Effects of continuous wave and pulsed laser on blood coagulation. An in vitro thromboelastographic study.

Besides being thrombogenic, lasers may have direct adverse effects on different constituents of blood itself, when used intraluminally in angioplasty. This pilot study was therefore designed to examine the effect of continuous wave (CW Nd: YAG) and pulsed wave (XeCl excimer) laser irradiation on whole blood coagulation and fibrinolysis in vitro using thromboelastography (TEG). TEG showed shortened reaction and coagulation times after three and six seconds with 10 W of continuous wave laser irradiation of 10 ml of blood. The clot formation rate and maximal amplitude were decreased with CW laser and the plasma clot lysis at one hour was significantly increased (P < 0.05). The effect of the pulsed wave laser was less pronounced. The exposure of whole blood to laser irradiation accelerated coagulation and enhanced fibrinolysis. The clinical significance of the findings is to be settled since the thrombogenicity of lasers is mainly caused by their effect on the vessel wall and thereby the on platelet-wall interaction.