Another type of dissecting and coagulating system is LigaSure®.18--22 It represents a new generation of instruments that use active feedback to optimise power output and innovative thermal engineering to enable the reduction of excess heat distant from the target region. It works with a combination of pressure and bipolar energy and incorporates impedance based feedback loops to modify the bipolar energy. It leads to sealing of vessels with high resistance against blood pressure and is comparable to a suture or a clip. It is able to close vessels with a diameter up to 7 mm. The blood vessel is fixed by the instrument and compressed with a calibrated force via a ratched scissor mechanism, and a pulse of radio frequency current is applied through the compressed tissue. The initial power level for each application is determined by a fast precusor voltage scan that elucidates the natural impedance of the compressed tissue. Then, by monitoring the temperature-dependent impedance of the compressed tissue during current activation, the microprocessor-controlled feedback loop automatically maintains an appropriate power level until the seal is complete. This process typically takes 1 to 6 seconds. Five and 10 mm instruments are available. A cutting device is integrated into the 10 mm instrument, and this makes the application more comfortable. It has been reported that when LigaSure® was used suture ligature, ties, clips, and other mechanical ligating techniques were rarely required.
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