2008B06 Outline the ideal properties of a colloid intravenous fluid.
Give examples of colloids and briefly describe the features of each.

 

List:

·         Colloid

·         Ideal colloid

·         Albumin

·         Gelofusin

·         Starches

·         Dextrans

 

Colloid solution:

·         Contains large particles (>30kDa) dispersed through solution, not dissolved

·         Doesn’t pass through semi-permeable membranes

·         Used for plasma volume expansion especially following haemorrhage

 

Ideal colloid:

PC

·   Synthetic

·   Cheap

·   Can be stored in PVC

·   Long shelf life

·   Isotonic

·   Iso-oncotic

·   Low viscosity

·   Causes no change in pH

·   No infection risk

·   No damage if extravasated

PK

·   Distributes almost entirely in plasma, low VD

·   Long plasma expansion time e.g. hours

·   Metabolised readily but slowly

·   Organ-independent metabolism

·   No toxic metabolites

·   Metabolites can be recycled

·   No products requiring renal elimination

PD

·   No renal failure

·   No coagulopathy

·   No interference with blood grouping

·   Improves microcirculatory flow

·   No anaphylaxis

·   No acid-base disturbance

·   No immune dysfunction

 

Albumin: e.g .4%

PC

·  Blood product

·  MW 66,000 Da

·  Produced by donation -> fractionation -> pasteurization

·  Alb 40g/L, Na+ 140mM, Cl- 128mM, octanoate 6.4mM

·  Osmolality 260mOsm/L, oncotic pressure 20-30mmHg

·  pH 7

PK

·  70-100% infused vol into plasma

·  Duration of expansion 12-24 hours

·  Metabolised and recycled by liver

·  t1/2β 20 days in body

PD

·  Uses: hypoalbuminaemia, hypovolaemia

·  Unclear benefit over crystalloids in many circumstances

·  Worse outcome in traumatic brain injury

·  Theoretical risk of infection

·  Risk of anaphylaxis

 

Gelofusin:

PC

·  Succinylated bovine gelatin

·  Gelatin 40g/L 9mmol/L, Na+ 154mM, Cl- 120mM

·  MW 35,000 Da

·  Osmolality 283mOsmol/L i.e. isotonic

·  Cheap

·  Long shelf life

·  Cattle bone -> hydrolysis, thermal degradation, cross-linking

PK

·  70-100% infused vol into plasma

·  Duration 8-12 hours

·  20% metabolized by peptidases

·  80% excreted in urine

PD

·  Anaphylaxis risk

 

Starches:

PC

·  Branched glucose polymer

·  Hydroxyl-substituted amylopectin

PK

·  100% infused vol into plasma

·  Duration 12-36 hours (longest)

·  Metabolism: amylase!

·  Elimination: urine (small particles), bile and faeces (medium), reticuloendothelial system (large)

PD

·  Increases risk of renal failure and mortality in unwell patients

·  Rarely used at present

 

Dextrans:

PC

·  Branched polysaccharides

·  High molecular weight

·  Preduced by recombinant technology

PK

·  100% infused vol into plasma

·  Duration 6-8 hours

·  Renal elimination

PD

·  Improves microcirculatory flow

·  Can cause coagulopathy

·  Impairs blood grouping

·  Most likely to cause anaphylaxis

 

 

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