T E C H N O L O G Y B A C K G R O U N D E R For information contact: Joni Morford, Communicore 714/721-8081 jmorford@communicore.com SHIELDING AND MONITORING AGAINST TISSUE INJURY DURING LAPAROSCOPIC MONOPOLAR ELECTROSURGERY Laparoscopic surgeons have continued to demonstrate a preference for monopolar electrosurgery over its alternatives--bipolar energy, lasers, and "harmonic scalpels"-- due to monopolar electrosurgery's coagulation (clotting) performance, familiarity, versatility, and affordability. The use of monopolar electrosurgery in minimally invasive surgery (MIS) can, however, introduce serious risk to patient safety if the electrical energy is not shielded and monitored properly (see Issues Backgrounder). Even though the risk of acquiring an electrosurgical burn is relatively low, the potential harm to the patient associated with such an injury is high. Burns to non- targeted tissue and organs can lead to organ perforation, infection, and even death if not recognized and treated in time. From a patient safety and liability standpoint, any incidence of internal injury due to stray electrical energy during electrosurgery is reason enough to incorporate proper shielding and monitoring techniques. The potential for complications while using monopolar electrosurgical techniques in MIS arises from radio frequency (RF) currents leaking from the shaft of the active electrode that directs current to the surgical site. Various surgical techniques, such as cutting and coagulation, require different waveforms. Those that require higher levels of electrical voltage increase the risk that current will leak from the active electrode into surrounding non-targeted tissues. Although there are several alternatives to the use of monopolar electrical instruments--which use a single electrode to deliver energy to the surgical site--in laparoscopic surgery, none has the same level of acceptance or range of applications. For example, bipolar electrical instruments--so termed because the electrosurgical instrument incorporates both the active and return electrodes--are not as clinically effective because they cannot perform cutting efficiently and require tissue to be grasped and pulled between the electrodes, which is impossible on dense tissue and dangerous on fragile tissue. They are also less effective for coagulation of diffuse capillary bleeding, an important application. Other alternatives--such as laser energy and rapidly vibrating harmonic scalpels--have also received only limited use due to their high cost, need for retraining of surgeons, and restricted clinical efficacy. While monopolar electrosurgery remains the only practical method for performing the full range of tissue cutting and coagulating functions in invasive surgery, the risk to which patients may be injured by stray electrical currents is unacceptable. ElectroScope, Inc., has responded to the need for a technology to make monopolar electrosurgery as safe as it is efficacious by providing shielding and monitoring with its Electroshield¨ System. As an integrated system, the Electroshield System makes use of Active Electrode Monitoring (AEMª) to eliminate the danger of stray electrical energy during monopolar electrosurgery in MIS. The Electroshield Monitoring System consists of an integrated shield within the surgical electrode as well as a monitoring module that interfaces with electrosurgical units (ESUs) in the operating room to help detect leaking RF currents and to interrupt the ESU when currents could injure the patient. By developing technology to ensure patient safety by monitoring the flow of the electrical current through the active monopolar electrode, ElectroScope has pioneered a method to ensure patient safety during laparoscopic electrosurgery and thereby opened the door for further expansion of MIS procedures. Causes of Patient Injury During Monopolar Laparoscopic Electrosurgery During minimally invasive procedures, surgeons utilize a laparoscope to provide a magnified view of the small area of tissue to which the surgeon expects all of the RF electrosurgical energy to be delivered. This restricted field of view, however, precludes visualization of 90 percent of the active electrode, and it is from this obscured portion that stray energy release can cause severe burns beyond the surgeon's view. Stray energy can be released from the active electrode in two ways: insulation breakdown or capacitive coupling. Insulation Breakdown The shaft of the active electrode is covered by a layer of insulation material to protect surrounding tissue from the high voltages used during electrosurgery. However, each use of the instrument increases the possibility of damage to the shaft insulation during surgery, postoperative clean-up, and instrument sterilization processes. Some hospitals have devised guidelines for their surgical staffs to examine the equipment for insulation failure. These guidelines, however, are not always adhered to, and even when they are, defective insulation can go unnoticed. Normal wear, improper handling, and damage from contact with sharp instruments, such as the edges of the trocar cannula (the tube through which the active electrode is inserted into the abdominal cavity) can impair electrode insulation. Even if the insulation is intact prior to surgery, insulation damage can also occur during the actual procedure. Although cumulative breakdown of insulation can be reduced by using disposable electrodes, even they can be damaged during electrosurgical procedures, resulting in failure. Cracks or breaks in the insulation allow electrical current to leak into and damage surrounding tissues; paradoxically, small cracks are worse than large breaks because the energy is more concentrated and therefore more likely to burn. Capacitive Coupling Electrosurgical burns can occur through a mechanism called capacitive coupling even when insulation surrounding the active electrode is intact. During electrosurgery, the electrode voltage switches from highly positive to highly negative at a very high frequency. The rapidly varying electrical field around the electrode passes easily through the insulation and induces electrical currents by alternately attracting and repelling the ions in the patient's tissue. The movement of these electrically charged ions produces an electric current that can heat the tissue enough to burn it. If the trocar cannula is metal, the concern for the tissue damage decreases because the current can be absorbed by the trocar cannula and dispersed over a relatively large area of contact with the abdominal wall. In contrast, hybrid (a combination of plastic and metal) trocars prevent the current from being transferred to the abdominal wall and dispersed. The current may therefore flow from any metal portion of the hybrid sleeve to surrounding non-targeted tissue and organs. Nevertheless, surrounding tissues can themselves become capacitively coupled to the active electrode, even with the use of a metal cannula. When this happens, currents may develop in the tissue that can cause burns if they reach a great enough current density. Electroshield Monitoring System The Electroshield Monitoring System integrates electrode shielding with a monitoring system based on proprietary Active Electrode Monitoring (AEM) technology. By monitoring the electrical currents in the shield, AEM can detect stray electrical energy currents due to insulation breakdown all along the shaft of the active electrode, even that part lying outside the surgeon's laparoscopic view. If stray currents are sufficiently strong, the AEM circuitry shuts down the ESU and an audible alarm notifies the surgeon and surgical staff, fully protecting the patient from tissue burns resulting from insulation failure. The Electroshield System also fully protects against patient injury due to capacitive coupling. ElectroScope's electrosurgical instruments include a metal shield that covers the insulating layer of the active electrode. The conductive shield itself becomes capacitively coupled to the active electrode to trap and drain away the high frequency electrical energy. Thus the shield prevents capacitive coupling between the electrode and surrounding tissues and completely eliminates the possibility of patient injury due to capacitive coupling. The complete monitoring system consists of three separate components. * The EM-2 Electronic Monitor is an electronic processing unit that monitors the current flow from the ESU through the active electrode and signals the ESU and the surgeon if stray electrical energy is detected. * For use in conjunction with the EM-2 monitor, the Electroshield System includes a complete line of electrosurgical instruments (ES-3500 and ES-5700 Series) that incorporate ElectroScope's unique shielding technology. Common fixed-tip and modular instruments, including hooks, spatulas, needles, scissors, graspers, and dissectors, are all available with the benefits of the Electroshield System. They are similar in shape, size, and feel to unshielded instruments, but they employ AEM to eliminate the release of stray electrical energy. The shielded instruments are easily disassembled for cleaning and sterilization. * A line of protective sheaths (ES-2000 Series) provides Electroshield technology compatible with laparoscopic instruments from other manufacturers. These sheaths give unshielded instruments the additional protection that AEM provides and allows their use in conjunction with the EM-2 monitor. The EM-2 electronic monitor has indicator lights and tone prompts that help guide the user through system setup. Once in use, the AEM System includes three alarms for three different situations. One alarm sounds when the current flow from the shield exceeds a predetermined value detecting either insulation failure or excessive capacitive coupling. Another notifies the surgeon whenever a discontinuity exists in the electrical pathway from the shield to the monitoring unit. The last alarm visually indicates if the EM-2 monitor does not have contact quality information from the electrosurgical unit connection. The Electroshield Monitoring System is easy to use and is "transparent" to the surgeon. Little training on the use of the system is required--the instruments are essentially identical to those unprotected instruments currently used, and the EM-2 electronic monitoring unit plugs directly into the operating room's electrosurgical generator. The initial capital investment in an entire Electroshield Monitoring System is negligible compared with the cost of post-surgery treatment for even one severe electrosurgical complication. The cost of the Electroshield instruments is comparable to the cost of otherwise similar reusable minimally invasive electrosurgery instruments. On a cost-per-use basis, Electroshield instruments are less expensive than disposable equipment. Third-Party Support for the Electroshield Monitoring System The Emergency Care Research Institute (ECRI), an independent, non-profit research agency that reviews and tests medical devices, has conducted unsolicited laboratory tests and determined that ElectroScope's Electroshield Monitoring System successfully and safely prevents current leakage from burning a patient at an unintended site. In its report published in Health Devices in January 1995, ECRI recommended the Electroshield System above other protective measures because it offers the highest level of protection against patient injury due to insulation failure and capacitive coupling. The AEM System has been recognized in prominent medical journals, such as Gynaecological Endoscopy, as well as in guidelines endorsed by professional societies, for its contribution to the safe and effective application of the monopolar electrosurgical technique. In its recommendations for preventing complications during intraoperative preparation for minimally invasive electrosurgery, the American Association of Gynecological Laparoscopists urges surgeons to consider use of the AEM System. Medical textbooks including general, gynecological, and urological surgery describe the fundamentals of operation of AEM and the clinical need to protect patients from harm. Conclusion As surgeons, healthcare providers, and indirectly healthcare insurers are responsible for their patients' well-being and safety, they have a responsibility to ensure the application of all appropriate measures to protect their patients from potential injury. Use of Active Electrode Monitoring greatly minimizes the possibility of non- targeted tissue burns and other complications as a result of stray electrical energy during minimally invasive electrosurgery. The use of Active Electrode Monitoring offers the only universal protection to the patient for the prevention of stray engergy burns. End of document.