Electrosurgery is commonly used to cauterize, cut and/or coagulate tissue. In typical electrosurgical devices, RF electrical energy is applied to the tissue being treated. Local heating of the tissue occurs, and, depending upon the waveform of the applied energy, the desired effect is achieved. By varying the power output and the type of electrical waveform, it is possible to control the extent of heating and, thus, the resulting surgical effect. For example, a continuous sinusoidal waveform is best suited for cutting, while a waveform having periodically spaced bursts of a partially rectified signal produces coagulation.
In bipolar electrosurgery, the electrosurgical device includes two electrodes. The tissue being treated is placed between the electrodes, and the electrical energy is applied across the electrodes. In monopolar electrosurgery, the electrical excitation energy is applied to a single electrode at the surgical site, and a grounding pad is placed in contact with the patient. The energy passes from the single monopolar electrode through the tissue to the grounding pad.
While tissue heating is the mechanism by which the various surgical treatments are realized, it can also cause various obstacles to optimum procedure performance. For example, the heat causes tissue fluids to evaporate. As the tissue is desiccated, the electrical resistance of the tissue increases, making it increasingly more difficult to supply adequate power to the tissue. Eventually, the resistance rises to such a high level that it is impossible to continue the procedure. This is such a well-known and common problem in prior electrosurgical devices that surgeons have become accustomed to it and have tailored their procedures to minimize its effects. Typically, surgeons operate prior electrosurgical devices at a very low power level. This prevents the electrode and the adjacent tissue from becoming too hot too fast. Unfortunately, it also requires the surgeon to perform the procedure much more slowly than he would if he could operate the device at full power. As a result, the procedure takes much longer, requiring more operating room time and longer exposure of the patient to dangerous anesthetics.
Heating also causes charring of the tissue. Like desiccated tissue, charred tissue is of very high resistance. Therefore, as the surface of the tissue being treated becomes charred, it becomes difficult, and eventually impossible, to continue delivering power to the tissue as desired. Once again, to avoid the problem, surgeons perform procedures much more slowly than is desirable.
Electrosurgical procedures are also hindered by adherence of tissue to heated electrodes. During electrosurgery, the heated tissue tends to transfer heat to the electrodes. As an electrode becomes hot, tissue tends to stick to it, resulting in various complications. First, the tissue stuck to the electrode can have a high resistance and can therefore hinder delivery of power to the tissue. In prior devices, while performing a procedure, a surgeon must periodically remove the device from the patient and clean it before continuing. In addition, surgeons typically perform the procedure at low power to reduce tissue adherence and thus the frequency of cleanings.
Tissue sticking can also cause unnecessary bleeding. During electrosurgical procedures, the tissue being treated often heats the electrode such that, when the electrode is removed from the tissue, a portion of the tissue sticks to the electrode and is torn away, which likely results in bleeding. Thus, as the surgeon is attempting to cauterize in order to stop bleeding, he is actually causing more bleeding. He must therefore make repeated attempts to cauterize the area, first cauterizing, then tearing away tissue, then recauterizing the torn tissue, etc. Once again, in an attempt to alleviate the problem, surgeons will typically operate at low power, resulting in a procedure requiring much more time to complete than is desirable.
Another problem caused by heated electrodes is the creation of steam and smoke in the proximity of the surgical site. As a result, the surgeon's visibility is reduced, and he must periodically interrupt the procedure to allow the steam or smoke to dissipate.
It has been recognized that cooling the surgical site during electrosurgery would be desirable. In response, systems have been developed which flush the surgical site with fluid during surgery. However, this results in much more steam being created at the surgical site and the associated reduction in visibility. Also, the fluid introduced at the site must be aspirated as the procedure is performed.