8. cardiovascular drugs

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  • 1. Chapter 8 Cardiovascular Drugs Copyright © 2011 Delmar, Cengage Learning
  • 2. Basic Anatomy and Physiology
    • The functions of the cardiovascular system include delivery of oxygen, nutrients, and hormones to the various parts of the body
    • The cardiovascular system also transports waste products to the appropriate waste removal system
    Copyright © 2011 Delmar, Cengage Learning
  • 3. Basic Anatomy and Physiology Copyright © 2011 Delmar, Cengage Learning
  • 4. Basic Anatomy and Physiology
    • The electrical impulses of the heartbeat originate in the sinoatrial node (SA node)
    • Heart rate is controlled primarily by the autonomic nervous system:
      • Stimulation of the parasympathetic nervous system slows heart rate
      • Stimulation of the sympathetic nervous system increases heart rate
    Copyright © 2011 Delmar, Cengage Learning
  • 5. Basic Anatomy and Physiology
    • Heart rhythm
      • Contractions at regular intervals
      • Systole is contraction of heart chambers
      • Diastole is relaxation of heart chambers
      • Normal heart beat is called normal sinus rhythm
    Copyright © 2011 Delmar, Cengage Learning
  • 6. Basic Anatomy and Physiology
    • Workload of the heart is divided into preload and afterload
      • Preload: volume of blood entering the right side of the heart
      • Afterload: force needed to push blood out of the ventricles
    • If the heart is not working properly, it can compensate by a few mechanisms:
      • Increase heart rate
      • Increase stroke volume
      • Increase efficiency
      • Enlarge itself
    Copyright © 2011 Delmar, Cengage Learning
  • 7. Basic Anatomy and Physiology
    • There are 3 major types of blood vessels: arteries, veins, and capillaries
      • An artery is a blood vessel that carries blood away from the heart
      • Veins are low-pressure collecting system that returns blood to the heart
      • Capillaries are single-cell-thick vessels that connect the arterial and venous systems
    Copyright © 2011 Delmar, Cengage Learning
  • 8. Basic Anatomy and Physiology
    • Blood pressure
      • Flows from areas of higher pressure to areas of lower pressure
      • Determined by heart rate, stroke volume, peripheral resistance
    Copyright © 2011 Delmar, Cengage Learning
  • 9. Basic Anatomy and Physiology
    • Blood supplies body tissues with oxygen, nutrients, and various chemicals
    • Blood transports waste products to various organs for removal from the body
    • Blood cells also play an important role in the immune and endocrine systems
    Copyright © 2011 Delmar, Cengage Learning
  • 10. Cardiovascular Conditions
    • Congestive heart failure is a syndrome that can occur with any disorder that damages or overworks the heart muscle
      • Conditions that lead to congestive heard failure include:
        • Cardiomyopathy (caused by infections, genetic disorders, or degeneration)
        • Hypertension
        • Valvular disease
    Copyright © 2011 Delmar, Cengage Learning
  • 11. Cardiovascular Conditions
    • Cardiac arrhythmias is a disruption in the cardiac rate or rhythm
      • Arrhythmias interfere with the work of the heart and can disrupt cardiac output
      • Can be caused by changes in the rate, stimulation from an ectopic focus, or by alterations in conduction of the muscle
      • These changes can be caused by electrolyte disturbances, decrease in oxygen delivered to the cells, structural damage, accumulation of waste products, and acidosis
    Copyright © 2011 Delmar, Cengage Learning
  • 12. Cardiovascular Disease
    • Alterations in blood pressure may result in hypertension (increased blood pressure) or hypotension (decreased blood pressure)
      • Hypertension results in prolonged force put on the vessels of the vascular system
        • Leads to left ventricle thickening
      • Hypotension results in the tissues of the body not receiving sufficient amount of oxygenated blood
        • Allows wasted products to accumulate and cells to die from lack of oxygen
    Copyright © 2011 Delmar, Cengage Learning
  • 13. Cardiovascular Drugs
    • Types of cardiovascular drugs
      • Positive inotropic drugs: increase the force of myocardial contraction
      • Negative inotropic drugs: decrease the force of myocardial contraction
      • Positive chronotropic drugs: increase heart rate by altering the rate of impulse formation at the SA node
      • Negative chronotropic drugs: decrease heart rate by altering the rate of impulse formation at the SA node
      • Positive dromotropic drugs: increase the conduction of electrical impulses
      • Negative dromotropic drugs: decrease the conduction of electrical impulses
    Copyright © 2011 Delmar, Cengage Learning
  • 14. Increasing Force
    • Positive inotropes
      • Cardiac glycosides:
        • Increase the strength of cardiac contractions, decrease heart rate, have an antiarrhythmic effect, and decrease signs of dyspnea
        • Side effects include anorexia, vomiting, diarrhea, and cardiac arrhythmias
        • Examples include digoxin and digitoxin
      • Catecholamines:
        • Increase the force and rate of myocardial contraction, constrict peripheral blood vessels, and increase blood glucose levels
        • Examples include epinephrine, dopamine, dobutamine, and isoproterenol
    Copyright © 2011 Delmar, Cengage Learning
  • 15. Increasing Force
    • Positive inotropes
      • Benzimidazole-pyridazinones:
        • Increase the force of contraction
        • Cause widening of the blood vessels
        • Side effects include anorexia, lethargy, diarrhea, and dyspnea
    Copyright © 2011 Delmar, Cengage Learning
  • 16. Fixing the Rhythm
    • Antiarrhythmic drugs
      • Used to correct variation in the normal beating of the heart (which can lead to reduced cardiac output)
      • Types of antiarrhythmic drugs include local anesthetics, membrane stabilizers, beta-adrenergic blockers, action potential prolongation drugs, and calcium-channel blockers
      • For examples of antiarrhythmic drugs refer to Table 8-3 in your textbook
    Copyright © 2011 Delmar, Cengage Learning
  • 17. Correcting Constriction
    • Vasodilators
      • Drugs used to dilate arteries and/or veins, which alleviates vessel constriction and improves cardiac output
      • Examples include angiotensin-converting enzyme inhibitors, arteriole dilators, venodilators, and combined vasodilators
    Copyright © 2011 Delmar, Cengage Learning
  • 18. Correcting Constriction
    • Calcium channel blockers are used to treat CHF and hypertension
    • Calcium channel blockers inhibit the movement of calcium through the the myocardial cell membranes and vascular smooth muscle
      • Decreases the force of cardiac contractions
      • Side effects include hypotension and anorexia
    Copyright © 2011 Delmar, Cengage Learning
  • 19. Losing Fluid
    • Diuretics
      • Drugs that increase the volume of urine excreted by the kidneys and thus promote the release of water from the tissues (lowers the fluid volume in tissue)
      • Used in the treatment of hypertension
      • Categories of diuretics include thiazides, loop diuretics, potassium-sparing diuretics, osmotics, and carbonic anhydrase inhibitors
      • For examples refer to Table 8-4 in your textbook
    Copyright © 2011 Delmar, Cengage Learning
  • 20. Clot Stopping
    • Anticoagulants
      • Inhibit clot formation by inactivating one or more clotting factors
      • Used to inhibit clotting in catheters, to prevent blood samples from clotting, to preserve blood transfusions, and to treat emboli
      • Examples include heparin, EDTA, coumarin derivatives, aspirin, and blood transfusion anticoagulants
    Copyright © 2011 Delmar, Cengage Learning
  • 21. Clot Stopping
    • Clopidogrel bisulfate is an oral platelet aggregation inhibitor
      • May prevent thrombi in cats
      • Improves circulation in cats following an embolic event
      • Side effects are gastrointestinal in nature and include vomiting and anorexia
    Copyright © 2011 Delmar, Cengage Learning
  • 22. Bleeding Control
    • Hemostatic drugs
      • Help promote the clotting of blood
      • May be parenteral or topical
      • Parenteral
        • Vitamin K 1
        • Protamine sulfate
      • Topical
        • Silver nitrate, hemostat powder, gelfoam gelatin sponges, thrombogen topical thrombin solution
    Copyright © 2011 Delmar, Cengage Learning
  • 23. Blood Enhancing Drugs
    • Affect RBCs
    • Affect the production or quality of RBCs
    • Examples:
      • Iron
      • Erythropoietin
    Copyright © 2011 Delmar, Cengage Learning
  • 24. Blood Enhancing
    • Erythropoietin is a protein made by the kidneys that stimulates the differentiation of bone marrow stem cells to form red blood cells
      • Used to treat anemia in animals with chronic renal failure
      • Allergic reactions are sometimes seen with erythropoietin products
      • Erythropoietin products must be refrigerated
    Copyright © 2011 Delmar, Cengage Learning
  • 25. Blood Enhancing
    • Cyanocobalamine is B 12 and is used to treat B 12 deficiencies
      • Oral forms are not appropriate for small animals
    • Folic acid is a B vitamin needed for normal erythropoiesis
      • May be seen in dogs, cats, and horses due to small intestinal disease
      • Very few side effects
    Copyright © 2011 Delmar, Cengage Learning