In-Service Exam
Microsurgery - 2003





Which of the following is NOT a proposed mechanism of action of dextran used in microsurgery?

(A) Decreased factor VIII and von Willebrand factor
(B) Increased alpha-2 antiplasmin
(C) Increased electronegativity
(D) Structural modification of fibrin
(E) Volume expansion
The correct response is Option B.

Although the benefits of dextran 40 used during microsurgery are controversial, this agent is still used frequently. Dextran decreases factor VIII and von Willebrand factor, resulting in a decrease in platelet function. It is thought to increase the electronegativity of platelets in the endothelium, which prevents platelet aggregation, and is also thought to modify the structure of fibrin, increasing its susceptibility to degradation. It alters the rheologic properties of blood and acts as a volume expander.

Dextran inhibits, not increases, alpha-2 antiplasmin, leading to a subsequent activation of plasminogen.

Because dextran has the potential for antigenicity, a test dose of 20 mL of 150 mg/mL solution is typically administered one to two minutes before infusion.

References
1. Conrad M, Adams WP. Pharmacological optimization of microsurgery in the new millennium. Plast Reconstr Surg. 2001;108:2008.
2. Salmerk L, Knudsen F, Dougan P. The effect of Dextran 40 on patency following severe trauma in small arteries and veins. Br J Plast Surg. 1995;48:121.
3. Salmerk L, Wieslander JB, Dougan P, et al. Studies of antithrombotic effects of Dextran 40 following microarterial trauma. Br J Plast Surg. 1991;44:15.
4. Zhang B, Wieslander JB. Dextran's antithrombotic properties in small arteries are not altered by low-molecular-weight heparin or the fibrinolytic inhibitor tranexamic acid: an experimental study. Microsurg. 1993;14:289.