Otology & Neurotology 36:600Y603 2015, Otology & Neurotology, Inc.
Does Electrocautery Damage Cochlear Implants? Anita Jeyakumar, Neal M. Jackson, Victoria B. Givens, Todd M. Brickman, and Moise´s A. Arriaga Department of Otorhinolaryngology, Louisiana State University-Health Science Center, New Orleans, Louisiana, U.S.A.
Objectives: 1) Evaluate the effects of monopolar cautery on cochlear implant devices. 2) Determine whether voltage fluctuations within the cochlear implant adversely affect the cochlear implant devices Study Design: Two Med-El cochlear implants modified to record voltage difference from the apical and proximal electrodes were implanted into an unembalmed, fresh cadaver. Cautery was applied to the ipsilateral pectoralis major muscle and ipsilateral temporalis muscle at bipolar, monopolar coagulation, and monopolar cut settings of 50 W. The intensity in each modality setting was increased by increments of 10 W to a maximum of 100 W. Integrity testing was performed before, during, and after each cautery setting. Voltage fluctuations were measured during cautery, and maximal voltage changes for each setting were noted. After explantation, devices were returned to the manufacturer for in-depth failure analysis to evaluate for any damage to the devices.
Setting: Tertiary medical center. Subjects: Cadaveric study. Methods: Basic science laboratory. Results: No change in impedance or integrity testing occurred at any cautery setting when applied to either to pectoralis major or temporalis. The maximum voltage change was 22 V. Comprehensive device analysis showed no evidence of device damage from the study. Conclusions: The cochlear implant devices had no evidence of electrical damage by monopolar cautery, even up to levels of 100 W in the temporalis muscle. The maximum voltage change was 22 V, likely resulting from protecting diodes within the implant. Additional study is necessary, but more flexible recommendations regarding electrosurgery in cochlear implant recipients should be considered. Key Words: Cochlear implantV Cochlear implant failureVElectrocautery. Otol Neurotol 36:600Y603, 2015.
Cochlear implantation (CI) has been used successfully in the management of pediatric and adult severe to profound sensorineural hearing loss. Cochlear implant devices enable partial restoration of hearing through electrical excitation of neural structures in the cochlea. The use of monopolar electrocautery has been widely regarded as a contraindication in the setting of a cochlear implant because of a
presumed risk to the implant and the patient. Though there is little conclusive evidence for this, the concerns are twofold. First, the electrical current may damage the device itself; second, the heat generated through monopolar electrocautery may damage the auditory neurons because of the close proximity of the electrode array within the cochlea. Antonelli et al. (2007) had examined the effects of monopolar electrocautery on cochlear implant devices implanted into cadaveric pigs and found no damage to the implants (1). Poetker et al. (2004) evaluated neural response telemetry before and after monopolar electrocautery on a patient undergoing open heart surgery and found no damage to neural integrity or the implant (2). Our group published preliminary data showing that monopolar electrocautery did not produce detectible damage to any of the cochlear implant devices (Med-El, Cochlear, Advanced Bionics) or produce detectible temperature change in the cochlea, at low (10 W) or high levels (50 W) of electrocautery in the oral cavity in our experimental cadaveric model (3). For the purpose of this paper, electrosurgery is surgery using a high-frequency electric current to generate heat. Electrocautery is a cautery using a needle or other
Address correspondence and reprint requests to Anita Jeyakumar, M.D., M.S., F.A.C.S., Department of Otorhinolaryngology, 200 Henry Clay Avenue, Suite 4119, New Orleans, LA 70118, U.S.A.; E-mail [email protected] This project was completed at Louisiana State University-Health Science Center. Financial Disclosure: Temporal Bone Course support at Louisiana State University from Stryker Corporation, Med-El Corporation, Advanced Bionics Corporation, Cochlear Corporation, Armamentarium Corporation, and Zeiss Corporation. M.A.A.: Surgeon’s Advisory BoardVMed-El Corporation and Royalties from Elsevier Corporation. Level of Evidence: 1C. Disclosures: Cochlear implants devices and damage analysis was provided free of charge by Med-El (two devices). No other financial contributions were made. This abstract was presented as a podium presentation at the annual meeting of the Triological Society, Friday, May 16, 2014.
600
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
DOES ELECTROCAUTERY DAMAGE COCHLEAR IMPLANTS?
601
conductive instrument that is electrically heated. The terms sometimes are used interchangeably. The objectives of the current study are to 1) evaluate the effects of electrocautery on cochlear implant devices and to 2) determine whether voltage fluctuations across the cochlear implant arising from electrocautery stray current affect the cochlear implant devices. METHODS Permission for the study was obtained from the anatomy department per the institutional IRB requirements. Med-El (Innsbruck, Austria, Europe) agreed to participate in the study and donated two modified Med-El Concert devices (Fig. 1). The devices were modified to be able to measure voltages between electrode 1 (most apical) and the grounding electrode, and electrode 12 (most basal) and the grounding electrode on the stimulator housing (Fig. 1). The modifications were made using insulated wires and miniature connectors connected to electrode wires and contacts. No modifications inside the hermetically sealed stimulator housing were made. Hermeticity of the devices was unaffected. An engineer from Med-El was present for the study and performed intraoperative integrity and impedance testing. The manufacturer had knowledge of the protocol of the study and was present for the real-time recordings done during the study. The manufacturer performed its own analysis upon completion of our testing but did not participate in the data analysis or preparation of the manuscript. A fresh, unembalmed human cadaver was used for the experiment. The cadaver was positioned supine and the grounding pad was placed on the right leg. A single skin incision from acromion to acromion was used to fully expose the pectoralis major muscle bilaterally. A wide skin incision was made and a large scalp flap was raised to expose the temporalis muscle and mastoid bone (Fig. 2). Mastoidectomy and drilling of the facial recess were performed using standard methods. A cochleostomy was made anterior to the round window. The steps were performed bilaterally. Monopolar electrosurgery was performed with the Valley Lab Force FX electrosurgery generator with the E2516 Electrosurgery pencil (Covidien, Mansfield, MA) and E4051-CT Bipolar forceps (Covidien, Mansfield, MA). Each device was tested at the factory before shipping to ensure normal function. Integrity and impedance testing was performed by standard methods before implantation, after implantation, and before any electrocautery. Impedance telemetry was checked at the beginning and after each use of electrocautery to ensure that the device was covered in saline and not insulated by air. Voltage measurements were taken in real time during cautery with each method of cautery.
FIG. 1. Cochlear implant modified to measure voltages between channels 1 and 12.
FIG. 2. The modified cochlear implant was inserted, and the inferior portion of the left-sided skin incision was partially closed to keep the implant in place while maintaining exposure of temporalis muscle for electrocautery.
The first device was implanted in the right ear. The electrode array was partially inserted because of anatomic obstruction (electrodes 10, 11, and 12 were extracochlear)Vfortuitously this allowed us to see if an incomplete insertion affected the device differently from a complete insertion. Furthermore, because the devices and electrodes were covered with saline, there was no concern about influencing the validity of the experimental model resulting from this incomplete insertion. Electrocautery was first performed on the ipsilateral pectoralis major muscle. Bipolar electrocautery was started at 50 W. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations between channel 1 and the stimulation reference electrode of the implant were measured during electrocautery. The second modality was monopolar electrocautery ‘‘cut’’ at 50 W. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations between channel 1 and the stimulation reference electrode of the implant were measured during electrocautery. The third modality was monopolar electrocautery ‘‘coagulation’’ at 50 W. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations between channel 1 and the stimulation reference electrode of the implant were measured during electrocautery. Each modality was repeated, increasing the power in increments of 10 W, until 100 W was reached. The testing was done by a trained representative from the manufacturer during testing. Electrocautery was then performed on the ipsilateral temporalis muscle using the same sequence of electrocautery settings and length of application. The second device was implanted in the left ear. The electrode array was completely inserted. Electrocautery was performed on the ipsilateral temporalis muscle only using bipolar electrocautery, monopolar electrocautery on ‘‘cut,’’ and electrocautery on ‘‘coagulate’’ using the same protocol described for the right ear. Each modality was repeated, increasing the power in increments of 10 W, until 100 W was reached. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations were measured during electrocautery. The testing was done by a trained representative from the cochlear implant manufacturer. Recording of the voltages between either channel 1 or channel 12 and the stimulation reference electrode on the implant stimulator was performed with an Agilent InfiniiVision MSO-X3024A storage oscilloscope (Agilent, Santa Clara, CA) by differential measurement, using two Agilent N2863B passive 10:1 probes (Agilent, Santa Clara, CA). Voltage recordings were done for Otology & Neurotology, Vol. 36, No. 4, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
602
A. JEYAKUMAR ET AL.
channels 1 and 12 in both devices, recognizing the right cochlear implant was partially inserted, and the left cochlear implant was completely inserted. Amplitudes were measured with cursors and voltage measurement function of the oscilloscope. Time base of the oscilloscope was set to 10 Ks/div, voltage settings to 50 V/div. After device removal, devices were repackaged, sealed, and returned to the manufacturer for an in-depth, piece-by-piece analysis to look for any damage caused by electrocautery.
RESULTS The protocol was completed for two devices. Cochlear Implant Analysis At each measured time point and at the end of electrocautery up to 100 W, there was no change in the impedance or integrity testing for both implants tested. Impedance testing at the beginning of testing and after each application of electrocautery served both as a functional check of the implant and as confirmation that the implant electrodes always had tissue contact and that testing was not invalid because of the presence of any air bubbles. In-depth analysis of each component of the cochlear implant did not show any evidence of electrical or thermal damage to the device. Voltage Analysis Screenshot evaluations from the oscilloscope showed voltage changes within the implant (between an intracochlear channel and the remote ground electrode on the implant housing) up to about 22 V. The voltage changes were the least for bipolar electrocautery and maximum for monopolar electrocautery on the ‘‘cut’’ modality. DISCUSSION Many patients who receive a cochlear implant will require an additional surgical procedure in their lifetime which may require the use of electrocautery. Some patients with cochlear implants may even require emergency surgery. Concern that electrosurgery may render a cochlear implant unusable continues to be a source of anxiety for patients and providers. Our preliminary published data found no damage to the implant device and no thermal change in the cochlea after high-current monopolar electrocautery (50 W), even in close proximity to the cochlea (3). Electrocautery devices such as the Bovie use radiofrequency energy delivered through an electrode and applied directly to tissues (4). The energy is transferred to the tissues and heat is generated through the electrical resistance of these tissues (4). The cochlear implant devices also use a radiofrequency current to transmit signal from the external transmitting coil to the receiver/stimulator implant (5). The receiver/stimulator then delivers electric stimulation pulses to the electrode array. The electrodes stimulate neural elements within the cochlea through a series of bipolar current pulses. Numerous papers and authors have raised concern regarding the use of electrocautery in patients with cochlear implants (6Y9). However, much of the opposition to elec-
trocautery in cochlear implant patients is based on extrapolated effects from cardiac pacemakers (10). Our in situ voltage measurements did show a voltage drop between implant electrodes with electrocautery, both with bipolar electrocautery as well as monopolar electrocautery. However, the maximum voltage drop across the implant was 22 V, reached at electrocautery settings of 50 W. Even with electrocautery settings of 100 W, the voltage drop across the implant did not exceed 22 V. This shows that the protecting diodes within the cochlear implant device limit the maximum voltage across the implant and dissipate energy, thus protecting the electronics from a high-voltage draw. Electrocautery was applied for 1 minute per test condition which represented a potential worst-case scenario for the protecting diodes during a thermal load. LIMITATIONS There are several limitations to our study. The most significant limitation is the use of a cadaveric specimen for the study. Though the cadavers were unembalmed, there may be differences in the current flow between living and non-living tissues. The second limitation of the study is that we only tested two examples of one cochlear implant device by one manufacturer. It is as yet unclear whether the results will apply to all devices used for cochlear implantation. Additionally, the study does not assess if a future soft failure of the device could happen as a result of the electrocautery. Our group is still not advocating use of monopolar electrocautery in patients with a cochlear implant. However, we need to start considering more flexible recommendations, as increasing data from our laboratory is showing no ill effects from electrocautery. We are pursuing additional investigations in our laboratory to study this further. CONCLUSION Electrocautery did not produce detectible damage to any of the cochlear implant devices or produce significant voltage fluctuations within the devices at up to 100 W levels of electrosurgery in the ipsilateral temporalis and ipsilateral pectoralis major muscles in this experimental model. This project extends the previous findings in our laboratory by showing that settings up to 100 W did not damage the cochlear implant devices and by defining the maximum voltage between the active electrode and the ground electrode. The maximum voltage change was 22 V likely resulting from protecting diodes within the implant. Additional study is necessary, but more flexible recommendations regarding electrocautery in cochlear implant recipients should be considered. Acknowledgments: We would like to thank the following individuals and groups: • Dr. Richard Whitworth for providing the temporal bones and for his full support of the study. • Med-El Ltd for their technical support and provision of the devices.
Otology & Neurotology, Vol. 36, No. 4, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
DOES ELECTROCAUTERY DAMAGE COCHLEAR IMPLANTS? • Martin Zimmerling for his technical assistance and enthusiasm for the project. • The study would not have been possible without the donors of the cadavers and their families.
REFERENCES 1. Antonelli PJ, Barateli R. Cochlear implant integrity after adenoidectomy with coblation and monopolar electrocautery. Am J Otolaryngol 2007;29:9Y12. 2. Poetker DM, Runge-Samuelson CL, Firszt JB, Wackym PA. Electrosurgery after cochlear implantation: eighth nerve electrophysiology. Laryngoscope 2004;114:2252Y4. 3. Jeyakumar A, Wilson M, Sorrel JE, et al. Monopolar cautery and adverse effects on cochlear implants. JAMA Otolaryngol Head Neck Surg 2013;139:694Y7.
603
4. Vilos GA, Rajakumar C. Electrosurgical generators and monopolar and bipolar electrosurgery. J Minim Invasive Gynecol 2013;20:279Y87. 5. Zierhofer CM, Hochmair IJ, Hochmair ES. The advanced Combi 40+ cochlear implant. Am J Otol 1997;18(6 Suppl):S37Y8. 6. Roland JT, Fishman AJ, Waltzman SB, Cohen NL. Shaw scalpel in revision cochlear implant surgery. Ann Otol Rhinol Laryngol Suppl 2000;185:23Y5. 7. Laszig R, Ridder GJ, Aschendorff A, Fradis M. Ultracision: an alternative to electrocautery in revision cochlear implant surgery. Laryngoscope 2002;112:190Y1. 8. Tognola G, Parazzini M, Sibella F, Paglialonga A, Ravazzani P. Electromagnetic interference and cochlear implants. Ann 1st Super Sanita 2007;43:241Y7. 9. Roberts S, West LA, Liewehr FR, Rueggeberg FA, Sharpe DE, Potter BJ. Impact of dental devices on cochlear implants. J Endod 2002;28:40Y3. 10. Mangar D, Atlas GM, Kane PB. Electrocautery-induced pacemaker malfunction during surgery. Can J Aneaesth 1991;38:616Y8.
Otology & Neurotology, Vol. 36, No. 4, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
Does Electrocautery Damage Cochlear Implants? Anita Jeyakumar, Neal M. Jackson, Victoria B. Givens, Todd M. Brickman, and Moise´s A. Arriaga Department of Otorhinolaryngology, Louisiana State University-Health Science Center, New Orleans, Louisiana, U.S.A.
Objectives: 1) Evaluate the effects of monopolar cautery on cochlear implant devices. 2) Determine whether voltage fluctuations within the cochlear implant adversely affect the cochlear implant devices Study Design: Two Med-El cochlear implants modified to record voltage difference from the apical and proximal electrodes were implanted into an unembalmed, fresh cadaver. Cautery was applied to the ipsilateral pectoralis major muscle and ipsilateral temporalis muscle at bipolar, monopolar coagulation, and monopolar cut settings of 50 W. The intensity in each modality setting was increased by increments of 10 W to a maximum of 100 W. Integrity testing was performed before, during, and after each cautery setting. Voltage fluctuations were measured during cautery, and maximal voltage changes for each setting were noted. After explantation, devices were returned to the manufacturer for in-depth failure analysis to evaluate for any damage to the devices.
Setting: Tertiary medical center. Subjects: Cadaveric study. Methods: Basic science laboratory. Results: No change in impedance or integrity testing occurred at any cautery setting when applied to either to pectoralis major or temporalis. The maximum voltage change was 22 V. Comprehensive device analysis showed no evidence of device damage from the study. Conclusions: The cochlear implant devices had no evidence of electrical damage by monopolar cautery, even up to levels of 100 W in the temporalis muscle. The maximum voltage change was 22 V, likely resulting from protecting diodes within the implant. Additional study is necessary, but more flexible recommendations regarding electrosurgery in cochlear implant recipients should be considered. Key Words: Cochlear implantV Cochlear implant failureVElectrocautery. Otol Neurotol 36:600Y603, 2015.
Cochlear implantation (CI) has been used successfully in the management of pediatric and adult severe to profound sensorineural hearing loss. Cochlear implant devices enable partial restoration of hearing through electrical excitation of neural structures in the cochlea. The use of monopolar electrocautery has been widely regarded as a contraindication in the setting of a cochlear implant because of a
presumed risk to the implant and the patient. Though there is little conclusive evidence for this, the concerns are twofold. First, the electrical current may damage the device itself; second, the heat generated through monopolar electrocautery may damage the auditory neurons because of the close proximity of the electrode array within the cochlea. Antonelli et al. (2007) had examined the effects of monopolar electrocautery on cochlear implant devices implanted into cadaveric pigs and found no damage to the implants (1). Poetker et al. (2004) evaluated neural response telemetry before and after monopolar electrocautery on a patient undergoing open heart surgery and found no damage to neural integrity or the implant (2). Our group published preliminary data showing that monopolar electrocautery did not produce detectible damage to any of the cochlear implant devices (Med-El, Cochlear, Advanced Bionics) or produce detectible temperature change in the cochlea, at low (10 W) or high levels (50 W) of electrocautery in the oral cavity in our experimental cadaveric model (3). For the purpose of this paper, electrosurgery is surgery using a high-frequency electric current to generate heat. Electrocautery is a cautery using a needle or other
Address correspondence and reprint requests to Anita Jeyakumar, M.D., M.S., F.A.C.S., Department of Otorhinolaryngology, 200 Henry Clay Avenue, Suite 4119, New Orleans, LA 70118, U.S.A.; E-mail [email protected] This project was completed at Louisiana State University-Health Science Center. Financial Disclosure: Temporal Bone Course support at Louisiana State University from Stryker Corporation, Med-El Corporation, Advanced Bionics Corporation, Cochlear Corporation, Armamentarium Corporation, and Zeiss Corporation. M.A.A.: Surgeon’s Advisory BoardVMed-El Corporation and Royalties from Elsevier Corporation. Level of Evidence: 1C. Disclosures: Cochlear implants devices and damage analysis was provided free of charge by Med-El (two devices). No other financial contributions were made. This abstract was presented as a podium presentation at the annual meeting of the Triological Society, Friday, May 16, 2014.
600
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
DOES ELECTROCAUTERY DAMAGE COCHLEAR IMPLANTS?
601
conductive instrument that is electrically heated. The terms sometimes are used interchangeably. The objectives of the current study are to 1) evaluate the effects of electrocautery on cochlear implant devices and to 2) determine whether voltage fluctuations across the cochlear implant arising from electrocautery stray current affect the cochlear implant devices. METHODS Permission for the study was obtained from the anatomy department per the institutional IRB requirements. Med-El (Innsbruck, Austria, Europe) agreed to participate in the study and donated two modified Med-El Concert devices (Fig. 1). The devices were modified to be able to measure voltages between electrode 1 (most apical) and the grounding electrode, and electrode 12 (most basal) and the grounding electrode on the stimulator housing (Fig. 1). The modifications were made using insulated wires and miniature connectors connected to electrode wires and contacts. No modifications inside the hermetically sealed stimulator housing were made. Hermeticity of the devices was unaffected. An engineer from Med-El was present for the study and performed intraoperative integrity and impedance testing. The manufacturer had knowledge of the protocol of the study and was present for the real-time recordings done during the study. The manufacturer performed its own analysis upon completion of our testing but did not participate in the data analysis or preparation of the manuscript. A fresh, unembalmed human cadaver was used for the experiment. The cadaver was positioned supine and the grounding pad was placed on the right leg. A single skin incision from acromion to acromion was used to fully expose the pectoralis major muscle bilaterally. A wide skin incision was made and a large scalp flap was raised to expose the temporalis muscle and mastoid bone (Fig. 2). Mastoidectomy and drilling of the facial recess were performed using standard methods. A cochleostomy was made anterior to the round window. The steps were performed bilaterally. Monopolar electrosurgery was performed with the Valley Lab Force FX electrosurgery generator with the E2516 Electrosurgery pencil (Covidien, Mansfield, MA) and E4051-CT Bipolar forceps (Covidien, Mansfield, MA). Each device was tested at the factory before shipping to ensure normal function. Integrity and impedance testing was performed by standard methods before implantation, after implantation, and before any electrocautery. Impedance telemetry was checked at the beginning and after each use of electrocautery to ensure that the device was covered in saline and not insulated by air. Voltage measurements were taken in real time during cautery with each method of cautery.
FIG. 1. Cochlear implant modified to measure voltages between channels 1 and 12.
FIG. 2. The modified cochlear implant was inserted, and the inferior portion of the left-sided skin incision was partially closed to keep the implant in place while maintaining exposure of temporalis muscle for electrocautery.
The first device was implanted in the right ear. The electrode array was partially inserted because of anatomic obstruction (electrodes 10, 11, and 12 were extracochlear)Vfortuitously this allowed us to see if an incomplete insertion affected the device differently from a complete insertion. Furthermore, because the devices and electrodes were covered with saline, there was no concern about influencing the validity of the experimental model resulting from this incomplete insertion. Electrocautery was first performed on the ipsilateral pectoralis major muscle. Bipolar electrocautery was started at 50 W. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations between channel 1 and the stimulation reference electrode of the implant were measured during electrocautery. The second modality was monopolar electrocautery ‘‘cut’’ at 50 W. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations between channel 1 and the stimulation reference electrode of the implant were measured during electrocautery. The third modality was monopolar electrocautery ‘‘coagulation’’ at 50 W. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations between channel 1 and the stimulation reference electrode of the implant were measured during electrocautery. Each modality was repeated, increasing the power in increments of 10 W, until 100 W was reached. The testing was done by a trained representative from the manufacturer during testing. Electrocautery was then performed on the ipsilateral temporalis muscle using the same sequence of electrocautery settings and length of application. The second device was implanted in the left ear. The electrode array was completely inserted. Electrocautery was performed on the ipsilateral temporalis muscle only using bipolar electrocautery, monopolar electrocautery on ‘‘cut,’’ and electrocautery on ‘‘coagulate’’ using the same protocol described for the right ear. Each modality was repeated, increasing the power in increments of 10 W, until 100 W was reached. Impedance and integrity testing was repeated after 1 minute of electrocautery. Voltage fluctuations were measured during electrocautery. The testing was done by a trained representative from the cochlear implant manufacturer. Recording of the voltages between either channel 1 or channel 12 and the stimulation reference electrode on the implant stimulator was performed with an Agilent InfiniiVision MSO-X3024A storage oscilloscope (Agilent, Santa Clara, CA) by differential measurement, using two Agilent N2863B passive 10:1 probes (Agilent, Santa Clara, CA). Voltage recordings were done for Otology & Neurotology, Vol. 36, No. 4, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
602
A. JEYAKUMAR ET AL.
channels 1 and 12 in both devices, recognizing the right cochlear implant was partially inserted, and the left cochlear implant was completely inserted. Amplitudes were measured with cursors and voltage measurement function of the oscilloscope. Time base of the oscilloscope was set to 10 Ks/div, voltage settings to 50 V/div. After device removal, devices were repackaged, sealed, and returned to the manufacturer for an in-depth, piece-by-piece analysis to look for any damage caused by electrocautery.
RESULTS The protocol was completed for two devices. Cochlear Implant Analysis At each measured time point and at the end of electrocautery up to 100 W, there was no change in the impedance or integrity testing for both implants tested. Impedance testing at the beginning of testing and after each application of electrocautery served both as a functional check of the implant and as confirmation that the implant electrodes always had tissue contact and that testing was not invalid because of the presence of any air bubbles. In-depth analysis of each component of the cochlear implant did not show any evidence of electrical or thermal damage to the device. Voltage Analysis Screenshot evaluations from the oscilloscope showed voltage changes within the implant (between an intracochlear channel and the remote ground electrode on the implant housing) up to about 22 V. The voltage changes were the least for bipolar electrocautery and maximum for monopolar electrocautery on the ‘‘cut’’ modality. DISCUSSION Many patients who receive a cochlear implant will require an additional surgical procedure in their lifetime which may require the use of electrocautery. Some patients with cochlear implants may even require emergency surgery. Concern that electrosurgery may render a cochlear implant unusable continues to be a source of anxiety for patients and providers. Our preliminary published data found no damage to the implant device and no thermal change in the cochlea after high-current monopolar electrocautery (50 W), even in close proximity to the cochlea (3). Electrocautery devices such as the Bovie use radiofrequency energy delivered through an electrode and applied directly to tissues (4). The energy is transferred to the tissues and heat is generated through the electrical resistance of these tissues (4). The cochlear implant devices also use a radiofrequency current to transmit signal from the external transmitting coil to the receiver/stimulator implant (5). The receiver/stimulator then delivers electric stimulation pulses to the electrode array. The electrodes stimulate neural elements within the cochlea through a series of bipolar current pulses. Numerous papers and authors have raised concern regarding the use of electrocautery in patients with cochlear implants (6Y9). However, much of the opposition to elec-
trocautery in cochlear implant patients is based on extrapolated effects from cardiac pacemakers (10). Our in situ voltage measurements did show a voltage drop between implant electrodes with electrocautery, both with bipolar electrocautery as well as monopolar electrocautery. However, the maximum voltage drop across the implant was 22 V, reached at electrocautery settings of 50 W. Even with electrocautery settings of 100 W, the voltage drop across the implant did not exceed 22 V. This shows that the protecting diodes within the cochlear implant device limit the maximum voltage across the implant and dissipate energy, thus protecting the electronics from a high-voltage draw. Electrocautery was applied for 1 minute per test condition which represented a potential worst-case scenario for the protecting diodes during a thermal load. LIMITATIONS There are several limitations to our study. The most significant limitation is the use of a cadaveric specimen for the study. Though the cadavers were unembalmed, there may be differences in the current flow between living and non-living tissues. The second limitation of the study is that we only tested two examples of one cochlear implant device by one manufacturer. It is as yet unclear whether the results will apply to all devices used for cochlear implantation. Additionally, the study does not assess if a future soft failure of the device could happen as a result of the electrocautery. Our group is still not advocating use of monopolar electrocautery in patients with a cochlear implant. However, we need to start considering more flexible recommendations, as increasing data from our laboratory is showing no ill effects from electrocautery. We are pursuing additional investigations in our laboratory to study this further. CONCLUSION Electrocautery did not produce detectible damage to any of the cochlear implant devices or produce significant voltage fluctuations within the devices at up to 100 W levels of electrosurgery in the ipsilateral temporalis and ipsilateral pectoralis major muscles in this experimental model. This project extends the previous findings in our laboratory by showing that settings up to 100 W did not damage the cochlear implant devices and by defining the maximum voltage between the active electrode and the ground electrode. The maximum voltage change was 22 V likely resulting from protecting diodes within the implant. Additional study is necessary, but more flexible recommendations regarding electrocautery in cochlear implant recipients should be considered. Acknowledgments: We would like to thank the following individuals and groups: • Dr. Richard Whitworth for providing the temporal bones and for his full support of the study. • Med-El Ltd for their technical support and provision of the devices.
Otology & Neurotology, Vol. 36, No. 4, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
DOES ELECTROCAUTERY DAMAGE COCHLEAR IMPLANTS? • Martin Zimmerling for his technical assistance and enthusiasm for the project. • The study would not have been possible without the donors of the cadavers and their families.
REFERENCES 1. Antonelli PJ, Barateli R. Cochlear implant integrity after adenoidectomy with coblation and monopolar electrocautery. Am J Otolaryngol 2007;29:9Y12. 2. Poetker DM, Runge-Samuelson CL, Firszt JB, Wackym PA. Electrosurgery after cochlear implantation: eighth nerve electrophysiology. Laryngoscope 2004;114:2252Y4. 3. Jeyakumar A, Wilson M, Sorrel JE, et al. Monopolar cautery and adverse effects on cochlear implants. JAMA Otolaryngol Head Neck Surg 2013;139:694Y7.
603
4. Vilos GA, Rajakumar C. Electrosurgical generators and monopolar and bipolar electrosurgery. J Minim Invasive Gynecol 2013;20:279Y87. 5. Zierhofer CM, Hochmair IJ, Hochmair ES. The advanced Combi 40+ cochlear implant. Am J Otol 1997;18(6 Suppl):S37Y8. 6. Roland JT, Fishman AJ, Waltzman SB, Cohen NL. Shaw scalpel in revision cochlear implant surgery. Ann Otol Rhinol Laryngol Suppl 2000;185:23Y5. 7. Laszig R, Ridder GJ, Aschendorff A, Fradis M. Ultracision: an alternative to electrocautery in revision cochlear implant surgery. Laryngoscope 2002;112:190Y1. 8. Tognola G, Parazzini M, Sibella F, Paglialonga A, Ravazzani P. Electromagnetic interference and cochlear implants. Ann 1st Super Sanita 2007;43:241Y7. 9. Roberts S, West LA, Liewehr FR, Rueggeberg FA, Sharpe DE, Potter BJ. Impact of dental devices on cochlear implants. J Endod 2002;28:40Y3. 10. Mangar D, Atlas GM, Kane PB. Electrocautery-induced pacemaker malfunction during surgery. Can J Aneaesth 1991;38:616Y8.
Otology & Neurotology, Vol. 36, No. 4, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
