What are Plasma expanders and how do they act?

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 haemorrhage or shock. Shock occurs due to reduced blood volume (usually due to haemorrhage) and it is necessary to get the blood volume back to normal as quickly as possible.

There are two main types of volume expanders: crystalloids and colloids. Crystalloids are aqueous solutions of mineral salts or other water-soluble molecules. Colloids contain larger insoluble molecules, such as gelatin; blood itself is a colloid. The most commonly used crystalloid fluid is normal saline, a solution of sodium chloride at 0.9% concentration, which is close to the concentration in the blood (isotonic). Ringer's lactate or Ringer's acetate is another isotonic solution often used for large-volume fluid replacement. A solution of 5% dextrose in water, sometimes called D5W, is often used instead if the patient is at risk for having low blood sugar or high sodium. The choice of fluids may also depend on the chemical properties of the medications being given.