Chapter 22- Positive Inotropic Drugs Flashcards
Atrial fibrillation
A common cardiac dysrhythmia involves atrial contraction that are so rapid that they prevent full depolarization of myocardial fibres between heart beats.
Automaticity
A property of specialized excitable tissue that allows self-activation through the spontaneous development of an action potential, as in the pacemaker cells of the heart.
Cardiac glycosides
Glycosides (Carbohydrates that yield a sugar and a nonuser upon hydrolysis) that are derived from the plant species Digitalis purpurea and are used in the treatment of heart disease.
Chronotropic drugs
Drugs that influence the rate of the heart beat.
Dromotropic drugs
Drugs that influence the conduction of electrical impulses
Ejection fraction
The proportion of blood that is ejected during each ventricular contraction compared with the total ventricular filling volume.
Heart Failure
The heart is unable to pump blood in sufficient amounts from the ventricles to meet the body’s metabolic needs. Symptoms depend on cardiac area affected: Left Ventricular failure= most common due to hypertension, often leads to R ventricular failure.
An abnormal condition in which cardiac pumping is impaired as the result of myocardial infraction, ischemic heart disease, or cardiomyopathy.
Inotropic drugs
Drugs that affect the force or energy of muscular contractions, particularly contraction of the heart muscle.
Left ventricular end-diastolic volume
The total amount of blood in the ventricle before it contracts, or the preload.
Phosphodiesterase inhibitors
A group of inotropic drugs that work by inhibiting the enzyme phosphodiesterase.
Refractory period
The period during which a pulse generator is unresponsive to an input signal of specified amplitude and it is impossible for the myocardium to respond.
Therapeutic Window
The range of drug levels in the blood that is considered beneficial as opposed to toxic or ineffective.
Cardiac Glycosides
Ex) Digoxin (Lanoxin). Narrow therapeutic window
Cardiac Glycosides Mech of Action
Increase myocardial contractility. Results in reduced heart rate and improved cardiac efficiency. Increase stroke volume Reduction in heart size during diastole Decrease in vein engorgement Increase in coronary circulation
Positive inotropic effect
Increase in force and velocity of myocardial contraction
Negative chronotropic effect
Reduced heart rate
Cardiac Glycosides Indication
Heart failure. Supra ventricular dysrhythmia- Atrial fibrillation and atrial flutter
Cardiac Glycosides Contraindications
Drug Allergy, sub aortic stenosis
Cardiac Glycosides Adverse Effects
Narrow therapeutic index
Low potassium levels increase its toxicity
Electrolyte levels must be monitored
Bradycardia- Check HR for a full minute (60-100)
Coloured vision, halo vision
Anorexia, nausea, vomiting, diarrhea
Digoxin Toxicity
Digoxin Immune Fab (Digibind) therapy.
Hyperkalemia- greater than 5mmol/L
Life-threatening cardiac dysrhythmias - symptomatic
Life-threatening digoxin overdoes
Predisposing conditions to Digoxin toxicity
Hypokalemia (low potassium)
Cardiac pacemaker
Hypercalcemia- makes bradycardic
Phosphodiesterase Inhibitors
ex) Milrinone
Increase contractility= vasodilation=hypotension
Phosphodiesterase Inhibitors Indications
Short-term management of heart failure
Phosphodiesterase Inhibitors Contraindications
Drug Allergy, presence of severe aortic or pulmonary valvular disease
Phosphodiesterase Inhibitors Adverse Effects
Hypotension
Phosphodiesterase Inhibitors Interactions
Diuretics=hypovolemia
digoxin (Lanoxin)=potentiates inotropic effects
Nesiritide (Natrecor)
Synthetic recombinant version of BNP (synthetic hormone)
Vasodilating effects on both arteries and veins
A final effort to treat severe, life-threatening acute heart failure.
Positive Inotropic Drugs Nursing Implications
Assess history, allergies, contraindications, BP, apical pulse for 1 full minute, heart and breath sounds, weight, labs, notify doctor of S&S of toxicity (anorexia, nausea, vomiting, visual disturbances).
Avoid giving Digoxin with high-fibre foods (fibre binds with digitalis)
Monitor for therapeutic effects- Increased urinary output, decreased edema, SOB, dyspnea, crackles, and fatigue.
