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Hemostatic properties of the free-electron laser
Nuclear Instruments and Methods in Physics Research B 144 (1998) 256±259
Hemostatic properties of the free-electron laser Gary P. Cram Jr., Michael L. Copeland
*
Department of Neurosurgery, Vanderbilt University Medical Center, Nashville, TN 37235, USA
Abstract We have investigated the hemostatic properties of the free-electron laser (FEL) and compared these properties to the most commonly used commercial lasers in neurosurgery, CO2 and Nd:YAG, using an acute canine model. Arterial and venous vessels, of varying diameters from 0.1 to 1.0 mm, were divided with all three lasers. Analysis of ®ve wavelengths of the FEL (3.0, 4.5, 6.1, 6.45, and 7.7 microns) resulted in bleeding without evidence of signi®cant coagulation, regardless of whether the vessel was an artery or vein. Hemorrhage from vessels less than 0.4 mm diameter was subsequently easily controlled with GelfoamÒ (topical hemostatic agent) alone, whereas larger vessels required bipolar electrocautery. No signi®cant charring, or contraction of the surrounding parenchyma was noted with any of the wavelengths chosen from FEL source. The CO2 laser, in continuous mode, easily coagulated vessels with diameters of 4 mm and less, while larger vessels displayed signi®cant bleeding requiring bipolar electrocautery for control. Tissue charring was noted with application of the CO2 laser. In super pulse mode, the CO2 laser exhibited similar properties, including signi®cant charring of the surrounding parenchyma. The Nd:YAG coagulated all vessels tested up to 1.4 mm, which was the largest diameter cortical artery found, however this laser displayed signi®cant and extensive contraction and retraction of the surrounding parenchyma. In conclusion, the FEL appears to be a poor hemostatic agent. Our results did not show any bene®t of the FEL over current conventional means of achieving hemostasis. However, control of hemorrhage was easily achieved with currently used methods of hemostasis, namely GelfoamÒ or bipolar electrocuatery. Although only cortical vessels in dogs were tested, we feel this data can be applied to all animals, including humans, and the peripheral, as well as central, vasculature, as our data on the CO2 and Nd:YAG appear to closely support previous reports of hemostasis of these two lasers obtained in other models. Ó 1998 Published by Elsevier Science B.V. All rights reserved. Keywords: Free-electron laser; CO2 laser; Nd:YAG laser; Brain; Surgery; Hemostasis; Bleeding; Dogs
1. Introduction The acceptance of lasers as a standard neurosurgical tool has been a long and tedious journey.
* Corresponding author. Tel.: 615 343 v6146; fax: 615 343 1103.
Despite high initial enthusiasm, the ®rst applications of the laser to neurosurgery using the ruby laser revealed discouraging results, with consistent animal deaths [1,2]. Safe and eective neurosurgery was subsequently achieved through careful manipulation of various properties of laser systems (i.e., varying power, frequency, and duration of exposure) [3±6]. With the re®nement of
0168-583X/98/$ ± see front matter Ó 1998 Published by Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 8 ) 0 0 3 1 2 - 7
G.P. Cram Jr., M.L. Copeland / Nucl. Instr. and Meth. in Phys. Res. B 144 (1998) 256±259
microsurgical techniques and the advancements in laser delivery systems, the CO2 and Nd:YAG lasers gained usefulness and popularity [7]. The Nd:YAG laser, well absorbed by vascular tissue and hemoglobin, has been demonstrated to have superior coagulation properties over other lasers and conventional hemostatic methods, such as topical treatments (Surgicell7 or Gelfoam7) and bipolar electrocautery [8,9]. The Nd:YAG thus gained popularity as an adjunct in the resection of AVMs and meningiomas [8±12]. However the Nd:YAG has poor absorption in nonpigmented tissues, resulting in deeper penetration, more scatter, and unacceptable collateral thermal injury to surrounding normal brain. The CO2 laser, demonstrating signi®cantly less collateral thermal injury than the Nd:YAG, yet still exhibiting moderate hemostatic properties, has thus become the gold standard for laser neurosurgery [13]. Hemostasis is of critical consideration in surgical procedures, perhaps most particularly for neurosurgical procedures. Currently, most neurosurgeons still rely on topical agents and bipolar electrocautery for hemostasis [13]. Topical agents are only eective for capillaries and small venules. Bipolar electrocautery, although eective in larger vessels, has demonstrated up to 4 mm of collateral thermal injury [14]. This becomes a serious concern for lesions located in eloquent areas of the brain. Using the FEL at 6.45 lm, collateral thermal injury in brain has been shown to be markedly reduced as compared to other surgical lasers [15]. The hemostatic properties of the FEL are unknown at any wavelength. Regardless of any number of advantages a new surgical tool may have for a particular procedure, if bleeding brought on by that tool is not easily controlled, that device will not gain acceptance. We set out to investigate and de®ne the hemostatic properties of the FEL as compared to the known coagulative properties of the CO2 and Nd:YAG lasers. 2. Material and methods Four adult dogs (approximately 20 kg) were induced under general anesthesia with TelazolÒ, intubated, and placed on a respirator delivering
257
oxygen and halothane gas. Generous bilateral craniotomies were performed and the dura divided and retracted, exposing both hemispheres and leaving the superior sagittal sinus intact. Cortical vessels, arterial and venous, were identi®ed and isolated based on external diameter of 1±14 mm. The FEL was set to ®ve wavelengths within the mid-infrared (3.0, 4.5, 6.1, 6.45, 7.7 lm), multipass mode delivering 29±32 mJ/macropulse at 500 Hz and a step length of 0.3 mm. For wavelengths near 6.45 lm, the spectral width typically is several percent and the micropulse duration is approximately 0.6 ps [16]. As a control, the CO2 laser, with an articulated arm delivery system set at 5 W in continuous and superpulse modes, and the Nd:YAG set to 60 W in continuous and pulse (0.1 s repeated) modes were also employed. Vessels were identi®ed and measured with a microsurgical ruler and then divided. The tissue was then observed for hemorrhage. If the vessel hemorrhaged, hemostasis was attempted at ®rst using topical treatments commonly used in neurosurgery, Gelfoam7 soaked in thrombin. If this was not successful, hemostasis was attempted using bipolar electrocautery and results were noted. At the end of the procedure the dogs were euthanised with pentobarbital, prior to arousing from anesthesia. 3. Results All wavelengths tested of the FEL exhibited no evidence of coagulation, inducing bleeding to a degree depending on vessel diameter (Table 1). In vessels less than or equal to 0.4 mm in diameter, the bleeding was easily arrested with GelfoamÒ. The larger vessels required bipolar electrocautery. There was no bleeding from a treated vessel that was not controllable with these techniques, regardless of the laser source. The CO2 laser coagulated all vessels less than or equal to 0.4 mm, with larger vessels requiring bipolar electrocautery to arrest bleeding. We found the superpulse mode and continuous modes to be essentially equivalent in ecacy. However both modes were associated with signi®cant charring of the surrounding parenchyma, with superpulse showing a somewhat greater tendency for such.
258
G.P. Cram Jr., M.L. Copeland / Nucl. Instr. and Meth. in Phys. Res. B 144 (1998) 256±259
Table 1 Vessel diameter (mm)
14 12 10 8 6 4 2 1
FEL wavelength in lm 3
4.5
6.1
6.45
7.7
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
The Nd:YAG coagulated all vessels analyzed. However, the Nd:YAG treatments were uniformly associated with signi®cant contraction and blanching of the surrounding brain parenchyma regardless of the pulse mode. 4. Discussion The FEL has previously demonstrated a remarkable ability to minimize collateral damage with soft tissue resection, however its fundamental properties of laser brain interaction has only begun to be investigated. One such property, hemostasis, is applicable to all surgical tools and specialities. This was studied here in a neurosurgical model. Our analysis demonstrates that the FEL is a poor hemostatic tool. The FEL displayed no bene®t over conventional means commonly employed to achieve hemostasis. Both the CO2 and the Nd:YAG lasers showed superior ability to control bleeding, with Nd:YAG being clearly the most pro®cient. This supports previous studies [17]. However, the price of these hemostatic properties appears grossly to be increased collateral thermal injury, as evidenced by the char deposition by the CO2 laser and the surrounding brain retraction and blanching by the Nd:YAG laser. Perhaps the most important observation of this experiment, however, was that there was no diculty controlling bleeding from any source using the conventional means of topical agents and point
CO2
Nd:YAG
Bleed Bleed Bleed Bleed Bleed Coag Coag Coag
Coag Coag Coag Coag Coag Coag Coag Coag
bipolar electrocautery. Perhaps this should not be surprising, considering that most brain and tumor resections are performed using a small aspirator, which physically divides small vessels without any hemostatic eect. Hemostasis for these such procedures is accomplished by topical agents for capillary and small vessel beeding and bipolar electrocautery targeted locally at larger vessels. Such is also the case for the FEL. The FEL, with its capabilities to deliver laser energy over a variety of wavelengths in the infrared spectrum, has great promise for a multitude of neurosurgical applications. Because of the poor initial clinical results obtained with surgical lasers, heightened scrutiny exists for demonstrating safety and ecacy for clinical applications. This present study demonstrates that while mid-infrared wavelengths show uniformly poor hemostatic ability, the resultant bleeding was easily controlled in the same manner currently widespread for non-laser neurosurgical procedures.
References [1] K.M. Earle, S. Carpenter, U. Rossman, M.A. Ross, J.R. Hayes, E.H. Zettler, Fed. Proc. 24 (1965) S129. [2] S. Fine, E. Klein, W. Nowak, R.E. Scot, Y. Laor, L. Simpson, J. Crissey, J. Donaghue, U.E. Dehr, Fed. Proc. 24 (1965) S35. [3] J.L. Fox, J.R. Hayes, M.N. Stein, R.C. Green, R. Paanen, J. Neurosurg. 27 (1967) 126. [4] S. Stellar, T.A. Polayni, H.C. Bredemeier, Med. Biol. Engrg. 8 (1970) 549.
G.P. Cram Jr., M.L. Copeland / Nucl. Instr. and Meth. in Phys. Res. B 144 (1998) 256±259 [5] F. Heppner, The laser scalpel on the nervous system, in: I. Kaplan (Ed.), ALaser Surgery II, Academic Press, New York, 1978, pp. 79±80. [6] P.W. Ascher, The use of CO2 in neurosurgery, in: I. Kaplan (Ed.), ALaser Surgery II, Jerusalem Academic Press, Jerusalem, 1978, pp. 28±30. [7] S. Krishnamurthy, S.K. Powers, Lasers in Surgery and Medicine 15 (1994) 126. [8] O.J. Beck, Neurosurg. Rev. 3 (1980) 261. [9] J. Takeuchi, H. Handa, W. Taki, Surg. Neurol. 18 (1982) 140. [10] E. Waidhauser, O.J. Beck, C.T. Oeckler, Lasers in Surgery and Medicine 10 (1990) 544. [11] F.P. Wirth, E.F. Downing, C.L. Cannon, R.P. Baker, Neurosurg. 21 (1987) 867.
[12] [13] [14] [15]
259
J.R. Belijan, JAMA 256 (1986) 900. K.K. Jain, J. Quantum Electronics QE 20 (1984) 1401. J.W. Cozzens, L.J. Cerullo, Neurosurgery 16 (1985) 449. G. Edwards, R. Logan, M.L. Copeland, L. Reinisch, J. Davidson, B. Johnson, R.J. Maciunas, M. Mendenhall, R. Osso, J. Tribble, J. Werkhaven, D. O'Day, Nature 371 (1994) 416. [16] A.G. Birch, H.S. Pratisto, G.S. Edwards, E.D. Jansen, Autocorrelation measurements of the Mark-III FreeElectron Laser. First Tennessee Conference on Biomedical Engineering, Memphis. Tennessee. USA, 1998. [17] M.S. Edwards, J.E. Boggan, T.A. Fuller, J. Neurosurg. 59 (1983) 555.
Hemostatic properties of the free-electron laser Gary P. Cram Jr., Michael L. Copeland
*
Department of Neurosurgery, Vanderbilt University Medical Center, Nashville, TN 37235, USA
Abstract We have investigated the hemostatic properties of the free-electron laser (FEL) and compared these properties to the most commonly used commercial lasers in neurosurgery, CO2 and Nd:YAG, using an acute canine model. Arterial and venous vessels, of varying diameters from 0.1 to 1.0 mm, were divided with all three lasers. Analysis of ®ve wavelengths of the FEL (3.0, 4.5, 6.1, 6.45, and 7.7 microns) resulted in bleeding without evidence of signi®cant coagulation, regardless of whether the vessel was an artery or vein. Hemorrhage from vessels less than 0.4 mm diameter was subsequently easily controlled with GelfoamÒ (topical hemostatic agent) alone, whereas larger vessels required bipolar electrocautery. No signi®cant charring, or contraction of the surrounding parenchyma was noted with any of the wavelengths chosen from FEL source. The CO2 laser, in continuous mode, easily coagulated vessels with diameters of 4 mm and less, while larger vessels displayed signi®cant bleeding requiring bipolar electrocautery for control. Tissue charring was noted with application of the CO2 laser. In super pulse mode, the CO2 laser exhibited similar properties, including signi®cant charring of the surrounding parenchyma. The Nd:YAG coagulated all vessels tested up to 1.4 mm, which was the largest diameter cortical artery found, however this laser displayed signi®cant and extensive contraction and retraction of the surrounding parenchyma. In conclusion, the FEL appears to be a poor hemostatic agent. Our results did not show any bene®t of the FEL over current conventional means of achieving hemostasis. However, control of hemorrhage was easily achieved with currently used methods of hemostasis, namely GelfoamÒ or bipolar electrocuatery. Although only cortical vessels in dogs were tested, we feel this data can be applied to all animals, including humans, and the peripheral, as well as central, vasculature, as our data on the CO2 and Nd:YAG appear to closely support previous reports of hemostasis of these two lasers obtained in other models. Ó 1998 Published by Elsevier Science B.V. All rights reserved. Keywords: Free-electron laser; CO2 laser; Nd:YAG laser; Brain; Surgery; Hemostasis; Bleeding; Dogs
1. Introduction The acceptance of lasers as a standard neurosurgical tool has been a long and tedious journey.
* Corresponding author. Tel.: 615 343 v6146; fax: 615 343 1103.
Despite high initial enthusiasm, the ®rst applications of the laser to neurosurgery using the ruby laser revealed discouraging results, with consistent animal deaths [1,2]. Safe and eective neurosurgery was subsequently achieved through careful manipulation of various properties of laser systems (i.e., varying power, frequency, and duration of exposure) [3±6]. With the re®nement of
0168-583X/98/$ ± see front matter Ó 1998 Published by Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 8 ) 0 0 3 1 2 - 7
G.P. Cram Jr., M.L. Copeland / Nucl. Instr. and Meth. in Phys. Res. B 144 (1998) 256±259
microsurgical techniques and the advancements in laser delivery systems, the CO2 and Nd:YAG lasers gained usefulness and popularity [7]. The Nd:YAG laser, well absorbed by vascular tissue and hemoglobin, has been demonstrated to have superior coagulation properties over other lasers and conventional hemostatic methods, such as topical treatments (Surgicell7 or Gelfoam7) and bipolar electrocautery [8,9]. The Nd:YAG thus gained popularity as an adjunct in the resection of AVMs and meningiomas [8±12]. However the Nd:YAG has poor absorption in nonpigmented tissues, resulting in deeper penetration, more scatter, and unacceptable collateral thermal injury to surrounding normal brain. The CO2 laser, demonstrating signi®cantly less collateral thermal injury than the Nd:YAG, yet still exhibiting moderate hemostatic properties, has thus become the gold standard for laser neurosurgery [13]. Hemostasis is of critical consideration in surgical procedures, perhaps most particularly for neurosurgical procedures. Currently, most neurosurgeons still rely on topical agents and bipolar electrocautery for hemostasis [13]. Topical agents are only eective for capillaries and small venules. Bipolar electrocautery, although eective in larger vessels, has demonstrated up to 4 mm of collateral thermal injury [14]. This becomes a serious concern for lesions located in eloquent areas of the brain. Using the FEL at 6.45 lm, collateral thermal injury in brain has been shown to be markedly reduced as compared to other surgical lasers [15]. The hemostatic properties of the FEL are unknown at any wavelength. Regardless of any number of advantages a new surgical tool may have for a particular procedure, if bleeding brought on by that tool is not easily controlled, that device will not gain acceptance. We set out to investigate and de®ne the hemostatic properties of the FEL as compared to the known coagulative properties of the CO2 and Nd:YAG lasers. 2. Material and methods Four adult dogs (approximately 20 kg) were induced under general anesthesia with TelazolÒ, intubated, and placed on a respirator delivering
257
oxygen and halothane gas. Generous bilateral craniotomies were performed and the dura divided and retracted, exposing both hemispheres and leaving the superior sagittal sinus intact. Cortical vessels, arterial and venous, were identi®ed and isolated based on external diameter of 1±14 mm. The FEL was set to ®ve wavelengths within the mid-infrared (3.0, 4.5, 6.1, 6.45, 7.7 lm), multipass mode delivering 29±32 mJ/macropulse at 500 Hz and a step length of 0.3 mm. For wavelengths near 6.45 lm, the spectral width typically is several percent and the micropulse duration is approximately 0.6 ps [16]. As a control, the CO2 laser, with an articulated arm delivery system set at 5 W in continuous and superpulse modes, and the Nd:YAG set to 60 W in continuous and pulse (0.1 s repeated) modes were also employed. Vessels were identi®ed and measured with a microsurgical ruler and then divided. The tissue was then observed for hemorrhage. If the vessel hemorrhaged, hemostasis was attempted at ®rst using topical treatments commonly used in neurosurgery, Gelfoam7 soaked in thrombin. If this was not successful, hemostasis was attempted using bipolar electrocautery and results were noted. At the end of the procedure the dogs were euthanised with pentobarbital, prior to arousing from anesthesia. 3. Results All wavelengths tested of the FEL exhibited no evidence of coagulation, inducing bleeding to a degree depending on vessel diameter (Table 1). In vessels less than or equal to 0.4 mm in diameter, the bleeding was easily arrested with GelfoamÒ. The larger vessels required bipolar electrocautery. There was no bleeding from a treated vessel that was not controllable with these techniques, regardless of the laser source. The CO2 laser coagulated all vessels less than or equal to 0.4 mm, with larger vessels requiring bipolar electrocautery to arrest bleeding. We found the superpulse mode and continuous modes to be essentially equivalent in ecacy. However both modes were associated with signi®cant charring of the surrounding parenchyma, with superpulse showing a somewhat greater tendency for such.
258
G.P. Cram Jr., M.L. Copeland / Nucl. Instr. and Meth. in Phys. Res. B 144 (1998) 256±259
Table 1 Vessel diameter (mm)
14 12 10 8 6 4 2 1
FEL wavelength in lm 3
4.5
6.1
6.45
7.7
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
Bleed Bleed Bleed Bleed Bleed Bleed Bleed Bleed
The Nd:YAG coagulated all vessels analyzed. However, the Nd:YAG treatments were uniformly associated with signi®cant contraction and blanching of the surrounding brain parenchyma regardless of the pulse mode. 4. Discussion The FEL has previously demonstrated a remarkable ability to minimize collateral damage with soft tissue resection, however its fundamental properties of laser brain interaction has only begun to be investigated. One such property, hemostasis, is applicable to all surgical tools and specialities. This was studied here in a neurosurgical model. Our analysis demonstrates that the FEL is a poor hemostatic tool. The FEL displayed no bene®t over conventional means commonly employed to achieve hemostasis. Both the CO2 and the Nd:YAG lasers showed superior ability to control bleeding, with Nd:YAG being clearly the most pro®cient. This supports previous studies [17]. However, the price of these hemostatic properties appears grossly to be increased collateral thermal injury, as evidenced by the char deposition by the CO2 laser and the surrounding brain retraction and blanching by the Nd:YAG laser. Perhaps the most important observation of this experiment, however, was that there was no diculty controlling bleeding from any source using the conventional means of topical agents and point
CO2
Nd:YAG
Bleed Bleed Bleed Bleed Bleed Coag Coag Coag
Coag Coag Coag Coag Coag Coag Coag Coag
bipolar electrocautery. Perhaps this should not be surprising, considering that most brain and tumor resections are performed using a small aspirator, which physically divides small vessels without any hemostatic eect. Hemostasis for these such procedures is accomplished by topical agents for capillary and small vessel beeding and bipolar electrocautery targeted locally at larger vessels. Such is also the case for the FEL. The FEL, with its capabilities to deliver laser energy over a variety of wavelengths in the infrared spectrum, has great promise for a multitude of neurosurgical applications. Because of the poor initial clinical results obtained with surgical lasers, heightened scrutiny exists for demonstrating safety and ecacy for clinical applications. This present study demonstrates that while mid-infrared wavelengths show uniformly poor hemostatic ability, the resultant bleeding was easily controlled in the same manner currently widespread for non-laser neurosurgical procedures.
References [1] K.M. Earle, S. Carpenter, U. Rossman, M.A. Ross, J.R. Hayes, E.H. Zettler, Fed. Proc. 24 (1965) S129. [2] S. Fine, E. Klein, W. Nowak, R.E. Scot, Y. Laor, L. Simpson, J. Crissey, J. Donaghue, U.E. Dehr, Fed. Proc. 24 (1965) S35. [3] J.L. Fox, J.R. Hayes, M.N. Stein, R.C. Green, R. Paanen, J. Neurosurg. 27 (1967) 126. [4] S. Stellar, T.A. Polayni, H.C. Bredemeier, Med. Biol. Engrg. 8 (1970) 549.
G.P. Cram Jr., M.L. Copeland / Nucl. Instr. and Meth. in Phys. Res. B 144 (1998) 256±259 [5] F. Heppner, The laser scalpel on the nervous system, in: I. Kaplan (Ed.), ALaser Surgery II, Academic Press, New York, 1978, pp. 79±80. [6] P.W. Ascher, The use of CO2 in neurosurgery, in: I. Kaplan (Ed.), ALaser Surgery II, Jerusalem Academic Press, Jerusalem, 1978, pp. 28±30. [7] S. Krishnamurthy, S.K. Powers, Lasers in Surgery and Medicine 15 (1994) 126. [8] O.J. Beck, Neurosurg. Rev. 3 (1980) 261. [9] J. Takeuchi, H. Handa, W. Taki, Surg. Neurol. 18 (1982) 140. [10] E. Waidhauser, O.J. Beck, C.T. Oeckler, Lasers in Surgery and Medicine 10 (1990) 544. [11] F.P. Wirth, E.F. Downing, C.L. Cannon, R.P. Baker, Neurosurg. 21 (1987) 867.
[12] [13] [14] [15]
259
J.R. Belijan, JAMA 256 (1986) 900. K.K. Jain, J. Quantum Electronics QE 20 (1984) 1401. J.W. Cozzens, L.J. Cerullo, Neurosurgery 16 (1985) 449. G. Edwards, R. Logan, M.L. Copeland, L. Reinisch, J. Davidson, B. Johnson, R.J. Maciunas, M. Mendenhall, R. Osso, J. Tribble, J. Werkhaven, D. O'Day, Nature 371 (1994) 416. [16] A.G. Birch, H.S. Pratisto, G.S. Edwards, E.D. Jansen, Autocorrelation measurements of the Mark-III FreeElectron Laser. First Tennessee Conference on Biomedical Engineering, Memphis. Tennessee. USA, 1998. [17] M.S. Edwards, J.E. Boggan, T.A. Fuller, J. Neurosurg. 59 (1983) 555.