Glyceryl Trinitrate Case Study Biology Essay


Pharmacology is a multidisciplinary division of medical science which involves examining the effect of drugs on biological system. It includes the study of the manner in which the function of living tissues and organisms is modified by chemical substances and the study of the effect of chemical agents on living processes . It is fascinating to develop knowledge on how drugs exert their effect on physiological systems. Drugs do not create new responses but affects the already existing functioning of the body. Pharmacology is commonly subdivided into pharmacodynamics (the biological effects of drugs) and pharmacokinetics (absorption, distribution, metabolism and excretion), also expressed as the effects of drugs on the body and the effect of the body on drugs . Studying about drugs enables a nurse to administer drugs aptly, recognise adverse reactions and appreciate the impact of the treatment on the client. Nurses having a sound knowledge of pharmacology is self-evident since nurses perform key roles in the implementation and evaluation of drug therapy, and provide client medication education .

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The heart is a vital organ in the human body, responsible for pumping blood throughout the coronary arteries and body tissues by rhythmic contractions in an organized manner. Coronary heart disease is the leading cause of disability and death . A diseased heart requires pharmacological intervention to sustain life. This assignment is a case study of a client who is prescribed with Glyceryl trinitrate; a vasoactive agent which is administered to reduce myocardial oxygen consumption, which decreases ischaemia and relieves pain. This essay gives a brief overview of the client heath history, a description of action of Glyceryl trinitrate and its effect on the various body systems and systemic approach physical assessment findings observed as a result of client taking this drug.

Mr. A is a 28 year old Indian male, admitted to the Coronary Care Unit, Labasa Hospital at 0500hrs on 07/04/2011 with a chief complain of central chest pain which was squeezing in nature, it was associated with profuse sweating and severe feeling of nausea for 3 hours. Electrocardiographic (ECG) changes are typical ST elevation in leads II, III and AvF. Laboratory investigations done showed cardiac enzyme increase after six hours. He has been diagnosed with Acute Inferior Wall Myocardial Infarction (MI). Mr. A was treated with Tab Glyceryl trinitrate 0.6mg sublingual p.r.n.

Mr. A is lean built, 170cm tall and weighs 60kg. Past medical history is not of relevance. His family history is evident of father and paternal grandfather being hypertensive whereas his maternal side of the family do not have any medical history. In his social history client is a school teacher by profession. He denies any use of tobacco, kava or drug use. He occasionally takes alcohol. He takes a 30 minute physical exercise daily. He is unmarried. Currently he is sexually active.

Objective data; Mr. A is of medium height and of slim built. Vital sign; BP: 125/76mm of Hg, pulse rate of 78 per minute, temperature of 36 degrees Celsius and respiratory rate of 20 per minute. Skin is warm to touch, no cyanosis. Level of consciousness; alert and oriented to time, place and people. Lung fields are clear and air entry is normal bilaterally, breath sounds normal. Cardiovascular system; no visible pulsation, thrills or heaves detected. S1 and S2 heard. Peripheral pulses felt bilaterally, no edema or cyanosis noted. Gastrointestinal tract; no trouble in swallowing, abdomen is soft and non tender on palpation, no mass felt. Genitourinary tract: nil abnormalities detected. Musculoskeletal system: normal muscle mass, good tone and gait.

Myocardial Infarction (MI) refers to a dynamic process by which one or more regions of the heart muscle experience a severe and prolonged decrease in oxygen supply because of insufficient coronary blood flow, subsequently leading to necrosis or "death" to the myocardial tissue . MI is often due to rupture of an atherosclerotic plaque, vasospasm of coronary arteries resulting in an increased demand for oxygen and less supply. Pain is the cardinal symptom of MI, is due to the accumulation of lactic acid as a result of anaerobic respiration by the cardiac muscles during ischemia, which may irritate the nerve endings and may radiate to the arm, shoulder jaw or back as the same nerve fiber is covering this area (Farrell, & Dempsey, 2011). But breathlessness, vomiting and collapse or syncope is also are common features of MI . Chest pain is often described as a tightness, heaviness or constriction in the chest. At its worst the pain is one of the most severe which can be experienced and the patient's expression and pallor may vividly convey the seriousness of the situation .

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Sublingual Glyceryl Trinitrate (GTN) administered as a 600µg tablet, allowed to dissolve under the tongue or crushed and retained in the mouth will usually relieve anginal attack in 2-3 minutes . This area of the mouth has a large supply of blood vessels which allows the medication to be absorbed rapidly. Heslett, Chilvers,Hunter and Boon state that sublingual GTN has a short duration of action which lasts 4 to 8 minutes at its peak. The duration of action may last for 10 to 30 minutes. GTN is subject to extensive first-pass metabolism in the liver so it is virtually ineffective when swallowed.

GTN is a prodrug which must first be denitrated to produce the active metabolite the nitric oxide (NO), a neurotransmitter also called endothelium-derived relaxing factor. NO is naturally produced by the body and has the effect of relaxing and dilating the smooth muscles primarily the veins and in higher doses also dilates the arteries (Farrell, & Dempsey, 2011). Dilatation of the veins causes venous pooling of blood throughout the body and less blood returns to heart to pump (preload). Nitrate also increases the blood flow to the coronary arteries and through collateral arteries which are underused until the body recognizes poorly perfused areas. These effects deceases the myocardial oxygen demand and increases the oxygen supply, which decrease ischemia and relieves pain. Glyceryl trinitrate relaxes smooth muscle throughout the body. In the vascular system it acts chiefly on the systemic veins and the large coronary arteries .

Effects of GTN on the body system include headache, hypotension and infrequently syncope. To avoid these symptoms the tablet may be spat out as soon as the pain is relieved. GTN should be used with caution in clients with decreased kidney and liver function, hypothyroidism, hypothermia, malnutrition and clients with low oxygen level in their blood may be due to lung disease. GTN should not be used in clients with nitrate allergy, hypotension, hypovolemia, constrictive pericarditis, cardiac tamponade, mitral valve stenosis, aortic stenosis, hypertrophic obstructive cardiomyopathy, head injury, cerebral haemorrhage, closed angle glaucoma, severe anaemia and in children (Netdoctor, 2007). Before administering the drug a good medical history needs to be obtained, the vital signs obtained and special consideration needs to be taken to inform patient not to swallow the tablet. GTN must not be used together with vasodilators that combat erectile disfunction, such as Viagra. The combination of the two can lead to severe hypotension, circulatory collapse and death (Lehne, 2004).

Adverse Effect of GTN in the central nervous system includes dizziness and headache due to cerebral vasodilation and dose dependence. In cardiovascular system tachycardia, postural hypotension and flushing could happen. Nausea and vomiting are possible in gastrointestinal system and contact dermatitis in integumentary system due to hypersensitivity to nitric compounds. Erythema, pruritus, burning and irritation may occur at the site of administration (Netdoctor, 2007).

Mr. A was reassessed after two days of admission: General Survey; patient lying comfortably is bed with no obvious signs of distress. Vital signs within the normal limits, temperature of 36 degrees Celsius, pulse of 78 beats per minute, respiratory rate of 20 per minute and blood pressure of 120/70 mm of Hg thus suggesting no hypotension. Mental status: alert, relaxed and cooperative. Thought process coherent. Oriented to time, place and person. Appropriate affect, mood and behaviour. Pupilary reaction normal. Extraocular muscle movement typical.

Skin warm and dry. No rash, echimosis, cyanosis, petechiae or signs of bleeding. Normal capillary refill. The head, eyes, ears, nose and throat had no changes. Examination of sclera showed no abnormalities. Thorax is symmetric with good lung expansion. Breath sounds were normal. Cardiovascular system; the jugular venous pulse above the sterna angle with the head of bed elevated to 300. Carotid upstroke are brisk without bruits At the left midclavicular line, the point of maximal impulse of tapping was felt. S1and S2 was normal with no murmurs or extra sounds. Rhythm on cardiac monitor was regular, showing ST elevation but no tachycardia.

Abdomen was soft, non tender, no mass felt with active bowel sounds. Liver span of 8cm, the edge is smooth. Spleen and kidneys could not be felt. No costovertibral angle tenderness. Patient is not having any nausea or vomiting. He is on low fat, low cholesterol diet and is tolerating meals well. He has normal bowel sounds and movements, Opened bowel once after admission. Passing urine well. Musculoskeletal good range of movements in all the joints, no swelling noted. On complete bed rest. No allergic reaction visualized on the skin. Laboratory investigations were within the normal range except for the cholesterol and triglyceride which were raised. Cardiac enzymes were raised after 6 hours of chest pain due to myocardial necrosis. ECG tracing was regular with reduced ST elevation in the inferior leads as compared with the initial ECG.

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Mr A's daily medication included Tab Aspirin 150 mg OD, Tab Isordil 10mg tds, Injection morphine 2.5mg p.r.n, Inj Maxalon 10mg p.r.n, and Injection Clexane 80mg s.c BD. Since Admission Mr. A had three episodes of chestpain which subsided within twenty minutes of taking tab GTN 600µg. Reflecting on his physical assessment after two days, Mr. A did not develop any side effect of the drug including the most common ones such as headache, dizziness and hypotension. This indicates an effective management of chest pain with the use of GTN.

In conclusion, a nurse should possess sufficient pharmacological knowledge in order to care for a hospitalized client in attaining a maximum recovery. All health professionals have segmental roles towards client management but the nurse is at the bedside more than the other health personals, therefore possessing detailed pharmacological and physical assessment is important. Such capability will help a nurse to provide holistic care to the client, encourage critical thinking and provide rationale for patient care.