- High molecular weight substances.
Desirable properties of plasma expander:
- Should exert oncotic pressure comparable to plasma.
- Should remain in circulation and not leak out in tissues, or be too rapidly disposed of.
- Should be pharmacodynamically inert.
- Should not be pyrogenic or antigenic.
- Should not interfere with grouping and cross-matching of blood.
- Should be stable, easily sterilizable & cheap.
- Primarily as plasma substitutes –
- Mainly in conditions where plasma is lost or moved to extravascular compartment.
- E.g. in burns (acute phase only), hypovolemic, endotoxin shock, severe trauma & extensive tissue damage.
- Severe anemia
- Heart failure
- Pulmonary edema
- Liver & kidney failure.
Substances used as plasma expanders:
- Albumin, Dextran, Polygeline & Hetastarch.
- Does not interfere with blood grouping or coagulation.
- Free of hepatitis transmission risk (as it is heat treated).
- Highly expensive.
- In hypovolemia
- Most commonly used plasma expanders.
- Interferes with blood grouping, coagulation & platelet function.
- Reduces blood viscosity.
- Decreases rouleau formation.
- Improves microcirculation.
- Longer-acting (24 hours)
- Rapid but short-acting.
- Has thromboprophylactic (anti-thrombotic) effect.
- Provides temporary improvement in patient’s ischaemic foot through intravenously.
- Degraded gelatin polymer.
- Polypeptide with average MW 30,000.
- Exerts oncotic pressure similar to albumin.
- Not antigenic.
- More expensive than dextran.
Uses: For priming of heart-lung & dialysis machines.
Adverse effects: Hypersensitivity reactions like flushing, rigor, urticaria, wheezing & hypotension.
- Complex mixture of ethoxylated amylopectin of various molecular sizes.
- Average MW 4.5 lac (range 10,000 to 1 million).
- Smaller molecules (MW < 50,000) are excreted renaly.
- Larger molecules are slowly broken down to smaller ones.
- Incompatible with many drugs
- Non-injectable drug is added to infusion.
- Plasma volume expands slightly in excess of infused volume.
- Colloidal properties of 6% hetastarch approximate human albumin.
- Blood grouping & cross matching may be vitiated.
- Used to improve harvesting of granulocytes – As it accelerates erythrocyte sedimentation.
- Hemodynamic status improved for 24hrs or more.
- Plasma expanders are high molecular weight substances.
- Plasma expanders are primarily used as plasma substitutes, mainly in burns (acute phase only), hypovolemic, endotoxin shock, severe trauma & extensive tissue damage.
- Substances used as plasma expanders are Albumin, Dextran, Polygeline & Hetastarch.
- As a plasma expander albumin are used in hypovolemia, burns, shock & hypoalbuminemia.
- Dextran is the most commonly used plasma expander.
- Dextran reduces blood viscosity, decreases rouleau formation & improves microcirculation.
- Dextran-40 has thromboprophylactic (antithrombotic) effect.
- Polygeline is a degraded gelatin polymer, used as plasma expander.
- Polygeline exhibits hypersensitivity reactions like flushing, rigor, urticaria, wheezing & hypotension.