Cardiac Stimulants and Depressants Chapter 17 Cardiac Stimulants and Depressants

The heart

Cardiac conduction p415

Autonomic innervation of the heart

Aspects of cardiac function affected by drugs p 415 Inotropic effects: force of contractions Chronotropic effects: heart rate Dromotropic effects: conduction of electrical impulses thru the myocardium These effects can be positive or negative.

Heart failure p416 Characterized by: Cardiac distention resulting from incomplete ventricle emptying Cardiac hypertrophy caused by heart’s adaptation to prolonged stretching (enlarged heart) Sodium and water retention caused by, in part, diminished renal blood flow

Symptoms of heart failure p416 Weight gain Peripheral edema Shortness of breath Pulmonary edema

Treatment of Heart Failure p416 Cardiac glycosides: prototype: digoxin (Lanoxin) Positive inotropic action Negative chronotropic action Negative dromotropic action Foxglove plant

Digoxin: Dose Considerations p416 Long duration of action Method of administration Oral route most preferable Digitalizing dose IV To bring serum levels to a therapeutic level All glycosides have a low therapeutic index

Cardiac glycosides: Side Effects p 417,418 Gastrointestinal effects Nausea and vomiting Anorexia Diarrhea Cardiac effects Cardiac arrhythmias

Cardiac glycosides: Toxicity p417,418 Neurological effects Restlessness, confusion Irritability Drowsiness Vision changes Headache

Cardiac Glycoside Toxicity p418 10-20% of pt experience toxicity Predispose to cardiac glycoside toxicity: Hypokalemia Renal impairment Rapid IV administration

Cardiac Glycoside Toxicity p418 Treatment Stop the drug Physical assessment Check potassium level Administer if needed Monitor heart rate Administer antiarrhythmics Digibind (digoxin immune fab) For life threatening toxicity

Nursing considerations when administering cardiac glycosides P 417 table 17-1 Administer with meals if GI upset occurs Hold dose and report to PCP for HR < 60 bpm Hold dose and report for HR > 100 bpm Observe pt for signs of toxicity, document, report Monitor labs K+ dig levels

Cardiac glycoside teaching Pt education teach pt to take radial pulse prior to taking his med instruct when to hold dose and contact physician instruct S/S dig toxicity

Antiarrhythmics and antidysrhythmics Drug Action p419 Obliterate or diminish rhythm disturbances: Decrease the automaticity in ectopic sites Alter dromotropic effects Alter the refractory period of cardiac muscle between consecutive contractions

Table 17-3 p425-428 Antiarrhythmic drugs Monitor apical pulse for 1 minute prior to drug administration Record rate and rhythm Patient should be supine if IV drugs

Quinidine gluconate p420, 428 Old antidysrhythmic agent Depressant of cardiac function Reduces the excitibility of cardiac muscle to electrical stimulation Negative chronotropic effect SA node regains control

Quinidine toxic effects p420 Quinidine therapy is discontinued in 1/3 of pt due to toxic effects GI distress N&V anorexia diarrhea Cardiovascular disorders: hypotension, AV block Hypersensitivity tinnitus headache dizziness impaired vision vertigo skin rashes

Procainamide (Pronestyl) p421, 427 Cardiac effects are the same as quinidine, but procainamide has fewer adverse cardiovascular effects Pt that are allergic to “caine” local anesthetics may have a sensitivity to procainamide

Lidocaine (Xylocaine) p421, 426 Widely used as a local anesthetic Has antidysrhythmic properties Drug of choice for treatment of premature ventricular contractions (PVCs) Constant EKG monitoring is necessary for all pt during administration of lidocaine as an antidysrhythmic

Beta-adrenergic Blocking Agents “beta blockers” (-olol) p423, 427 Inhibit beta1 and beta2 sympathetic receptors Cardiac effects of beta blockers negative inotropic effect negative chronotropic effect negative dromotropic effect Decrease arrhythmias Decrease blood pressure

Beta-adrenergic blocking agents Adverse effects Cause bronchoconstriction Contraindications: pt with respiratory disease Cause heart failure Contraindications: pt with heart failure Examples Propanolol (Inderal) (prototype) Metoprolol (Lopresor) Atenolol (Tenormin)

Amiodarone HCL (Cordarone) p423 425 Effective in treating dysrythmias Adverse effect: pulmonary toxicity Persistent nonproductive cough Chest pain with deep inhalation dyspnea

Calcium Channel Antagonists “calcium channel blockers” p424, 428 Reduces the influx of calcium into the cell relaxation of vascular smooth muscle Coronary artery dilation (treat angina) Reduction of myocardial oxygen consumption Lowered blood pressure Negative dromotropic effect Negative inotropic effect Example: verapamil (Calan) prototype

Drugs to treat shock p428 Adrenergic Causes increase in heart rate Causes peripheral vasoconstriction Reverses hypotension from shock Anticholinergic Atropine sulfate Frequently given to treat bradycardia