • Loading dose or digitalizing dosage will be higher until this therapeutic level has been reached. • Dosage 0.75 to 1.5 mg every 6 to 8 hours • When adequate levels have been reached than a maintenance dose can be started
Maintenance Dose • Dosing is 0.125 – 0.5 mg • Average dose is 0.25 mg • Take daily at same time of day • Give with food or after meals
Dosing by mcg/kg in Adults • IV digitalizing dose = 0.6 to 1 mg (10 -15 mcg/kg) given at 50% initially and additional fractions given at 4-8 hour intervals. • PO adults digitalizing dose 0.75 – 1.25 mg (10 – 15 mcg/kg) • PO children digitalizing dose 10 to 15 mcg/kg
Nursing Responsibilities • Take apical pulse for one full minute before giving the medication – listen for any irregular heart beats • Specific guidelines for holding the drug and notifying physician • Adults: apical pulse less than 60 • Older child: apical pulse less than 60 • Infant or younger child: apical pulse less than 100
Nursing Responsibilities • Monitor ECG throughout IV administration and periodically during therapy. • Notify physician if bradycardia (heart rate less than 60 bpm) or new arrhythmias occur. • Assess for peripheral edema and auscultate lunge for rales/crackles
Laboratory Values • Electrolyte imbalance: potassium, calcium and magnesium values need to be monitored • Hypokalemia (low potassium) or Hypomagnesemia (low magnesium) can lead to irregular heart rate • Hypercalcemia (elevated calcium) enhances effect of drug
Digoxin Toxicity • Anorexia, nausea, and confusion are symptoms of digoxin toxicity • HR below 60 in adults and 100 in infants and small children • Digoxin should be discontinued – takes about 1 week for drug to be eliminated
Evaluation of Effectiveness • Decrease in severity of CHF • Increase in cardiac output • Decrease in ventricular response in atrial tachyarrhythmia • Termination of paroxysmal atrial tachycardia
Antianginal Drugs Chapter 50
Antianginal Drugs • Angina pectoris is a clinical symptoms characterized by episodes of chest pain. • There is deficit in myocardial oxygen supply (myocardial ischemia) in relation to myocardial oxygen demand. • Can be caused by coronary vasospasm
Classification of Angina • Class I: ordinary physical activity does not cause angina – strenuous activity only • Class II: angina occurs with walking or climbing stairs rapidly or up hill • Class III: marked limitation in ordinary daily activity • Class IV: anginal symptoms may be present at rest
Nitroglycerin • Most widely used nitrate • Antianginal • Used to relieve acute angina
Drug Action • Increases coronary blood flow by dilating coronary arteries and improving collateral flow to ischemic regions
Therapeutic Effect • Relief or prevention of anginal attacks • Increased cardiac output • Reduction of blood pressure
Dosing • Oral dosage is rapidly metabolized in the liver and only small doses reach the systemic circulatory system • For more effective absorption is given: • Sublingually – under the tongue – acts in 1 to 3 minutes • PO: sustained-released tablet • Transdermal ointments – applied on hairless area on back, chest or upper arm • Patches – takes 2 hours – patches need to be removed to defibrillate a patient
Sublingual Administration • Tablet should be held under tongue until dissolved. Avoid eating, drinking, or smoking until tablet is dissolved.
Sustained Released Tablet • Administer dose 1 hour before of 2 hour after meal with a full glass of water for faster absorption. • Note: Sustained released preparations should be swallowed whole, do not crush, break or chew.
Nitroglycerin Patch • Place the patch on a hairless area of chest or upper arm each day. • Move patch to a different place on your body each day to prevent skin irritation • Remove the patch for 8 to 12 hours each night and put on a fresh patch each day • Do not leave on all the time
Nitroglycerine Ointment • Comes with paper with a ruled line for measuring the dose • Squeeze ointment onto the paper, carefully measuring the amount specified on the prescription label • Use the paper to spread ointment in a thin layer on a hair-free area of skin (2 by 3 inches) • Keep paper in place with bandage or tape • Ointment is applied three or four times a day
Side Effects • Dizziness or light-headedness • Flushing of face and neck • Increased heart rte • Restlessness • Rare side effects: • Blurred vision • Dry mouth • Weakness • Fatigue
Antihypertensive Drugs Chapter 52
Antihypertensives • Used to treat hypertension, a common, chronic disorder affecting about 50 to 60 million adults in the USA.
Why is Hypertension a Problem? • Increases risks of myocardial infarction, heart failure, cerebral infarction, hemorrhage and renal disease
What is Hypertension? • Hypertension is persistently high blood pressure that results from abnormalities in regulatory mechanisms. • It is defined as a systolic pressure above 140 and a diastolic pressure above 90 on multiple blood pressure measures
Two Types of Hypertension • Primary: no cause can be found – can usually be controlled by drugs • Secondary: due to renal, endocrine, or central nervous system disorders and from drugs that stimulate the SNS or cause retention of sodium and water – may need a combination of surgery and drugs
Hypertension Guidelines • Normal = systolic less than 120 and diastolic less than 80 • Pre-hypertension = systolic 120 – 139 or diastolic 80 – 89 • Stage I hypertension = systolic 140 -159 or diastolic 90 to 99 • Stage II hypertension = systolic greater than 160 or diastolic 100 or more
Guidelines for Higher than Normal BP • Life style modifications: diet and exercise • Stage I: single drug therapy such as thiazide or diuretic – • More that 1/3 of all patients will not respond - if diuretics do not work add one or more drugs from for other classifications of antihypertensives
Antihypertensive 6 Classifications • Angiotension – converting Enzyme Inhibitors or ACE Inhibitors • Angiotension II Receptor Blockers or ARB • Calcium Channel Blockers • Beta Blockers • Diuretics
Action of Antihypertensives • Except for the diuretics, most antihypertensive drugs lower BP by causing vasodilation. • Alpha 1 blockers, beta-blockers, and calcium channel blockers also affect heart rate, contractility of the heart or both
Vasodilation • Action: directly relax smooth muscle in blood vessels resulting in blood vessel dilation and decreased peripheral vascular resistance. Usually need to be used with other drugs because they can trigger SNS and compensatory mechanism
