FT Cardio PDF

Drugs Acting on the Cardiovascular System NCM 106 Pharmacology Name the parts of the heart Introduction to the Cardiovascular System The heart, a hollow muscle with four chambers comprising two upper atria and two lower vent...

Drugs Acting on the Cardiovascular System NCM 106 Pharmacology Name the parts of the heart Introduction to the Cardiovascular System The heart, a hollow muscle with four chambers comprising two upper atria and two lower ventricles, pumps oxygenated blood to the body’s cells and pumps deoxygenated blood to the lung tissues. Introduction to the Cardiovascular System The two-step process known as the cardiac cycle includes diastole (resting period when the veins carry blood back to the heart) and systole (contraction period when the heart pumps blood out to the arteries for distribution to the body). Introduction to the Cardiovascular System If the nerves supplying the heart are severed, the heart will continue to beat. The cells that possess the property of automaticity are called pacemaker cells. The SA node serves as the heart’s primary pacemaker and has an intrinsic (natural) rate of 60 to 100 beats per minute. Introduction to the Cardiovascular System The heart’s conduction (or stimulatory) system consists of the SA node, the atrial bundles, the AV node, the bundle of His, the bundle branches, and the Purkinje fibers. Introduction to the Cardiovascular System The normal ECG waveform is made up of five main waves: the P-wave, which is formed as impulses originating in the SA node or pacemaker pass through the atrial tissues; the QRS complex, which represents depolarization of the bundle of His (Q) and the ventricles (RS); and the T wave, which represents repolarization of the ventricles. The heart muscle is stimulated to contract by impulses generated in the heart, not by stimuli from the brain or nervous system. However, the autonomic nervous system can affect the heart to increase (sympathetic)or decrease (parasympathetic) activity. Blood pressure is maintained by stimulus from the sympathetic system and reflex control of blood volume and pressure by the renin– angiotensin system and the aldosterone–ADH system. Alterations in blood pressure (hypotension or hypertension) can upset the balance of the cardiovascular system and lead to problems in blood delivery. The renin– angiotensin– aldosterone system for reflex maintenance of blood pressure control.  Drugs Affecting Blood Pressure Review of Blood Pressure Control Baroreceptors Heart rate As the blood leaves the Stroke volume, or the left ventricle through the amount of blood that is pumped aorta, it influences out of the ventricle with each specialized cells in the heartbeat (primarily determined by the volume of blood in the system) arch of the aorta called Total peripheral baroreceptors (pressure resistance, or the resistance receptors) of the muscular arteries to the blood being pumped through Trivia Check the dose and preparation carefully because digoxin has a small margin of safety, and inadvertent drug errors can cause serious problems Follow dilution instructions carefully for intravenous (IV) use; use promptly to avoid drug degradation. Administer IV doses slowly over at least 5 minutes to avoid cardiac arrhythmias and adverse effects. Avoid intramuscular (IM) administration, which could be quite painful. Arrange for the patient to be weighed at the same time each day in the same clothes to monitor for fluid retention and HF. Assess dependent areas for edema; note the amount and degree of pitting to evaluate the severity of fluid retention. Maintain emergency equipment on standby: potassium salts, lidocaine (for treatment of arrhythmias), phenytoin (for treatment of seizures), atropine (to increase heart rate), and a cardiac monitor in case severe toxicity should occur Antidote : digoxin toxicity is digoxin immune fab Activated Charcoal Adults and teenagers : Dose is usually 50 to 100 grams of activated charcoal given one time Heart Trivia  Clear Point - HF First-line medication therapy for HF would be to decrease the work of the heart with medications that decrease preload, afterload, and heart rate. These are shown to slow the progression of HF and decrease mortality and hospitalizations. Cardiotonic (inotropic) agents are one class of drugs used in the treatment of HF. These agents directly stimulate the muscle to contract more with more force.  Cardiac glycosides increase the movement of calcium into the heart muscle. This results in increased force of contraction, which increases blood flow to the kidneys (causing a diuretic effect), slows the heart rate, and slows conduction through the AV node. Phosphodiesterase inhibitors block the breakdown of cAMP in the cardiac muscle. This allows more calcium to enter the cell (leading to more intense contraction) and increases the effects of sympathetic stimulation (which can lead to vasodilation but also can increase pulse, blood pressure, and workload on the heart). Because these drugs are associated with severe effects, they are reserved for use in extreme situations.  HCN blockers slow the repolarization of the heart’s pacemaker, leading to a slower heart rate. Slowing the heart rate allows more time for filling and improves cardiac output. This class of drugs does not affect ventricular cell activity. The systemic effects seen with the use of betablockers do not occur with this class of drugs.  Clear points - Arrythmias Antiarrhythmics are drugs that alter the action potential of the heart cells and interrupt arrhythmias. The medications may trigger dangerous heart arrhythmias, so the patients starting the medications need to be closely monitored. Class I antiarrhythmics block sodium channels, depress phase 0 of the action potential, leading to a slowing of conduction and automaticity.  Clear points Class II antiarrhythmics are beta-adrenergic receptor blockers that prevent sympathetic stimulation. Class III antiarrhythmics block potassium channels and prolong phase 3 of the action potential. Class IV antiarrhythmics are calcium channel blockers that shorten the action potential, disrupting ineffective rhythms and rates.  Clear points A patient receiving an antiarrhythmic drug needs to be constantly monitored while being stabilized and throughout the course of therapy to detect the development of arrhythmias or other adverse effects associated with alteration of the action potentials of other muscles or nerves.  Clear points - Angina Angina can be treated by drugs that either increase the supply of oxygen or decrease the heart’s workload, which decreases the demand for oxygen. Nitrates are used to cause vasodilation and to decrease venous return and arterial resistance—effects that decrease cardiac workload and oxygen consumption.  Clear points - Angina Nitroglycerin is the drug of choice for treating an acute anginal attack. It is available in various forms. Beta-blockers prevent the activation of sympathetic receptors, which normally would increase heart rate, increase blood pressure, and increase cardiac contraction. All of these actions would increase the demand for oxygen; blocking these actions decreases the demand for oxygen.  SUBLINGUAL, TRANSBUCCAL, AND TRANSDERMAL ADMINISTRATION OF NITROGLYCERIN Check under the tongue to make sure there are no lesions or abrasions that could interfere with the absorption of the drug. Have the patient take a sip of water to moisten the mucous membranes so the tablet will dissolve quickly. Then instruct the patient to place the tablet under the tongue, close the mouth, and wait until the tablet has dissolved. Caution the patient not to swallow the tablet; its effectiveness would be lost if the tablet entered the stomach. If the patient uses translingual drugs often, encourage the patient to alternate sides of the tongue, placing it under the left side for one dose and under the right side for the other dose. To help in administering sublingual medications to patients who cannot do it themselves or who cannot open their mouths, use a tongue depressor to move the tongue aside and place the tablet, or slide the tablet down through a straw to the underside of the tongue.  SUBLINGUAL, TRANSBUCCAL, AND TRANSDERMAL ADMINISTRATION OF NITROGLYCERIN Transbuccal administration. Make sure that the tablet the patient is going to use is designed for buccal administration: Check the inside of the cheeks to be sure there are no ulcerations or abrasions that could interfere with the absorption of the drug. Have the patient place the tablet between his or her gums and cheek pocket and then hold it in place until the tablet dissolves. Again, caution the patient not to swallow the tablet, and instruct the patient to rotate the site of placement from side to side with each dose. Transdermal administration. Errors have been reported with inappropriate use of nitroglycerin patches and nitroglycerin paste. Make sure to discuss safe administration with the patient  Clear points - Angina Calcium channel blockers block muscle contraction in smooth muscle and decrease the heart’s workload, relax vasospasm in Prinzmetal angina, and possibly block the proliferation of the damaged endotheliumin coronary vessels. The newest drug approved for the treatment of angina is the piperazine acetamide agent ranolazine. The mechanism of action of this drug is not understood. It prolongs QT intervals, does not slow heart rate or blood pressure, but decreases myocardial oxygen demand.  Clear points - CAD HMG–CoA reductase inhibitors, or statins, block the enzyme HMG–CoA reductase, resulting in lower serum cholesterol levels, a resultant breakdown of LDLs, and a slight increase in HDLs. The cholesterol absorption inhibitor ezetimibe works in the brush border of the small intestine to prevent the absorption of dietary cholesterol, which leads to increased clearance of cholesterol by the liver and a resultant fall in serum cholesterol.  Safe Medication Patients who are taking HMG–CoA inhibitors need to be cautioned to avoid drinking grapefruit juice while taking these drugs. Grapefruit juice alters the metabolism of the drugs, leading to an increased serum level of drug and increased risk for adverse effects, such as the potentially fatal rhabdomyolysis with renal failure.  Clear points - CAD The PCSK9 inhibitors are monoclonal antibodies that bind to PCSK9, which increases the liver’s ability to clear LDL from the blood. Other agents used to lower cholesterol include fibrates, niacin, and omega-3 fatty acids. Often lipid-lowering agents are used in combination to lower the cholesterol at different sites.  Clear points - Coagulation Anticoagulants block blood coagulation by interfering with one or more of the steps involved, such as blocking platelet aggregation or inhibiting the intrinsic or extrinsic pathways to clot formation. Thrombolytic drugs dissolve clots or thrombi that have formed. They activate the plasminogen system to stimulate natural clot dissolution. Hemostatic drugs are used to stop bleeding. They may replace missing clotting factors or prevent the plasminogen system from dissolving formed clots.  Safe Medication Heparin overdose, the antidote is protamine sulfate (generic). Protamine is given to a patient who has not received heparin, it has anticoagulant effects. The drug must be administered slowly, not to exceed 50 mg IV in any 10-minute period. Care must be taken to calculate the amount of heparin that has been given to the patient. Potentially fatal anaphylactic reactions have been reported with the use of protamine sulfate, so life support equipment should be readily available when it is used.  Safe Medication Injectable vitamin K is used to reverse the effects of warfarin. Vitamin K promotes the liver synthesis of several clotting factors. When these pathways have been inhibited by warfarin, clotting time is increased. A prothrombin time response within 6 to 8 hours after parenteral doses or 12 to 48 hours after oral doses will determine the need for a repeat dose.  Clear points - Anemia Folic acid and vitamin B12 are needed to produce a strong supporting structure in the RBC so that it can survive 120 days of being propelled through the vascular system. These are usually found in adequate amounts in the diet. Deficiencies are treated with folic acid and vitamin B12 replacement. A dietary lack of or inability to absorb folic acid, vitamin B12, or both will produce a megaloblastic anemia, in which the RBCs are large and immature and have a short lifespan.  Clear points - Anemia Pernicious anemia is a lack of vitamin B12, which is also used by the body to maintain the myelin sheath on nerve axons. If vitamin B12 is lacking, these neurons will degenerate and cause many CNS effects. Pernicious anemia is caused by the deficient production of intrinsic factor by gastric cells. Intrinsic factor is needed to allow the body to absorb vitamin B12. If intrinsic factor is lacking, vitamin B12 must be given parenterally or intranasally for life to ensure absorption.  Z-TRACK INJECTIONS The Z-track method is used when injecting iron to reduce the risk of subcutaneous staining and irritation Next meeting nah!