Plasma Volume Expanders

INTRODUCTION

Blood:

Is a fluid connective tissue that circulates continuously around the body, allowing constant communication between tissues distant from each other.

Plasma:

Plasma is a clear, straw-colored, watery fluid in which several different types of blood cells are suspended.

• Plasma expanders are agents that have relatively high molecular weight and boost the plasma volume by increasing the osmotic pressure.
• They are used to treat patients who have suffered hemorrhage or shock.
• Volume expanders are the intravenous fluid solutions that are used to increase or retain the volume of fluid in the circulating blood.
• Generally, volume expanders are used to replace fluids that are lost due to illness, trauma, or surgery.
• These are used to correct hypovolemia due to loss of plasma or blood.

TYPES OF VOLUME EXPANDERS

• There are two main types of volume expanders:

1. Crystalloids: Crystalloids are aqueous solutions of mineral salts or other water-soluble molecules. E.g. normal saline, dextrose, Ringer’s solution, etc.

2. Colloids: Colloids are larger insoluble molecules, such as dextran, human albumin, gelatin, blood. Blood itself is a colloid.

• The larger molecules of colloids are retained more easily in the intravascular space & increase osmotic pressure. So, more effective resuscitation of plasma volume occurs by colloids than produced by crystalloids.
• Duration of action of colloid relatively longer than crystalloid.

Colloid:

• Increase plasma volume.
• Less peripheral edema.
• Smaller volume for resuscitation.
• Intravascular half-life 3-6 hrs.

Crystalloid:

• Inexpensive.
• Use for maintenance of fluid and initial resuscitation.
• Intravascular half-life 20-30 minutes.

Ideal properties of PVEs (Plasma Volume Expanders):

• Iso-oncotic with plasma.
• Distributed to intravascular compartment only.
• Pharmacodynamically inert.
• Non-pyrogenic, non-allergenic & non-antigenic.
• No interference with blood grouping or cross-matching.
• Stable, easily sterilizable, and cheap.

Generally used Plasma Expanders:

• Human albumin.
• Dextran.
• Degraded gelatin polymer (Polygeline).
• Hydroxyethyl starch (Hetastarch/HES).
• Polyvinyl pyrrolidone –PVP.

Mechanism of Action:

• Generally works on the principle of osmosis.
• Increases plasma osmotic pressure, drawing water into plasma from interstitial fluid.
• Since the lost blood is replaced with a suitable fluid, now the diluted blood flows more easily, even in small vessels.
• As a result of chemical changes, more oxygen is released into the tissues.

Uses of Plasma Expanders:

• Used in conditions where blood or plasma has been lost or has moved to extravascular compartments e.g., in burns, hypovolaemic shock, endotoxin shock, severe trauma, and extensive tissue damage.
• Can also be used as a temporary measure in cases of whole blood loss till the same can be arranged.
• Note: They do not have oxygen-carrying capacity.

1. Human Albumin:

• It is obtained from pooled human plasma.
• It can be used without regard to the patient’s blood group and doesn’t interfere with coagulation.
• It is free of risk of transmission of hepatitis because the preparation is heat treated.
• The crystalloid solution must be infused concurrently for optimum benefit.
• It has been used in acute hypoproteinaemia, acute liver failure, and dialysis.
• It is comparatively expensive.
• Available products:

1. Albudac, Albupan 50, 100 ml injection
2. Album 5%, 20% infusion (100 ml)

2. Dextran:

• It is a highly branched polysaccharide molecule obtained from sugar beet.
• It is produced by using the bacterial enzyme dextran sucrase from the bacterium Leuconostoc mesenteroides which grows in a sucrose medium.
• Most commonly used plasma expanders and is available in two forms.

(a) Dextran 70

(b) Dextran 40

(a) Dextran 70:

 1. It is the most commonly used preparation.

2. It expands plasma volume for nearly 24 hrs.

3. Excreted slowly by glomerular filtration as well as oxidized in the body over weeks.

4. Some amount is deposited in reticuloendothelial cells.

Dextran 70 has nearly all the properties of an ideal plasma except:

• It may interfere with blood grouping and cross-matching.
• It can interfere with coagulation and platelet function and thus prolong bleeding time.
• Some polysaccharide reacting antibodies, if present, may cross-react with dextran and trigger an anaphylactic reaction like Urticaria, itching, bronchospasm, fall in BP.

(b) Dextran 40:

• It is a 10% solution in Dextrose or Saline.
• It acts more rapidly than dextrose – 70.
• It reduces blood viscosity.
• It is excreted through renal tubules and occasionally may produce acute renal failure.
• The total dose should not exceed 20 ml/kg in 24 hr.
• Dextrans can be stored for 10 years and are cheap so are the most commonly used plasma expanders.

Caution: Dextran doesn’t provide necessary electrolytes and can cause hyponatremia or other electrolyte disturbances.

3. Degraded Gelatin Polymer (Polygeline)

• It is a synthetic polymer (polypeptide) of MW-30,000.
• It doesn’t interfere with blood grouping and cross matching and is non-antigenic.
• Expands plasma volume for 12 hrs.
• It is more expensive than dextran and can also be used for priming heart-lung and dialysis machines.

Brands: Haemaccel; Seraccel 500 ml vaccine.

4. Hydroxyethyl Starch(Hetastarch)

• It is a complex mixture of ethoxylated amylopectin of various molecular sizes; average MW 4.5 lacs.
• It maintains blood volume longer.
• It doesn’t cause acute renal failure or coagulation disturbances.
• It improves hemodynamic status for 24 hrs.

Adverse effects:

• Vomiting, mild fever, itching, chills, flu-like symptoms, swelling of salivary glands, Urticaria, bronchospasm, etc.

Brand:

• Expand 6% inj. (100 , 500 ml vac).
• It has also been used to improve the harvesting of granulocytes because it accelerates erythrocyte sedimentation.

Adverse effects:

• Anaphylactic reactions, mild fever, chilling, periorbital edema, Urticaria, itching.

5. Polyvinylpyrrolidone(PVP)

• It is a synthetic polymer of average MW 40,000 used as a 3.5% solution.
• PVP was used as a blood plasma expander for trauma victims after the 1950s.
• It interferes with blood grouping and cross matching and is a histamine releaser.
• It binds to penicillin and Insulin.
• It is excreted by the kidney and small amounts by the liver into bile.
• A fraction is stored in RE cells for prolonged periods.
• It is a less commonly used plasma expander.

Uses of PVP:

• PVP is also used in personal care products such as shampoos and toothpaste, hair sprays, and gels.
• It is used as a binder in many pharmaceutical tablets.
• PVP added to iodine forms a complex called Povidone- Iodine that posses disinfectant properties. And known under the trade name of Betadine and Pyridine.

Some Crystalloids:

1. Normal Saline (Isotonic):

• It is the crystalloid fluid containing 0.9% NaCl.
• The pH of isotonic saline is considerably lower than the plasma pH.
• NS is frequently used in patients who cannot take fluids orally and have developed dehydration or hypovolemia.

2. Lactated Ringer’s solution:

• It was introduced in 1880 by Sydney ringer, a British physician.
• The solution was designed to promote the contraction of frog hearts and was contained with calcium and potassium in NaCl diluents.
• It is contraindicated as diluents for blood transfusions.

3. Dextrose solutions:

• Generally, 5% dextrose solutions are used which provides 170 kcal/lit.
• It is an IV sugar solution that provides some energy to the body parts.
• Osmolarity is lower than serum.
• Useful when kidney function is impaired.

Contraindications to Plasma Expanders:

• Allergy
• Heart failure
• Severe anemia
• Thrombocytopenia
• Pulmonary edema
• Renal insufficiency.

Make sure you also check our other amazing Article on : Antiplatelet Drugs