Comparison between the laser surgical unit and the electrosurgical unit.

Thermal effects on the brain, spinal cord and muscles were studied in electrocoagulation and laser photocoagulation. The experiments were performed on cats and rabbits. The monopolar and bipolar electrodes of the electrosurgical unit were applied to the tissues in comparison with the carbon dioxide laser surgical unit. The experiments were divided into the following two groups: 1) Morphological studies with optical microscope and electron microscope. 2) Temperature measurements with the non-contact infrared thermometer, microthermistor and thermograph. Minimal lesion was obtained by laser photocoagulation in comparison with elec trocoagulation. The size of the lesion increased proportionately to the output power in electrocoagulation, but in laser photocoagulation the width of the brain edema remained within 300 ƒÊ. Only tissue defects produced by laser vaporization increased proportionately to the output power and the exposure time. The temperature at the focus of the laser beam was measured with the non-contact infrared thermometer which indicated 1,500•Ž. The temperature within the tissue adjacent to the focus was measured with a microthermistor. In laser photocoagulation, the maximum increase was about 10•Ž at a point 1 mm from the focus. The temperature change occured within 30 sec when the laser irradiation lasted for 2 sec at 15 W. In bipolar coagulation, the temperature rise was 2.5•Ž at 3 mm from the electrode and the change lasted for 23 sec. In monopolar coagulation, the maximum rise was about 18•Ž at 3 mm from the electrode at an output power of 2 W, and the change lasted also for 23 sec. A conspicuous feature in thermography was the very steep temperature gradient extending from the laser focus to the surrounding tissue. This means that in lasing the thermal effect is highly restricted. But the most prominent feature of the laser is the so-called "vaporization": The laser can vaporize tissues hemostatically in situ, which is impossible with the electrosurgical unit.