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Pharmacology in Nursing

Pharmacology in Nursing. Positive Inotropic Agents. Definition. Drugs that increase the force of myocardial contraction Used to treat heart muscle failure Cardiac glycosides digoxin Phosphodiesterase inhibitors ( PDIs). Heart Failure.

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Pharmacology in Nursing

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  1. Pharmacology in Nursing Positive Inotropic Agents

  2. Definition • Drugs that increase the force of myocardial contraction • Used to treat heart muscle failure • Cardiac glycosides • digoxin • Phosphodiesterase inhibitors ( PDIs)

  3. 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 • Right ventricular failure

  4. 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

  5. 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

  6. Heart Failure: Causes • Cardiac defect • Myocardial infarction • Valve deficiency • Defect outside the heart • Coronary artery disease/Hypertension • Pulmonary hypertension • Diabetes • Supraventriculardysrhythmias • Atrial fibrillation • Atrial flutter

  7. Treatment of Heart Failure • Block the compensatory mechanisms • Treat underlying conditions • Goal is to decrease SVR, decrease volume, • Increase cardiac output

  8. 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

  9. Cardiac Glycosides:Mechanism of Action • Increase myocardial contractility • Change electrical conduction properties of the heart • Decrease rate of electrical conduction • Prolong the refractory period • Area between SA node and AV node Result: reduced heart rate and improved cardiac efficiency

  10. Drug Effects:General Terms • Inotropic • Force or energy of muscular contractions • Chronotropic • Rate of the heartbeat • Dromotropic • The conduction of electrical impulses

  11. How Positive Inotropic Agents Work

  12. Cardiac Glycosides:Drug Effects • Positive inotropic effect • Increase in force and velocity of myocardial contraction (without an increase in oxygen consumption) • Negative chronotropic effect • Reduced heart rate • Negative dromotropic effect • Decreases automaticity at SA node, decreases AV nodal conduction, and other effects

  13. 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

  14. Cardiac Glycosides:Indications • Heart failure • Supraventricular dysrhythmias • Atrial fibrillation and atrial flutter

  15. Heart Failure

  16. Atrial Fibrillation/Flutter

  17. Cardiac Glycosides:Adverse Effects • Digoxin (Lanoxin) • Very narrow therapeutic window • Drug levels must be monitored • Low potassium levels increase its toxicity • Electrolyte levels must be monitored

  18. Digoxin: Adverse Effects • Cardiovascular • Dysrhythmias, including bradycardia or tachycardia • CNS • Headaches, fatigue, malaise, confusion, convulsions

  19. Digoxin: Adverse Effects (cont’d) • Eye • Colored vision (seeing green, yellow, purple), halo vision, flickering lights • GI • Anorexia, nausea, vomiting, diarrhea

  20. Digoxin Toxicity • digoxin immune Fab (Digibind) therapy • Hyperkalemia (serum potassium greater than 5 mEq/L) in a digitalis-toxic patient • Life-threatening cardiac dysrhythmias • Life-threatening digoxin overdose • Therapeutic drug level= 0.5 – 2 ng/ml

  21. Conditions That Are Predisposing to Digoxin Toxicity • Hypokalemia • Use of cardiac pacemaker • Hepatic dysfunction • Hypercalcemia • Dysrhythmias • Hypothyroid, respiratory, or renal disease • Advanced age

  22. 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

  23. Phosphodiesterase Inhibitors Work by inhibiting the enzyme phosphodiesterase • Results in: • Positive inotropic response • Vasodilation • Two drugs (inodilators) • Inamrinone (Inocor) and milrinone (Primacor)

  24. 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 • Decreased readmissions for heart failure episodes

  25. Phosphodiesterase Inhibitors:Adverse Effects • Inamrinone (Inocor) • Thrombocytopenia, most worrisome • Dysrhythmia, nausea, hypotension • Elevated liver enzymes with long-term use • Milrinone (Primacor) • Dysrhythmia, mainly ventricular • Hypotension, angina, hypokalemia, tremor, thrombocytopenia

  26. Cardiostimulatory Drugs • Enhance cardiac function by: • Increasing heart rate • Increasing myocardial contractility • Positive Inotrop

  27. 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

  28. Beta-AgonistsCardiac Effects • Increase contractililty • Increase heart rate • Increase conduction velocity

  29. Beta AgonistsVascular & Other Effects • Smooth muscle relaxation • Bronchodilatation • Hepatic glycogenolysis • Pancreatic release of glucagon • Renin release by kidney

  30. Beta-Agonist Drugs • Epinephrine • Norepinephrine (Levophed) • Dopamine • Dobutamine • Isoproterenol

  31. Major Side Effects • Arrhythmias • Increase myocardial demand for oxygen • Increase in heart rate • Can precipitate angina

  32. 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

  33. Positive Inotropic Drugs:Nursing Implications • Assess history, drug allergies, contraindications • Assess clinical parameters, including: • BP • Apical pulse for 1 full minute • Heart sounds, breath sounds

  34. Positive Inotropic Drugs:Nursing Implications (cont’d) • Assess clinical parameters (cont'd) • Weight, I&O measures • EKG • Serum labs: potassium, sodium, magnesium, calcium, renal and liver function studies

  35. 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 • Notify prescriber

  36. Positive Inotropic Drugs:Nursing Implications (cont’d) • Hold dose and notify prescriber if patient experiences signs/symptoms of toxicity • Anorexia, nausea, vomiting, diarrhea • Visual disturbances (blurred vision, seeing green or yellow halos around objects)

  37. 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

  38. Positive Inotropic Drugs: Nursing Implications (cont’d) • Inamrinone or Milrinone • Use an infusion pump • Monitor I&O, heart rate, BP, daily weights, respirations, etc. • IV Inamrinone • Do not mix with dextrose • Solution color is true yellow

  39. Positive Inotropic Drugs: Nursing Implications (cont’d) • Monitor for therapeutic effects • Increased urinary output • Decreased edema, shortness of breath, dyspnea, crackles, fatigue • Resolving of paroxysmal nocturnal dyspnea • Improved peripheral pulses, skin color, temperature • Monitor for adverse effects

  40. 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 • B. Flickering lights or halos around lights • C. dizziness when standing up • D. Increased urine output

  41. Question • During assessment of a patient receiving Digoxin, which finding would indicate an increased possibility of toxicity? • A. Apical rate of 62 • B. Digoxin level of 1.5 ng/ml • C. Serum potassium level of 2 mEq/L • D. Serum potassium level of 4.8 mEq/L

  42. Question • When monitoring a patient who is receiving an IV infusion of Inocor, the nurse will look for which adverse effect? • A. Thrombocytopenia • B. Proteinuria • C. Anemia • D. Decreased BUN/Creatinine levels

  43. Question • When administering the daily dose of digoxin 0.125mg 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. • B. Monitor the patient for dysrhythmias. • C. Administer it 1 hour before the morning dose of insulin. • D. Withhold dose if the apical heart rate is less then 80 beats per minute.

  44. Case ScenarioHeart 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: • AAOx1 • Vitals: P 110, RR 33, BP 110/56 SAO2 92% • +2 pedal edema • Bilateral basilar crackles, SOB on minimal exertion

  45. Scenario con’t • Weight gain of 2 lbs over past 5 days • Urine output =240 ml/8 hr shift

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