Underwater Nd:YAG Laser Coagulation of Blood Vessels in a Rat Model

Abstract

Endoscopic coagulation of placental and umbilical cord vessels has been suggested as a treatment for selected cases of twin-twin transfusion syndrome and of acardiac twin. The feasibility, safety and hemostatic effect of neodymium:yttriumaluminium-garnet (Nd:YAG) laser in an underwater environment were experimentally studied in an in vivo model, mimicking the in utero situation and fetoplacental vessels. In 10 male Wistar rats, immersed in normal saline at 38 °C, femoral vessels, carotid artery, abdominal aorta and vena cava were coagulated under endoscopic control. A 100-Watt Nd:YAG laser was used in continuous mode with a 600-μm fiber. Outcome measurements were vascular diameter, total energy (joules) used to obtain visual coagulation and subsequent vascular obliteration. Overall failure rate was 32% and perforation of the vessel occurred in 7.7% of cases.

Umbilical Cord Occlusion via Laser Coagulation in Monochorionic Multifetal Gestations before and after 20 Weeks of Gestation

“…The umbilical cord size is typically cited as the limiting factor, although most authors describe this subjectively, without defining the dimensions of the cord. However, this concern has been substantiated in underwater rodent studies, which showed a higher failure rate of L-UCO using Nd-YAG laser with increasing vessel diameter [15] . The indication for the UCO and subsequent cord vessel hemodynamics may also contribute to UCO failure.…”

Instrumental requirements for minimal invasive fetal surgery

“…At that moment, the amount of water wherein the energy can spread is limited to that entrapped in the cannula, increasing the risk for vessel perforation. 25 At present, it is uncertain what the best technique for cases with anterior placentas is. Moreover, published data do not show that results are clinically different.…”

Alternative technique for Nd : YAG laser coagulation in twin‐to‐twin transfusion syndrome with anterior placenta

“…Further, the laser fiber, exiting the sheath along the axis of the scope, will not arrive at an inclination angle close to 90 o towards the vessels on the placenta. This may limit laser performance, and cause incomplete obliteration, particularly at larger vessel diameters 20 . Using this technique, with a flexible cannula and an angled fetoscope, one can cover a larger surface of the placenta as well as approaching the vessels with the laser fiber at a more functional angle.…”