Thrombin-soaked coils: estimation of thrombin dose.

Thrombin-soaked coils have been used as embolic agents for the treatment of various conditions. Intravascular injection of thrombin also has been used for thrombus formation; however, the effects of high doses of intravascular thrombin may be detrimental. In an in vitro experiment, the dose of thrombin associated with transcatheter use of thrombin-soaked steel coils was estimated. The 8 mm x 5 cm, 0.038-inch coils absorbed an overall average dose of 38.4 U (USP) of thrombin when soaked in a solution of 10,000 U of thrombin per 10 mL of saline. The same size coils absorbed an overall average dose of 71.6 U of thrombin when soaked in a concentration of 20,000 U of thrombin per 10 mL of solution. Maximum single-coil absorbed doses were 45.6 and 88.2 U for 1,000 and 2,000 U/mL, respectively. A plateau in thrombin absorption occurred after 1 minute of soaking. Absorption of thrombin was maximized by soaking the coils in a vertical orientation; almost no thrombin was absorbed when the coils were soaked in a horizontal position.