April 24, 2024
Plasma Expander

Plasma Expander: A Lifesaving Fluid for Treatment of Hypovolemic Shock

Healthcare professionals commonly use plasma expanders or volume expanders for the rapid treatment of hypovolemic shock in hospital emergency departments. During hypovolemic shock, there is a significant loss of intravascular volume in the circulating blood which can be life threatening if not treated promptly. Plasma expanders help restore the lost intravascular volume by expanding plasma volume and increasing effective circulating blood volume. This helps increase tissue perfusion and oxygen delivery to vital organs.

Plasma expanders, also known as volume expanders, are intravenous fluids administered to increase plasma volume and circulating blood volume. They work by staying inside blood vessels and expanding the intravascular compartment after intravenous infusion. Common plasma expanders include crystalloids like normal saline and lactated Ringer’s solution, colloids like hetastarch, dextran and albumin. Crystalloids are the first line treatment in most cases due to lower cost and side effect profile compared to colloids.

Mechanism of action of plasma expanders

Plasma expanders work by drawing fluid from the interstitial space back into blood vessels via osmosis. Crystalloid solutions like normal saline contain sodium chloride which remains in the blood vessels after infusion and raises the osmotic pressure of plasma. This leads to an osmotic gradient causing fluid shift from tissues into the intravascular space, thereby expanding plasma volume. Colloid solutions contain large soluble molecules that remain in circulation for longer duration. The large molecules in colloids exert greater oncotic pressure more effectively retaining fluid within blood vessels compared to crystalloids.

Importance in emergency medicine

Plasma volume expansion is critical in emergency treatment of hypovolemic shock caused by bleeding, severe burns, gastrointestinal fluid losses etc. Rapid fluid resuscitation is needed to restore depleted intravascular volume and reverse tissue hypoperfusion. Current Surviving Sepsis Campaign guidelines recommend initial fluid resuscitation with crystalloids like normal saline over colloids for sepsis related shock. Studies show early goal directed fluid therapy within the first 3 hours can reduce mortality in septic shock. Plasma Expander play a pivotal role in preventing organ dysfunction or failure by promptly restoring circulating volume in hemorrhagic, traumatic and septic shock.

Commonly used plasma expanders

Normal Saline (0.9% NaCl)

Normal saline or sodium chloride 0.9% solution remains the most widely used crystalloid for initial fluid resuscitation in hypovolemic shock. It has an osmolarity and sodium concentration similar to plasma and does not cause fluid shifts between intracellular and extracellular spaces. It expands plasma volume effectively while being relatively inexpensive. However, its effect is short acting as it readily distributes into the interstitial compartment.

Lactated Ringer’s Solution

Compared to normal saline, lactated Ringer’s solution contains physiological concentrations of sodium, potassium, calcium and lactate ions. These make its composition closer to extracellular fluids and plasma. It is generally preferred over normal saline for fluid resuscitation. Lactated Ringer’s solution has a longer intravascular retention time and expands plasma volume almost equivalent to colloids. However, it too is quickly absorbed into the interstitium.


Hetastarch is a hydrogenated polysaccharide and belongs to the starch-based hyperoncotic colloid class of plasma expanders. It remains in circulation for up to 12 hours after intravenous administration, exerting greater oncotic pressure than crystalloids. This means it can restore and maintain circulating volume more effectively. However, hetastarch is associated with increased risk of bleeding, renal impairment and mortality especially with large volumes. So it is not recommended as a first-line colloid.


Albumin is a plasma protein derived from human blood. As the main determinant of plasma oncotic pressure, albumin is highly efficient at retaining fluid inside blood vessels and improving circulatory volume status. It has anti-inflammatory and antioxidant properties too. Albumin solutions remain intravascular for over 18 hours and are ideal for correcting hypoalbuminemia. But the high cost limits its extensive clinical use as a primary volume expander.

Prompt restoration of intravascular volume with plasma expanders is essential to reverse shock and prevent morbidity and mortality from inadequate tissue perfusion. While crystalloids like saline are preferred initially due to safety profile, judicious use of colloids may provide longer lasting volume correction in life-threatening hemorrhagic shock. Plasma expanders remain a mainstay in resuscitation algorithms and evidence-based guidelines for emergency fluid management in shock. Further research is ongoing to develop safer, more efficacious plasma expanders for improved critical care.

1. Source: Coherent Market Insights, Public sources, Desk research
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