Plasma expanders, also known as volume expanders or intravenous fluids, are medical fluids that are administered to patients who have lost a significant amount of blood or other fluids from their circulatory system. These fluids help expand plasma volume and increase oxygen delivery to tissues when administered intravenously. Plasma expanders have become a vital component of trauma and emergency care by helping patients with conditions like severe burns, hemorrhagic shock, or major surgery.
Types of Plasma Expanders
There are several options available when it comes to choosing the right plasma expander depending on the clinical scenario. Some of the major types include:
- Crystalloids: Fluids like normal saline and lactated ringer's solution are the most widely used crystalloid solutions. They primarily expand the extracellular space but are less effective at expanding plasma volume compared to colloids. However, crystalloids are cheap and associated with fewer adverse effects.
- Colloids: Solutions like dextran, hydroxyethyl starch, and gelatin are colloid plasma expanders. They remain longer in the circulation compared to crystalloids, making them more effective at plasma expansion. However, they are associated with higher costs and possible side effects like allergic reactions, coagulopathies, and kidney injuries.
- Albumin: Human albumin is exclusively used as a colloid volume expander. It is safe for long-term use but has a very high cost, limiting its widespread adoption compared to artificial colloids.
- Hemoglobin-based oxygen carriers: Products like hemopure work by carrying and delivering oxygen like red blood cells. However, concerns over side effects have limited their clinical use so far.
Mechanism of Action
The basic mechanism by which all Plasma Expander work is by increasing intravascular oncotic (osmotic) pressure and returning fluid back to the blood vessels from the interstitial compartment after fluid loss. Crystalloids exert their effect primarily through increasing hydrostatic pressure while colloids directly increase colloid osmotic pressure. This osmotic gradient helps pull more fluid back into the circulation from tissues. Plasma expanders also help positively influence hemodynamics by increasing preload and cardiac output.
Benefits in Trauma Care
The ability of plasma expanders to rapidly restore intravascular volume makes them extremely valuable for trauma patients with hemorrhagic shock. Some key benefits in trauma settings include:
- Prevention of hypotension: Early administration of fluids helps support blood pressure and organ perfusion until definitive hemostasis and bleeding control.
- Improvement in outcomes: Multiple studies have found early fluid resuscitation within the first hour improves survival in trauma patients.
- Decreased blood product use: Judicious use of plasma expanders can reduce overall blood product transfusions needed in many scenarios.
- Less infectious risks: Compared to blood products, crystalloids and colloids carry virtually no risk of transfusion-transmitted infections.
- Ease of administration: Intravenous fluids are simpler to administer than processing and transfusing blood products under emergency conditions.
- Bridge to surgery/procedures: Plasma expanders buy valuable time by temporizing hemodynamic instability until patients can be rushed to the operating room or interventional radiology suite.
Contraindications and Adverse Effects
While lifesaving in many cases, plasma expanders are not without risks. Some contraindications and potential complications include:
- Heart failure: Rapid fluid administration can precipitate or exacerbate pulmonary edema in patients with cardiomyopathy or severe heart disease.
- Coagulopathies: Synthetic colloids may impair coagulation and increase bleeding through various mechanisms.
- Kidney injury: Especially with hydroxyethyl starch use, renal dysfunction is a notable concern even in previously healthy patients.
- Allergic reactions: True IgE-mediated hypersensitivity can occur rarely with any colloid solution.
- Metabolic disturbances: Solutions with high sodium content may cause hypernatremia while dextrose-containing fluids could induce hyperglycemia.
- Resource intensive: Continuous monitoring of fluid balance is needed to prevent potential adverse effects of fluid overload.
Future Directions
With the limitations and risks associated with current options, research into next-generation plasma expanders is ongoing. Some areas receiving attention include hemoglobin-based carriers with fewer adverse events, perfluorocarbon emulsions, and synthetic oxygen therapeutics. Tailoring resuscitation regimens based on precision medicine approaches may allow for individualization in the future. Additionally, hemorrhage control methods like tourniquets and hemostatic dressings can decrease fluid requirements in trauma. Overall, safe and effective volume replacement will remain a key challenge in critical care.
Plasma expanders have emerged as fundamental tools in modern emergency medicine and trauma resuscitation. While none are without risks, judicious use guided by evidence and hemodynamic endpoints helps maximize benefits and minimize harm. Continuous efforts towards developing novel therapeutic agents with improved profiles hold promise to further advance prehospital and in-hospital trauma management.
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