ELECTROSURGERY

Most concerns with electrical safety in the operating room arise from the use of electrosurgical units because they are capable of causing electric shock, burns, explosions, arrhythmias, and disturbances in pacemaker functioning. ^[41] Electrosurgical units operate at frequencies of approximately 300,000 to 2,000,000 cycles/sec (300 kHz to 2 MHz) to minimize the likelihood of ventricular fibrillation (see Fig. 87-5 ). During electrosurgery, high currents enter the patient through a small-area surface electrode at the tip of the cutting tool. The combination of high resistance (R), which is attributable to the small area, and high current (I) causes local tissues heating proportional to I² R, which produces cutting or coagulation. The tip of the electrode is also designed to produce lower current densities (low I² R) at points farther than a few millimeters from the electrode tip. Figure 87-6 shows fanning out of the electric current. Electrosurgery is therefore a form of highly controlled localized burning of tissue.

Because there is often smoke where there is fire, concerns have been expressed regarding the safety of inhaling the smoke from the electrocautery. One group, assisted by the National Institute of Occupational Safety and Health, used the Ames test to examine the potential mutagenicity of electrocautery smoke collected during breast surgery.^[42] Although the compounds collected were mutagenic, it is not known whether electrocautery smoke represents a serious health risk to operating room personnel. Nevertheless, the study recommended that surgeons minimize the production of electrocautery smoke and the exposure of human beings to the smoke.

Figure 87-6 The flow of electric current through the body when small-area or large-area grounding pads are used.

Because there often is fire where there is smoke, it is also important that nonflammable materials be used during electrosurgery. Fires have occurred in operating rooms because highly combustible surgical boundary drapes were placed close to electrosurgical units.^[43] The smoke from such fires can contain toxic substances.

From the preceding discussion, it is not surprising to find that electrosurgical units are powerful enough to provide excess electric currents capable of causing extensive tissue burns. Surgical patients who become wet with blood, saline, urine, or other conducting fluids can form electrical contacts with the operating table, the ground, or other conductors, including monitoring electrodes and surgical retractors. Such contacts can create potentially dangerous current pathways. For example, current from an electrosurgical unit may enter a patient through the grounding pad and return to the unit through one or more ECG electrodes. In this situation, the electrosurgical unit can provide current that burns the patient but never passes through the tip of the electrosurgical pencil used in the operative procedure.

The dangers of electrosurgery in a wet environment, especially the possibility of establishing ground faults through wet connections, accounts for the presence of an isolation transformer (and LIM) in modern operating rooms. GFCI outlets can protect against ground faults by causing sudden power deprivation. However, isolation transformers, by having the ground fault turn on an LIM alarm instead of causing a disconnect from the power, permit less disruptive detections of ground faults. Loss of electrical power during cardiac surgery can be a serious concern, which is one reason why anesthesiologists must know how to hand-crank cardiopulmonary bypass pumps.^[44] Desflurane vaporizers require electricity for operation. The NFPA requires first ground fault detectors in operating rooms. However, anesthesiologists, surgical colleagues, and hospital administrators are free to choose GFCIs or isolation transformers with LIMs, whichever best suits local conditions and practices.^{[20] [21]}

Unipolar Electrosurgery

It is important to understand the difference between unipolar and bipolar electrosurgery. In both cases, the surgeon applies electrodes directly to tissue, producing electrical currents that burn and cut or burn and coagulate. In unipolar electrosurgery, the more common of the two,

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A much more powerful unipolar electrosurgical tool, the argon beam coagulator (ABC), has become popular among surgeons who must cut or coagulate very vascular tissue.^[48] Operating room personnel unfamiliar with the ABC's design and use can easily mistake it for an argon laser because a well-collimated, brightly colored beam of argon light glows at the tip of the electrosurgical pencil. The glow, which has the same color as light emitted from an argon laser, represents a continuous electrical discharge in a small, flowing column of argon gas having a density that supports electric current. The ABC was developed to solve a problem occurring with metal coagulation or cutting tips. In regions where there is lots of blood, electrosurgical currents result in sticky, burned tissue adhering to the tip of the cutting electrode, electrically insulating it and making further use impossible until the tissue is scraped off. Surgery must stop while the tip is scraped clean. When large areas of vascular tissue must be traversed (e.g., in hepatic resection or repair of traumatic lacerations of the liver), conventional metal tips become difficult surgical tools. With the ABC, no metal surface is present to attract sticky, burned tissue. The tip of the cutting electrode is a cushion of argon gas that can transmit current as long as it touches tissue.

The anesthesiologist must understand that use of the ABC means that much electrosurgery is taking place and that safety measures are more important than ever. As in conventional electrosurgery, surgical cutting and coagulation with the ABC come from local I² R heating losses at the point where the electrosurgical pencil is applied—in this case, where the argon gas meets the tissue. ABC operation therefore resembles conventional arc welding. Because the ABC is perhaps the ultimate spark generator, its use illustrates the extent to which we have abandoned one safety concern that was prominent in the days of inflammable anesthetic gases.

Some locations of the body are never safe for unipolar electrosurgery. This situation is encountered frequently during neurosurgery and in patients with implanted cardiac pacemakers. The solution is bipolar electrosurgery.