2Edema:The abnormal accumulation of fluid in a specific organ vs generalized.In capillary: Balance between hydrostatic pressure and oncotic (colloid osmotic) pressure.
3Hydrostatic pressure: Intra-capillary vs interstitialCapillary pressures vary:Nail bed capillaries: 32 mmHg at arteriolar end and 15 mmHg at venous end. Mean 25 mmHg.Hydrostatic pressure gradient:Intra-capillary hydrostatic pressure – interstitial fluid hydrostatic pressure
4Interstitial hydrostatic pressure: Varies from one organ to another:Subcutaneous tissue: Subatmospheric (-2 mmHg)Liver, kidney: +Brain: As high as 6 mmHg
5Oncotic pressure:Capillary wall usually impermeable to plasma proteins and other colloids.Only water and small solutes cross capillary wall.Crystalloids vs colloids
6These colloids exert an osmotic pressure of about 25 mmHg. The colloid osmotic pressure due to the plasma colloids=oncotic pressure.
7Edema:Due to disturbance in hydrostatic and/or oncotic pressure between intra-capillary and interstitial component.
16Clinical physiological approach to edema: Hypervolemia:VsNormovolemia:
17Jugular venous pressure: Elevated and pulsating:=hypervolemiaThen edema:Due to increased capillary hydrostatic pressure:Cardiac failure, or isolated RV (pulm HT)Hypervolemia caused by transfusion
18Normal JVP: Unilateral Unilateral increase in capillary pressure Deep venous thrombosisOR:Unilateral increase in interstitial colloid osmotic pressureLymphatic obstruction (radiation, filariasis, congenital)
19Edema due to capillary hypertension with normal venous pressure: Pre-capillary dilatation:Calcium channel blockers
20Generalized edema without hypervolemia: Decreased capillary colloid oncotic pressure: liver, kidney, catabolic states, malnutrition.Increased interstitial colloid oncotic pressure: lymphatic.Increase in capillary permeability: Inflammation, toxins, severe anaemia
21Pressure changes in the heart: Atria: Study curve in Ganong: jugular venous pressure curve, also known as flobogram, indicative of pressure changes in superior vena cava/ right atrium.3 waves in the curve:
22a-wave: atrial systole c-wave: bulging of tricuspid valve into R atriumv-wave: rise in atrial pressure, just before tricuspid valve opens during diastole.Clinical application of these 3 waves:
23Sinus rhythm or not.Pulmonary hypertension3`rd degree heart blockPatency between SVC and RATricuspid regurgitation and stenosis