Chapter 15: Alterations in Blood Flow (Updated Summer 2020) PDF

Chapter 15 Alterations in Blood Flow Dr. Tashea S. Hilliard, Associate Professor Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Learning Objectives 1) Explain how arterial and venous obstructions...

Chapter 15 Alterations in Blood Flow Dr. Tashea S. Hilliard, Associate Professor Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Learning Objectives 1) Explain how arterial and venous obstructions develop. 2) Identify the clinical consequences of acute and chronic arterial obstruction. 3) Identify the clinical consequences of superficial and deep venous obstructions. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow ► Reduction in flow impairs ability to transport gases and nutrients to body tissues resulting in: ► Hypoxia ► Ischemia ► Venous engorgement ► Venous obstruction Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Blood Vessels: Obstructions ► May involve arterial or venous system ► Obstruction results in reduced flow beyond the obstruction (downstream) and increased pressure before the obstruction (upstream) ► In the arterial system obstruction manifests as distal ischemia, in the venous system obstruction manifests as edema Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Thrombosis ► Thrombus: a stationary blood clot formed within a vessel or a chamber of the heart ► Causes: blood flow slows dramatically, becomes more turbulent, if there is damage to intimal walls or drugs ► Arterial thrombosis results in ischemia ► Venous thrombosis results in edema. ► Inflammation in a vein: phlebitis ► Inflammation with a clot in a vein: thrombophlebitis Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Thrombosis ► Clinical manifestations ► Arterial: intermittent claudication, cool, cyanotic, painful ulcer around one toe ► Venous: none or life threatening (pulmonary embolism), calf/groin tenderness, swelling, + Homan’s sign ► Prophylactic interventions include oral/parenteral anticoagulant therapy, or drugs that block platelet activation/aggregation. Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Thrombosis ► Once a thrombus has formed, anticoagulant therapy is initiated to prevent clot enlargement. ► May need thrombolytic drugs ► Additional medical prophylactic interventions: antiembolic stockings or sequential compression devices, ambulation as soon as possible ► Another option: surgery to remove thrombus Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Embolus ► Can be called thromboembolus ► Material that forms a clot within the bloodstream; traveling clot ► Embolus leaving L ventricle = ischemic stroke ► Differ depending on brain area affected, loss of cognitive function, motor changes, and different levels of sensory loss Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Embolus ► Embolus leaving R ventricle = pulmonary embolus ► Vague, nonspecific; most common: sudden onset of shortness of breath, increased respiratory rate, chest pain, sudden death ► Treatment: embolectomy (for thromboemboli) or a filter in the inferior vena cava (Greenfield filter) Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Vasospasm ► Sudden constriction of arterial smooth muscles resulting in obstruction of flow ► May be mediated by hormonal changes, food additives, or environmental factors ► Manifestations include: ► Prinzmetal angina ► Hemorrhagic stroke ► Migraine headaches Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Inflammation ► Can increase risk of thrombotic process ► Vasculitis—inflammation of the intima of an artery ► Phlebitis—inflammation of the lining of a vein ► Arteritis—inflammatory process of autoimmune origin in arteries Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Mechanical Compression ► External forces to the vascular system may result in partial or complete obstruction ► May be caused by: ► Trauma ► Tight casts, dressings, or stockings ► Compartment syndrome Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Blood Vessels: Structural Alterations ► Types of structural alterations ► Valvular incompetence ► Arteriosclerosis/atherosclerosis ► Aneurysms ► Arteriovenous fistulas Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. General Mechanisms That Cause Altered Flow (Cont.) Lymphatic Vessels ► Changes in capillary or interstitial oncotic pressure increase filtration into tissues resulting in edema ► Lymphedema results from impairment in the circulation of lymph Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow Alterations in arterial flow result from: ► Obstruction ► Arteriosclerosis/atherosclerosis ► Inflammation ► Vasospasm ► Thrombi/emboli ► Acute occlusion ► Mechanical alterations ► Arteriovenous fistulas ► Aneurysms Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Arteriosclerosis/Atherosclerosis ► Includes three pathologic processes: ► Mönckeberg sclerosis ► Arteriolar sclerosis ► Atherosclerosis ► Underlying pathologic condition leading to hypertension, cardiac and renal disease, peripheral arterial disease, and stroke ► Identification and interventions directed toward modifiable risk factor reduction Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Arteriosclerosis/Atherosclerosis ► Atherosclerosis ► Low-density serum lipoproteins breach intimal layer; leukocytes and endothelial cells oxidize the lipids, producing further damage. ► Simultaneously, platelets aggregate at the site; release platelet-derived growth factor (PDGF); stimulates growth of smooth muscle cells. ► Media smooth muscle cells, normally confined to the other tunicas, were drawn to the intima where they proliferate. Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Arteriosclerosis/Atherosclerosis ► Atherosclerosis ► Result: atherosclerotic plaque, primarily composed of smooth muscle cells, lipoproteins, and inflammatory debris ► Plaques slowly enlarge, the orifice of the artery is decreased, and perfusion is diminished. ► Can lead to hypertension, cardiac (CAD) and renal disease, peripheral arterial disease, stroke and myocardial infarction Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Arteriosclerosis/Atherosclerosis ► Identification and interventions directed toward modifiable risk-factor reduction ► Tobacco ► Injures endothelium ► Elevates LDL, cholesterol, triglycerides ► Decreases HDL ► Produces vasospasms ► Increases platelet aggregation ► Increases BP and heart rate ► Increases risk of coronary heart disease (CHD) ► Cessation of smoking ► 50% risk reduction for CHD (1 year) ► Risk for CHD same as nonsmokers (10 years) Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Arteriosclerosis/Atherosclerosis ► Identification and interventions directed toward modifiable risk-factor reduction ► Hypertension: increases risk ► Cholesterol, lipoproteins, and triglycerides ► Excess cholesterol acts as irritant causing plaque formation ► High levels of LDL promote atherosclerosis ► High levels of HDL inhibit atherosclerosis ► Glucose intolerance/metabolic syndrome and diabetes: increase risk ► Obesity: accelerates atherosclerotic process Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Arteriosclerosis/Atherosclerosis ► Identification and interventions directed toward modifiable risk-factor reduction ► Physical activity ► Increase HDL levels, collateral circulation, and vessel size ► Decrease total cholesterol levels, glucose intolerance, body weight, and blood pressure ► Stress and mental health ► Stress and depression increase risk ► Nonmodifiable risk factors ► Age, gender, family history of CAD, ethnicity Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Arteriosclerosis/Atherosclerosis ► Diagnosis ► Doppler flow ► Plethysmography ► Ankle-brachial index ► Exercise/Stress test ► Angiography ► First-line treatment: nonpharmacologic interventions such as weight reduction, smoking cessation, exercise, and low-fat diet ► If not successful: drug therapy added ► Surgery: balloon/laser angioplasty, stents, CABG Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Thromboangiitis Obliterans (Buerger Disease) ► Rare inflammatory condition affecting small and medium-size arteries and veins of upper and lower extremities resulting in varying degrees of obstruction ► Treatment entails smoking cessation (if applicable) and use of prostaglandins Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Raynaud Syndrome ► Extreme vasoconstriction producing cessation of flow to fingers and toes ► Intrinsic structural factors, extrinsic neuroregulation, and locally produced mediators are involved ► Treatment directed toward enhancing circulation through biofeedback, relaxation, calcium-channel blockers, sympatholytic drugs, and prostaglandins Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Aneurysms ► Localized arterial dilations ► Classified as true or false aneurysms ► Frequently found in cerebral circulation and thoracic and abdominal aorta ► Dissecting aortic aneurysms are a medical emergency and treated medically and/or surgically Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Classification of Aneurysms Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.  Alterations in Arterial Flow (Cont.) Aneurysms ► Clinical manifestations ► Cerebral: increasing intracranial pressure, hemorrhagic stroke ► Aortic: sudden severe tearing pain, radiates into back/abdomen, shock ► Tests ► Cerebral: CT, MRI, cerebral angiography ► Aortic: CT, TEE ► Dissecting aortic aneurysms: medical emergency; treated medically and/or surgically ► Vasodilators, graft Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow Acute Arterial Occlusion ► Absence of arterial circulation—emergency ► May result from thrombi/emboli or mechanical compression ► Classic signs and symptoms (6 Ps) ► Pallor ► Paresthesia ► Paralysis ► Pain ► Polar ► Pulseless Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Arterial Flow (Cont.) Acute Arterial Occlusion ► Treatment ► Loosen tight dressing ► Cut cast ► Anticoagulant therapy ► Thrombolytic therapy ► Bypass surgery ► Embolectomy ► Amputation Copyright © 2019, Elsevier Inc. All rights reserved. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Venous Flow ► Incompetent valves (obesity, pregnancy, right heart failure, prolonged standing) producing varicose veins, chronic venous insufficiency, and obstruction by deep vein thrombosis ► Accompanied by edema, venous stasis ulcers, and pain ► Deep vein thrombosis can be life threatening Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Venous Flow (Cont.) Valvular Incompetence ► Overstretching of the valves owing to excessive venous pressures resulting in backflow of blood ► Results in: ► Venous insufficiency ► Varicose veins ► Treatment is directed toward smoking cessation and regular exercise Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Venous Flow (Cont.) Varicose Veins ► Impaired venous return results in increased capillary pressure causing edema, and superficial, darkened, raised, and tortuous veins ► Greater saphenous vein most commonly affected ► Treatment directed toward increasing venous flow and reducing venous pressure; sclerotherapy and surgical interventions may be used for severe cases Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Venous Flow (Cont.) Chronic Venous Insufficiency ► Results when valvular incompetence involves the deep veins ► Venous stasis ulcers are typically present ► Venous ulcers treated with compression therapy and infection control Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Venous Flow (Cont.) Deep Vein Thrombosis ► Most frequently due to thrombus in a deep vein of the lower extremity ► May be asymptomatic ► Treated aggressively with anticoagulation therapy ► Previous DVT is a risk factor for further hypercoagulation Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Lymphatic Flow Lymphedema ► Occurs when normal flow is obstructed or altered in some fashion ► Primary lymphedema due to congenital anomaly or dysfunction of the lymphatic system ► Secondary lymphedema associated with a disease process or iatrogenic Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Alterations in Lymphatic Flow (Cont.) Lymphedema ► Typically affects extremities ► Interventions are medical (external compression therapy and exercise) and surgical (resection of subcutaneous fatty tissue) Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.