Lec5-6 Hemodynamics Flashcards
Distribution of water in body– percent of body mass? Intracellular vs interstitial vs intravascular?
Body is 60% water by mass:
40% intracellular [in cell]
15% intercellular or interstitial [between cells]
5% intravascular [in blood vessels]
Normal plasma osmolality? Major osmole? Osmolarity intracellular vs intercellular vs intravascular?
280 mosm/L
major osmole is sodium
electrolytes, glucose, proteins, urea also contribute
Intravascular, interstitial, intracellular spaces always have equal osmolarity
Osmosis– definition? 2 requirements for osmosis to occur?
Fluid moves from one chamber to equalize osmotic gradient
2 requirements:
1. driving force [difference in osmolarity]
2. semipermeable membrane
Water and molecule movement and distributions – what can move where (between intracellular, intercellular, intravascular?
- water moves freely between intravascular, interstitial, intracellular so always equal osmolarity
- small solutes move through clefts in blood vessel endothelium between intravascular and interstitial [together = extracellular] so always same concentration of small solutes
- small solutes can’t pass through cell membrane so have conc. gradient between intra and extracellular
- large molec [proteins] and cells do not move freely, trapped inside cell or inside intravascular space so get concentration gradients
Effect of half normal vs normal saline fluid on hypotensive patient
Half normal: decreases osmolarity of intravascular space, so water moves to intracellular/intrerstitial space to equalize osmotic pressure, all 3 spaces expand a little
Normal: osmolarity of intravascular stays the same, water and electrolytes move to interstitial to equalize concentration gradient, extracellular spaces expand [by more than for half normal]
Normal saline = better treatment for increasing intravascular volume
Starling’s Equation
Jv = Kf * [(Pc + Πi) – (Πc + Pi)]
- Jv = fluid movement in ml/min
- Kf = hydraulic conductance, easyness of getting out of tube
- Filtration [movement out] = (Pc + Πi)
- Pc = outward hydrostatic P by blood in capillary
- Πi = outward oncotic P by proteins in interstitium
- Absorption [movement in] = (Πc + Pi)
- Πc = inward oncotic P by proteins in capillary
- Pi = inward hydrostatic P by interstitium
How does fluid end up in wrong place? [4 Mech]
When filtration > absoprtion
- low Πc: hypoalbuminemia, lose protein in urine
- – nephrotic syndrome, hepatic cirrhosis, malnutrtion [kwashiokor] - high Pc: heart failure
- – right sided = peripheral edema
- – left sided = pulmonary edema - high Kf: sepsis and inflammation
- – capillary leak syndrome in meningitis - lymphatic impairment [from surgery, mechanical]
- – increased interstitial fluid
- – increased Πi
Cause/effect of low capillary oncotic pressure
caused by hypoalbuminemia = losing protein in urine
get more filtration than absorption, fluid leaves intravascular = edema
Cause/effect of high capillary hydrostatic pressure
caused by heart failure
- right sided heart failure –> peripheral edema
- left sided heart failure –> pulmonary edema
Cause/effect highly permeable blood vessels
- High Kf [hydraulic conductance] due to sepsis and inflammation
- ex. capillary leak syndrome in meningitis
Cause/effect impaired lymphatics
- due to surgery or mechanical reason
- extra filtrate in interstitial space can’t get returned to circulatory system
- get increased interstitial fluid
- get increased Πi
Definition of Edema
- Too much interstitial [intercellular] fluid
- Can be localized or generalized
- different from hydropic change/cell swelling which is intracellular edema
Definition of Anasarca
generalized edema
Definition of Effusion
type of edema - excess fluid in body cavity
Definition of Hydrothorax
- Pleural Effusion
- Excess free fluid in pleural cavity
Causes of Transudate
- high intravascular hydrostatic P [high Pc]
- – cardiac/vascular problem, deep vein thrombus, congestive heart failure
- low intravascular osmotic P [low Πc]
- – low plasma protein, nephrotic syndrome, chronic liver disease, protein malnutrition
- Lymphatic obstruction [high Πi]
- – inflammation, post-surgical, tumor
- Excess body fluid due to Na retention in setting of renal dysfunction
- increase Na intake –> retention water
What is Dependent pitting edema? Exudate or transudate? 3 main Causes?
- swelling occurs underneath skin usually in arms/legs/ankles, can be depressed
- transudate edema
- due to congestive heart failure, pulmonary edema, renal disfunction
What is Hemostasis? Functional components?
Arrest of hemorrhage in response to vascular injury Functional components: - blood coagulation - platelet aggregation - endothelial cell interaction
What is Hemorrhage
bleeding, escape of blood from vessels
What is a Hematoma
localized collection of blood [usually clotted] within tissue or space
What is Thrombosis
Active process of transformation flowing liquid blood to semisolid in heart/vessel of living organism
What is a Thrombus
coagulated blood containing platelets, fibrin, entrapped cellular elements
Blood coagulation pathway steps
- vessel severed/injured
- plasma in vessel contacts tissue factor [TF]
- TF binds factor VII and activates it
- active VIIa-TF complex activates factor X
- Xa converts prothrombin –> thrombin and fibrinogen to fibrin
- VIIa-TF activates IX to amplify thrombin generation through intrinsic pathway
Fibrinolysis controls size of thrombus
What is Tissue Factor
extrinsic to blood, plays key role in initiating coagulation