Laparoscopic partial nephrectomy using a flexible CO2 laser fiber.

BACKGROUND AND OBJECTIVES: Laparoscopic partial nephrectomy (LPN) is a challenging surgery that requires precise tissue cutting and meticulous hemostasis under warm ischemia conditions. In this study, we tested the feasibility of performing LPN using CO2 laser energy transmitted through a specialized flexible mirror optical fiber. METHODS: General anesthesia and pneumoperitoneum were induced in 7 farm pigs. Various portions of a kidney, either a pole or a midportion of the kidney, were removed using a novel flexible fiber to transmit CO2 laser energy set at a power of 45W and energy per pulse of 100mJ. The collecting system was approximated with a suture or 2, but no hemostatic measures were taken besides applying a few pulses of the laser to bleeding points. The pigs were sacrificed 3 wk later. RESULTS: Average renal mass removed was 18% of the total kidney weight. All pigs tolerated surgery well. Sharp renal cutting was accomplished in a single continuous incision, with minimal tissue charring and minimal blood loss (<10cc) in all animals. Necropsy revealed no peritoneal or retroperitoneal abnormalities. Histologic examination of the cut surface showed a thin sector of up to 100 m of coagulation necrosis. CONCLUSIONS: We report on the first LPN done using a CO2 laser transmitted through a flexible fiber in an animal model. This novel application of the CO2 laser produced excellent parenchymal incision and hemostasis along with minimal damage to adjacent renal tissue, thus, potentially shortening ischemia time and kidney function loss. Further studies comparing this laser to standard technique are necessary to verify its usefulness for partial nephrectomy.

Multi-wavelength reflectance pulse oximetry.

The performance of current reflectance pulse oximeters is hindered by poor signal-to-noise ratio. To overcome this problem a new reflectance oximeter has been developed with a sensor which consists of three LEDs and two continuous photodetector rings placed equidistant from the center of the LEDs. In addition, ultra low noise electronics and adaptive algorithm assure improved performance. A validation study was performed on 10 healthy volunteers. Sensors were placed on several sites and measurements were compared to reference arterial blood samples. During the study progressive hypoxemia was induced by lowering the inspired oxygen concentration (FiO2) to 10%, followed by a recovery phase. Twelve blood samples were taken during each cycle, yielding a total of 120 measured data points. Data from randomly selected 5 subjects was used for calibration and subsequently tested on the other 5 subjects. Results proved to be well within clinically acceptable boundaries for all 3 sampling sites with high correlation (R2 > 0.9) and SD around 2%. In conclusion, a new 3 wavelength reflectance pulse oximeter with unique sensor geometry and improved algorithms provides enhanced performance and is less susceptible to poor signal to noise conditions when compared to existing reflectance oximetry systems.