II. Definitions
- Colloid Solution
- Solution with incompletely dissolving particles, which create an osmotic force and attract water
III. Background
- Normal fluid state (maintained capillary plasma volume)
- Normal capillary hydrostatic pressure varies between 10 mmHg (near arteries) and 30 mmHg (near veins)
- Normal capillary osmotic pressure is 28 mmHg (primarily due to albumin), favoring fluid shift into capillaries
- Abnormal fluid states with capillary fluid loss and Interstitial Edema (e.g. Hypoalbuminemia)
- Fluid Shifts to interstitial space as capillary pressure exceeds capillary osmotic pressure
- Fluid effects
- Crystalloid infusions further decrease capillary osmotic pressure, increasing interstitial fluid
- For every liter of isotonic crystalloid infused, only 275 ml remains intravascularly
- Colloid fluid infusion related increased osmotic pressure either maintains capillary volume or increases it
- For every liter of colloid infused, only 700 ml remains intravascularly (~3 fold more than crystalloid)
- Crystalloid infusions further decrease capillary osmotic pressure, increasing interstitial fluid
IV. Preparations: Albumins
- Background
- Heat sterilized human Serum Albumin
- Albumin is preferred over other Colloid Solutions
- Albumin 5%
- Dose: 250 ml aliquot (expands plasma volume ~250 ml/aliquot)
- Osmotic pressure 20 mmHg
- Expands plasma volume 0.7 to 1.3 times the volume infused (maintained for up to 12 hours)
- May be beneficial in Fluid Replacement (e.g. Sepsis)
- Avoid in Traumatic Brain Injury
- Albumin 25%
- Dose: 50-100 ml aliquot (expands plasma volume 4 fold, with fluid pulled from intersitium)
- Osmotic pressure 70 mmHg (hyperoncotic)
- Limit to hypoalbuminemic states (NOT Hypovolemic Shock) due to Fluid Shifts out of interstitium
- Increased risk of Renal Failure and death in Hypovolemia
- Schortgen (2008) Intensive Care Med 34:2157-68 +PMID:18685828 [PubMed]
V. Preparations: Hydroxyethyl Starch (HES)
- Background
- Synthetic polysacharide chains resistant to enzymatic degradation
- Precautions
- Increased risk of Bleeding Diathesis (Factor 7 and vWF inhibition)
- Increased Nephrotoxicity Risk
- Hetastarch (5%)
- Osmotic pressure 30 mmHg
- Expands plasma volume 1.0 to 1.3 times the volume infused (maintained for up to 24 hours)
VI. Preparations: Dextran
- Background
- Precautions
- Increased risk of Bleeding Diathesis (Factor 7 and vWF inhibition), esp. at doses >20 ml/kg
- Increased Nephrotoxicity Risk
- Risk of Adverse Drug Reactions
- High rates of Anaphylaxis with older preparations (now rare)
- Dextran-40 10%
- Osmotic pressure 40 mmHg (hyperoncotic)
- Expands plasma volume 1.0 to 1.5 times the volume infused (maintained for up to 6 hours)
- Dextran-70 6%
- Osmotic pressure 40 mmHg (hyperoncotic)
- Expands plasma volume 1.0 to 1.5 times the volume infused (maintained for up to 12 hours)
VII. Precautions
- Do NOT use hyperoncotic Colloid Solutions in hypovolemic states
- Increased risk of Renal Failure and death as Fluid Shifts from the interstitium
VIII. Contraindications
-
Traumatic Brain Injury
- Colloid Solutions are associated with increased mortality compared with crystalloid
- (2007) N Engl J Med 357:874-84 +PMID:17761591 [PubMed]
IX. Advantages
- Most colloid infused remains in the intravascular space for hours
X. Disadvantages
- Risk of sensitivity reactions
- Original studies in 1998 showed increased mortality with Colloid Solutions
- However, more recent studies have reestablished the safety of Colloid Solutions (e.g. 5% Albumin)
- (2004) N Engl J Med 350:2247-56 [PubMed]
XI. References
- Loflin (2015) Crit Dec Emerg Med 29(9): 11-18
- Marino (2014) ICU Book, p. 227-37