Device and method to prevent surgical burns

[0001] This application claims the benefit of Provisional U.S. Patent Application No. 60/745,850 filed on Apr. 27, 2006. The details of Application No. 60/745,850 are incorporated by reference into the present application in its entirety.

[0002] The present invention relates to devices and methods for electrosurgical and similar procedures. In particular, but not by way of limitation, the present invention relates to systems and methods for providing an electrosurgical system with a safety device capable of deactivating the electrical current upon the occurrence of a fault condition.

[0003] Minimally invasive surgical procedures continue to experience explosive growth. Such procedures are often preferred to other more invasive procedures in that incisions are kept to a minimum size and thus such procedures facilitate shorter hospital stays and lower costs. For example, with laparoscopic surgery, a patient can return to normal activity within about one week, whereas with procedures where a large incision is made, about a month for full recovery may be required. It should be understood that hereinafter and in the claims, whenever the term “laparoscopic” is employed, similar procedures such as pelviscopic, arthroscopic, thoroscopic, and other procedures where small incisions of the foregoing type are made are also encompassed by this term. FIG. 1 described herein represents the general concept behind an electrosurgical apparatus and how it is used in a surgical setting. Referring to FIG. 1, there is illustrated an electrosurgical laparoscopic surgical system 100 including an electrosurgical tool 104 which is conventionally used to perform various surgical procedures such as ablation, incision, cauterization, etc. As is known in the laparoscopic field, a portion of the tool 104 is provided through a small incision in a patient's skin into, for example, the peritoneal cavity. The electrosurgical tool is typically provided with an active electrode probe 106 which includes an electrode and an insulative coating thereon. The tip of the probe 106 may be of different conventional shapes such as needle-shape, hook-shape, spatula-shape, graspers, scissors, etc. and serve various conventional functions such as suction, coagulation, irrigation, cutting, etc. Current is supplied to the electrosurgical tool by a generator or other electrosurgical unit 102. In order to prevent burns or other trauma to a patient 120 due to the flow of electrical current through uncontrolled paths, a return electrode 110 is placed on the patient. The return electrode 110 is then connected to the electrosurgical unit 102 via conductors 112 and 114 so that the electrical current is returned to the ESU 102 through a controlled path. While laparoscopic devices have enjoyed much success, several problems continue to present themselves.

[0004] First, if the insulation on the active electrode is damaged thereby allowing the active current (possibly in the form of arcing) to pass therethrough directly to the patient's tissue (possibly the bowel or colon), peritonitis may set in within several days. The arcing may occur out of the surgeon's field of view which may extend as little as about 2 centimeters from the tip of the active electrode (or the surgical field). The field of view is typically established by illumination and viewing sources inserted through one or more other trocar sheaths at other incisions.

[0005] Out of the field of view, there can be many centimeters of insulated active electrode which extend between the trocar sheath and the field of view. This area which is out of the field of view is potentially dangerous. Here, the insulated active electrode may come into contact with the bowel in procedures where the gall bladder, for example, is removed. If the damaged insulation and thus the attendant arcing were to occur within the field of view, the surgeon normally would immediately observe this and deactivate the generator. However, the damaged insulation can and more probably will occur at a site removed from the field of view and thus the surgeon will not be able to observe the arcing which is occurring at the bowel. Furthermore, due to the repeated insertion of the active electrode probe through the trocar sheath, the insulation thereon can be damaged especially since this accessory is quite often pushed through the trocar sheath rather roughly. Hence, damage to the active electrode insulation is particularly a problem in that the full active current may pass through the area of damaged insulation to the return electrode via an unintended site such as the bowel.

[0006] A second problem which can arise with the prior art device of FIG. 1 is caused by a capacitive effect where one electrode of the capacitance is the active electrode and the other electrode of the capacitance is the metallic trocar sheath and the dielectric between these elements is the insulation on the active electrode, as can be seen in FIG. 2B. Current from the active electrode will be capacitively coupled to the trocar sheath and then returned through the body and the return electrode to the generator. If this current becomes concentrated, for example, between the trocar sheath and an organ such as the bowel, the capacitive current can cause a burn to the organ.

[0007] A third potential problem occurs if the active electrode contacts another instrument within the peritoneal cavity such as metallic graspers or the like. The above-mentioned capacitive effect also arises in this situation where the first electrode is the active electrode and the second electrode is the metallic graspers or the like. Thus, where the graspers contact a unintended site, injury may occur.

[0008] As a first, and effective way to prevent the problems described above from presenting themselves, monitored electrosurgical tools, where a return shield is actively monitored in order to prevent unwanted current from burning or otherwise injuring a patient were developed. Systems of this type are known in the art and are exemplified by U.S. Pat. No. 5,312,401 (“the '401 patent”). The details of the '401 patent are hereby incorporated by reference in its entirety.

[0009] FIGS. 2A-3B represent a generalized representation of an AEM (“Active Electrode Monitoring”) system 200 embodied by the '401 patent. This system 200 generally includes an electrosurgical generator 102 connected to a laparoscopic instrument 210 via conductors 212 and 214. The instrument 210 includes a tube assembly 220 whereby the instrument 210 provides electrical current from the generator 102 via an active electrode 215. Interposed between a patient return electrode 108 and the generator 102 is an active monitoring system 202 that monitors for one or more fault conditions in the instrument 210. FIG. 2B shows various details of the construction of the monitored instrument 220, including a metal active conductor 222, a high dielectric insulator 224, a metal shield 226, and a non-conductive outer insulating sheath 228. To render laparoscopic electrosurgical procedures more safe and thus overcome the above-mentioned problems, AEM systems such as those described in the '401 patent provide a tubular, insulated, conductive safety shield which extends at least from the trocar sheath to the field of view (that is, typically within less than two centimeters from the active electrode tip). This provides the protection which is needed with respect to the above-discussed first problem where arcing may occur at an unintended site out of the field of view.

[0010] Assuming the insulation on the active electrode 222 is damaged, current will pass through the damaged insulation to the shield and then be returned to the return lead via a low impedance electrical connection between the shield and the return lead of the electrosurgical generator where the impedance should be less than about 20 ohms. A monitor circuit responsive to the shield current preferably deactivates the electrosurgical generator whenever the shield current corresponds to an abnormal condition such as an insulation breakdown. FIGS. 3A and 3B show another representation of the electrosurgical tool 210, including active electrode tip 230. Devices constructed in accordance with the '401 patent have been commercialized by Encision, Inc. of Boulder, Colo.

[0011] Despite the success obtained, and increased patient safety realized, by the inventions embodied in the '401 patent, as well as the electrosurgical tools that embody those inventions, there remain certain problems and drawbacks, as well as room for improvement.

[0012] These drawbacks include, among other things, the need for highly sophisticated and expensive electronics in addition to the actual surgical tool itself. For example, monitoring circuitry associated with these systems often includes a separate stand-alone monitor that interfaces with the electrosurgical generator. This additional piece of hardware increases total operating cost and represents an additional capital investment for a hospital or physician. Because the monitoring unit must interface with electrosurgical generators made by various manufacturers, compatibility issues may arise with traditional electrosurgical tools and systems. Finally, by requiring a separate piece of hardware, it becomes necessary to convince hospitals, doctors, and service providers to purchase a separate monitoring system for their electrosurgical needs. Modern electrosurgical generators come equipped with their own contact quality monitoring circuitry and it would be beneficial to take advantage of this existing hardware in order to provide a monitored electrosurgical tool that provides increased safety to a patient.

[0013] Thus, there is a need for a simpler way to provide a monitored electrosurgical circuit that deactivates the current source of the device when there is a fault condition or other problem. The various aspects of the present invention provide a way to benefit from the increased patient safety associated with monitored electrosurgical instruments while eliminating the above described downsides.

[0014] An instrument constructed in accordance with one or more aspects of the present invention comprises a safety shield having an inner surface and an outer surface, a layer of insulation disposed over the outer surface of the safety shield, an active conductor having a first end adapted to connect with an electrode and a second end adapted to connect with an electrosurgical generator, the electrosurgical generator including contact quality monitoring circuitry, an insulator surrounding the active conductor and disposed between the active conductor and the safety shield, and a circuit interruption device in electrical communication with the safety shield. The circuit interruption device is adapted to couple to the contact quality monitoring circuitry of the electrosurgical generator and disable the flow of current to the electrode upon the occurrence of a fault condition.

[0015] In another aspect of a device constructed in accordance with the present invention, a laparoscopic surgical instrument comprises a safety shield having an inner surface and an outer surface, a layer of insulation disposed over the outer surface of the safety shield, an active conductor having a first end adapted to connect with an electrode and a second end adapted to connect with an electrosurgical generator, the electrosurgical generator including contact quality monitoring circuitry, an insulator surrounding the active conductor and disposed between the active conductor and the safety shield, and a sensing layer in series with the contact quality monitoring circuitry of the electrosurgical generator. Preferably, the sensing layer disables the flow of current to the electrode upon the occurrence of a fault condition.

[0016] Other aspects and features of a method and device constructed in accordance with the present invention are contemplated and are more fully described in the following description and as would be known to one of skill in the art.

[0028] Generally, embodiments of the present invention provide the ability to monitor the current flow within an electrosurgical tool without the need for separate and/or stand-alone monitoring equipment and specialized circuitry to monitor the electrical characteristics of the current flow. Aspects of the present invention enable a monitored device by utilizing one or more techniques and structures to turn off the current flow based on a fault condition in one or more types of sensors, circuit interruption devices, or other sensing techniques that are incorporated into the electrosurgical tool, the shield within the tool or other features of the electrosurgical tool itself FIGS. 4A and 4B, illustrate a device constructed in accordance with one aspect of the present invention. A tubular assembly 300 of a laparascopic instrument is shown with the various layers of concentric materials highlighted. A metal active conductor 302 is surrounded by an insulator 304 that preferably has a high dielectric strength. A metal shield 306 surrounds the insulator 304 which is then surrounded by a non-conductive outer insulation 308. The metal shield 306 includes on its surface or embedded within its structure, one or more temperature sensors 312. The temperature sensors 312 are in turn connected to a central temperature monitoring circuit. Preferably, the central temperature monitoring circuit is directly wired to the Contact Quality Monitoring (CQM) circuit located within the existing electrosurgical generator unit. In this embodiment, the patient is protected from thermal burns by utilizing one or more temperature sensors 312 on the surface of the metal shield. The types and number of temperature sensors used can vary and may incorporate a variety of available technologies. For example, the temperature sensors may be connected in parallel as shown in FIG. 4B and interconnected by one or more conductive wires or traces 314. Types of temperature sensors include thermocouples, thermistors, resistance based sensors, and any of various other known temperature sensors. The temperature sensors 312 are preferably strategically placed around and along the shield and are adapted to monitor the shield for any rapid rise in temperature. However, any number of alternate configurations of the temperature sensors 312 are possible as would be know to one of skill in the art. All sensors are preferably tied into a central circuit 310 where any abnormal signal from the sensors would trigger an opening of one lead of the patient monitoring circuit thereby activating an alarm from the ESU (electrosurgical unit) generator. Parallel circuits are also contemplated. Preferably the patient monitoring circuit is already contained and/or integrated within the ESU generator, eliminating the need for a separate monitoring unit. The system can be set to trigger the alarm or shut off the supply of electrical current to the instrument at various temperature thresholds, depending on the particular application, equipment configuration or specific surgical procedure being performed.

[0029] In accordance with another aspect of a device constructed in accordance with the present invention, FIGS. 5A-5C show an additional interior concentric sensing layer 406 placed on the interior of the metal shield tube 408. The sensing layer 406 preferably lies between the insulator 404 and the metal shield tube 408. The sensing layer 406 is adapted to provide the insulation and dielectric properties replacing the separate insulation layer around the active conductor. While the sensing layer 406 may be incorporated as an additional layer between the dielectric 404 and the shield 408, it may alternately be constructed and adapted to provide the same function as the dielectric insulation while simultaneously providing a sensing function.

[0030] The sensing layer 406 may be an additional layer such as a thin walled tube that contains multiple temperature sensors (such as described above in conjunction with FIGS. 4A and 4B) or one homogeneous sheet of sensing material 420 as depicted in FIG. 5C. For example, PVDF piezoelectric film sensors are available in very thin sheets or photographically etched into patterns on a polymer based sheet. This type of piezoelectric film provides an electrical signal, in the form of a current surge, when either physically flexed, exposed to a temperature change, or electrically activated. In a device constructed in accordance with an aspect of the present invention were to experience a short between the active electrode and the shield, the electrical path would cross through the film sensor. Either a temperature rise in the shield tube, thermally conducted to the thin piezo film, or an electrical current surge as the short passes through the piezo film, would alert the monitoring circuit of the short which in turn would open one leg of the CQM circuit initiating an alarm in the ESU that would stop activation of the active electrode.

[0031] In addition, the flexure or strain exerted on such a film or other sensing layer may be monitored during use, providing either feedback to the user to gauge physical characteristics of the anatomy being manipulated or additional feedback to the monitoring circuit for possible overuse that could trigger a short due to material breakage.

[0032] For the applications described above that rely on one or more forms of a temperature sensor, the monitoring circuit provides a trip point for opening the return electrode monitoring circuit and thereby stopping the electrical activation of the electrosurgical instrument. In both cases of temperature sensing, the monitoring circuit may be replaced with either a multiple or a single fuse. The fuse is preferably designed for maximum current based on all compatible electrosurgical generators. FIGS. 6A and 6B illustrate this concept.

[0033] In FIGS. 6A and 6B, a device 500 includes an active electrode 502, insulator 504, fuse layer 506 and outer insulation 508. The sensing layer 506 is connected to a fuse 510 and then to the CQM via a conductor to the CQM circuitry of the generator and provides a circuit interruption upon the occurrence of a fault condition in the instrument.

[0034] The concept outlined above utilizes either a series of fuses associated with each temperature sensor or a centrally located fuse that is in series with the CQM circuit. Therefore, if a set current is exceeded, the fuse blows, opening the CQM circuit and shutting down the ESU through it's own CQM monitoring circuit.

[0035] In another embodiment, and as illustrated in FIGS. 7-9, a type of thermal fuse in the form of a thin sensing layer 606 resides between the interior dielectric 604 and the outer metal shield tube 608. The sensing layer 606 surrounds the interior dielectric 604 and extends beyond the outer metal shield tube 608. The sensing layer 606 may be constructed from several different types of material but preferably has a continuous conductive trace that is connected in series via a conductor 612 with the CQM circuit of the electrosurgical generator. The trace is located either on the sensing layer's surface or interior. If a short occurs through a break in the interior dielectric 604, the electric arc would seek a path toward the closest patient reference potential which in this case is the shield circuit 606. Since the sensing layer circuit has the patient reference potential conductive trace running through it's interior, the electrical path would seek the conductive trace first, as opposed to the outer metal shield 608.

[0036] The sensing layer conductive trace 606 is preferably designed thin enough so that it would vaporize or extensively melt in a fault condition causing the shield circuit and then the CQM circuit to open. This then triggers a CQM shutdown sequence in the generator. Because the conductive trace is in series with the CQM circuit, it is preferably electrically capable of handling the normal current of the CQM circuit from both the patient pad and capacitive coupling. This current is usually under 1 amp. The trace preferably also has a low enough total resistance that it will not interfere with the patient CQM pad (return electrode). In addition, the conductive traces are preferably close enough together so as to not allow any electrical arcs to pass between the traces toward the outer shield without first breaking the sensing layer trace.

[0037] With reference to FIGS. 8A-8C, construction of the sensing layer can be accomplished by any of several techniques. For example, as shown in FIG. 8A, a sensing layer 700 may consist of a flex circuit 702 with a continuous trace pattern 704. The pattern can be any of a zig-zag format, helix, or double helix configurations or any of many other known configurations. The flex circuit 700 can be a single sided trace or a more complex pattern of a double sided trace where the trace pattern forms a crisscrossed grid of traces nearly side-by side.

[0038] As shown in FIG. 8B, the sensing layer 710 can also be constructed by applying a metal film 712 through vapor deposition or ionic deposition techniques to a non-conductive tube. The metal deposition can be selectively applied in the final pattern desired through masking or could be achieved by machining off the metal layer in the final pattern.

[0039] As shown in FIG. 8C, an additional technique for construction of the sensing layer can be achieved by using current wire wrapped extrusions 714. A non-conductive thin walled tubing 716 can be wrapped with a double helix of copper wire then over molded with additional polymer for insulation, smoothness, and protection. While this is the preferred method due to pricing, availability, and varieties of tubing, various other means for construction of the sensing layer are contemplated.

[0040] In all examples of construction, the sensing layer may be designed thicker to also provide the same function as the interior dielectric surrounding the active electrode. In one preferred method, the sensing layer is applied on top of the dielectric insulator.

[0041] An additional property of this fusible shield is the possibility of providing full shielding of the electrical energy. This will replace the outer stainless tube currently used for shielding on many existing devices.

[0042] FIGS. 9A and 9B show a cross section of the sensing shield 754 and its orientation with respect top the active electrode 750, insulator 752, outer shield 756 and outer insulator 758. The representation of FIGS. 9A and 9B can be applied to any of the previously described sensing shield embodiments.

[0043] FIGS. 10A and 10B show circuit diagrams corresponding to several of the embodiments and concepts described above. In FIG. 10A, a circuit configuration is shown that corresponds to configurations where the shield fault sensing may have a direct connection to the generator CQM system. This configuration may preferably be used in connection with the fuse-based systems described above. In FIG. 10B, a circuit configuration is shown that corresponds with one or more type of electronic processing such as the previously described embodiments that incorporated temperature sensors or strain gauges. The corresponding electronics (E) may be contained within the cabling itself or within the instrument assembly. The circuit diagrams depicted in FIGS. 10A and 10B may be used with one or more of the embodiments described above and the reference numbers used are not meant to limit the use of these circuit diagrams to any particular embodiment.

[0044] A device and method constructed in accordance with various aspects of the present invention solves the foregoing problems by allowing a physician to utilize a monitored electrosurgical system without needing any special equipment setup. Namely, when compared to prior AEM systems, a device constructed in accordance with an aspect of the present invention eliminates the need for a separate AEM monitor while still providing a way to monitor the electrosurgical circuit. The system may replace instruments that the doctor is currently using and will likely be bought as a disposable product rather than capital. Because it utilizes existing hardware, it is portable between suites and hospitals. The compatibility features results in less additional education and training being needed for the physician and hospital.

[0045] Because the system is adapted to interface directly with an ESU generator rather than a separate monitor, compatibility with existing systems is further enhanced. System constructed in accordance with one or more aspects of the present invention can preferably use a common plug style that will make the attachment more universal.

[0046] Finally, because the system described above needs fewer or no complicated electronics, this technology can be incorporated more easily and for less money into competitive instruments without needing to affect their generators.

[0047] It is to be understood, however, that there is no intention to limit the invention to the forms described in the foregoing description and drawings. One skilled in the art can recognize that there are numerous modifications, equivalents and alternative constructions that fall within the spirit and scope of the invention and that are fully recognized by those of skill in the art. For example, it is contemplated that various other circuit interruption techniques as known in the art can be used in conjunction with a device and method constructed in accordance with as aspect of the present invention. The above-described embodiments and implementations are for illustration purposes only.

[0048] For example, the disclosed inventions could also open the active electrode circuit thus stopping the flow of current to the instrument independent of the ESU. The instrument could also alert the user of a fault condition through it's own internal alarm or initiate the ESU alarm by also opening the CQM circuit. By opening the active circuit independently of the ESU, the instrument can respond quicker to shutting down the current to the active electrode rather than waiting on the reaction time of the CQM circuit which varies in each ESU. Any of the above mentioned sensing methods could open the ESU active circuit through the use of a fuse, relay, or switch. In addition, any known mechanism can be used to shut off the flow of current either in the CQM circuitry or in the active circuit itself.

[0049] Those skilled in the art can readily recognize that numerous variations and substitutions may be made in the invention, its use and its configuration to achieve substantially the same results as achieved by the embodiments described herein. Accordingly, there is no intention to limit the invention to the disclosed exemplary forms. Many variations, modifications and alternative constructions fall within the scope and spirit of the disclosed invention as expressed in the claims.