Microcirculation/ESL

Question 1

What are the two main components of the Glycocalyx. Name examples for each component (2 and 4)

Answer 1

glycoproteins

proteoglycans
* syndecan
* glypican-1

glycosaminoglycans
* heparan-sulfate
* hyaluronan
* chondroitin
* dermatan sulfate

Question 2

What percentage of the plasma volume does the immobile perimeter constitute?

Answer 2

15%

Question 3

Explain the controversial “no absorption rule” of the new Starling principle

Answer 3

implies that the opposing oncotic pressure is the subglycocalyx space, which usually has a colloid osmotic pressure close to zero

this also implies that filtration occurs throughout the length of the capillaries

no reabsorption except for in severe capillary hydrostatic pressure drop, usually only filtration and lymph removes fluid lost

Question 4

Explain how the endothelial glycocalyx affects inflammation and vice versa

Answer 4

destruction of the glycocalyx removes its barrier and allows rolling and attachement of leukocytes –> release of inflammatory cytokines

inflammatory cytokines have direct shedding effects on GC –> exposure of adhesion molecules for leukocytes

Question 5

What are the 2 proposed mechnisms of IV fluids causing glycocalyx shedding

Answer 5

• dilute plasma protein levels - important for GC integrity
• increased BP –> natriuretic peptide release –> direct shedding effect on GC

Question 6

Explain videomicroscopic examination of the glycocalyx

Answer 6

sidestream darkfield microscopy –> measures prefused boundary region and immobile plasma edge –> can measure thickness of GC with this

Question 7

What is the range of microvascular hydrostatic pressure in different organs?

Answer 7

7-17 mm Hg

Question 8

What are approximate lymph to plasma albumin cc ratios?

Answer 8

0.8-0.9

Question 9

What is the reflection coefficient in the brain and liver sinusoids?

Answer 9

brain close to 1 - almost impermeable to protein

close to 0 - very permeable in liver sinusoids

Question 10

Name the modified Ohm’s law for lymphatic drainage

Answer 10

lymphatic drainage = [(interstitial pressure + lymphatic pump) - systemic venous pressure] / lymphatic vessel resistance

Question 11

List the 4 antiedematic changes that reduce further edema after an edematic insult

Answer 11

• upregulated lymphatic pump
• increased interstitial pressure - promotes outflow of lymph
• decreased interstitial colloid osmotic pressure
• increased transerosal flow

Question 12

What is edemagenic gain?

Answer 12

defines the sensitivity of tissue to further edemagenic insult e.g., fluid therapy

Question 13

Explain why septic patients are so much more susceptible to further edematic challenges (e.g., fluid bolus)

Answer 13

incrased intravascular pressure and surface area from vasodilation –> increaes microvascular permeability to protein –> increaes interstitial oncotic pressure pull

Question 14

Explain increased negativity of interstitial hydrostatic pressure

Answer 14

increaed negativity i.e., drop in interstitial pressure from loss of extracellular matrix skeleton build of collagen fibers and fibroblasts

destroyed by inflammation and immune-mediated disease