Dextran

What is Dextran?

Dextran is a complex, branched glucan (a polysaccharide made of many glucose molecules) that is used as a plasma volume expander. It is a synthetic macromolecule derived from bacterial fermentation of sucrose. Administered intravenously, Dextran solutions are classified as colloid solutions, meaning they contain large molecules that do not readily pass through capillary walls, thus remaining in the intravascular space and exerting osmotic pressure.

There are primarily two forms of Dextran used clinically: Dextran 40 and Dextran 70. The number refers to the approximate average molecular weight in kilodaltons (kDa). Dextran 40 has a lower molecular weight, allowing it to improve microcirculation more effectively, while Dextran 70 has a higher molecular weight, providing a more sustained volume expansion effect.

How Does it Work?

The primary mechanism of action for Dextran involves its ability to expand plasma volume. As a colloid, Dextran remains in the bloodstream and creates an oncotic pressure gradient. This pressure draws fluid from the interstitial (extravascular) space into the intravascular compartment, effectively increasing circulating blood volume. This effect is crucial in treating conditions characterized by insufficient blood volume.

Beyond its volume-expanding capabilities, Dextran, particularly Dextran 40, also possesses unique rheological properties. It reduces blood viscosity and inhibits platelet aggregation, improving blood flow, especially in the microcirculation. This antithrombotic effect contributes to its use in preventing blood clot formation and enhancing perfusion in areas of compromised blood flow.

The duration of Dextran's action depends on its molecular weight. Lower molecular weight Dextran (Dextran 40) is metabolized and excreted more rapidly, providing a shorter but more immediate effect on microcirculation. Higher molecular weight Dextran (Dextran 70) persists longer in the circulation, offering a more prolonged volume expansion.

Medical Uses

Dextran is a versatile medication with several important medical applications, primarily focused on fluid management and coagulation modulation:

• Treatment of Hypovolemia: Dextran is widely used to treat or prevent hypovolemia (low blood volume) resulting from various causes, including surgical blood loss, trauma, burns, and other conditions leading to significant fluid depletion. It helps restore circulating blood volume and maintain cardiovascular stability.
• Thromboprophylaxis: Dextran 40 is particularly effective in thromboprophylaxis, the prevention of venous thromboembolism (VTE) such as deep vein thrombosis (DVT) and pulmonary embolism (PE), especially after surgery. Its ability to reduce platelet adhesion and improve blood flow helps prevent clot formation.
• Adjunct in Vascular Surgery: In reconstructive vascular surgery, Dextran 40 is sometimes used to improve blood flow in small vessels and reduce the risk of thrombosis at the surgical site.
• Priming Solution: It can be used as a priming solution for heart-lung machines during cardiopulmonary bypass.
• Prevention of Re-stenosis: Although less common now, Dextran has been explored for its potential to prevent re-stenosis after angioplasty procedures due to its antithrombotic properties.

Dosage

The dosage of Dextran varies significantly based on the specific type (Dextran 40 or Dextran 70), the patient's condition, weight, and the therapeutic goal. It is always administered intravenously under strict medical supervision.

• For Hypovolemia: Initial doses typically range from 500 mL to 1000 mL, administered rapidly to achieve immediate volume expansion. Subsequent doses and infusion rates are adjusted based on the patient's hemodynamic response, urine output, and central venous pressure. Total daily doses usually do not exceed 20 mL/kg body weight.
• For Thromboprophylaxis (Dextran 40): A common regimen involves administering 500 mL during surgery, followed by 500 mL daily for 2-3 days, and then 500 mL every 2-3 days for up to two weeks, depending on the risk factors.

Close monitoring of fluid balance, renal function, and coagulation parameters is essential during Dextran therapy to prevent complications such as fluid overload or renal impairment.

Side Effects

While generally safe, Dextran can cause side effects. Most are mild, but serious reactions can occur:

• Allergic Reactions: These range from mild symptoms like flushing, itching, urticaria, and rash to severe anaphylactic reactions, which can be life-threatening. Pre-treatment with hapten Dextran (Dextran 1) can sometimes reduce the risk of anaphylaxis.
• Fluid Overload: Due to its volume-expanding effect, there is a risk of fluid overload, especially in patients with pre-existing cardiac or renal conditions. This can lead to pulmonary edema or congestive heart failure.
• Acute Renal Failure: High doses or rapid infusion of Dextran, particularly in dehydrated patients or those with pre-existing renal impairment, can lead to osmotic nephrosis and acute kidney injury.
• Coagulation Abnormalities: Dextran can interfere with platelet function and blood coagulation, potentially increasing the risk of bleeding, especially with prolonged use or in patients already on anticoagulants. It can also interfere with blood typing and cross-matching tests.
• Other Side Effects: Nausea, vomiting, fever, and headache may also occur.

Drug Interactions

Dextran can interact with other medications, potentially altering their effects or increasing the risk of adverse reactions:

• Anticoagulants and Antiplatelet Agents: Concurrent use with anticoagulants (e.g., heparin, warfarin) or antiplatelet drugs (e.g., aspirin, clopidogrel) significantly increases the risk of bleeding due to Dextran's own antithrombotic properties. Close monitoring of coagulation parameters is crucial.
• Other Plasma Expanders: While sometimes used in conjunction, caution is advised when combining Dextran with other plasma expanders to avoid excessive volume expansion.
• Drugs Affecting Renal Function: Drugs that are nephrotoxic or affect renal blood flow should be used cautiously with Dextran, as both can contribute to kidney impairment.
• Blood Products: Dextran can interfere with blood typing and cross-matching tests. Inform the laboratory if a patient has received Dextran.

FAQ

Q: What is the main difference between Dextran 40 and Dextran 70?

A: The main difference lies in their average molecular weight. Dextran 40 (40 kDa) primarily improves microcirculation and has a shorter plasma half-life, making it useful for preventing thrombosis. Dextran 70 (70 kDa) provides more sustained volume expansion due to its larger molecules staying longer in the circulation.

Q: Can Dextran cause kidney problems?

A: Yes, Dextran can potentially cause acute renal failure, especially with high doses, rapid infusion, dehydration, or in patients with pre-existing kidney disease. It's crucial to monitor renal function during treatment.

Q: How quickly does Dextran work?

A: Dextran acts relatively quickly, with volume expansion effects often seen within minutes of administration, particularly with rapid infusions for acute hypovolemia.

Q: Is Dextran safe during pregnancy?

A: Dextran should be used during pregnancy only if clearly needed and the potential benefits outweigh the potential risks to the fetus. Consult a healthcare professional for specific guidance.

Products containing Dextran are available through trusted online pharmacies. You can browse Dextran-based medications at ShipperVIP or Medicenter.

Summary

Dextran is a crucial intravenous colloid solution used primarily as a plasma expander to treat hypovolemia and as a prophylactic agent against thromboembolism. Available in different molecular weights (Dextran 40 and Dextran 70), it works by increasing intravascular volume and, particularly Dextran 40, improving microcirculation and reducing blood viscosity. While highly effective, its administration requires careful monitoring for potential side effects such as allergic reactions, fluid overload, and renal impairment. Awareness of its drug interactions, especially with anticoagulants, is essential for safe and effective use. Always consult a healthcare professional for appropriate dosage and management.