[Music] welcome to this presentation on nitrates after completion and reflection on this session you should be able to describe the usage and effects of nitrates and outline how nitrates may affect your practice and the patient's cardiac status and care in this slide you will see that nitrates are a category of vasodilator drugs that primarily work as veno dilators they also work at other sites of action but their primary action is on venous beds nitrates provide an exogenous or external source of the vasodilator nitric oxide that induces coronary vasodilation and it binds to nitrate receptors in the vascular smooth muscle wall the effects of nitrates occur even when our own internally present nitric oxide is impaired such as in coronary artery disease and whether or not the endothelium is intact nitrates cause relaxation of vascular smooth muscle which produces a marked dilation of veins and thus a reduction in preload ventricular wall stress myocardial oxygen consumption and myocardial oxygen demand they cause a modest dilation in coronary arteries and thus an increased coronary blood flow and myocardial oxygen supply and they cause a lesser arterial dilation and thus a minimal reduction in afterload ventricular wall stress myocardial oxygen consumption and myocardial oxygen demand this slide will discuss the properties of anti-anginals and vasodilators anti-anginal and vasodilator properties differ in that anti-anginals are used to treat acute angina and ischemic attacks increasing myocardial oxygen supply by dilating coronary arteries they are used to prevent angina and ischemic attacks decreasing myocardial oxygen demand by vasodilation of peripheral arteries vasodilators act by decreasing vascular tone resulting in vasodilation vasodilators also decrease afterload preload and workload resulting in a decrease in myocardial oxygen demand nitrates dilate large coronary arteries and redistribute blood flow along collateral channels and from epicardial to endocardial regions they relieve coronary spasm and dynamic stenosis including arterial constriction induced by exercise nitrates are effective coronary vasodilators for acute angina or ischemic attacks an example of a nitrate used for this purpose is nitro spray nitrates are also effective as venous and arterial vasodilators and thus effective to prevent angina and ischemic attacks an example of a nitrate used for its peripheral and arterial vasodilator properties is a nitro patch let's compare other peripheral vasodilators beta blockers and calcium channel blockers which act as peripheral vasodilators more distally in the arterial tree are not effective coronary vasodilators for anginal or ischemic attacks as they risk diverting blood from the ischemic area to the periphery this diversion of blood away from the coronary circulation is called by the term coronary steel anti-anginals restore the balance of myocardial oxygen supply and demand they also relieve and prevent angina and ischemic attacks as coronary vasodilators nitrates increase oxygen supply beta blockers and calcium channel blockers as peripheral vasodilators decrease afterload and thus decrease oxygen demand nitrates as peripheral vasodilators decrease preload and afterload and thus decrease oxygen demand let's review how nitrates affect oxygen supply and demand nitrates decrease oxygen demand by dilating veins resulting in decreased venous return preload ventricular wall stress workload and myocardial oxygen consumption nitrates dilate arteries resulting in less vasoconstriction decreased afterload blood pressure ventricular wall stress workload and myocardial oxygen consumption nitrates increase oxygen supply by dilating coronary arteries and thus increasing coronary artery perfusion and myocardial oxygen supply in summary nitrates decrease oxygen demand and increase oxygen supply this image summarizes the action of nitrates on oxygen supply and demand in the event of a patient with chest pain due to angina let's reflect on one of the things that makes nitrates different from other vasodilators why don't nitrates cause coronary steel during angina attacks while some other vasodilators do recall that coronary steel refers to diverting blood from the ischemic area to the periphery coronary steel happens when peripheral vasodilation occurs rather than coronary vasodilation nitrates are modest coronary vasodilators unlike calcium channel blockers and beta blockers which are predominantly peripheral vasodilators nitroglycerin and isosorbide are two types of nitrates nitrates are absorbed from the mucous membranes skin and gastrointestinal or gi tract nitroglycerin is the gold standard for acute angina attacks sublingual nitroglycerin spray and tablets have a half-life of a few minutes long but are converted to active metabolites that are longer acting isosorbidi nitrate and oral tablet is converted in the liver to active mononitrates that have a half-life of four to six hours half-life is the time required by the body tissue or organ to metabolize or inactivate half the amount of a substance taken in and is used in determining the dose and frequency of a drug in this slide you will see the different routes of nitroglycerin along with alternate generic names of the drug used in canada nitroglycerin can be administered as a spray a patch an iv infusion oral tablets sublingual tablets and an ointment adverse effects of nitrates include syncope and hypotension due to decreased preload and decreased afterload that can be worsened with consumption of alcohol and use of other vasodilator drugs tachycardia which is often a reflex to hypotension caused by vasodilation bradycardia occasionally in acute mi high-dose intravenous nitrates can induce heparin resistance headaches are common and can be treated by limiting the dose and often resolves with aspirin and facial fleshing sublingual nitrates may cause halitosis and nitroglycerin tablets lose potency if they are not kept in an airtight dark container continuous therapy and high dose frequent therapy can lead to tolerance of the nitrate drugs continuous administration of nitroglycerin in any form can result in tolerance within 24 to 48 hours in order to prevent this tolerance a nitrate-free interval is recommended a nitrate-free interval of 10-12 hours is needed to prevent tolerance and is usually at night for example ice or dill is given at 0 800 hours and 1300 hours and a nitro patch can be put on at 0 800 hours and removed at 200 hours contraindications for the use of nitrate therapy are hypertrophic obstructive cardiomyopathy also known as hcm or severe aortic stenosis acute inferior mi with right ventricular involvement as this decrease in filling pressures can lead to hemodynamic deterioration the use of viagra or other similar agents as it may lead to excessive hypotension or even acute mi cardiac tamponade constrictive pericarditis or tight mitral stenosis ms as those conditions are dependent on diastolic filling which may be worsened by the decrease in venous return and decreased preload glaucoma and severe hypotension nitrates are used in the treatment of unstable angina non-st elevated myocardial infarction and st elevated myocardial infarction these are all conditions which fall under the diagnosis of acute coronary syndrome and the form of acs depends on the degree of coronary obstruction and associated ischemia and symptoms for example a partially occlusive coronary thrombus typically causes unstable angina and n-stemi unstable angina has no necrosis or tissue death whereas n-stemi and stemi both have necrosis and tissue death in this slide we will discuss the typical angina procedure and the use of nitroglycerin when a patient experiences and complains of chest pain one to two sprays of nitroglycerin can be given every five minutes as needed up to a maximum of three sprays in 15 minutes first we check the pain scale from zero to 10 where 0 is no pain and 10 is the worst pain imaginable at this time nitro spray is given after 5 minutes we check the pain scale again and the blood pressure if the patient is still experiencing chest pain we apply low flow oxygen and can repeat nitrous spray at five minute intervals while checking blood pressure and the paint scale between each dose if the pain is not resolved within 15 minutes and after three doses it is a medical emergency if the patient is in the hospital we would call the doctor and if this patient was in the community we would call 9-1-1 further to this initial procedure and once the md has been notified a 12-lead ecg will be ordered to be performed stat or without delay blood work will also be ordered to test for heart cell death nitroglycerin can continue via continuous iv infusion at a dose of 5 micrograms per minute which can be further increased to achieve symptom control while maintaining a systolic blood pressure greater than 100 millimeters of mercury or as ordered by the physician at this time morphine may also be used for ongoing pain as a cardio cardiotechnologist this will be a common procedure you will witness and take part in let's review the kinetics of nitrates by thinking on this question why are patients told to take off their nitrate patches each night nitrate patches are taken off during the evening to allow for 10 to 12 hours of nitrate-free time to pass this is required to avoid a unique phenomenon known as nitrate tolerance and keep nitrate therapy effective for subsequent doses this brings us to the end of this presentation on nitrates [Music] you