Post on 14-Jan-2016
The physiology of edema.The physiology of edema.
Edema:Edema:
• The abnormal accumulation of fluid The abnormal accumulation of fluid in a specific organ vs generalized.in a specific organ vs generalized.
• In capillary: Balance between In capillary: Balance between hydrostatic pressure hydrostatic pressure and and oncotic oncotic (colloid osmotic) pressure.(colloid osmotic) pressure.
Hydrostatic pressure:Hydrostatic pressure:
• Intra-capillary vs interstitialIntra-capillary vs interstitial
• Capillary pressures vary:Capillary pressures vary:
• Nail bed capillaries: 32 mmHg at Nail bed capillaries: 32 mmHg at arteriolar end and 15 mmHg at venous arteriolar end and 15 mmHg at venous end. Mean 25 mmHg.end. Mean 25 mmHg.
• Hydrostatic pressure gradient:Hydrostatic pressure gradient:
• Intra-capillary hydrostatic pressure – Intra-capillary hydrostatic pressure – interstitial fluid hydrostatic pressureinterstitial fluid hydrostatic pressure
Interstitial hydrostatic Interstitial hydrostatic pressure:pressure:
• Varies from one organ to another:Varies from one organ to another:
• Subcutaneous tissue: Subcutaneous tissue: Subatmospheric (-2 mmHg)Subatmospheric (-2 mmHg)
• Liver, kidney: +Liver, kidney: +
• Brain: As high as 6 mmHgBrain: As high as 6 mmHg
Oncotic pressure:Oncotic pressure:
• Capillary wall usually impermeable to Capillary wall usually impermeable to plasma proteins and other colloids.plasma proteins and other colloids.
• Only water and small solutes cross Only water and small solutes cross capillary wall.capillary wall.
• Crystalloids vs colloidsCrystalloids vs colloids
• These colloids exert an osmotic These colloids exert an osmotic pressure of about 25 mmHg.pressure of about 25 mmHg.
• The colloid osmotic pressure due to The colloid osmotic pressure due to the plasma colloids=oncotic the plasma colloids=oncotic pressure.pressure.
Edema:Edema:
• Due to disturbance in hydrostatic Due to disturbance in hydrostatic and/or oncotic pressure between and/or oncotic pressure between intra-capillary and interstitial intra-capillary and interstitial component.component.
Organ specific:Organ specific:
• Brain: Cerebral edemaBrain: Cerebral edema
• Lung: Intra-alveolar=pulmonary edema, Lung: Intra-alveolar=pulmonary edema, intra-pleural=pleural effusionintra-pleural=pleural effusion
• Peritoneum=ascitesPeritoneum=ascites
• Severe generalized edema=anasarcaSevere generalized edema=anasarca
Reduced oncotic pressure:Reduced oncotic pressure:
• Reduction in production of colloids--- Reduction in production of colloids--- plasma proteins.plasma proteins.
• Liver failureLiver failure
• MalnutritionMalnutrition
• Increase in loss of colloids--- plasma Increase in loss of colloids--- plasma proteins.proteins.
• Nephrotic syndromeNephrotic syndrome
• Catabolic statesCatabolic states
Increase capillary hydrostatic Increase capillary hydrostatic pressure:pressure:
• Venous end: Heart failure, deep Venous end: Heart failure, deep venous thrombosis, superior vena venous thrombosis, superior vena cava obstruction etc.cava obstruction etc.
• Arterial end: Pre-capillary dilatation. Arterial end: Pre-capillary dilatation. Calcium channel blockers.Calcium channel blockers.
Increased interstitial oncotic Increased interstitial oncotic pressure:pressure:
• Lymphatic obstruction:Lymphatic obstruction:
• Primary vs secondary group.Primary vs secondary group.
Capillary leaks:Capillary leaks:
• Result of capillary damage:Result of capillary damage:
• Pleura: Infections, tumorsPleura: Infections, tumors
• Alveoli: Inhalation of noxious Alveoli: Inhalation of noxious substance, eg chlorine gas etcsubstance, eg chlorine gas etc
Diverse causes of edema:Diverse causes of edema:
• AnaemiaAnaemia
• HypothyroidismHypothyroidism
Hormones involved in Hormones involved in edema:edema:
• Renin angiotensin aldosterone Renin angiotensin aldosterone system: system: secondary secondary hyperaldosteronismhyperaldosteronism
• ADH (Vasopressin)ADH (Vasopressin)
• ANPANP
Clinical physiological approach Clinical physiological approach to edema:to edema:
• Hypervolemia:Hypervolemia:
• VsVs
• Normovolemia:Normovolemia:
Jugular venous pressure:Jugular venous pressure:
• Elevated Elevated andand pulsating: pulsating:
• =hypervolemia=hypervolemia
• Then edema:Then edema:
• Due to increased capillary hydrostatic Due to increased capillary hydrostatic pressure:pressure:
• Cardiac failure, or isolated RV (pulm Cardiac failure, or isolated RV (pulm HT)HT)
• Hypervolemia caused by transfusionHypervolemia caused by transfusion
Normal JVP:Normal JVP:
• UnilateralUnilateral• Unilateral increase in capillary pressureUnilateral increase in capillary pressure• Deep venous thrombosisDeep venous thrombosis• OR:OR:• Unilateral increase in interstitial colloid Unilateral increase in interstitial colloid
osmotic pressureosmotic pressure• Lymphatic obstruction (radiation, Lymphatic obstruction (radiation,
filariasis, congenital)filariasis, congenital)
• Edema due to capillary hypertension Edema due to capillary hypertension with normal venous pressure:with normal venous pressure:
• Pre-capillary dilatation:Pre-capillary dilatation:
• Calcium channel blockersCalcium channel blockers
Generalized edema without Generalized edema without hypervolemia:hypervolemia:
• Decreased capillary colloid oncotic pressure: Decreased capillary colloid oncotic pressure: liver, kidney, catabolic states, malnutrition.liver, kidney, catabolic states, malnutrition.
• Increased interstitial colloid oncotic Increased interstitial colloid oncotic pressure: lymphatic.pressure: lymphatic.
• Increase in capillary permeability: Increase in capillary permeability: Inflammation, toxins, severe anaemiaInflammation, toxins, severe anaemia
Pressure changes in the Pressure changes in the heart:heart:
• Atria: Study curve in Ganong: Atria: Study curve in Ganong: jugular venous pressure curvejugular venous pressure curve, , also known as also known as flobogramflobogram, indicative , indicative of pressure changes in superior vena of pressure changes in superior vena cava/ right atrium.cava/ right atrium.
• 3 waves in the curve:3 waves in the curve:
• a-wave: atrial systolea-wave: atrial systole
• c-wave: bulging of tricuspid valve c-wave: bulging of tricuspid valve into R atriuminto R atrium
• v-wave: rise in atrial pressure, just v-wave: rise in atrial pressure, just before tricuspid valve opens during before tricuspid valve opens during diastole.diastole.
• Clinical application of these 3 Clinical application of these 3 waves:waves:
• Sinus rhythm or not.Sinus rhythm or not.
• Pulmonary hypertensionPulmonary hypertension
• 3`rd degree heart block3`rd degree heart block
• Patency between SVC and RAPatency between SVC and RA
• Tricuspid regurgitation and stenosisTricuspid regurgitation and stenosis