Colloids (Lanaux) Flashcards

1
Q

Fliud compartments

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

Which is most permeable part of vasculature?

A

Capillaries

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3
Q

Permeability

Intravascular space

A
  • Conducting vessels relatively impermeable
    • Arteries, Arterioles
    • Venules Veins
  • Capillaries
    • Semipermeable membrane
      • water
      • small ions (Na+, K+, Cl-)
      • Small molecules
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4
Q

Permeability

Intracellular space

A
  • Phospholipid bilayer
    • Semipermeable
      • water
      • glucose - facilitated diffusion
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5
Q

Colloids

A
  • 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
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6
Q

Volume of distribution

A
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7
Q

Volume of distribution

A
  • 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
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8
Q

J

A
  • transcapillary fluid flux
    • net movement of fluid into interstitium
    • returned to systemic circulation via lymphatics
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9
Q

K

A
  • Filtration coefficient
    • correlates to permeability of the vessel
    • varies along circulatory system
    • arteries and veins less permeable than capillaries
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10
Q

reflection coefficient (omega?!?!)

A
  • 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
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11
Q

Starling forces and dz states

A
  • changes in filtration and reflection coefficients
    • difficult to predict pharmacokinetics of colloids in vivo
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12
Q

Colloid osmotic pressure (COP)

A
  • 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

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13
Q

Normal COP

A
  • Dogs
    • 15.3 to 26.3 mmHg
  • Cats
    • 17.6 to 33.1 mmHg
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14
Q

Proposed benefits of colloids

A
  • Longer Intravascular effects
  • smaller volume requriements for intravascular expansion
  • Less dilutional coagulopathies
  • dec tissue edema formation
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15
Q

Pharmacology of colloids

A
  • Size of particle is unimportant
    • Na is as imp as albumin
  • large molecules persist in the circulation longer
  • Charge is important
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16
Q

Gibbs-Donnan effect

A
  • Electroneutrality must be maintained
  • Large proteins
    • negatively charged
    • nondiffusible across semipermeable membrane
  • Draws posibitve ions across membrans
  • Increases COP by 7-8 mmHg
17
Q

Types of Colloids

A
  • Natural colloids
    • Albumin
    • Blood products
  • Synthetic colloids
    • hydroxyethyl starch
    • gelatin
    • dextran
18
Q

Natural colloids

A
  • Albumin products
    • human albumin 5% and 25%
    • lyophilized canine albumin
  • Fresh frozen plasma
  • Whole blood
19
Q

Albumin

A
  • 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
20
Q

Lyophilized canine albumin

A
  • purified canine albumin
  • sold as 5 gram vials
  • adverse reactions less frequent and less sever than huma albumin in dogs
  • not currently available
21
Q

Human albumin

A
  • 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
22
Q

Blood products

A
  • Fresh frozen plasma
  • Whole blood
    • weak colloids
    • used primarily for replacement of clotting factors
      • patients with coagulopathy
23
Q

normal amount albumin in a patient

24
Q

Synthetic colloids

A
  • Starches
    • hetestarch
    • pentastarch
    • tetrastarch (voluven)
  • Gelatines
  • Dextrans
25
Adverse Effects
* acute renal failure * anaphylaxis * volume overload * coagulopathy * immunosuppresion
26
Hydroxyethyl starch | (Hetestarch)
* Primary synthetic colloid used in vet med * Polydisperse solutions * many sized particles * reported molecular weight is calculated based on different particle sizes and distribution
27
Hydroxyethyl starch
* Described by * molecular weight * degree of substitution * proportion of glucose moieties that have been substituted with hydroxyethyl groups * ranges from 0-1
28
Hydroxyethyl starch
* 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
29
Hydroxyethyl starch Reported adverse reactions
* Reported adverse reations * acute renal failure * anaphylaxis * immunosuppression * volume overload * coagulopathy
30
**Which has the greater correlation wtih negative effects on coagulation?** ## Footnote **A. Degree of substitution** **B. Molecular weight**
* A. Degree of substitution
31
Hydroxyethyl starches and coagulation
* 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
32
Hetestarch recommendations
* 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
33
Voluven
* 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)
34
Colloidsd and COP * Hetestarch 6% * Volvulen * Human albumin 5% / 25% * Canine fresh frozen plasma
* 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
35
Monitoring colloid therapy
* CS: clinical response * what is HR, BP * Can you stabilize them * Can do COP but most people don't have one
36
Effect of HES
* osmalality and specific gravity probably won't correlate in presence of large molecules
37
Summary WHAT TO KNOW
* 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