Electrosurgery Burns and the Urologist

Vol. 116, August

THE JOURNAL OF UROLOGY

Printed in U.S.A.

Copyright© 1976 by The Williams & Wilkins Co.

ELECTROSURGERY BURNS AND THE UROLOGIST GERALD R. GOODMAN From the St. Luke's Episcopal Hospital, Texas Children's Hospital, Texas Heart Institute, Houston, Texas

ABSTRACT

Investigations into the problems associated with electrosurgery machines have concentrated on protecting the patient from radio frequency burns. While protection of the patient is essential an equally serious and dangerous situation exists in protecting the surgeon, particularly the urologist during transurethral resection of the prostate. The 2 subtle causes of burns to the surgeon are reviewed-capacitive coupling and grounding paths that include the surgeon. Protection of the surgeon as well as the patient depends upon an awareness of the peculiar mating of high frequency current and the grounded environment of the operating room. Investigations into the problems associated with electrosurgery machines have concentrated on protecting the patient from radio frequency bums and, more recently, protection against current levels sufficient to cause ventricular fibrillation. The newer generation of electrosurgery machines includes various means to limit 60-cycle leakage current in the patient circuit and to eliminate from the electrosurgery patient circuit any grounding paths for radio frequency current. Naturally, protection of the patient from equipment failures is necessary. The present set of codes and laws dealing with medical equipment safety was prompted by the consideration for the safety of patients. However, in electrosurgery an equally serious and dangerous situation exists in providing protection for the surgeon from the same radio frequency bums that plague the patient. There has been a small but constant stream of incidents involving radio frequency bums to the hands, face and scrotum of the surgeon. The real danger, of course, is the secondary reaction of the surgeon to the painful bum and the disruption of the surgical procedure. The most often affected surgeon is the urologist during transurethral resection of the prostate. Regular preventive maintenance of electrosurgery machines can eliminate most bum problems caused by faulty connectors and alarm systems 1 ·• and can guarantee that all machines of the same model type have similar output current and performance. Our p:ieventive maintenance program has each of our 32 electrosurgery machines checked for safety and output power at least once every 4 months. We provide the operating room with a composite graph of the output current versus control settings once a year as documentation of this performance uniformity (fig. 1). Poorly positioned or defective grounding plates are a well documented cause of burns. 5 ' 6 More subtle causes of bums are capacitively coupled high frequency current and stray grounding paths that involve the surgeon. Many times the stray grounding path is a result of this capacitive coupling. CAPACITNE COUPLING

Prevention of radio frequency bums to the surgeon is a problem of electrically isolating the surgeon while he is in an operating room that by law must have all instrumentation and metal electrically grounded. 7 The achievement of electrical isolation is complicated because of the high frequency current generated by the electrosurgery machine. Capacitive coupling is invariably present. As frequency increases the electrical impedance presented by a capacitor decreases. Consequently, Accepted for publication November 14, 1975. 218

procedures such as measuring a resectoscope or loop for good resistance with a direct current ohmmeter relate its resistance to low frequency current. Other than detecting a direct short the procedure relates nothing about radio frequency current resistance. An example of the effect of capacitive coupling in electrosurgery is shown by the test set-up of figure 2. The amount of radio frequency current that passes through the jacket of an electrosurgery active cable is demonstrated. This test set-up also can demonstrate the amount of radio frequency current available on the metal of a resectoscope during a normal procedure (no faults in either the patient circuit or the electrosurgery machine). The results of the tests are shown in figure 3. The test set-up is a duplication of one used by the Emergency Care Research Institute. 8 However, we tested for leakage current levels at all cut and coagulation positions rather than just the higher power cut 2 position. To test the active cables they were attached to the active terminal of the electrosurgery machine. A section of the cable was then taped to a metal ground plate. The return cable from the plate was attached in series to a dummy patient load and radio frequency ammeter and then to the patient terminal of the machine. In the case of the resectoscope an alligator clip was secured to the resectoscope's metal frame in substitution of the ground plate. The test meter is a O to 250 milliamp radio frequency thermocouple ammeter with a 500 ohm non-inductive test load to simulate a patient. The test load also prevents a short circuit condition from developing should one of the accessories under test fail. Figure 3 shows the output current curves for solidstate and CSV machines. The total current available from the machines into a 500 ohm test load is given along with the leakage current levels from an active cable (typical values) and a resectoscope with and without a loop inserted. Figure 3 also shows that while the solid-state machine has a higher average current output the higher frequency and greater peak current of the Bovie increase the leakage current. Our solid-state machine had a cut 1 frequency of 588 kilohertz, the Bovie a cut 1 frequency of 2 megahertz. The leakage current increases with the loop inserted into the resectoscope is owing to the current leakage through the entire length of the loop as opposed to the current being confined to the isolation block when the loop is not inserted. A figure of 100 milliamps per cm. 2 for 10 seconds can cause skin damage. 9 Sufficient current exists on the resectoscope metal to consider it to be a potential hazard at best. A modification involving direct grounding of the resectoscope will serve to drain off the current. A drawback to this is that a fault in the patient return circuit could make the grounded resectoscope the patient return circuit pathway.

219

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FIG. 2. Test set-up to demonstrate effect of capacitive coupling and resulting radio frequency leakage current available during electrosurgery GROUNDING PATHS

Ungrounding the surgeon, as previously mentioned, is complicated by the fact that the operating room is a grounded environment (fig. 4). Typically, the patient is in direct contact with a grounded table by lying on a conductive mattress. During transurethral resection of the prostate further contact between the patient and table is provided by the leg supports. The patient serves as an electrically common point between earth ground and the patient return of the circuit of the electrosurgery machine (point A of figure 4). The urologist is in direct contact with the patient, the grounded table, a conductive floor and usually a grounded floor drain. Listed in the table are the radio frequency current readings made between the 2 simulated conduction paths available during transurethral resection of the prostate. A CSV Bovie and a machine with an isolated patient circuit were used for this test. It is evident from the readings that an alternate current path exists through the urologist even though an intact and functioning patient return circuit exists. As much as 180 current passes through the surgeon circuit. The actual value of resistive load

presented by the patient and surgeon may vary but the pathway still exists. CONCLUSION AND SUMMATION

Radio frequency bums to the patient are typically the result of poor connectors, cables or an improperly placed patient plate or pad. For radio frequency burns to the surgeon the problem is much more complex because of the need to unground the surgeon from the grounded operating theater. The degree to which a surgeon, and particularly a urologist, can be isolated from grounding paths that include the electrosurgery machine will depend upon the individual operating room facility in which the surgeon is working. The individual situation must be systematically examined to determine the extent of grounding used to meet National Fire Protection Association codeso Inadvertent grounding paths such as floor drain covers need to be examined and eliminated if possible. VVooden stools have been suggested as a means of 1 source of surgeon Thicker rubber put on vvhe:n both are can reduce the effects of

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hydration on the gloves and thereby provide some insulation against stray current. 10 Better insulation of resectoscopes and loops would seem appropriate. Even the technique of the urologist during transurethral resection of the prostate can help. Rapid, forceful twisting of the resectoscope combined with the extremely wet operating field can cause connections to loosen and admit water. The water then couples the radio frequency current to the resectoscope metal. Effective connection of the patient to the patient plate or pad is still a primary consideration. This circuit, by providing the path of least re-

1. Battig, C. G.: Electrosurgical burn injuries and their prevention. J.A.M.A., 204: 1025, 1968. 2. Holder, A. R.: Electrosurgical instruments. J .A.M.A., 223: 111, 1973. 3. Leeming, M. N., Ray, C., Jr. and Howland, W. S.: Low voltage, direct-current burns. J.A.M.A., 214: 1681, 1970. 4. Wald, A. S., Mazzia, V. D. B. and Spencer, F. C.: Accidental burns associated with electrocautery. J.A.M.A., 217: 916, 1971. 5. Billin, A. G.: Patient safety and electrosurgery. A.0.R.N. J., 14: 62, August 1971. 6. Church, R. T.: ·safety considerations for electrosurgical unit use. A.O.R.N. J., 16: 79, September 1972. 7. Inhalation Anesthetics, National Fire Protection Association, 56A, 1973. 8. Disposable electrosurgical active handles. Health Devices, 2: 256, 1973. 9. Becker, C. M., Malhotra, I. V. and Hedley-Whyte, J.: The distribution of radiofrequency current and burns. Anesthesiology, 38: 106, 1973. 10. Miller, J. M., Collier, C. S. and Griffith, N. M.: Permeability of surgical rubber gloves. Amer. J. Surg., 124: 57, 1972.