In order to further evaluate the role of lasers in microvascular tissue closure, we modified an existing CO2 surgical laser (Xanar XA-20) by adding a partially reflecting mirror to attenuate the beam. This allowed the laser to operate at an output of approximately 100 mW, which was appropriate to achieve microvascular closures. In each of 43 rats, one carotid artery was transected and then anastomosed with standard suture technique with 10 to 12 simple interrupted sutures of size 10-0 Ethilon nylon suture (Ethicon, Inc.). The opposite carotid in each rat was anastomosed by the placement of three stay sutures followed by the application of laser irradiation to the tissue between the stay sutures at 90 to 100 mW, spot size of 0.2 mm, pulse duration 0.2 seconds, approximately 20 to 30 pulses per anastomosis. In vivo test periods were 1 hour, 1 day, 3 days, 7 days, 10 days, 14 days, 28 days, 91 days, and 180 days. All anastomoses were evaluated for patency, and selected samples were utilized for light microscopy, scanning electron microscopy, transmission electron microscopy, and mechanical testing (intraluminal pressure raised to 300 mmHg).
It was determined that similar patency rates and slightly faster time to perform the same procedure could be achieved with the use of the low-powered CO2 laser. However, histologic evidence of significant medial damage raises concern about the long-term risk of a higher aneurysm rate. Vessel damage and the lack of simple intraoperative methods to verify the quality of the laser technique restrict these authors from advocating the clinical introduction of the procedure until further advances are made.
We have hypothesized the mechanism of laser closure to be an enhancement of the normal physiological fibrin clotting system and do not expect the techniques employed here to be capable of being scaled to the closure of larger, more mechanically demanding tissues.
