Plasma expander

Plasma expanders are a group of substances used to manage and treat hypovolemia, which is a condition characterized by a decrease in the volume of blood plasma in the body. Plasma expanders are crucial in medical treatments where blood loss has occurred, or when there is a need to improve blood circulation and oxygen delivery to tissues. They are commonly used in surgeries, trauma care, and to treat various conditions such as shock and burns.

Types of Plasma Expanders

Plasma expanders can be broadly categorized into two main types: colloids and crystalloids.

Colloids

Colloids contain large molecules that remain in the blood vessels and increase the osmotic pressure, leading to an increase in blood volume. Examples of colloids include:

• Albumin: A protein made by the liver that helps maintain the blood's osmotic pressure.
• Hydroxyethyl starch (HES): A synthetic colloid that has been widely used but is now less favored due to concerns over side effects.
• Dextran: A complex polysaccharide that is effective in expanding plasma volume but can cause side effects such as anaphylaxis and kidney damage.

Crystalloids

Crystalloids are solutions of minerals and other small molecules that easily pass through cell membranes. They are less expensive and have fewer side effects compared to colloids. Examples include:

• Saline solution: A common crystalloid that consists of water and sodium chloride.
• Ringer's lactate: A solution containing sodium, chloride, potassium, calcium, and lactate, which is often used in fluid resuscitation.

Mechanism of Action

Plasma expanders work by increasing the oncotic pressure (osmotic pressure exerted by proteins) or the hydrostatic pressure in the blood vessels. This leads to a movement of fluid from the interstitial space (the space between cells) into the circulatory system, thereby increasing the volume of blood plasma.

Indications

Plasma expanders are indicated in situations where there is a need to rapidly expand the blood volume. This includes:

• Treatment of shock due to blood loss or burns.
• Supporting blood pressure during surgery.
• Managing sepsis, where blood volume can decrease due to increased vascular permeability.

Risks and Complications

While plasma expanders are essential in many medical treatments, they are not without risks. Potential complications include:

• Allergic reactions and anaphylaxis, especially with colloids.
• Fluid overload, leading to edema and heart failure.
• Electrolyte imbalances, particularly with the use of crystalloids.
• Increased risk of bleeding with some colloids due to interference with platelet function.

Conclusion

Plasma expanders play a vital role in the management of hypovolemia and the support of circulatory function. The choice between colloids and crystalloids depends on the clinical situation, the patient's condition, and the potential risks and benefits of each type of expander. Ongoing research and clinical trials continue to refine their use and develop safer, more effective plasma expanding agents.