Perfusion Study Guide - Concepts for Nursing Practice PDF

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Perfusion Unit Study Guide...

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PERFUSION refers to the flow of blood through arteries and capillaries delivering nutrients and oxygen to cells. It requires the heart to generate sufficient cardiac output to transport blood through patent blood vessels for distribution in tissues throughout the body. SCOPE Ranges from optimal to impaired to no perfusion. Changes in perfusion can be temporary, long term or permanent. Disorders that lead to changes in perfusion include acute conditions (such as myocardial infarction, stroke, or shock) chronic disorders (such as hypertension, heart failure, sickle cell, or hemophilia). Conditions that specifically involve perfusion include neurologic (interfering with blood flow within the brain), pulmonary (impairing blood flow to and from the lungs), and cardiovascular (interfering with blood flow in heart, arteries and veins). Causes of these disorders include congenital defects, genetic disorders, injury, inflammation, and infections. CENTRAL PERFUSION is generated by cardiac output—the amount of blood pumped by the heart each minute. Central perfusion propels blood to all organs and their tissues form patent arteries through capillaries and returns blood to the heart through patent veins. It begins when the heart is stimulated by an electrical impulse that originates from the sinoatrial (SA) node and travels to the atrioventricular (AV) node. From the AV node, the impulse moves through a series of branches (bundle of His) and Purkinje fibers in the myocardium, which causes the ventricles to contract. Systole is the phase of the cardiac cycle during which the ventricles contract. Cardiac output influences the heart rate. Increased volume in ventricles means a stronger contraction. Stroke volume is the amount of blood ejected from each ventricle during contraction. It is affected by three factors: preload, contractility, and afterload. Preload is the amount of blood in the ventricles at the end of diastole, called the end diastolic pressure. Contractility refers to the strength of myocardial contraction. The greater the volume of blood in the ventricles (preload), the greater the stretch of the myocardium, and the stronger the myocardial contraction. Afterload is the force the ventricles must exert to open the semilunar valves (aortic and pulmonic). It is influenced by resistance to the ejected blood created by the diameter of blood vessels receiving the blood, also called systemic vascular resistance (SVR). TISSUE PERFUSION Arterial blood pressure is determined by the cardiac output and SVR. When vascular injury occurs, a complex coagulation process involving platelets, and clotting factors work together to stop bleeding. Vasoconstriction reduces blood flow and allows the clotting process to start. Platelets are activated and stick to the injured blood vessel to form a platelet plug. Next, clotting factors are activated and proceed in a coagulation

cascade to the common final pathway where thrombin stimulates fibrinogen to form insoluble fibrin that stabilizes the clot. AGE RELATED DIFFERENCES INFANTS- In infancy, the size of the heart in relation to the total body size is larger. The systolic blood pressure after birth is low due to the weaker left ventricle of the neonate. The left side of the heart develops strength, and the systolic pressure rises rather sharply during the first 6 weeks. ADULTS- after puberty the systolic pressure rises to adult levels, the heart size increases, and arteries and veins lengthen to keep pace with growth. OLDER ADULTS- stiffening and thickening of the myocardial tissue and decreased elasticity of the arterial walls. The heart valves tend to calcify and become fibrose. Collectively these changes lead to reduced cardiac efficiency (decreased stroke volume and cardiac output) during exercise and with other factors contributing to increased oxygen demand. Arterial stiffening contributes to an increase in blood pressure. A decrease in blood pressure upon standing (orthostatic hypotension) may contribute to falls. The valves in the veins become less efficient contributing to lower extremity edema. Orthostatic hypotension is considered a FALL RISK. IMPAIRED CENTRAL PERFUSION Many conditions result in decreased cardiac output. Myocardial infarction, changes in myocardial conduction, ineffective heart valves and congenital defects. Impairment of central perfusion occurs in conditions that decrease cardiac output or cause shock. Any occlusion or constriction of coronary arteries that reduces blood flow to the myocardium can result in a myocardial infarction that decreases cardiac output. This impairment prevents the myocardium from performing the mechanical function of pumping blood to the body. IMPAIRED TISSUE PERFUSION Interference with tissue perfusion reduces blood flow through capillaries reducing delivery of oxygen, fluid, and nutrients to cells. Some organs, such as the brain and intestines, require larger volumes of blood compared to skeletal tissue, for example. Inadequate tissue perfusion can result from poor central perfusion or from a mechanism within the vessel or organ itself, such as a blocked or narrowed blood vessel leading to or from the tissue or from excessive edema within the tissue interfering with the cellular oxygen exchange. Impairment of tissue perfusion is associated with occlusion, constriction, or dilation of arteries or veins as well as blood loss. Atherosclerosis or thrombi can occlude arteries (which reduce the blood flow to tissues) and thrombi can occlude veins (which interrupt the return of blood to the heart). Vasoconstriction can result in hypertension, which increases the risk for stroke or myocardial infarction. ISCHEMIA- is a reversible cellular injury that occurs when the demand for oxygen exceeds the supply because of a reduction or cessation of blood flow. When ischemia is prolonged, it may result in a lack of oxygen to tissues followed by necrosis and irreversible cellular injury.

RISK FACTORS OLDER ADULTS- Coronary artery blood flow, stroke volume, and cardiac output decrease, increasing the risk for heart failure. Also, the stiffening and thickening of the heart tissues decreases the ability to respond to the need for increased circulation and prolongs the time needed for the heart to return to a resting state after stress. Decreased elasticity of arteries limits the consistent forward movement of blood to organs. The valves in veins become less efficient, contributing to peripheral edema, and the sluggishness of blood flow contributes to deep vein thrombosis. Low income and low educational level are contributing factors. Social and psychological factors such as access to healthcare, medical compliance, eating habits, depression, and stress also play a role. Individual Risk Factors for Impaired Perfusion Modifiable Risk Factors • Smoking: Nicotine vasoconstricts • Elevated serum lipids: Contribute to atherosclerosis • Sedentary lifestyle: Contributes to obesity • Obesity: Increases risk for type 2 diabetes mellitus and atherosclerosis • Diabetes mellitus: Increases risk of atherosclerosis • Hypertension: Increases work of myocardium

Unmodifiable Risk Factors • Age: Increases with age • Gender: Men > women • Genetics: Family history

Assessment Health Assessment Questions Cardiovascular Focus • Are you having chest pain? If so, rate it on a scale of 0 to 10. • How long have you had the pain? • Is the pain located in one area, or does it radiate to other areas? • Do activities or medications make it worse or better? • Are symptoms such as shortness of breath or sweating associated with the pain? • Do you have increased fatigue? • Have you had recent weight gain? • Have you had changes in skin texture, color, or temperature? • Do you take medications that prevent blood clots? • Have you had sores on your lower extremities that have not healed? • Have you had episodes of dizziness or loss of consciousness? • Do you have other chronic diseases? Pulmonary Focus • Have you had breathing difficulties when you are exercising or at rest? • Have you had a loss of appetite, weight loss, or weakness? • Have you ever smoked? • If so, are you still smoking, or did you quit smoking? • How many packs per day (ppd)? • Do you sleep on one or more pillows?

• How much do you exercise? • Do you have wheezing, pain with breathing, or difficulty clearing your secretions? • Have you had asthma, bronchitis, or other lung diseases in the past? • Do you use oxygen at home? • What type of work have you done, and were you exposed to hazardous materials? • Do you have anxiety related to your breathing condition? • Do you have a cough? For how long? • Are you coughing anything up? Color of sputum? • Is it worse when you lie down? VITALS Including blood pressure while lying, sitting and standing, apical and peripheral pulses. Assess the skin, anterior chest and neck for symmetry, color. Ulcers, if skin is pale and lacks hair, redness, increased circumference of extremities. Auscultate for normal heart sounds, Base (2nd intercostal), Apex (5th intercostal). Listen for S1 and S2. Listen to Aortic, pulmonic, tricuspid and mitral. DIAGNOSITIC TESTS CBC, (RBC, HGB, HCT) understand lipids, coagulation and platelet count, PRIMARY- BOX 18.1 Giddens, healthy diet, physical activity, no smoking, normal blood pressure, normal weight. SECONDARY- Blood pressure screening TERITARY- treat the cause. PHARMACOTHERAPY- aspirin NURSE ROLES- Assess capillary refill, reposition patient, medication administration, stockings, cardiac monitoring....