Pharmacology in Nursing Positive Inotropic Agents Mosby items

Definition Drugs that increase the force of myocardial contraction Used to treat heart muscle failure Cardiac glycosides Ø digoxin Phosphodiesterase inhibitors ( PDIs) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Heart Failure The heart is unable to pump blood in sufficient amounts from the ventricles to meet the body’s metabolic needs Impairs heart’s ability to fill or eject properly Symptoms depend on cardiac area affected Left ventricular failure Ø Right ventricular failure Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

What happens when the heart fails? Weakened heart is unable to pump blood in sufficient amounts Decrease in CO, decrease tissue perfusion Compensatory mechanisms help to maintain CO and arterial blood pressure Renin-angiotensin-aldosterone system activated as a compensatory mechanism As cardiac output decreases, SNS releases catecholamines which increase HR, contractility & vasoconstriction Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

What happens when the heart fails? As renal perfusion decreases, renin is released by kidney Vasoconstriction increases SVR, which increases afterload End result, the failing heart must now work HARDER to pump blood Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Heart Failure: Causes Cardiac defect Myocardial infarction Ø Valve deficiency Ø Defect outside the heart Coronary artery disease/Hypertension Ø Pulmonary hypertension Ø Diabetes Ø Supraventricular dysrhythmias Atrial fibrillation Ø Atrial flutter Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

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Treatment of Heart Failure Block the compensatory mechanisms Treat underlying conditions Goal is to decrease SVR, decrease volume, Increase cardiac output Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Cardiac Glycosides Originally obtained from Digitalis plant, foxglove Digoxin is the prototype Used in heart failure and to control ventricular response to atrial fibrillation or flutter Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Cardiac Glycosides: Mechanism of Action Increase myocardial contractility Change electrical conduction properties of the heart Ø Decrease rate of electrical conduction Ø Prolong the refractory period • Area between SA node and AV node Result: reduced heart rate and improved cardiac efficiency Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Drug Effects: General Terms Inotropic Ø Chronotropic Ø Force or energy of muscular contractions Rate of the heartbeat Dromotropic Ø The conduction of electrical impulses Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

How Positive Inotropic Agents Work Mosby items and derived items © 2007, 2005, 2002

Cardiac Glycosides: Drug Effects Positive inotropic effect Ø Negative chronotropic effect Ø Increase in force and velocity of myocardial contraction (without an increase in oxygen consumption) Reduced heart rate Negative dromotropic effect Ø Decreases automaticity at SA node, decreases AV nodal conduction, and other effects Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Cardiac Glycosides: Drug Effects (cont’d) Increased stroke volume Reduction in heart size during diastole Decrease in venous BP and vein engorgement Increase in coronary circulation Promotion of diuresis due to improved blood circulation Palliation of exertional and paroxysmal nocturnal dyspnea, cough, and cyanosis Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Cardiac Glycosides: Indications Heart failure Supraventricular dysrhythmias Ø Atrial fibrillation and atrial flutter Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Heart Failure Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc.

Atrial Fibrillation/Flutter Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc.

Cardiac Glycosides: Adverse Effects Digoxin (Lanoxin) Very narrow therapeutic window Ø Drug levels must be monitored Ø Low potassium levels increase its toxicity Ø Electrolyte levels must be monitored Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Digoxin: Adverse Effects Cardiovascular Ø Dysrhythmias, including bradycardia or tachycardia CNS Ø Headaches, fatigue, malaise, confusion, convulsions Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Digoxin: Adverse Effects (cont’d) Eye Ø Colored vision (seeing green, yellow, purple), halo vision, flickering lights GI Ø Anorexia, nausea, vomiting, diarrhea Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Digoxin Toxicity digoxin immune Fab (Digibind) therapy Hyperkalemia (serum potassium greater than 5 m. Eq/L) in a digitalis-toxic patient Ø Life-threatening cardiac dysrhythmias Ø Life-threatening digoxin overdose Ø Therapeutic drug level= 0. 5 – 2 ng/ml Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Conditions That Are Predisposing to Digoxin Toxicity Hypokalemia Use of cardiac pacemaker Hepatic dysfunction Hypercalcemia Dysrhythmias Hypothyroid, respiratory, or renal disease Advanced age Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Dosing Digoxin Adult Digitalizing Dose: PO or IV : 1 -1. 5 mg/day (4 doses) Usual maintenance dose 0. 125 mg- 0. 5 mg day Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Phosphodiesterase Inhibitors Work by inhibiting the enzyme phosphodiesterase Results in: Ø Positive inotropic response Ø Vasodilation Two drugs (inodilators) Ø Inamrinone (Inocor) and milrinone (Primacor) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Phosphodiesterase Inhibitors: Indications Short-term management of heart failure Given when patient has not responded to treatment with digoxin, diuretics, and/or vasodilators Often given as weekly 6 -hour infusions Improved quality of life Ø Decreased readmissions for heart failure episodes Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Phosphodiesterase Inhibitors: Adverse Effects Inamrinone (Inocor) Ø Thrombocytopenia, most worrisome Ø Dysrhythmia, nausea, hypotension Ø Elevated liver enzymes with long-term use Milrinone (Primacor) Ø Dysrhythmia, mainly ventricular Ø Hypotension, angina, hypokalemia, tremor, thrombocytopenia Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Cardiostimulatory Drugs Enhance cardiac function by: Increasing heart rate Increasing myocardial contractility Positive Inotrop Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Beta-adrenoceptor agonists Sympathomimetic drugs that bind to beta receptors located in cardiac nodal tissue, conducting tissue Beta-1 & beta-2 adrenoceptor activation stimulates heart rate & contractility Net effect: Increase in cardiac output Used to treat heart failure, cardiogenic and circulatory shock Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Beta-Agonists Cardiac Effects Increase contractililty Increase heart rate Increase conduction velocity Mosby items and

Beta Agonists Vascular & Other Effects Smooth muscle relaxation Bronchodilatation Hepatic glycogenolysis Pancreatic release of glucagon Renin release by kidney Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Beta-Agonist Drugs Epinephrine Norepinephrine (Levophed) Dopamine Dobutamine Isoproterenol Mosby items and derived items ©

Major Side Effects Arrhythmias Increase myocardial demand for oxygen Increase in heart rate Can precipitate angina Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

B-type natriuretic peptide New class Nesiritide ( Natrecor) Synthetic recombinant version of B-type natriuretic peptide Vasodilating effects on arteries and veins Used in ICU setting as last alternative Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Positive Inotropic Drugs: Nursing Implications Assess history, drug allergies, contraindications Assess clinical parameters, including: BP Ø Apical pulse for 1 full minute Ø Heart sounds, breath sounds Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Positive Inotropic Drugs: Nursing Implications (cont’d) Assess clinical parameters (cont'd) Weight, I&O measures Ø EKG Ø Serum labs: potassium, sodium, magnesium, calcium, renal and liver function studies Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Positive Inotropic Drugs: Nursing Implications (cont’d) Before giving any dose, count apical pulse for 1 full minute For apical pulse less than 60 or greater than 120 beats/minute Hold dose Ø Notify prescriber Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Positive Inotropic Drugs: Nursing Implications (cont’d) Hold dose and notify prescriber if patient experiences signs/symptoms of toxicity Anorexia, nausea, vomiting, diarrhea Ø Visual disturbances (blurred vision, seeing green or yellow halos around objects) Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Positive Inotropic Drugs: Nursing Implications (cont’d) Check dosage forms carefully, and follow instructions for giving Avoid giving digoxin with high-fiber foods (fiber binds with digitalis) Patients should report immediately a weight gain of 2 or more pounds in 1 day or 5 or more pounds in 1 week Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Positive Inotropic Drugs: Nursing Implications (cont’d) Inamrinone or Milrinone Use an infusion pump Ø Monitor I&O, heart rate, BP, daily weights, respirations, etc. Ø IV Inamrinone Do not mix with dextrose Ø Solution color is true yellow Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Positive Inotropic Drugs: Nursing Implications (cont’d) Monitor for therapeutic effects Increased urinary output Ø Decreased edema, shortness of breath, dyspnea, crackles, fatigue Ø Resolving of paroxysmal nocturnal dyspnea Ø Improved peripheral pulses, skin color, temperature Ø Monitor for adverse effects Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Question When teaching the patient the signs and symptoms of cardiac glycoside toxicity, the nurse should alert the patient to watch for; A. Visual changes such as photophobia Ø B. Flickering lights or halos around lights Ø C. dizziness when standing up Ø D. Increased urine output Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Question During assessment of a patient receiving Digoxin, which finding would indicate an increased possibility of toxicity? A. Apical rate of 62 Ø B. Digoxin level of 1. 5 ng/ml Ø C. Serum potassium level of 2 m. Eq/L Ø D. Serum potassium level of 4. 8 m. Eq/L Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Question When monitoring a patient who is receiving an IV infusion of Inocor, the nurse will look for which adverse effect? A. Thrombocytopenia Ø B. Proteinuria Ø C. Anemia Ø D. Decreased BUN/Creatinine levels Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Question When administering the daily dose of digoxin 0. 125 mg PO to a patient with IDDM who is now in heart failure, it is most important for the nurse to: A. Give medication with a class of orange juice. Ø B. Monitor the patient for dysrhythmias. Ø C. Administer it 1 hour before the morning dose of insulin. Ø D. Withhold dose if the apical heart rate is less then 80 beats per minute. Ø Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.

Case Scenario Heart Failure Mrs. Allen is a 76 year old female admitted with heart failure. She has been started on Digoxin 0. 125 mg po. Your initial assessment of this patient revealed the following: AAOx 1 Vitals: P 110, RR 33, BP 110/56 SAO 2 92% +2 pedal edema Bilateral basilar crackles, SOB on minimal exertion Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc. , an affiliate of Elsevier Inc.