Colloids

Duane J. Funk MD FRCP(C)
What this talk will hopefully accomplish
• What is a colloid?
• How do colloids work?
• How do the colloids differ?
• Are there any bad effects?
What are we going to talk about
• Physiology of fluid movement
• Types of fluids and distribution
• Physiology of Colloids
• Some of the controversies
My last day in the OR
• 80kg, 40 year old male, traumatic fall, compartment syndrome and ‘smashed ankle’.
• Here for a free flap.
• Cases starts at 0730. ends at 2130.
How much fluid should I give him?
• Have to account for several factors:
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Deficit
Maintenance
3rd space losses
Blood loss
How do you calculate this?
• 4‐2‐1‐ rule gives you maintenance rate.
• 4cc/kg/hr for the 1st 10kg
• 2cc/kg/hr for the 2nd 10kg
• 1cc/kg/hr for every kg above 20kg
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40cc + 20cc + 60 cc= 120cc/hr maintenance.
Assume 8 hours of fasting, so 1L deficit.
14hr Surgery x 120cc/hr= 1700cc
3rd space losses=6700cc
Blood loss 1000cc=4000cc cryst.
Total=13,400cc
The next day
Does it matter at all?
Why give fluids?
Reduced
Reduced Circulating
Circulating Volume
Volume
Inadequate
Inadequate Tissue
Tissue Perfusion
Perfusion
Gut Mucosal Barrier Disruption
Translocation of Bacteria/Endotoxin
Activation
Activation of
of Inflammatory
Inflammatory Pathways
Pathways
MODS
MODS
What’s the downside?
What’s the downside?
What’s the downside?
Complications
Hypovolemic
Optimal
Overloaded
Volume Load
Physiology of fluid movement
• How does the fluid get to where we don’t want it?
• Governed by starling forces
Volumes of body fluid compartments
Distribution of various solutions
Plasma Volume Expansion=
Volume of compartment Infused into
Volume of Distribution
For Example
• Infuse 1L of D5W
• It distributes evenly throughout fluid compartments
So 3L
≅ 7%PVE
45L
• Infuse 1L of NaCl
3L
≅ 20%PVE
15L
• Infuse 1L of colloid
3L
≅ 100%PVE
3L
Why use a colloid?
Less volume
Longer lasting
‘Suck fluid’ from the interstitium
Able to replace blood volume 1:1 versus 3:1 or 4:1
• Associated with better outcomes
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Why wouldn’t you use a colloid?
• Expense
• Bleeding risk
• Risk of adverse renal outcomes
• Not a believer
What kind of colloids are there?
Synthetic Colloids
Produced by hydroxyethylating maze.
Synthetic Colloids
Synthetic Colloids
® 450/0.6
• 6% Hespan
6% • 6% Hextend® 670/0.7
• 10% Pentaspan® 260/0.45
• 6% Haes‐Steril® 200/0.5 • 6% Voluven® 130/0.4
Classification of Colloids
• Concentration
• Molecular weight
• Degree of Substitution
• C2:C6 ratio
Concentration
• In Canada, 10% and 6% solutions available.
• 10% Solution is Hyperoncotic, 6% isooncotic.
What does oncotic refer to?
• Oncotic pressure or colloid osmotic pressure
• The pressure required to prevent the movement of small ions and solvent.
• Normal in plasma is ~25mmHg.
• Pentaspan 80mmHg
• Voluven 36mmHg
• 25% HSA 80mmHg
What do all the numbers mean?
264/0.45/13
First Number: Molecular Weight
• HES are ploydisperse substances.
• They contain a distribution of molecular weights.
• The number on the package is the average.
•After infusion the molecules are broken down by endo‐
amylases.
•If their size is below the renal threshold, they are excreted.
•Hydroxyethylation slows down the rate of breakdown.
• Low MW solutions have more molecules per volume.
• This gives them a greater oncotic effect.
• Also gives them less persistence in plasma.
• Contrast this with larger molecules.
Second number: Molar substitution
• This is where the drugs derive their name.
• 0.6 = Hextend
• 0.5 = Pentaspan
• 0.4 = Voluven (a tetrastarch)
Second number: Molar substitution
• Proportion of the carbon atoms that are hydroxyethylated.
• Expressed as a number from 0 to 1.
• Most starches are substituted in the C2 or C6 position.
Third Number: C2:C6 ratio
• Refers the the proportion of molecules that are hydroxyethylated at the C2 vs he C6 position.
• A higher C2:C6 ratio results in longer intravascular half life.
Adverse effects of colloids
• Hemostatic
• Dermatologic
• Renal
Hemostatic Effects
Hemostatic Effects
• Seems to be more pronounced with the slowly degraded starches.
• Predominant effect is on vWF:VIII.
• Some platelet effects, but these are non‐
significant.
Hemostatic Effects
• We’re Ok using Pentaspan, Voluven.
• There is a dilutional effect, but this is only relevant at very high doses. Hemostatic Effects
• Dinosaur Starches are associated with bleeding, the newer ones aren’t.
Hemostatic Effects
• Numerous studies have shown no change in bleeding with the newer starches.
• (Chest tube losses, coagulation factors, TEG).
Renal Effects
Renal Effects
Renal Effects
• The starch was 240/0.6
• Similar but different.
• Probably not the best group to test your hypothesis in.
Renal Effects
What does VISEP answer?
• What happens when you give a toxic dose of a drug?
•This wasn’t Pentaspan or Voluven.
•10% 200/0.5 (Hemohes).
•It was a hyperoncotic
solution.
•This drug can accumulate in plasma.
• The dose was as high as 500‐750cc/day.
Good thing 25% Albumin is OK!!
Albumin in the critically ill
Albumin in the critically ill
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Cochrane review in 1998 of the 30 trials of albumin involving over 1400 patients
6 additional deaths for every 100 patients treated.
•Randomized patients to either 4% albumin or abnormal saline.
Not so good for the brain!
Not so good for the brain!
DON’T MINIMIZE THE EFFECT OF HYPERONCOTIC SOLUTIONS!
• PEff= (Pcap –PBow ) ‐ Ppla
Remember, it’s 25% Albumin
• Hyperoncotic albumin has been known to be a cause of renal failure since the 1980s.
• Using a hyperoncotic solution with little crystalloid may be bad.
Albumin
10 Commandments of Fluids
D5W and D5 ½ NS have no role in resuscitation.
Crystalloids have an ephemeral intravascular presence.
Normal Saline is not Normal.
Colloids are drugs, and have a dosage and side effects.
Aim for a balanced resuscitation.
Blood transfusions are bad, but anemia might be worse.
Your average, stable ICU patient is (almost) NEVER hypovolemic.
VIII. There is no role for ‘maintenance fluids’ for patients on full tube feeds.
IX. Positive fluid balance is associated with worse outcomes.
X. Don’t covet my slides. I.
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