Pathophysiology of Congestion and Oedema Flashcards
<p>What is meant by congestion?</p>
<p>•Relative excess of blood in vessels of a tissue or organ</p>
<p>Describe the nature of congestion (active or passive)?</p>
<p>Passive, acute inflammation is acive</p>
<p>What are clinical examples of congestion?</p>
<p>•Local acute congestion</p>
<p>–Deep vein thrombosis</p>
<p>•Local chronic congestion</p>
<p>–Hepatic cirrhosis</p>
<p>•Generalised acute congestion</p>
<p>–Congestive cardiac failure</p>
<p>Why does DVT in the leg cause congestion?</p>
<div>•Blood backs up in veins, venules, capillaries</div>
<div>• Reduced outflow of blood</div>
<div>• local, acute congestion</div>
<div>• Reduced pressure gradient</div>
<div>•Reduced flow across system (by Darcy's law)</div>
<div>•No O2 - ischaemia and infarction</div>
<p>What does hepatic cirrhosis result from?</p>
<p>•Serious liver damage eg HBV, alcohol</p>
<p>How does hepatic cirrhosis result in local chronic congestion?</p>
<p>Regenerating liver forms nodules of hepatocytes surrounded by fibrous tissue (fibrosis)</p>
<p>Loss of normal architecture (inherrent loss of function) - altered hepatic blood flow</p>
<p>Portal blood flow blocked:</p>
<ol> <li>Congestion in portal vein branches</li> <li>Increased portal venous pressure</li> <li>Collateral circulation - several sites anastomose with systemic circulation</li></ol>
<p>Local chronic congestion - haemorrhagic risk.</p>
<p>What is the risk of local chronic congestion?</p>
<p>Haemorrhagic risk</p>
<p>Portal - systemic shunts (shunt between the portal vein which carries blood from the intestines to the liverand the hepatic vein which carries blood from theliverback to the heart.)</p>
<p>What is the root cause of congestive heart failure?</p>
<p>•Heart unable to clear blood, right & left ventricles</p>
<p>Caused by ineffective pump eg ischaemia, valve disease</p>
<p>How does congestive heart failure result in an increase in the overall amount of fluid in the body</p>
<p><strong>Reduced cardiac output</strong></p>
<p><strong>Reduced GFR </strong></p>
<p>- activating•renin-angiotensin-aldosterone system (perhaps by renal baroreceptors or reduced sodium concentration detected by macula densa)</p>
<p>- Incrase in sodium and H2O retention</p>
<p>Increasing the amount of fouid in the body</p>
<p>•Fluid (overload) in veins (Treatment: diuretics)</p>
<p>What are the effects of congestive cardiac failure?</p>
<p>Back pressure - blood dammed back in the veins</p>
<p>•Lungs - pulmonary oedema</p>
<p>–Left heart failure – blood dams back into lungs</p>
<p>–Clinically, crepitations in lungs, tachycardia</p>
<p>•Liver - central venous congestion</p>
<p>–Right heart failure- blood dams back to systemic circulation</p>
<p>– JVP, hepatomegaly, peripheral oedema</p>
<p>What is the oxygen supply of pericentral and periportal hepatocytes like?</p>
<p>Pericentral - stasis of poorly oxygenated blood. Red in colour</p>
<p>Periportal - Better oxygenated due to proximity of hepatic arterioles</p>
<p>What balances the hysrostatic pressure from the heart in the microcirculation?</p>
<p>Osmotic pressures and endothelial permeability</p>
<p>Where does filtration from capillary beds go?</p>
<p>To the interstitium</p>
<p>What is Oedema defined as?</p>
<p>Accumulatiuon of abnormal amounts of fluid in the extravascular compartment</p>
<p></p>
<p>–intercellular tissue compartment (extracellular fluid)</p>
<p>–body cavities</p>
<p>What is meant by peripheral oedema?</p>
<p>Increasedinterstitial fluid in the tissues</p>
<p>What are effusions?</p>
<p>Fluid collections in the body cavities.</p>
<p>- Pleural, pericardial, joint effusions</p>
<p>Abdominal cavity - ascites</p>
<p>What is the aetiology of transudates?</p>
<p>•Alterations in the haemodynamic forces which act across the capillary wall</p>
<p>•Cardiac failure, fluid overload</p>
<p>Describe the components of transudates</p>
<p>Lots of H2O and electrolytes</p>
<p>Not much protein/albumin</p>
<p>Low specific gravity</p>
<p>What is the aetiology of exudate?</p>
<p>Part of the inflammatory process due to increase in the vascular permeability</p>
<p>Tumour, inflammation, allergy</p>
<p>Describe the components of exudates</p>
<p>Higher protein/albumin content</p>
<p>H2O and Electrolytes</p>
<p>High specific gravity</p>
<p>How does left ventricular failure result in pulmonary oedema (transudate)?</p>
<p>There is a resultant increase in left atrial pressure - <u>passive retrograde flow</u> to the pulmonary veins, capillaries and arteries</p>
<p>Increase pulmonary vasculature pressure</p>
<p>Increase in pulmonary blood volume</p>
<p>Increase in filtration and pulmonary oedema</p>
<p>What happens to the alveoli when there is pulmonary oedema? Caused by perivascular interstitial transudate</p>
<p>Progressive oedematous widening of the alveolar septa</p>
<p>Accumulation of oedema fluid in the alveolar spaces</p>
<p>What is the aetiology of peripheral oedema?</p>
<p>Right heart failure - cannot empty right side in systole</p>
<p>Blood retained in systemic veins - increase in the pressure in capillaries - increase filtration and therefore peripheral oedema</p>
<p>What is congestive heart failure?</p>
<p>RIght and left heart failure at the same time</p>
<p>Pulmonary oedema and peripheral odema at the same time</p>
<p></p>
<p>What causes lymphoedema?</p>
<p>Blockage of the lymphatic system, can stem from radiotherapy where potential damage to the lymph may occur, specifically breast cancer</p>
<p>How does abnormal renal function result in oedema?</p>
<p>•Abnormal renal function results in Salt (NaCl) and H2O retention</p>
<p>•Secondary in heart failure - reduced renal blood flow</p>
<p>•Primary: acute tubular damage eg hypotension (as a result of shock or blood loss)</p>
<p>Decrease in renal function is the result of both</p>
<p>Increase insalt and H2O</p>
<p>Increase in intravascular fluid volume</p>
<p>Resulting inoedema</p>
<p>What are the causes of low protein oedema?</p>
<p>Nephrotic syndrome: leaky renal glomerular basement membrane; lose protein; generalised oedema</p>
<p>Hepatic cirrhosis: diffuse fibrosis in liver, liver unable to synthesis enough protein</p>
<p>Malnutrition - insufficient intake or protein</p>
<p>How does permeability oedema arise?</p>
<p>Endothelal permeability increases so (excudate)</p>
<p>Damage to the endothelial lining resulting in pores in the membrane</p>
<p>Proteins and larger molecules can leak out</p>
<p>Results from acute inflammation such as pneumonia</p>
<p>Results from burns</p>
