Original Article
The Effects of Electrocautery on Peripheral Nerve: An Experimental Study Ender Koktekir2
Serhat Yildirim3
1 Department of Orthopaedic Surgery, Necmettin Erbakan University,
Konya, Turkey 2 Department of Neurosurgery, Selcuk University, Konya, Turkey 3 Department of Orthopaedic Surgery, Medline Hospital, Konya, Turkey 4 Department of Pathology, Necmettin Erbakan University, Konya, Turkey 5 Experimental Medicine Research and Application Center, Necmettin Erbakan University, Konya, Turkey 6 Department of Orthopaedic Surgery, Acibadem Hospital, Istanbul, Turkey
Hatice Toy4
Mehmet Oz5
Aydin Yuceturk6
Address for correspondence Ender Koktekir, Selcuk Universitesi, Tip Fakultesi, Beyin ve Sinir Cerrahisi Anabilim Dali, Alaeddin Keykubat Kampusu, 42100, Selcuklu, Konya, Turkey (e-mail: [email protected]).
J Neurol Surg A
Abstract
Keywords
► electrocautery ► nerve ► stimulation
Background The aim of this study was to assess the usability of an electrocautery device as nerve stimulator and to investigate histopathologically the adverse effects of electrocautery at low power on rat sciatic nerves. Methods A total of 36 female Sprague-Dawley albino rats were divided into six groups according to the power applied to their sciatic nerves (1, 2, 3, 4, 5 and 6 W, respectively). Pathologic changes were studied by microscopic examination and scored (no change ¼ 0, mild ¼ 1, moderate ¼ 2, severe ¼ 3). Multiple comparisons were provided for all groups by the Bonferroni test (one-way analysis of variance). A p value < 0.05 was accepted as statistically significant. Results The average scores were 2.66 0.51, 3.66 0.51, 5.83 1.83, 10.0 1.78, 11.0 1.54, and 13.8 0.89 in groups 1 to 6, respectively. Significant differences were found between all groups (p < 0.01), except between groups 1 and 2, groups 2 and 3, and groups 4 and 5 (p > 0.05) Variable motor responses and foot deformities were observed at the different power levels. Conclusion Although electrocautery devices provoke motor responses if getting in contact with peripheral nerves as do nerve stimulators, their use induces histopathologically adverse effects even at the lowest power. Their use around peripheral nerves should be avoided.
Introduction The three most important physiologic effects of electricity when applied to tissues are electrolysis, neural stimulation, and heating. 1–4 These effects relate to the type of current applied. If the applied current has a frequ-
received August 25, 2013 accepted after revision May 21, 2014
ency < 10 kHz, the expected effect is electrolysis, a useful property in laboratory tests such as protein electrophoresis. At frequencies > 10 kHz, the most important biological effect is heating of tissues. Electrocautery devices work with 400 to 4000 voltages, 80 kHz 10 kHz frequencies. They
© Georg Thieme Verlag KG Stuttgart · New York
DOI http://dx.doi.org/ 10.1055/s-0034-1389094. ISSN 2193-6315.
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Nazim Karalezli1
Karalezli et al.
apply a high-intensity electrical current to tissues and are commonly used for coagulation or cutting.1,4 Although their electrical properties are believed to be inappropriate for nerve stimulation because of the high-intensity current and sinusoidal pattern, it is known that electrocautery devices have stimulation effects on nerves, especially in bipolar mode. However, no study has investigated the stimulating effects of electrocautery on peripheral nerves. The aim of this study was to assess the usability of an electrocautery device as a nerve stimulator and to observe the histopathologically adverse effects of electrocautery at low power on rat sciatic nerves.
Materials and Methods We randomly divided 36 female Sprague-Dawley albino rats, weighing 200 to 220 g and ranging in age from 6 to 8 months, into six groups according to the power to be applied to their sciatic nerves. The animal experiment was approved by the Institutional Animal Care and Use Committee. The rats were acclimatized for 1 week in rooms with controlled conditions before the study. General anesthesia was achieved by intraperitoneal administration of ketamine (Ketalar; Eczacıbası IS, Luleburgaz, Turkey) (50 mg/kg body weight). All surgery was performed in a veterinary operating theater. The sciatic nerves were approached through a posterior longitudinal thigh incision, and 1, 2, 3, 4, 5, and 6 W were applied to the sciatic nerves with an electrocautery device (Valleylab Inc., Force FX-8C, Part Number 945 103 068, Boulder, Colorado, United States) in groups 1, 2, 3, 4, 5, and 6, respectively. The counter electrode of the electrocautery device was placed on the contralateral hind paw of the rat. The power was applied to all subjects five times by lightly touching the sciatic nerves at 1 cm proximal of its bifurcation for 1 second with a sharp-ended 2-mm monopolar electrocautery needle. The nerve was touched with the needle, and then the stimulation was turned on for 1 second. The proximal and distal extensions of the stimulated parts of the nerves were marked with 10–0 nylon epineural sutures; then muscles and skin were closed in layers. Each group was kept in a separate cage and followed
up weekly. Postoperative analgesia was ensured with intraperitoneal paracetamol 400 mg/kg daily. The rats were euthanized by decapitation 3 weeks after the nerve stimulation because the maximal degeneration of the nerve fascicle occurs after 2 weeks. All histopathologic specimens were taken from the stimulation site. The sciatic nerves were excised and immediately fixed in 10% formalin, embedded in paraffin, and stained with hematoxylin and eosin for microscopic examination of neural and perineural degeneration. Perineural and/or intrafascicular inflammation, connective tissue increase, vascular proliferation, granulomatous reaction, and fascicular degeneration were studied by microscopic examination. Each parameter was assigned a degree from 0 to 3, with 0 representing no change; 1, mild if any histopathologic change was seen in one highpower microscopic field; 2, moderate if any histopathologic change was seen in two high-power microscopic fields; and 3, severe if any histopathologic change was seen in three high-power microscopic fields. According to the histopathologic changes, a rating system was developed in which 0 to 5 represented mild; 6 to 10, moderate; and 11 to 15, severe changes (►Table 1). The sciatic nerves to be examined were numbered randomly and noted elsewhere. All specimens were examined by the same pathologist (H.T.) who was unaware of the level of power applied to the specimens.
Statistical Analysis Statistical analysis was performed by analysis of variance test and confirmed with the Bonferroni (post hoc test) test for multiple comparisons using SPSS v.16.0. A p value < 0.05 was accepted as statistically significant.
Results Motor responses of the lower limb muscles occurred in all groups when the needle touched the nerve. More gross movements were observed in groups 3, 4, 5, and 6 during touching. Macroscopic fascicular degeneration in the sciatic nerves was observed in groups 4, 5, and 6 during the administration of the electricity. Although foot drop and
Table 1 Summary of pathologic changes in all groupsa Groups
Perineural inflammation and/or interfascicular inflammation
Connective tissue increase
Vascular proliferation
Granulomatous inflammation
Fascicular degeneration
Total scores of pathologic changes
Average scores of pathologic changes, SD
Group 1 (n ¼ 6)
6/6
4/6
6/6
0/6
0/6
15
2.66 0.51
Group 2 (n ¼ 6)
6/6
5/6
6/6
0/6
2/6
22
3.66 0.51
Group 3 (n ¼ 6)
6/6
6/6
6/6
2/6
5/6
35
5.83 1.83
Group 4 (n ¼ 6)
6/6
6/6
6/6
6/6
6/6
60
10.0 1.78
Group 5 (n ¼ 6)
6/6
6/6
6/6
6/6
6/6
66
11.0 1.54
Group 6 (n ¼ 6)
6/6
6/6
6/6
6/6
6/6
83
13.8 0.89
Abbreviation: SD, standard deviation. a Scoring of the pathologic changes according to the average scores: 0–5 (mild), 6–10 (moderate), 11–15 (severe). Journal of Neurological Surgery—Part A
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Effects of Electrocautery on Peripheral Nerve
Karalezli et al.
Fig. 1 Posture of the foot after electrocautery application with 2 W.
foot atrophy were not observed in the rats in groups 1 and 2, it was observed in the rats in groups 4, 5, and 6 (►Figs. 1–3). In groups 1 and 2, the average scores of the pathologic changes were 2.66 0.51 and 3.66 0.51(►Table 1), respectively. According to the rating system, these changes were mild. We saw slight perineural inflammation, connective tissue increase, and vascular proliferation in these groups. Furthermore, there was no granulomatous reaction in these groups (►Fig. 4). The average scores of groups 3 and 4 were 5.83 1.83 and 10.0 1.78, respectively, indicating moder-
Fig. 2 Posture of the foot after electrocautery application with 4 W. Foot deformity is seen.
Fig. 3 Posture of the foot after electrocautery application with 6 W. Foot deformity is seen.
ate reactions (►Table 1). Fascicular degeneration was higher in groups 3 and 4 than in groups 1 and 2, especially in group 4 where pathologic changes were evident (►Fig. 5). The average scores of groups 5 and 6 were 11.0 1.54 and 13.8 0.89, respectively, which indicated severe changes (►Table 1). A granulomatous reaction was observed in groups 5 and 6 (►Fig. 6).
Fig. 4 Slight perineural inflammation without any granulomatous reaction in the specimen after electrocautery application with 2 W (original magnification 10, hematoxylin and eosin). Journal of Neurological Surgery—Part A
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Effects of Electrocautery on Peripheral Nerve
Effects of Electrocautery on Peripheral Nerve
Karalezli et al. change in the feet in groups 1 and 2, whereas the rats in groups 5 and 6 had severe histopathologic changes with foot drop and deformities.
Fig. 5 Mild granulomatous reaction after electrocautery application with 4 W (original magnification 40, hematoxylin and eosin).
Fig. 6 Severe granulomatous reaction after electrocautery application with 6 W (original magnification 20, hematoxylin and eosin).
Multiple comparisons of all groups regarding the scores of the pathologic changes were provided by the Bonferroni test. There were significant differences between all groups (p < 0.01), except between groups 1 and 2, groups 2 and 3, and groups 4 and 5 (p > 0.05) (►Table 2). There was also a correlation between the histopathologic values and the aspect of the feet. There was no remarkable
Electrocautery was first described by Dr. W.T. Bovie, and the clinical use of these devices was popularized by Dr. Harvey Cushing in 1925.5 Although these early studies showed an excellent effect on hemostasis, potential injury to the nerves was also demonstrated. Injury to the nerves can occur by direct transection or leakage of the current to the nerve from the electrocautery. The effect of the power on the nerve depends on the voltage, the type of stimulation (unipolar versus bipolar), size of the area of contact between electrode and nerve, ambient humidity, cleanliness of the electrode contact, connective tissue around the nerve, and how the nerve was touched. To prevent the complications related to nerve injury, some rules are suggested: (1) A small amount of saline should be used to cool the surrounding tissue, (2) the time of coagulation should be minimal, and (3) a coagulation current should be used rather than a cutting current.5 Although several studies have investigated the effect of electrocautery on nerve injury, none of these studies quantified the effect of power dosage on peripheral nerves.3,6 During surgical treatment of nervous system disorders that surround the peripheral nerves, intraoperative nerve monitoring is necessary to avoid devastating complications.7–10 However, nerve monitoring is not widely available because of cost issues and the lack of qualified technicians. Nerve stimulators are inexpensive and widely available, and can be used in these situations. Unlike electrocautery, these devices work with 5 to 10 voltages and apply a low-intensity electrical current with a short pulse (square wave pulse).11–13 This low-intensity current is commonly used by anesthesiologists for regional anesthesia and by surgeons for nerve stimulation.14–17 However, to use nerve stimulators, the nerve should be exposed first. During this procedure, electrocautery is used to dissect the surrounding tissues around the nerve. The term of the sensation threshold is the total current that is passed between a pair of surface electrodes and depends on the electrode area.1,12 At frequencies higher than 10 kHz, the heating of the tissue is the most important biological
Table 2 Multiple comparisons of all groups regarding the scores of the pathologic changes were provided by Bonferroni test Multiple comparisons, p
Group1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 1
NA
0.83
0.003
0.001
0.001
0.001
Group 2
0.83
NA
0.113
0.001
0.001
0.001
Group 3
0.003
0.113
NA
0.001
0.001
0.001
Group 4
0.001
0.001
0.001
NA
0.96
0.001
Group 5
0.001
0.001
0.001
0.96
NA
0.006
Group 6
0.001
0.001
0.001
0.001
0.006
NA
Abbreviation: NA, not applicable. A p value < 0.05 was accepted as statistically significant. Journal of Neurological Surgery—Part A
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Discussion
Effects of Electrocautery on Peripheral Nerve
drop in the amplitude of compound muscle action potentials.18 Second, we could not correlate the macroscopic findings of foot muscles with quantitative methods such as histopathologic evaluation of muscles or paw reaching tests because we had not predicted that these changes would occur. Third, we used the electrocautery device at lower power (1 to 6 W) that may not reflect clinical applications. However, our aim was to emphasize the adverse effects of electrocautery devices on peripheral nerves.
Conclusion Although electrocautery devices provoke motor responses in peripheral nerves as do nerve stimulators, their use induces histopathologically adverse effects even at the lowest power. Electrocautery devices should therefore not be used to stimulate nerves or dissect tissues around peripheral nerves.
References 1 Brown BH, Smallwood RH, Barber DC, et al. Medical Physics and
2 3
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9
10
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13
Biomedical Engineering. Bristol, UK, and Philadelphia, PA: IOP Publishing Ltd; 2001:289–291 Burnett MG, Zager EL. Pathophysiology of peripheral nerve injury: a brief review. Neurosurg Focus 2004;16(5):E1 Tun K, Cemil B, Gurcay AG, et al. Ultrastructural evaluation of pulsed radiofrequency and conventional radiofrequency lesions in rat sciatic nerve. Surg Neurol 2009;72(5):496–500; discussion 501 Winograd JM, Mackinnon SE. Peripheral nerve injuries: repair and reconstruction. In: Mathes SJ, Hentz VR, eds. The Hand and Upper Limb. Part I. Philadelphia, PA: Saunders Elsevier; 2006:471–514. Plastic Surgery; vol 7 Greenwood J Jr. Two point coagulation: a follow-up report of a new technic and instrument for electrocoagulation in neurosurgery. Arch Phys Ther 1942;23(9):552–554 Moradzadeh A, Brenner MJ, Whitlock EL, et al. Bipolar electrocautery: A rodent model of Sunderland third-degree nerve injury. Arch Facial Plast Surg 2010;12(1):40–47 Ashram YA, Jackler RK, Pitts LH, Yingling CD. Intraoperative electrophysiologic identification of the nervus intermedius. Otol Neurotol 2005;26(2):274–279 Brauckhoff M, Gimm O, Thanh PN, et al. First experiences in intraoperative neurostimulation of the recurrent laryngeal nerve during thyroid surgery of children and adolescents. J Pediatr Surg 2002;37(10):1414–1418 Echeverri A, Flexon PB. Electrophysiologic nerve stimulation for identifying the recurrent laryngeal nerve in thyroid surgery: review of 70 consecutive thyroid surgeries. Am Surg 1998; 64(4):328–333 Jonas J, Bähr R. Intraoperative electromyographic identification of the recurrent laryngeal nerve [in German]. Chirurg 2000;71(5): 534–538 Barthram CN. Nerve stimulators for nerve location—are they all the same? A study of stimulator performance. Anaesthesia 1997; 52(8):761–764 Dalkiliç N, Pehlivan F. Comparison of fiber diameter distributions deduced by modeling compound action potentials recorded by extracellular and suction techniques. Int J Neurosci 2002;112(8): 913–930 Hadzic A, Vloka J, Hadzic N, Thys DM, Santos AC. Nerve stimulators used for peripheral nerve blocks vary in their electrical characteristics. Anesthesiology 2003;98(4):969–974
Journal of Neurological Surgery—Part A
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effect. Electrocautery devices work with this effect; they generate heat by using electrical energy to cut and coagulate tissues. Even though most surgeons are prone to use bipolar forceps to reduce nerve injury, due to its lacking simultaneous hemostasis and dissection, monopolar cautery may be preferred for the dissection of surrounding tissues to expose the peripheral nerves and ensure hemostasis at the same time and thus reduce operative time.18 Although it has been thought that the electrocautery devices do not have a stimulating effect, surgeons have discovered while working with the electrocautery device near a motor nerve that it may stimulate the nerve. This effect can be promoted by the heating effect of the device. Adverse effects on nerves can be seen with excessive temperatures. For this reason surgeons decrease the current to apply as low power as possible. In this study our aims were to investigate the usability of electrocautery devices as a nerve stimulator and demonstrate the histopathologic effects at different levels of power. We used monopolar cautery to address the clinical correlation. We observed that the sciatic nerves of the rats were all stimulated with the electrocautery device in all groups. Although with lower voltages (1–2 W) we did not observe foot drop or any foot deformities, when the powers applied were increased to 4 to 6 W, there was a burning effect on the nerves macroscopically; moreover, foot drop and foot deformities were seen in all subjects. In this study, the effect of electrocautery on the sciatic nerve was evaluated according to pathologic changes. Animals were euthanized 3 weeks after the initial procedure for pathologic evaluation of the nerves because the maximal degeneration of the nerve fascicle occurs after 2 weeks.17 The microscopic changes of nerve injury including perineural and/or intrafascicular inflammation, connective tissue increase, vascular proliferation, granulomatous reaction, and fascicular degeneration were evaluated. Although all of these changes were seen in moderately and severely injured groups, granulomatous reaction and fascicular degeneration were not prominent in the mildly injured group. These results indicate that granulomatous reaction and fascicular degeneration are the most reliable markers to detect severe nerve injury. Each histopathologic finding was classified as mild, moderate, or severe. Total scores were graded to make a more quantitative evaluation of the exact nerve injury effects. Our results indicated that the electrocautery devices have adverse effects even at the lowest powers, and the severity of the nerve injury is power dependent. Although there were no macroscopic adverse effects seen when lower powers were applied (groups 1 and 2), perineural and interfascicular inflammatory changes were seen in these subjects that might be related to peripheral neuropathic pain.19 Our study must be viewed in light of some limitations. First, if we had connected the electrocautery device to an electronic time controller to control the duration of the current and if we could add an electrophysiologic parameter to the results, the study would have been more reliable. However, Tanimoto et al evaluated the motor function with electromyography after using monopolar electrocautery and concluded that the electrocautery device resulted in a marked
Karalezli et al.
Effects of Electrocautery on Peripheral Nerve
Karalezli et al. 17 Burkel WE, McPhee M. Effect of phenol injection into peripheral
stimulator for nerve location controlled by the scrubbed anaesthetist. Anaesthesia 2002;57(10):995–998 15 De Andrés J, Sala-Blanch X. Peripheral nerve stimulation in the practice of brachial plexus anesthesia: a review. Reg Anesth Pain Med 2001;26(5):478–483 16 Fukuhara T, Kamata I. Selective posterior rhizotomy for painful spasticity in the lower limbs of hemiplegic patients after stroke: report of two cases. Neurosurgery 2004;54(5):1268–1272; discussion 1272–1273
nerve of rat: electron microscope studies. Arch Phys Med Rehabil 1970;51(7):391–397 18 Tanimoto K, Khoury B, Feng K, Cavanaugh JM. Evaluation of sciatic nerve function after ultrasonic and electrocautery muscle dissection: an electromyographic study. J Neurol Surg A Cent Eur Neurosurg 2013; August 8 ( Epub ahead of print) 19 Choi S, Choi HJ, Cheong Y, Lim YJ, Park HK. Internal-specific morphological analysis of sciatic nerve fibers in a radiofrequency-induced animal neuropathic pain model. PLoS ONE 2013;8(9):e73913
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14 Ayoub C, Lteif A, Rizk M, Khalili Z, Aoude S. A peripheral nerve
Journal of Neurological Surgery—Part A
The Effects of Electrocautery on Peripheral Nerve: An Experimental Study Ender Koktekir2
Serhat Yildirim3
1 Department of Orthopaedic Surgery, Necmettin Erbakan University,
Konya, Turkey 2 Department of Neurosurgery, Selcuk University, Konya, Turkey 3 Department of Orthopaedic Surgery, Medline Hospital, Konya, Turkey 4 Department of Pathology, Necmettin Erbakan University, Konya, Turkey 5 Experimental Medicine Research and Application Center, Necmettin Erbakan University, Konya, Turkey 6 Department of Orthopaedic Surgery, Acibadem Hospital, Istanbul, Turkey
Hatice Toy4
Mehmet Oz5
Aydin Yuceturk6
Address for correspondence Ender Koktekir, Selcuk Universitesi, Tip Fakultesi, Beyin ve Sinir Cerrahisi Anabilim Dali, Alaeddin Keykubat Kampusu, 42100, Selcuklu, Konya, Turkey (e-mail: [email protected]).
J Neurol Surg A
Abstract
Keywords
► electrocautery ► nerve ► stimulation
Background The aim of this study was to assess the usability of an electrocautery device as nerve stimulator and to investigate histopathologically the adverse effects of electrocautery at low power on rat sciatic nerves. Methods A total of 36 female Sprague-Dawley albino rats were divided into six groups according to the power applied to their sciatic nerves (1, 2, 3, 4, 5 and 6 W, respectively). Pathologic changes were studied by microscopic examination and scored (no change ¼ 0, mild ¼ 1, moderate ¼ 2, severe ¼ 3). Multiple comparisons were provided for all groups by the Bonferroni test (one-way analysis of variance). A p value < 0.05 was accepted as statistically significant. Results The average scores were 2.66 0.51, 3.66 0.51, 5.83 1.83, 10.0 1.78, 11.0 1.54, and 13.8 0.89 in groups 1 to 6, respectively. Significant differences were found between all groups (p < 0.01), except between groups 1 and 2, groups 2 and 3, and groups 4 and 5 (p > 0.05) Variable motor responses and foot deformities were observed at the different power levels. Conclusion Although electrocautery devices provoke motor responses if getting in contact with peripheral nerves as do nerve stimulators, their use induces histopathologically adverse effects even at the lowest power. Their use around peripheral nerves should be avoided.
Introduction The three most important physiologic effects of electricity when applied to tissues are electrolysis, neural stimulation, and heating. 1–4 These effects relate to the type of current applied. If the applied current has a frequ-
received August 25, 2013 accepted after revision May 21, 2014
ency < 10 kHz, the expected effect is electrolysis, a useful property in laboratory tests such as protein electrophoresis. At frequencies > 10 kHz, the most important biological effect is heating of tissues. Electrocautery devices work with 400 to 4000 voltages, 80 kHz 10 kHz frequencies. They
© Georg Thieme Verlag KG Stuttgart · New York
DOI http://dx.doi.org/ 10.1055/s-0034-1389094. ISSN 2193-6315.
Downloaded by: Collections and Technical Services Department. Copyrighted material.
Nazim Karalezli1
Karalezli et al.
apply a high-intensity electrical current to tissues and are commonly used for coagulation or cutting.1,4 Although their electrical properties are believed to be inappropriate for nerve stimulation because of the high-intensity current and sinusoidal pattern, it is known that electrocautery devices have stimulation effects on nerves, especially in bipolar mode. However, no study has investigated the stimulating effects of electrocautery on peripheral nerves. The aim of this study was to assess the usability of an electrocautery device as a nerve stimulator and to observe the histopathologically adverse effects of electrocautery at low power on rat sciatic nerves.
Materials and Methods We randomly divided 36 female Sprague-Dawley albino rats, weighing 200 to 220 g and ranging in age from 6 to 8 months, into six groups according to the power to be applied to their sciatic nerves. The animal experiment was approved by the Institutional Animal Care and Use Committee. The rats were acclimatized for 1 week in rooms with controlled conditions before the study. General anesthesia was achieved by intraperitoneal administration of ketamine (Ketalar; Eczacıbası IS, Luleburgaz, Turkey) (50 mg/kg body weight). All surgery was performed in a veterinary operating theater. The sciatic nerves were approached through a posterior longitudinal thigh incision, and 1, 2, 3, 4, 5, and 6 W were applied to the sciatic nerves with an electrocautery device (Valleylab Inc., Force FX-8C, Part Number 945 103 068, Boulder, Colorado, United States) in groups 1, 2, 3, 4, 5, and 6, respectively. The counter electrode of the electrocautery device was placed on the contralateral hind paw of the rat. The power was applied to all subjects five times by lightly touching the sciatic nerves at 1 cm proximal of its bifurcation for 1 second with a sharp-ended 2-mm monopolar electrocautery needle. The nerve was touched with the needle, and then the stimulation was turned on for 1 second. The proximal and distal extensions of the stimulated parts of the nerves were marked with 10–0 nylon epineural sutures; then muscles and skin were closed in layers. Each group was kept in a separate cage and followed
up weekly. Postoperative analgesia was ensured with intraperitoneal paracetamol 400 mg/kg daily. The rats were euthanized by decapitation 3 weeks after the nerve stimulation because the maximal degeneration of the nerve fascicle occurs after 2 weeks. All histopathologic specimens were taken from the stimulation site. The sciatic nerves were excised and immediately fixed in 10% formalin, embedded in paraffin, and stained with hematoxylin and eosin for microscopic examination of neural and perineural degeneration. Perineural and/or intrafascicular inflammation, connective tissue increase, vascular proliferation, granulomatous reaction, and fascicular degeneration were studied by microscopic examination. Each parameter was assigned a degree from 0 to 3, with 0 representing no change; 1, mild if any histopathologic change was seen in one highpower microscopic field; 2, moderate if any histopathologic change was seen in two high-power microscopic fields; and 3, severe if any histopathologic change was seen in three high-power microscopic fields. According to the histopathologic changes, a rating system was developed in which 0 to 5 represented mild; 6 to 10, moderate; and 11 to 15, severe changes (►Table 1). The sciatic nerves to be examined were numbered randomly and noted elsewhere. All specimens were examined by the same pathologist (H.T.) who was unaware of the level of power applied to the specimens.
Statistical Analysis Statistical analysis was performed by analysis of variance test and confirmed with the Bonferroni (post hoc test) test for multiple comparisons using SPSS v.16.0. A p value < 0.05 was accepted as statistically significant.
Results Motor responses of the lower limb muscles occurred in all groups when the needle touched the nerve. More gross movements were observed in groups 3, 4, 5, and 6 during touching. Macroscopic fascicular degeneration in the sciatic nerves was observed in groups 4, 5, and 6 during the administration of the electricity. Although foot drop and
Table 1 Summary of pathologic changes in all groupsa Groups
Perineural inflammation and/or interfascicular inflammation
Connective tissue increase
Vascular proliferation
Granulomatous inflammation
Fascicular degeneration
Total scores of pathologic changes
Average scores of pathologic changes, SD
Group 1 (n ¼ 6)
6/6
4/6
6/6
0/6
0/6
15
2.66 0.51
Group 2 (n ¼ 6)
6/6
5/6
6/6
0/6
2/6
22
3.66 0.51
Group 3 (n ¼ 6)
6/6
6/6
6/6
2/6
5/6
35
5.83 1.83
Group 4 (n ¼ 6)
6/6
6/6
6/6
6/6
6/6
60
10.0 1.78
Group 5 (n ¼ 6)
6/6
6/6
6/6
6/6
6/6
66
11.0 1.54
Group 6 (n ¼ 6)
6/6
6/6
6/6
6/6
6/6
83
13.8 0.89
Abbreviation: SD, standard deviation. a Scoring of the pathologic changes according to the average scores: 0–5 (mild), 6–10 (moderate), 11–15 (severe). Journal of Neurological Surgery—Part A
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Effects of Electrocautery on Peripheral Nerve
Karalezli et al.
Fig. 1 Posture of the foot after electrocautery application with 2 W.
foot atrophy were not observed in the rats in groups 1 and 2, it was observed in the rats in groups 4, 5, and 6 (►Figs. 1–3). In groups 1 and 2, the average scores of the pathologic changes were 2.66 0.51 and 3.66 0.51(►Table 1), respectively. According to the rating system, these changes were mild. We saw slight perineural inflammation, connective tissue increase, and vascular proliferation in these groups. Furthermore, there was no granulomatous reaction in these groups (►Fig. 4). The average scores of groups 3 and 4 were 5.83 1.83 and 10.0 1.78, respectively, indicating moder-
Fig. 2 Posture of the foot after electrocautery application with 4 W. Foot deformity is seen.
Fig. 3 Posture of the foot after electrocautery application with 6 W. Foot deformity is seen.
ate reactions (►Table 1). Fascicular degeneration was higher in groups 3 and 4 than in groups 1 and 2, especially in group 4 where pathologic changes were evident (►Fig. 5). The average scores of groups 5 and 6 were 11.0 1.54 and 13.8 0.89, respectively, which indicated severe changes (►Table 1). A granulomatous reaction was observed in groups 5 and 6 (►Fig. 6).
Fig. 4 Slight perineural inflammation without any granulomatous reaction in the specimen after electrocautery application with 2 W (original magnification 10, hematoxylin and eosin). Journal of Neurological Surgery—Part A
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Effects of Electrocautery on Peripheral Nerve
Effects of Electrocautery on Peripheral Nerve
Karalezli et al. change in the feet in groups 1 and 2, whereas the rats in groups 5 and 6 had severe histopathologic changes with foot drop and deformities.
Fig. 5 Mild granulomatous reaction after electrocautery application with 4 W (original magnification 40, hematoxylin and eosin).
Fig. 6 Severe granulomatous reaction after electrocautery application with 6 W (original magnification 20, hematoxylin and eosin).
Multiple comparisons of all groups regarding the scores of the pathologic changes were provided by the Bonferroni test. There were significant differences between all groups (p < 0.01), except between groups 1 and 2, groups 2 and 3, and groups 4 and 5 (p > 0.05) (►Table 2). There was also a correlation between the histopathologic values and the aspect of the feet. There was no remarkable
Electrocautery was first described by Dr. W.T. Bovie, and the clinical use of these devices was popularized by Dr. Harvey Cushing in 1925.5 Although these early studies showed an excellent effect on hemostasis, potential injury to the nerves was also demonstrated. Injury to the nerves can occur by direct transection or leakage of the current to the nerve from the electrocautery. The effect of the power on the nerve depends on the voltage, the type of stimulation (unipolar versus bipolar), size of the area of contact between electrode and nerve, ambient humidity, cleanliness of the electrode contact, connective tissue around the nerve, and how the nerve was touched. To prevent the complications related to nerve injury, some rules are suggested: (1) A small amount of saline should be used to cool the surrounding tissue, (2) the time of coagulation should be minimal, and (3) a coagulation current should be used rather than a cutting current.5 Although several studies have investigated the effect of electrocautery on nerve injury, none of these studies quantified the effect of power dosage on peripheral nerves.3,6 During surgical treatment of nervous system disorders that surround the peripheral nerves, intraoperative nerve monitoring is necessary to avoid devastating complications.7–10 However, nerve monitoring is not widely available because of cost issues and the lack of qualified technicians. Nerve stimulators are inexpensive and widely available, and can be used in these situations. Unlike electrocautery, these devices work with 5 to 10 voltages and apply a low-intensity electrical current with a short pulse (square wave pulse).11–13 This low-intensity current is commonly used by anesthesiologists for regional anesthesia and by surgeons for nerve stimulation.14–17 However, to use nerve stimulators, the nerve should be exposed first. During this procedure, electrocautery is used to dissect the surrounding tissues around the nerve. The term of the sensation threshold is the total current that is passed between a pair of surface electrodes and depends on the electrode area.1,12 At frequencies higher than 10 kHz, the heating of the tissue is the most important biological
Table 2 Multiple comparisons of all groups regarding the scores of the pathologic changes were provided by Bonferroni test Multiple comparisons, p
Group1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 1
NA
0.83
0.003
0.001
0.001
0.001
Group 2
0.83
NA
0.113
0.001
0.001
0.001
Group 3
0.003
0.113
NA
0.001
0.001
0.001
Group 4
0.001
0.001
0.001
NA
0.96
0.001
Group 5
0.001
0.001
0.001
0.96
NA
0.006
Group 6
0.001
0.001
0.001
0.001
0.006
NA
Abbreviation: NA, not applicable. A p value < 0.05 was accepted as statistically significant. Journal of Neurological Surgery—Part A
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Discussion
Effects of Electrocautery on Peripheral Nerve
drop in the amplitude of compound muscle action potentials.18 Second, we could not correlate the macroscopic findings of foot muscles with quantitative methods such as histopathologic evaluation of muscles or paw reaching tests because we had not predicted that these changes would occur. Third, we used the electrocautery device at lower power (1 to 6 W) that may not reflect clinical applications. However, our aim was to emphasize the adverse effects of electrocautery devices on peripheral nerves.
Conclusion Although electrocautery devices provoke motor responses in peripheral nerves as do nerve stimulators, their use induces histopathologically adverse effects even at the lowest power. Electrocautery devices should therefore not be used to stimulate nerves or dissect tissues around peripheral nerves.
References 1 Brown BH, Smallwood RH, Barber DC, et al. Medical Physics and
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Biomedical Engineering. Bristol, UK, and Philadelphia, PA: IOP Publishing Ltd; 2001:289–291 Burnett MG, Zager EL. Pathophysiology of peripheral nerve injury: a brief review. Neurosurg Focus 2004;16(5):E1 Tun K, Cemil B, Gurcay AG, et al. Ultrastructural evaluation of pulsed radiofrequency and conventional radiofrequency lesions in rat sciatic nerve. Surg Neurol 2009;72(5):496–500; discussion 501 Winograd JM, Mackinnon SE. Peripheral nerve injuries: repair and reconstruction. In: Mathes SJ, Hentz VR, eds. The Hand and Upper Limb. Part I. Philadelphia, PA: Saunders Elsevier; 2006:471–514. Plastic Surgery; vol 7 Greenwood J Jr. Two point coagulation: a follow-up report of a new technic and instrument for electrocoagulation in neurosurgery. Arch Phys Ther 1942;23(9):552–554 Moradzadeh A, Brenner MJ, Whitlock EL, et al. Bipolar electrocautery: A rodent model of Sunderland third-degree nerve injury. Arch Facial Plast Surg 2010;12(1):40–47 Ashram YA, Jackler RK, Pitts LH, Yingling CD. Intraoperative electrophysiologic identification of the nervus intermedius. Otol Neurotol 2005;26(2):274–279 Brauckhoff M, Gimm O, Thanh PN, et al. First experiences in intraoperative neurostimulation of the recurrent laryngeal nerve during thyroid surgery of children and adolescents. J Pediatr Surg 2002;37(10):1414–1418 Echeverri A, Flexon PB. Electrophysiologic nerve stimulation for identifying the recurrent laryngeal nerve in thyroid surgery: review of 70 consecutive thyroid surgeries. Am Surg 1998; 64(4):328–333 Jonas J, Bähr R. Intraoperative electromyographic identification of the recurrent laryngeal nerve [in German]. Chirurg 2000;71(5): 534–538 Barthram CN. Nerve stimulators for nerve location—are they all the same? A study of stimulator performance. Anaesthesia 1997; 52(8):761–764 Dalkiliç N, Pehlivan F. Comparison of fiber diameter distributions deduced by modeling compound action potentials recorded by extracellular and suction techniques. Int J Neurosci 2002;112(8): 913–930 Hadzic A, Vloka J, Hadzic N, Thys DM, Santos AC. Nerve stimulators used for peripheral nerve blocks vary in their electrical characteristics. Anesthesiology 2003;98(4):969–974
Journal of Neurological Surgery—Part A
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effect. Electrocautery devices work with this effect; they generate heat by using electrical energy to cut and coagulate tissues. Even though most surgeons are prone to use bipolar forceps to reduce nerve injury, due to its lacking simultaneous hemostasis and dissection, monopolar cautery may be preferred for the dissection of surrounding tissues to expose the peripheral nerves and ensure hemostasis at the same time and thus reduce operative time.18 Although it has been thought that the electrocautery devices do not have a stimulating effect, surgeons have discovered while working with the electrocautery device near a motor nerve that it may stimulate the nerve. This effect can be promoted by the heating effect of the device. Adverse effects on nerves can be seen with excessive temperatures. For this reason surgeons decrease the current to apply as low power as possible. In this study our aims were to investigate the usability of electrocautery devices as a nerve stimulator and demonstrate the histopathologic effects at different levels of power. We used monopolar cautery to address the clinical correlation. We observed that the sciatic nerves of the rats were all stimulated with the electrocautery device in all groups. Although with lower voltages (1–2 W) we did not observe foot drop or any foot deformities, when the powers applied were increased to 4 to 6 W, there was a burning effect on the nerves macroscopically; moreover, foot drop and foot deformities were seen in all subjects. In this study, the effect of electrocautery on the sciatic nerve was evaluated according to pathologic changes. Animals were euthanized 3 weeks after the initial procedure for pathologic evaluation of the nerves because the maximal degeneration of the nerve fascicle occurs after 2 weeks.17 The microscopic changes of nerve injury including perineural and/or intrafascicular inflammation, connective tissue increase, vascular proliferation, granulomatous reaction, and fascicular degeneration were evaluated. Although all of these changes were seen in moderately and severely injured groups, granulomatous reaction and fascicular degeneration were not prominent in the mildly injured group. These results indicate that granulomatous reaction and fascicular degeneration are the most reliable markers to detect severe nerve injury. Each histopathologic finding was classified as mild, moderate, or severe. Total scores were graded to make a more quantitative evaluation of the exact nerve injury effects. Our results indicated that the electrocautery devices have adverse effects even at the lowest powers, and the severity of the nerve injury is power dependent. Although there were no macroscopic adverse effects seen when lower powers were applied (groups 1 and 2), perineural and interfascicular inflammatory changes were seen in these subjects that might be related to peripheral neuropathic pain.19 Our study must be viewed in light of some limitations. First, if we had connected the electrocautery device to an electronic time controller to control the duration of the current and if we could add an electrophysiologic parameter to the results, the study would have been more reliable. However, Tanimoto et al evaluated the motor function with electromyography after using monopolar electrocautery and concluded that the electrocautery device resulted in a marked
Karalezli et al.
Effects of Electrocautery on Peripheral Nerve
Karalezli et al. 17 Burkel WE, McPhee M. Effect of phenol injection into peripheral
stimulator for nerve location controlled by the scrubbed anaesthetist. Anaesthesia 2002;57(10):995–998 15 De Andrés J, Sala-Blanch X. Peripheral nerve stimulation in the practice of brachial plexus anesthesia: a review. Reg Anesth Pain Med 2001;26(5):478–483 16 Fukuhara T, Kamata I. Selective posterior rhizotomy for painful spasticity in the lower limbs of hemiplegic patients after stroke: report of two cases. Neurosurgery 2004;54(5):1268–1272; discussion 1272–1273
nerve of rat: electron microscope studies. Arch Phys Med Rehabil 1970;51(7):391–397 18 Tanimoto K, Khoury B, Feng K, Cavanaugh JM. Evaluation of sciatic nerve function after ultrasonic and electrocautery muscle dissection: an electromyographic study. J Neurol Surg A Cent Eur Neurosurg 2013; August 8 ( Epub ahead of print) 19 Choi S, Choi HJ, Cheong Y, Lim YJ, Park HK. Internal-specific morphological analysis of sciatic nerve fibers in a radiofrequency-induced animal neuropathic pain model. PLoS ONE 2013;8(9):e73913
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14 Ayoub C, Lteif A, Rizk M, Khalili Z, Aoude S. A peripheral nerve
Journal of Neurological Surgery—Part A
