Download No Slide Title

Chapter 8
Cardiovascular Drugs
Copyright © 2011 Delmar, Cengage Learning
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
Basic Anatomy and Physiology
Copyright © 2011 Delmar, Cengage Learning
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Bleeding Control
• Hemostatic drugs
– Help promote the clotting of blood
– May be parenteral or topical
– Parenteral
• Vitamin K1
• Protamine sulfate
– Topical
• Silver nitrate, hemostat powder, gelfoam gelatin
sponges, thrombogen topical thrombin solution
Copyright © 2011 Delmar, Cengage Learning
Blood Enhancing Drugs
• Affect RBCs
• Affect the production or quality of RBCs
• Examples:
– Iron
– Erythropoietin
Copyright © 2011 Delmar, Cengage Learning
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
Blood Enhancing
• Cyanocobalamine is B12 and is used to treat B12
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