Plasma Expanders

PLASMA EXPANDERS


PLASMA EXPANDERS

Introduction:

  • 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.

Uses:

  • 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.

Contraindications:

  • Severe anemia
  • Heart failure
  • Pulmonary edema
  • Liver & kidney failure.

Substances used as plasma expanders:

  • Albumin, Dextran, Polygeline & Hetastarch.

Individual substances:

1. Albumin:

  • Does not interfere with blood grouping or coagulation.
  • Free of hepatitis transmission risk (as it is heat treated).
  • Highly expensive.

Uses:

  • In hypovolemia
  • Burns
  • Shock
  • Hypoalbuminemia.

2. Dextran:

  • Most commonly used plasma expanders.
  • Interferes with blood grouping, coagulation & platelet function.
  • Reduces blood viscosity.
  • Decreases rouleau formation.
  • Improves microcirculation.

Dextran-70:

  • Longer-acting (24 hours)

Dextran-40:

  • Rapid but short-acting.
  • Has thromboprophylactic (anti-thrombotic) effect.
  • Provides temporary improvement in patient’s ischaemic foot through intravenously.

3. Polygeline:

  • 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.

4. Hetastarch:

  • 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.

Uses:

  • Used to improve harvesting of granulocytes – As it accelerates erythrocyte sedimentation.
  • Hemodynamic status improved for 24hrs or more.

Exam Important

PLASMA EXPANDERS

  • 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.

 

Don’t Forget to Solve all the previous Year Question asked on PLASMA EXPANDERS

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