Colloids (Lanaux)

Question 1

Fliud compartments

Answer 1

• Intracellular (2/3)
• Extracellular (1/3)
  
  • Intravascular (1/5)
    
    • Plasma
  • Extravascular (4/5)
    
    • interstitial

Question 2

Which is most permeable part of vasculature?

Answer 2

Capillaries

Question 3

Permeability

Intravascular space

Answer 3

• Conducting vessels relatively impermeable
  
  • Arteries, Arterioles
  • Venules Veins
• Capillaries
  
  • Semipermeable membrane
    
    • water
    • small ions (Na+, K+, Cl-)
    • Small molecules

Question 4

Permeability

Intracellular space

Answer 4

• Phospholipid bilayer
  
  • Semipermeable
    
    • water
    • glucose - facilitated diffusion

Question 5

Colloids

Answer 5

• Fluids that contain large, insoluble molecules that don’t freely cross a semipermeable membrane
• Act to hold water within the vascular space for longer than crystalloids

Question 6

Volume of distribution

Answer 6

Question 7

Volume of distribution

Answer 7

• Directly related to plasma volume expansion
  
  • saline approx 20% of infused volume
    
    • rest diffuses out to interstitial space
  • Colloid theoretically 100% of infused volume
    
    • varies by type of colloid

Question 8

J

Answer 8

• transcapillary fluid flux
  
  • net movement of fluid into interstitium
  • returned to systemic circulation via lymphatics

Question 9

K

Answer 9

• Filtration coefficient
  
  • correlates to permeability of the vessel
  • varies along circulatory system
  • arteries and veins less permeable than capillaries

Question 10

reflection coefficient (omega?!?!)

Answer 10

• Degree to which membrane prevents transfer of colloid molecules
• value between 0 and 1
  
  • 0 indicates free passage
  • 1 indicates no passage
• The lower the value the less effect colloid will have on fluid dynamics

Question 11

Starling forces and dz states

Answer 11

• changes in filtration and reflection coefficients
  
  • difficult to predict pharmacokinetics of colloids in vivo

Question 12

Colloid osmotic pressure (COP)

Answer 12

• pressure exerted by large molecules
  
  • don’t leave vasculature easily in health
  • hold water within vascular space
• albumin major contributor (80%)

*COP measured using colloid osmometer

Question 13

Normal COP

Answer 13

• Dogs
  
  • 15.3 to 26.3 mmHg
• Cats
  
  • 17.6 to 33.1 mmHg

Question 14

Proposed benefits of colloids

Answer 14

• Longer Intravascular effects
• smaller volume requriements for intravascular expansion
• Less dilutional coagulopathies
• dec tissue edema formation

Question 15

Pharmacology of colloids

Answer 15

• Size of particle is unimportant
  
  • Na is as imp as albumin
• large molecules persist in the circulation longer
• Charge is important

Question 16

Gibbs-Donnan effect

Answer 16

• Electroneutrality must be maintained
• Large proteins
  
  • negatively charged
  • nondiffusible across semipermeable membrane
• Draws posibitve ions across membrans
• Increases COP by 7-8 mmHg

Question 17

Types of Colloids

Answer 17

• Natural colloids
  
  • Albumin
  • Blood products
• Synthetic colloids
  
  • hydroxyethyl starch
  • gelatin
  • dextran

Question 18

Natural colloids

Answer 18

• Albumin products
  
  • human albumin 5% and 25%
  • lyophilized canine albumin
• Fresh frozen plasma
• Whole blood

Question 19

Albumin

Answer 19

• uniform size
  
  • > 95% of particles have weight of 69 kDa
  • only monodisperse colloid known
• Highly preserved across species
• Accounts for 80% of colloid osmotic pressure in health
• Carrier molecule
  
  • divalent cations (Ca²⁺ and Zn²⁺)
  • hormones
  • drugs
• Maintain oncotic pressure
• coagulation and inflammation
• role in healing

Question 20

Lyophilized canine albumin

Answer 20

• purified canine albumin
• sold as 5 gram vials
• adverse reactions less frequent and less sever than huma albumin in dogs
• not currently available

Question 21

Human albumin

Answer 21

• Human albumin 5% and 25%
• May be used in critically ill patients
• Adverse reactions
  
  • Anaphylaxis
  • Delayed hypersensitivity reactions
• never admin to a healthy patientf
  
  • ​Sever anaphylaxis
  • Delayed hypersensitivity reactions
  • death
• never give to a patient that had human albumin in the past

Question 22

Blood products

Answer 22

• Fresh frozen plasma
• Whole blood
  
  • weak colloids
  • used primarily for replacement of clotting factors
    
    • patients with coagulopathy

Question 23

normal amount albumin in a patient

Answer 23

3-4g/dL

Question 24

Synthetic colloids

Answer 24

• Starches
  
  • hetestarch
  • pentastarch
  • tetrastarch (voluven)
• Gelatines
• Dextrans

Question 25

Adverse Effects

Answer 25

• acute renal failure
• anaphylaxis
• volume overload
• coagulopathy
• immunosuppresion

Question 26

Hydroxyethyl starch

(Hetestarch)

Answer 26

• Primary synthetic colloid used in vet med
• Polydisperse solutions
  
  • many sized particles
  • reported molecular weight is calculated based on different particle sizes and distribution

Question 27

Hydroxyethyl starch

Answer 27

• Described by
  
  • molecular weight
  • degree of substitution
    
    • proportion of glucose moieties that have been substituted with hydroxyethyl groups
      
      • ranges from 0-1

Question 28

Hydroxyethyl starch

Answer 28

• 6% hetastarch in 0.9% saline
  
  • molecular weight = 670kDa
  • DS = 0.75
• 10% pentastarch
  
  • molecular weight = 200kDa
  • DS = 0.5
• 6% Tetrastarch (volvulen)
  
  • molecular weight = 130 kDa
  • DS = 0.4

*I think degree of substitution is related to potential adverse effects

Question 29

Hydroxyethyl starch

Reported adverse reactions

Answer 29

• Reported adverse reations
  
  • acute renal failure
  • anaphylaxis
  • immunosuppression
  • volume overload
  • coagulopathy

Question 30

Which has the greater correlation wtih negative effects on coagulation?

A. Degree of substitution

B. Molecular weight

Answer 30

• A. Degree of substitution

Question 31

Hydroxyethyl starches and coagulation

Answer 31

• Higher degree of substitution corelates to greater negative effect on coagulation
• Interferes with factor VIII and von Willebrand factor
  
  • leads to plately dysfunction
• May also be incorporated into fibrin clot
  
  • weakens clot

Question 32

Hetestarch recommendations

Answer 32

• Higher degree of substitution
  
  • greater adverse effect on coagulation
• Daily recommended max dose is 20 mL/kg
  
  • admined as 2-5 mL/kg IV bolus
  • unclear if CRI is efficacious
• Larger molecules persist in vasculature longer
  
  • minimal effect due to much fewer numbers of large molecules

Question 33

Voluven

Answer 33

• 130/0.4
  
  • lesser degree of substitution
    
    • minimal effect on coagulation
  • Daily max dose 40 mL/kg
    
    • admined as 2-5 mL IV boluses
  • shorter half-life than Hetastarch (16 vs 46 hours)

Question 34

Colloidsd and COP

• Hetestarch 6%
• Volvulen
• Human albumin 5% / 25%
• Canine fresh frozen plasma

Answer 34

• Hetestarch 6%: 32.7 +/- 2%
• Volvulen: 37.1 +/- 0.8
• Human albumin 5% / 25%: 23.2 +/- 0.1/ > 200
• Canine fresh frozen plasma: 17.1 +/- 0.6

Question 35

Monitoring colloid therapy

Answer 35

• CS: clinical response
  
  • what is HR, BP
  • Can you stabilize them
• Can do COP but most people don’t have one

Question 36

Effect of HES

Answer 36

• osmalality and specific gravity probably won’t correlate in presence of large molecules

Question 37

Summary

WHAT TO KNOW

Answer 37

• Know characteristics of maintenance fluid vs Replacement fluids
  
  • resembles plasma
  • lower sodium
  • higher potassium
• Know examples of replacement fluids
  
  • LRS
  • 0.9% saline
  • Normosol R
• Be aware of adverse effects and such