Edema: PDF Study Guide

Edema Definition: Edema is increased fluid in the interstitial tissue spaces or it is a fluid accumulation in the body cavities in excessive amount. Depending on the site, fluid accumulation in body cavities designated as: a) Hydrothorax – fluid accumulation in pleural cavity in a pathologic amoun...

Edema Definition: Edema is increased fluid in the interstitial tissue spaces or it is a fluid accumulation in the body cavities in excessive amount. Depending on the site, fluid accumulation in body cavities designated as: a) Hydrothorax – fluid accumulation in pleural cavity in a pathologic amount. b) Hydropericardium – pathologic amount of fluid accumulated in the pericardial cavity. c) Hydroperitoncum (ascites) – fluid accumulation in peritoneal cavity. d) Anasarca – is a severe & generalized edema of the body with profound subcutaneous swelling Mechanism of edema formation: Approximately 60% of the lean body weight is water, two-thirds of which is intracellular with the remainder in the extracellular compartment. Mechanisms of edema: Increased capillary pressure. Diminished colloid osmotic pressure. Lymphatic obstruction. Sodium retention Factors effecting fluid balance across capillary wall and interstitial spaces: 1. Hydrostatic pressure(HP): Pressure of plasma fluid or water, that normally about 32 mmHg at arterial side of capillary bed and 20 mmHg at venous side, Its push out flow of water into interstitial spaces carrying oxygen and nutrient for energy production to maintain health of cells, tissue and organs. 2. plasma oncotic pressure(OP), or plasma colloid pressure: pressure of plasma albumin that normally 25 mm Hg in both sides of capillary beds and it control the inflow of fluid from interstitial spaces into venous circulation carrying wastes products of energy metabolism ShowFigure Show: Starling Factors Red arrow: Capillary hydrostatic pressure (HP) push fluid to interstitial spaces Blue arrow: Capillary osmotic pressure OP) Return fluid to veins. Net loss or gain of fluid across the capillary bed zero. The excess fluid in the interstitial spaces is drained by the lymphatic vessels, and returning to the bloodstream via the thoracic duct. A. Causes of increase (HP): Increase fluid volume: 1. Localized: Inflammation, Venous obstruction 2. Generalized: Right side heart failure B. Causes of Decrease Oncotic pressure (OP): Decrease plasma protein (albumin), Due to: 1- decrease intake 2- decrease absorption 3- decrease synthesis : liver cirrhosis 4- Increase loss: Nephrotic syndrome , Ulcerative colitis , Burn  Classification of edema Three systems of Classification: 1. According to pathophysiological mechanism: a) Transudate: (Non-inflammatory) b) Exudate: (Inflammatory) 2) According to clinical finding: a) Pitting : (cardiac , renal , and liver) b) Non-pitting : (inflammatory and lymphatic). 3) According to site 1. Localized: A. Inflammatory (most common), and allergic (skin infection, insect bite) B. Non-inflammatory: 1. obstruction of Venous and Lymphatic drainage 2. Pulmonary edema of left side heart failure 2. Generalized: (Cardiac , Hepatic , Renal) edema. 1. Exudative edema (inflammatory edema): Usually localized edema related to local increases in hydrostatic pressure and/or vascular permeability causing exudation of plasma albumin (protein-rich edema), inflammatory cells and excess water, with specific gravity (>1.020). 2. Transudative edema: (Non-inflammatory edema); Systemic or localized edema result from increased hydrostatic pressure or decrease plasma osmotic pressure leads to a net accumulation of extravascular fluid (edema). It is protein-poor edema with specific gravity (