Enhancement of fibrinolytics with a laser-induced liquid jet

There are several problems inherent in the treatment of cerebral embolisms, such as the narrow therapeutic time window and the severe side effects of fibrinolytic drugs. There is thus need of a new method of removing a cerebral thrombus more rapidly using smaller amounts of fibrinolytics.

The liquid-jet generator was made by insertion of an optical fiber (diameter: 0.6 mm) into a balloon catheter (6 Fr). A pulsed holmium (Ho) YAG laser (pulse duration time = 350 micros) was used as a laser source. The maximum penetration depth of a liquid jet generated with this device into a gelatin artificial thrombus was measured at various stand-off distances (L; distance between the optical fiber end and the catheter exit). Based on the result, a stand-off distance of 13 mm was chosen to investigate the enhancement of urokinase (UK) efficacy by only a single operation of the liquid-jet device in artificial thrombi made of human blood.

Maximum penetration depth increased in proportion to L and reached a maximum value (9 mm) when L was around 13 mm. Fibrinolysis rates (%) after incubation with a small amount of UK for 10 and 30 minutes were predominantly raised by a single use of the laser-induced liquid jet (5.4 +/- 2.4 vs. 22.6 +/- 6.1 and 7.3 +/- 3.8 vs. 38.3 +/- 5.6, respectively (mean +/- SD, P < 0.001)).

A laser-induced liquid jet effectively promoted fibrinolysis in vitro with use of only a small amount of fibrinolytics.