Indifferent Electrode In Electrosurgical Procedures And Method Of Use

Abstract

A disposable indifferent electrode easily contoured to body surfaces including an electrode electrolyte assembly in which the electrode is relatively small in size yet provides very effective electrical contact between it and the body surface by virtue of an interposed electrolyte composition of predetermined characteristics; and, in surgical diathermy, a method of conducting high frequency radio waves to ground.

Parent Case Text

This application is a continuation-in-part of pending U.S. application Ser. No. 223,107, filed Feb. 3, 1972 and now abandoned by Charles T. Patrick, Jr. and Charles L. Milligan and entitled INDIFFERENT ELECTRODE IN ELECTROSURGICAL PROCEDURES.

Description

BACKGROUND

As far back as 1919, Iredell and Turner were primarily responsible for surgical diathermy as we know it today, wherein current used to sever tissue is conducted to ground by the use of an indifferent electrode, also called a patient ground plate. While a great many innovations have been made in electrosurgical procedures since Iredell and Turner demonstrated the effectiveness of a 72 square inch (6 .times. 12 inches) ground plate, surprisingly enough the field of surgical diathermy has zealously retained and promoted the concept that a relatively large area of body surface should be in contact with an equally large patient ground plate to avoid burns.

Present day literature is replete with allusions to the necessity for ground plates measuring 6 .times. 5 inches, 6 .times. 8 inches, etc., a rule of thumb being about 9 square inches of plate surface per 100 watts of power generated by the electrosurgical apparatus. As is well known, in surgical diathermy such apparatus generates high frequency electric current which is fed to an active electrode used to cut tissue and coagulate blood vessels, a large patient ground plate being used to provide a low current density path to complete the electrosurgical circuit and minimize tissue heating at the plate/skin interface. To lower skin resistance at the interface, electrolytes are generally used, e.g., conductive pastes, jellies or saline solutions. Caution is generally given, however, that during extended electrosurgery the electrolytes will dry up and it is therefore very important, to avoid burns and other complications, to maintain a large skin contact area with the ground plate.

Obviously, the large ground plates in common use have their drawbacks: they are not easily contoured to the body and, of course, relatively few body surface areas can accommodate them; when placed under a patient, for instance, it is difficult to know whether substantial plate/body contact is being maintained, particularly when the patient moves or is moved; depending upon area contacted and method of applying the ground plate, circulation can readily be affected, thus increasing the possibility of burns; the general stiffness of plates and the inflexible and, at times, sharp edges thereof can cause substantial discomfort to the patient, especially in the case of a prolonged operation; of course, a large patient ground plate inherently increases the possibility of accidental contact with surgical instruments or other metal objects that can result in a burn to the patient; etc.

It is therefore the purpose of the present invention to provide an indifferent electrode and method of use which overcomes the drawbacks of the conventional patient ground plates. Other objects of the present invention are to provide an indifferent electrode which is: relatively small in size; easily contoured to various body surfaces, thus allowing many sites for application; disposable; readily and securely attached to the body without restricing circulation; capable of maintaining good and stable electrode/electrolyte/skin contact for long periods of time with minimum electrolyte evaporation and impedance increase; capable of being pre-wet, pre-sterilized and/or pre-packaged, if desired; etc. These and other objects and advantages will be apparent from the more detailed description infra.

Of interest are the following references:

U.s. pat. Nos. 3,601,126, 3,590,322, 3,568,662, 3,543,760, and 3,518,984;

Canadian Pat. No. 675,494;

French Pat. Nos. 1,255,797 and 915,335;

Mitchell, J. P., Lumb, G. N.: The Principles of Surgical Diathermy and Its Limitations, Brit. J. Surg. 50 pp. 314-320 (Nov) 1962;

Mitchell, J. P., Lumb, G. N.: A Handbook of Surgical Diathermy, Bristol, John Wright and Sons Ltd. 1966, pp. 34-38;

Nicholson, Morris J., Anesthesia and Analgesia -- Current Researches, Vol. 49, No. 8, (May-June) 1970;

Dobbie, A. K., The Electrical Aspects of Surgical Diathermy, Bio Medical Engineering, 1969 pp. 206-216;

Battig, Charles G., Electrosurgical Burn Injuries and Their Prevention, JAMA June 17, 1968, Vol. 204, No. 12, pp. 91-95; and

Wald, Alvin, S., Mazzia, Valentino D. B., Spencer, Frank C., Accidental Burns, JAMA Aug. 16, 1971, Vol. 217, No. 7, pp. 916-921.

The later (1966) Mitchell and Lumb reference above teaches that the conventional size patient ground plate (usually lead) is 6 .times. 5 inches, i.e., 30 square inches. It points out: "In practice, however, it is found that the size can be reduced to a total of 12 square inches, and will still carry the maximum output without heating, provided adequate contact is made over the whole of its surface."

The A. K. Dobbie reference, supra, in rejecting the impression that ECG monitoring causes diathermy burns has this to say on p. 214, column 3:

"This is virtually impossible when the patient plate electrode (or electrodes) is correctly fitted to the patient and the surgeon is not using heavy diathermy currents within a few inches of an earthed monitoring electrode, since only a small current will take the alternative ECG path back to the diathermy set earth terminal owing to the presence of the much lower impedance presented by the plate electrode with its short return path. An ECG electrode 5 cm .times. 3 cm has a contact impedance of around 15 ohms at diathermy frequencies and is capable of carrying a current of 600 mA continuously for 120 seconds without undue heat being produced if the electrode is placed directly over a muscle; if it is fixed over fat the maximum current is around 500 mA."

The article goes on to say: "A properly fixed ECG electrode is capable of carrying the currents used in pediatric surgery with an output setting of 2 or 3."

U.S. Pat. No. 3,601,126 in FIGS. 2 through 6 of its drawing teaches an indifferent electrode having a metallized sheet electrode on which is superimposed a spongy sheet containing viscous electrolyte.

Canadian Pat. No. 675,494 discloses an electrode made of a foil sandwiched between a plastic sheet (having a pressuresensitive adhesive on its inner surface) and an absorbent felt or fabric material "...adapted to be wetted with an electrical conducting agent." The peripheral edge of the plastic sheet lamina extends considerably beyond the peripheral edges of each of the other two laminae. A snap fastener terminal is carried by the plastic sheet and the foil through opposed apertures in these laminae.

As will be seen from the detailed description to follow, the above references and selected excerpts therefrom are readily distinguishable.

U.S. Pat. No. 3,701,346 hereby incorporated herein by reference describes in detail electrolyte compositions of the type contemplated herein and a pre-filled body suitable for sensing the bioelectrical potentials of a living animal body.

THE INVENTION

The present invention concerns an indifferent electrode for electrosurgical procedures utilizing high frequency radio waves. More particularly, the instant discovery concerns a novel electrode/electrolyte assembly easily contoured to body surfaces and useful in surgical diathermy for conducting harmlessly to ground the current used to sever tissue.

Still more particularly, the instant discovery relates to an electrode/electrolyte assembly in which the electrode is an electrically conductive means having a predetermined area of its conductive surface adaptable to be applied in essentially complete conductive contact with the skin of a patient through an interposed electrolyte means which, in turn, has sufficient thickness to properly space any part of said conductive means from the skin. Preferably, according to the present invention, the electrode/electrolyte assembly comprises an electrically conductive electrode element, such as a disc or wire, usually made of metal or other like conductive material, having at least about 0.038 square inch conductive surface thereof in essentially complete contact with an electrolyte composition having at least about 2.0 square inches of its conductive surface adaptable to be applied in essentially complete conductive contact with the skin of a patient and having a thickness of at least about 10 mils to thus space any part of said conductive element a distance of at least about 10 mils from the skin of a patient. The thickness of the interposed electrolyte composition should be greater than 10 mils, generally at least about 165 mils, when the conductive element surface area is less than about 0.10 square inch, i.e., between about 0.038 and 0.10 square inch, thus spacing any part of said conductive element a distance of at least about 165 mils from the skin surface of a patient.

For example, when a wire is used and, say, embedded in an electrolyte composition, the surface of the wire is preferably spaced from the skin of a patient by at least about 190 mils, the electrolyte composition generally being interposed and thus providing efficient current transfer from the skin to the wire-shaped electrode.

Quite surprisingly, it has been found that a wide variety of electrode shapes and configurations may be employed having at least the minimum conductive surface area hereinbefore described. The wire shape, for instance, may be that of a loop, a straight line, a convolution, a square, an ellipse, etc., provided, of course, the minimum conductive element surface area and electrolyte thickness are maintained. Other electrode shapes within the purview of the present invention include snap-fasteners, foils, discs, wire mesh, and so on. Preferably, while always maintaining the conductive electrode surface properly spaced from the skin, the interposed electrolyte essentially covers the total skin-side surface of the electrode.

Illustrative of an electrolyte/electrode assembly of the type wherein the electrolyte composition does not totally cover the skin-side surface of the electrode is one made up of a disc of non-conductive plastic material containing multiple apertures therethrough resembling, for example, the hexagonal cells of a honeycomb and laminated to one surface of the honeycomb disc, closing off the apertures, is an electrode disc which thus forms individual honeycomb-shaped cups. While all of these cups may be filled with an electrolyte composition, such as a gel or a paste, it is only necessary, pursuant to the present invention, to fill sufficient of these cups to establish conductive contact, as described hereinbefore, with at least about 0.038 square inch of the electrode disc and, of course, provide at least about 2.0 square inches of the conductive surface of the electrolyte composition adaptable to be applied in essentially complete conductive contact with the skin of a patient. The honeycomb disc must, of course, be thick and rigid enough, in the case of a thin disc, to space the skin side of the electrode disc at least about 10 mils from the skin of the patient.

Obviously, many other shapes of electrode means and electrolyte means are within the purview of the present invention and will become readily apparent from the general and specific descriptions herein contained.

One of the preferred embodiments comprises an electrode/electrolyte assembly wherein the electrode is a relatively small thin flexible sheet of conductive metal having one side thereof essentially completely covered by and in essentially complete contact with a viscous electrolyte composition having a substantially uniform thickness, the surface area of said covered side of the electrode being in the range of about 0.5 square inch to about 10 square inches, generally about 2 square inches to about 5 square inches, and the thickness of the electrolyte composition being in the range of about 62 mils to about 500 mils.

The thin flexible sheet or foil of conductive metal in this embodiment is preferably of stainless steel and the electrolyte is an alkali metal sulfate, e.g., sodium sulfate, the electrolyte comprising an aqueous highly viscous semisolid composition containing, by weight, from about 0.5 percent to about 20 percent alkali metal sulfate.

While the alkali metal sulfates, such as sodium, potassium and lithium sulfates, are very effective for use herein as electrolytes, other water-soluble, ionizable, inorganic and organic salt electrolytes are contemplated herein, including alkali metal halides and nitrates, e.g., sodium chloride, potassium bromide, potassium nitrate, and the like; ammonium halides, nitrate and sulfate; magnesium halides, nitrate and sulfate; and other like ionizable alkaline earth metal salts; ionizable organic salts or organic acid salts of citric, tartaric, salicylic, benzoic, lactic or other like acids with metals, such as alkali and alkaline earth metals, including sodium, potassium, magnesium, and the like.

Preferably a small but effective amount of a water-soluble, water swellable mucilage is present in the electrolyte composition, such as the aqueous alkali metal sulfate solution, to provide a viscous electrolyte mixture which, according to a still further embodiment, is absorbed or uniformly distributed throughout the interstices of a sponge-like cellular matrix (e.g., polyurethane foam or other like absorbent material) to provide a highly viscous semisolid electrolyte composition.

Among the water-soluble, water-swellable mucilages (also known as gelling acids and water-soluble resins) useful herein are carboxymethylcellulose, polyvinyl alcohols, cellulosic gums, polymethylene oxide, sodium alginate, gum tragacanth, polyacrylic acids, such as those hydrophilic, high viscosity, polyacrylic acids having a molecular weight of about 1 million to about 6 million and useful in cosmetic and pharmaceutical preparations, e.g., the Carbopol water-soluble resins. (Carbopol is a trademark used by B. F. Goodrich Chemical Co.)

Best results are achieved with the polyacrylic acids by neutralizing same with any of a number of neutralizing agents, such as the fairly strong organic and inorganic bases, including but not limited to NaOH, KOH, NH.sub.4 OH, alkyl amines(mono-, di-, and tri-), alkanol amines(mono-, di-, and tri-), such as triethanolamine, triamylamine, dodecylamine, di(2-ethylhexyl) amine, and the like.

The resulting neutralized mucilage is usually present in the concentration of about 0.2 percent to about 8.0 percent, preferably from about 0.85 percent to about 5.0 percent, by weight, based upon the total weight of the electrolyte composition.

If desired, conventional additives, such as mold inhibitors and the like, may be present in small quantities, usually less than about 1 percent. For example, very desirable results are achieved with chlorinated aromatic hydrocarbons, including 2-chloro-meta-5-xylenol, salts of organic acids, such as sodium benzoate, etc.

While the blending sequence of the electrolyte components of these preferred embodiments admits of numerous variations, it is desirable and preferred to make the aqueous alkali metal sulfate solution separately and add thereto, with adequate stirring, the mucilage component which may then be neutralized in situ. The mold inhibitor or the like, if any, is preferably introduced with the neutralizing agent for more effective disbursement.

Generally, the electrolyte components are blended at ambient temperature and atmospheric pressure. If desired, however, elevated temperatures and pressure conditions, for instance, could be used very satisfactorily.

If desired, the electrolyte may comprise a column or multiple columns (e.g., the honeycomb disc hereinbefore discussed) of electrolyte paste, gels, or the like. Also, the electrolyte may comprise a paste or gel having therein interspersed finely-divided particulate materials, usually inert, such as powdered talc, regenerated cellulose, sand, fumed silica (SiO.sub.2), silica gel, or other similar fillers. Generally, from about 5 to 60 percent by weight filler is present, based upon the total weight of the electrolyte (e.g., gel or paste) and filler composition, preferably about 20 to about 50 percent.

While stainless steel is one of the preferred electrode elements, the invention is not limited thereto. The electrode may be made out of any conductive material, e.g., aluminum, copper, silver, silver/silver chloride, brass, platinum, gold, and the like. The conductive metal can, for instance, merely be present as a plating on a substrate of, for example, another metal, plastic, or the like. A flexible conductive metal sheet may, for instance, be prepared from powdered metal which is sintered to the desired shape; the pulverized metal may be shaped into a sheet by embedding the metal particulates in a binder, such as a polymeric binder or matrix. The expression "conductive metal" is intended to encompass, also, other conductive materials including, for instance, a carbon disc.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a protective covering for an electrode.

FIG. 1A is a schematic of the electrosurgical current source, active electrode, patient and indifferent electrode.

FIG. 2 is a cross sectional view of the electrode and protective covering taken along line 2--2 of FIG. 1.

FIG. 3 is partially exploded perspective view of the electrode with the protective covering removed.

FIG. 4 is a partially exploded perspective view of the electrode with the protective covering and the protective releasable cover sheet removed.

FIG. 5 is a partially exploded perspective view of the electrode with the protective covering, the protective releasable cover sheet, the non-conductive cup member, the snap fastener, and the flexible and resilient sheet removed, and the electrolyte-saturated cellular matrix of FIG. 4 is substituted by a single non-woven cotton fabric disc, likewise electrolyte-saturated.

FIG. 6 is the same as FIG. 5 with the exception that multiple non-woven cotton fabric discs are stacked and, of course, electrolyte-saturated.

FIG. 7 is a perspective view of a disc-shaped sponge-like cellular electrolyte matrix having a wire electrode therein embedded.

FIG. 8 is a partially exploded perspective view of the electrode with the protective covering, the protective releasable cover sheet, the non-conductive cup member, the snap fastener, and the flexible and resilient sheet removed, and the conductive metal sheet is covered with a polymeric film partly broken away to show the metal sheet.

FIG. 9 is a cross sectional view of the polymeric film covered conductive metal sheet taken along line 9--9 of FIG. 8.

FIG. 10 is a partially exploded perspective view of the electrode with the protective covering, the protective releasable cover sheet, the non-conductive cup member, the snap fastener, and the flexible and resilient sheet removed, and the disc-shaped sponge-like cellular electrolyte matrix is covered with a polymeric film partly broken away to show the electrolyte matrix.

FIG. 11 is a cross sectional view of the polymeric film covered disc-shaped sponge-like cellular electrolyte matrix, the polymeric film partly broken away to show the electrolyte matrix.

FIG. 12 is a partially exploded perspective view of the electrode with the protective covering, the protective releasable cover sheet, the non-conductive cup member, the snap fastener, and the flexible and resilient sheet removed, and the conductive metal sheet and disc-shaped sponge-like cellular electrolyte matrix are each covered with a polymeric film partly broken away in each case to show the metal sheet and electrolyte matrix, respectively.

FIG. 13 is a partially exploded perspective view of the electrode with the protective covering, the protective releasable cover sheet, the non-conductive cup member, the snap fastener, and the flexible and resilient sheet removed, and the electrolyte-containing member is a disc of non-conductive polymer having honeycomb apertures therethrough, some filled with electrolyte gel and some empty.

FIG. 14 is a partial central cross sectional view of the electrode with the protective covering and the cellular electrolyte matrix removed, the non-conductive cup member being shown filled with an electrolyte gel.

DESCRIPTION OF A PREFERRED EMBODIMENT

The drawing illustrates an electrode, generally designated 10, consisting of a substantially rectangular flexible and resilient sheet 12 (as here shown) carrying a generally centrally located non-conductive cup member 14, the surface of the flexible and resilient sheet 12 in coplanar relationship to the outer surface of the flat base 16 of the cup member 14. The latter, in turn, in its cavity which opens to the body surface (not shown) carries coplanar to and resting on the interior surface of its flat base 16 flexible sheet (or foil) of conductive metal electrode 17. The diameter of the cup member 14 is substantially greater than its height, thus defining a low profile.

The flexible and resilient sheet 12, the cup member 14 and the flexible sheet of conductive metal 17 are held together by a metallic conductor formed from a male snap fastener member, generally designated 18, and which includes a lower, circular plate portion 20, from the center of which a hollow stud 22 projects upwardly, and an upper plate portion 24 having an upwardly protruding hollow socket portion 26 receiving the stud 22.

The parts are assembled and held together by centrally locating and aligning the cup member 14 containing the likewise centrally located and aligned flexible sheet of conductive metal 17 and the upper plate portion 24 with its upwardly protruding hollow socket portion 26 on opposite sides of sheet 12. The stud 22 is then inserted through aligned apertures in the centers of flexible conductive sheet 17, base 16 and resilient sheet 12 and into the socket 26. The pressing together of the snap fastener portions causes the upper end of the stud 22 to fold inwardly and its side walls to collapse outwardly whereupon the snap fastener parts are tightly wedged together.

The bottom surface of the sheet 12 has a commercially available, medical grade acrylic pressure sensitive adhesive coating 28. Until the electrode 10 is to be used, the adhesive coating 28 is covered by a protective paper sheet 30 having a release coating on its face which engages the adhesive coating 28. The outer surface of flat base 16 of flexible cup member 14 is not only mounted on resilient sheet 12 by means of the above-described snap fastener but the outer surface of flat base 16 is adhered to the bottom surface of resilient sheet 12 by means of the pressure adhesive coating 28 on sheet 12. For this purpose protective paper sheet 30 has an opening therein through which cup member 14 projects.

The sheet 12 is preferably formed of a foamed plastic, such as polyurethane, polyvinyl chloride, or the like, which provides for adequate aeration or ventilation of the skin. Such a sheet is quite flexible, readily conforming to skin contours and permitting free movement of the skin to which it is applied. The cup member 14 may be vacuum formed from a non-conductive thermoplastic sheet material which is flexible but sufficiently rigid to prevent its collapse. A variety of plastic materials may be used to form the cup member 14, examples being linear polyethylene, polyvinyl chloride, cellulose acetate butyrate, or the like.

The electrolyte may be preassembled with the electrode 10 by soaking a disc-shaped sponge-like cellular matrix 32 of non-conductive, open-cell material with an electrode jelly. The sponge-like matrix 32 preferably has a diameter substantially equal to the diameter of the base 16 of the cup member 14 and a thickness greater than the depth of the cup member 14. It is sufficiently heavily laden with electrode jelly that, when the electrode 10 is pressed on the skin, the jelly fills the entire volume of the cavity between the skin and the conductive metal sheet 17 and plate portion 20 whereupon good electrical contact between the skin and the conductive metal sheet electrode 17 and conductive plate 20 through the jelly is assured.

The sponge-like matrix 32 may be manufactured from open-cell polyurethane foam material although other cellular materials would be suitable. The sponge-like matrix 32 may be soaked with the jelly (e.g., sodium sulfate) by immersing it in a quantity of jelly, squeezing it under pressure and then gradually releasing the pressure before removing it from the jelly in the same manner that one would load a sponge with water. Of course it could be soaked with electrolyte by other methods.

In view of being wetted by the viscous electrolyte, the soaked sponge-like matrix 32 tends to adhere to conductive metal sheet electrode 17, conductive plate portion 20 and the inner surfaces of cup member 14. As shown, the sponge-like cellular matrix 32 is fastened to the electrode assembly conductive plate portion 20 by means of a plastic (e.g., nylon, polyacetate) non-conductive rivet 34 having a shaft 35 which passes upwardly through apertured aqueous highly viscous semisolid electrolyte composition 32 into and in locking engagement in the hollow neck portion 22 of said stud 20.

Further in accordance with this invention, a protective cover 38 in FIGS. 1, 2 and 3 is provided for the cup member 14 and the jelly soaked sponge-like matrix 32 so that the electrode 10 may be stored ready for immediate use. The cover 38 comprises an essentially flat strip of non-conductive plastic sheet having flat ends 40 and a raised center portion 42 formed as a cylinder, the inner diameter of which is substantially the same as the outer diameter of the cup member 14. The height of the cylindrical center portion 42 is at least the combined height of the cup member 14 and the sponge-like matrix 32. The protective cover 38 is lightly adhered to protective sheet 30 such that removal of releasable sheet 30 carries with it protective cover 38, yet cover 38 may be readily separated from sheet 30 without disturbing the latter.

The cover 38 is assembled on the non-adhesive face of the protective sheet 30 with the cylindrical center section 42 slipped over the cup member 14. The protective cover 38 serves to prevent soiling and evaporation of the aqueous semisolid matrix 32. As suggested hereinbefore, when the electrode 10 is to be used, the protective sheet 30 is merely peeled away from the sheet 12, taking with it the protective cover 38.

Pursuant to another embodiment of the present invention, FIG. 5, the sponge-like disc-shaped cellular electrolyte matrix 32 of FIG. 3 is replaced by a non-woven cotton fabric disc 50, which disc is at least 10 mils thick, is saturated with an electrolyte jelly and completely covers the lower or skin-side surface of the electrode sheet 17, i.e., the diameter of the disc 50 being preferably greater than that of the disc-shaped conductive metal sheet 17.

The embodiment shown in FIG. 6 resembles the structure of FIG. 5 in every essential respect with the exception that the electrolyte composition structure comprises multiple laminated non-woven cotton fabric discs 60, also saturated or soaked with electrolyte jelly.

The FIG. 7 embodiment comprises a disc-shaped sponge-like cellular electrolyte matrix 70 having no central aperture yet having a thin wire electrode 72 transversely embedded therein along its diametric plane, one end of the wire terminating within the cellular electrolyte matrix disc and the other end of the wire directed to ground and away from the skin-surface of the cellular matrix disc, as shown. When this wire provides a conductive surface in contact with the electrolyte in the range of 0.038 and 0.10 square inch, the electrolyte composition should be at least about 165 mils in thickness, i.e., the conductive wire should be maintained (spaced) a distance of at least about 165 mils from the skin.

A still further embodiment is shown in FIG. 8 wherein the sponge-like cellular electrolyte matrix 32 of FIG. 3 (without a central aperture) is spaced from conductive metal sheet disc 17 by a polymer film 80, the edges and sides of conductive metal sheet 17 both being covered, as shown, with continuous polymeric film 80, neither the matrix 32 nor film 80 being centrally apertured. FIG. 9 is a cross sectional view of the conductive metal sheet 17/polymer film 80 of FIG. 8 when assembled.

The embodiment of FIG. 10 teaches the cellular matrix 32 of FIG. 3 (without a central aperture) covered on the skin and lateral sides with a continuous polymeric film 80 of the type shown in FIGS. 8 and 9. FIG. 11 is merely a cross sectional view of the covered cellular matrix of FIG. 10.

The embodiment shown in FIG. 12 comprises a structure in which the sponge-like disc-shaped cellular matrix 32 and the conductive metal sheet 17 are each covered on their skin-side and lateral surfaces with continuous polymeric film 80.

In the FIG. 13 embodiment, the electrode/electrolyte assembly of FIG. 3 in which the electrolyte-containing member 32 is substituted with a disc 90 of non-conductive material, e.g., polymeric material, having honeycomb hexagonal apertures 92 therethrough, or the like, and certain of these apertures (as shown) are filled with electrolyte gel while others are devoid of same.

In FIG. 14 a still further embodiment is shown in which non-conductive cup member 14 is filled with an electrolyte gel or paste 100 in lieu of the sponge-like matrix 32 of FIG. 3.

Referring to FIG. 13, electrolyte-containing polymer disc 90 may be made of any number of polymeric, preferably non-conductive, plastics usually rigid enough so that they do not collapse under the conventional pressure of use. Typical polymers are polyamides, polyethylene, polyvinyl chloride, polyurethane, oxymethylene polymers, and the like. Of course, as suggested hereinbefore, the apertures may be other than hexagonal, such as round, rectangular, elliptical, or the like.

Referring to FIGS. 8 through 12, the polymeric sheet or film material 80 may likewise be of a non-conductive nature and would include such polymers as polyvinylidene chloride (saran), nylon, polyethylene, polyester, polyacrylic, and the like.

Additional advantages accruing in the use of a polymeric film as shown in FIGS. 8 through 12 are the fact that the skin surface of a patient need not be in direct contact with electrolyte, such as sodium chloride, thus providing greater comfort to the patient; also, for storage purposes and to avoid corrosion, a caustic electrolyte, such as sodium chloride, may be kept out of direct contact with the metal electrode disc.

It is obvious that many other configurations are inherent in the description herein with respect to the electrolyte/electrode assembly, without losing the superior effectiveness thereof in grounding current under electrosurgical conditions while at the same time preventing burns and the other complications indigenous to the large ground plates. As will be seen hereinafter, current is very effectively dissipated through the assembly of the present and the large ground plate hazards obviated.

It may be desirable under certain circumstances to use rectangular or ribbon-type electrolyte bodies in conjunction with any of the electrode configurations described or suggested herein to provide a ground for extremities or difficultly accessible human body areas. Since the present invention provides for such uniform current density distribution across the surfaces of, and through the electrolyte and electrode components, it will be apparent to the person skilled in the art that a multitude of shapes and uses for the assembly are suggested and contemplated.

EXAMPLES

The present invention will best be understood from the following examples in which, unless otherwise indicated, percentages and parts are by weight.

Example I

The following components are blended into an electrolyte composition:

93.3 parts water

2.0 parts Carbopol* 940

1.6 parts triethanolamine

0.1 parts 2-chloro-m-xylenol

3.0 parts sodium sulfate (anhydrous) L6 *Trademark used by B. F. Goodrich Chemical Co. for carboxypolymethylene (polyacrylic acid of 4-6 million molecular weight)

The anhydrous sodium sulfate is dissolved in water with mild stirring and the polyacrylic acid is then slowly sifted into the aqueous salt solution with rigorous stirring until the polyacrylic acid is homogeneously dispersed and/or dissolved. A solution of the triethanolamine and 2-chloro-m-xylenol, which is prepared by mild heating and stirring of the two components, is rapidly added to the mixture (with rigorous stirring and following the method used just above for polyacrylic acid). Rigorous stirring is continued for 10-60 minutes until the proper viscosity is obtained.

Example II

The following components are blended into an electrolyte composition:

79.1 parts water

2.4 parts Carbopol 940

3.0 parts triethanolamine

0.5 part 2-chloro-m-xylenol

15.0 parts sodium sulfate (anhydrous)

Blending is carried out essentially as in Example I, above, with the exception that 2-chloro-m-xylenol and triethanolamine are added (after the polyacrylic acid) separately and sequentially with vigorous stirring upon each addition.

Example III

The following components are blended into an electrolyte composition essentially as taught in Example I, above:

74.3 parts water

2.4 parts Carbopol 940

3.1 parts triethanolamine

0.2 part 2-chloro-m-xylenol

20.0 parts sodium sulfate (anhydrous)

Example IV

The electrolyte composition of each of the above examples is used to soak a sponge-like cellular flexible polyurethane matrix and the resulting semisolid composition tested by placing same in an electrode of the type shown in FIGS. 1 to 4 of the drawing and having the following dimensions.

Sponge (polyurethane foam) matrix 32 has a diameter of about 2.25 .+-. inches, a thickness of 310 mils, and a density of 2 pounds per cubic foot. Electrode stainless steel conductive sheet 17 has a diameter of 1.80 .+-. inches, a thickness of 0.003 inch, and an aperture diameter of 0.165 .+-. inch.

Polyvinyl chloride cup 14 has an outside diameter of 2.48 .+-. inches, a shoulder (wall) radius of 0.063 .+-. inch, a base 16 thickness of 0.040 .+-. inch, and an aperture diameter of 0.070 .+-. inch.

Polyurethane soft resilient flexible sheet 12 has a length of 7.5 inches, a width of 3 inches, a thickness of three-sizteenths inch, and a radius (each end) of 1.56 .+-. inches.

Protective cover 38 of polyvinyl chloride sheet (10 mil thickness and semi-rigid) has a cylindrical portion 42 having a diameter (inside) of 2.57 .+-. inches.

Male snap fastener 18 components 20, 22, 24 and 26 are made of stainless steel; circular plate portion 20 of stud 22 has a diameter of 0.42 .+-. inch and height of 0.205 inch, and a stud outside diameter of 0.126 .+-. inch; circular plate portion 24 has a diameter of 0.42 .+-. inch, a height of 0.135 .+-. inch, and a socket (barrel) outside diameter of 0.155 .+-. inch, and an inside diameter of 0.125 .+-. inch.

Polyacetal rivet (accordion) 34 has a tapered shaft 35 which is 0.380 .+-. inch in length and its widest diameter is 0.160 .+-. inch.

This just described indifferent electrode is connected through snap fastener 18 to a suitable conductive locking means and cable, the latter leading to the ground receptacle of a conventional Model CSV Bovie high frequency radio wave electrosurgical unit. The unit has a variable output.

Test Procedure (Example IV-continued)

The just described electrode is applied (adhered) to the upper arm (bicep) of an adult male (in his 30's, 180 lb., 6 ft.) for experimental purposes, the electrolyte thereof having the sodium sulfate composition and concentration of Example II, supra. The electrode snap fastener 18 is attached to a conductive locking device and cable leading to the ground receptacle of a Model CSV Bovie electro-surgical unit. The patient holds a piece of fresh beef liver (8 .times. 3 .times. 3/4 inches) placed in his hand, the latter having been smeared with the electrolyte jelly of Example II to reduce impedance between the patient's skin (hand) and the liver he is gripping.

The unit (CSV) is activated and using a conventional active ball (1/8 inch diameter) electrode surgery is performed on the liver using the following bursts of current settings which are substantially more severe than employed in conventional surgery:

1. At cutting power control setting of 60 (cutting current selector of 1) on the CSV unit dial for two continuous minutes.

2. Pause one minute.

3. Repeat (1) above only using setting of 70.

4. Pause one more minute.

5. Repeat (1) above only using setting of 80.

A temperature increase at the interface of the electrolyte sponge 32 and the patient's skin of less than 1.degree. F. is noted and absolutely no heat sensations (and, of course, no burn) is experienced by the patient.

Example V

Example IV is repeated in every essential respect only a coagulating power control setting (cutting current selector of 4) is used in lieu of the cutting setting. Again the results are the same.

Example VI

In over 600 actual surgical procedures in over a dozen hospitals throughout the U.S.A. during 1971, the disposable indifferent electrodes of Example III were tested and the reports are that the electrodes not only did not cause any burns or other harm but they functioned excellently.

Example VII

The liver test of Example IV is repeated using the electrode of Example III only the area of the sheet conductive metal electrode 17 (on its electrolyte surface) is only 0.5 square inch, the diameter of the sponge matrix electrolyte 32 is only 0.8 inch and rivet 34 is not used. The current bursts are as follows:

1. Cutting power control setting of 30 (cutting current selector of 1) for 0.5 continuous minute.

2. Pause 0.5 minute.

3. Cutting power control setting of 40 (cutting current selector of 1) for 1.0 continuous minute.

4. Pause 0.5 minute.

5. Cutting power control setting of 50 (cutting current selector of 1) for 0.5 continuous minute.

6. Pause 0.25 minute.

7. Cutting power control setting of 50 (cutting current selector of 1) for 0.5 minute.

8. Pause 0.5 minute.

9. Cutting power control setting of 60 (cutting current selector of 1) for 2.0 continuous minutes.

10. Pause 0.5 minute.

11. Cutting power control setting of 70 (cutting current selector of 1) for 2.0 continuous minutes.

A temperature rise of less than 3.degree. F. is experienced and no deleterious effects are experienced by the patient.

As is obvious from the above, the indifferent electrode of the present invention quite surprisingly overcomes the drawbacks discussed hereinabove and accomplishes the objectives hereinbefore described.

Example viii

the advantages attending isolation of the metallic conductor of the electrode/electrolyte assembly contemplated herein from the skin are illustrated as follows:

1. Experimental Procedure

An active electrode which is described below is attached to the underside of the forearm of an individual. This active electrode is electrically connected to the active terminal of a commercial electrosurgical unit of the type described in Example IV, above, (CSV Bovie, manufactured by Liebel-Florsheim Company). This electrical connection contains a thermocouple amp. meter. The ground electrode under test is mounted on the outside of the upper arm (same arm as used for the active electrode). The ground electrode is electrically connected through a thermocouple RF amp. meter to the ground terminal of the electrosurgical unit.

The electrosurgical unit is then activated. Current flow (amperes) through the active and ground loops, and power settings of the unit are recorded. The time of continuous activation (Time of Activation) in which heat is developed under either the ground or active electrode to the point where it is very uncomfortable (heat sensation) is also recorded.

2. Experimental Data

a. Active electrode of Example IV is used, i.e., a 0.9 inch radius stainless steel (316) disc (3 mil thick) which contains in its center a stainless steel (316) crimped snap. The active electrode also contains on top of the disc 310 mils thick .times. 2.25 inch diameter polyurethane foam matrix -- medium density -- saturated with 15 percent sodium sulfate gel (of Example II).

b. Ground Test Electrodes

1. Ground electrode A is of the same construction as the above described active electrode.

2. Ground electrode B consists of a 0.9 inch radius stainless steel (316) disc (3 mil thick) which contains in its center a stainless steel (316) crimped snap. This disc is placed directly onto the skin.

3. Ground electrode C consists of a 0.9 inch radius stainless steel (316) disc (3 mil thick) which contains in its center a stainless steel (316) crimped snap. The surface of this disc is lightly smeared with 15 percent, by weight, sodium sulfate gel (of Example II).

__________________________________________________________________________ GROUND CSV BOVIE ACTIVE GROUND TIME OF ELECTRODE SUBJECT SETTINGS AMP. AMP. ACTIVATION __________________________________________________________________________ A Male I #1 Cut/33 0.73 0.72 35.0 sec. B Male I #1 Cut/33 -- 0.70 7.5 sec. C Male I #1 Cut/33 0.72 0.72 9.5 sec. A Male II #1 Cut/33 0.74 0.76 110.0 sec. B Male II #1 Cut/33 0.72 0.73 12.5 sec. C Male II #1 Cut/33 0.72 0.74 19.0 sec. __________________________________________________________________________

Example ix

experiments demonstrating the height requirements for separation of the metallic conductor from the skin are carried out as follows:

1. Height of Separation: 10 mil

a. The active electrode of Example VIII(2a) is used.

b. Ground electrode A consists of a 0.9 inch radius stainless steel (316) disc (3 mil thick) which contains in its center a stainless steel (316) crimped snap. The disc is covered with a 2 inch .times. 2 inch section of porous paper* (lab paper 10 mils thick) which is saturated with 15 percent sodium sulfate gel (of Example II).

c. Ground electrode B (see FIG. 5) is similar in construction to ground electrode A except that the disc is covered by a 2.25 inch diameter piece of non-woven cotton fabric (10 mils thick) saturated with 15 percent sodium sulfate gel (of Example II).

__________________________________________________________________________ GROUND CSV BOVIE ACTIVE GROUND TIME OF ELECTRODE SUBJECT SETTINGS AMP. AMP. ACTIVATION __________________________________________________________________________ A Male IV #1 Cut/28 0.58 0.65 47.0 sec. B Male V #1 Cut/30 0.63 0.72 46.0 sec. __________________________________________________________________________

2. One Inch Electrolyte Matrix

a. The active electrode of Example VII(2a) is used.

b. The ground electrode consists of 0.9 inch radius stainless steel (316) disc (3 mils thick) which contains in its center a crimped stainless steel (316) snap. A 1 inch thick .times. 2.25 inch diameter polyurethane foam matrix-medium density-saturated with 15 percent sodium sulfate gel is placed on top of the stainless steel disc, instead of the 310 mil thick .times. 2.25 inch diameter polyurethane foam matrix of the active electrode (Example VII(2a)). For gel see Ex. II.

______________________________________ CSV BOVIE ACTIVE GROUND TIME OF SUBJECT SETTINGS AMP. AMP. ACTIVATION ______________________________________ Male III #1 Cut/33 0.73 0.76 58.0 sec. Male IV #1 Cut/34 0.74 0.79 >120.0 sec. ______________________________________

Example x

the following experiments demonstrate that a variety of inert supports (fillers) can be used in the gel for improving the performance of the electrolyte/electrode assembly (cautery pad) of the present invention:

1. The construction of the active electrode is the same as that previously described for Example VIII(2a).

2. Ground Test Electrodes

a. Ground electrode A consists of a 0.9 inch radius stainless steel (316) disc (3 mils thick) which contains at its center a stainless steel (316) crimped snap. The disc is lightly smeared with electrolyte gel (Example II).

b. Ground electrode B consists of a 0.9 inch radius stainless steel (316) disc (3 mils thick) containing in its center a stainless steel (316) crimped snap. The electrode contains on top of the disc a 125 mil high .times. 2.25 inch diameter column of electrolyte. The electrolyte consists of a 50/50 by volume mixture of 15 percent sodium sulfate gel (Example II) and washed sand (approx. 40-80 mesh). The electrolyte is retained in the cylindrical shape by means of a vinyl plastisol cup which has internal dimensions of 125 mil high .times. 2.25 inch diameter.

c. Ground electrode C consists of a 0.9 inch radius stainless steel (316) disc (3 mils thick) which contains on top of the disc a 125 mil thick .times. 2.25 inch diameter column of electrolyte, the electrolyte consisting of a 50/50 by volume mixture of 15 percent sodium sulfate gel (Example II) and regenerated cellulose (chemical cotton). The electrolyte is retained in the cylindrical shape by means of a vinyl plastisol cup (see FIG. 14) which has internal dimensions of 125 mil high .times. 2.25 inch diameter. The disc, of course, has at its center a stainless steel (316) crimped snap.

d. Ground electrode D consists of a 0.9 inch radius stainless steel (316) disc (3 mils thick) which contains at its center a crimped stainless steel (316) snap. The electrode contains on top of the disc a 125 mil high .times. 2.25 inch diameter column of electrolyte. The electrolyte consists of a 24.3 percent by weight mixture of powdered talc in 15 percent sodium sulfate gel (Example II). The electrolyte is retained in the cylindrical shape by means of a vinyl plastisol cup (see FIG. 14) which has internal dimensions of 125 mil high .times. 2.25 inch diameter.

e. Ground electrode E consists of a 0.9 inch radius stainless steel (316) disc (3 mils thick) which contains at its center a crimped stainless steel (316) snap. The electrode contains on top of the disc 40 layers .times. 2.25 inch diameter (see FIG. 6) of a non-woven cotton fabric (10 mils thick each layer) saturated with 15 percent sodium sulfate gel (Example II).

f. Ground electrode F consists of a 0.9 inch radius stainless steel (316) disc (3 mils thick) which contains at its center a crimped stainless steel (316) snap. The electrode contains on top of the disc a 210 mil .times. 2.25 inch diameter polyether urethane foam (density = 1.5 lb./ft..sup.3) matrix saturated with 15 percent sodium sulfate gel (Example II).

g. Ground electrode G is the same as F except the polyether urethane foam matrix 178 mils thick .times. 2.25 inch diameter and a density of 4.8 lb./ft..sup.3.

__________________________________________________________________________ GROUND CSV BOVIE ACTIVE GROUND TIME OF ELECTRODE SUBJECT SETTINGS AMP. AMP. ACTIVATION __________________________________________________________________________ A Male IV #1 Cut/30 0.59 0.65 18.5 sec. B Male IV #1 Cut/33 0.68 0.70 55.0 sec. C Male IV #1 Cut/33 0.69 0.71 40.0 sec. E Male IV #1 Cut/33 0.72 0.76 59.0 sec. F Male IV #1 Cut/33 0.68 0.70 90.0 sec. G Male IV #1 Cut/33 0.69 0.71 69.0 sec. D Male V #1 Cut/33 0.73 0.77 51.0 sec. __________________________________________________________________________

Example xi

various surface areas for both electrolyte composition and metal electrode conductors are illustrated in the following experiments:

1. Construction of the active electrode is exactly the same as that of Example VIII(2a).

2. Ground Test Electrodes

a. Ground electrode A consists of a 0.8 inch radius stainless steel (316) conductor (2.0 sq. in., and 3 mils thick) containing in its center a crimped stainless steel (316) snap. The conductor is lightly smeared with 15 percent sodium sulfate gel (Example II) prior to placing the electrode on the skin.

b. Ground electrode B consists of a 0.012 inch diameter .times. 1.0 inch long silver wire as the metal contact (surface area = 0.038 sq. in.) (see FIG. 7). This wire is embedded in a 0.8 inch radius (surface area = 2.0 sq. in.) polyether-urethane foam matrix (188 mils thick) which is saturated with 15 percent sodium sulfate gel (Example II); the wire is embedded in the upper surface of the foam matrix at least over 175 mils from the skin surface thereof.

__________________________________________________________________________ GROUND CSV BOVIE ACTIVE GROUND TIME OF ELECTRODE SUBJECT SETTINGS AMP. AMP. ACTIVATION __________________________________________________________________________ A Male III #1 Cut/33 0.64 0.74 11.0 sec. B Male III #1 Cut/33 0.64 0.72 22.0 sec. __________________________________________________________________________

c. Ground electrode C consists of a 1.86 inch radius stainless steel (3 mils thick) conductor (surface area = 10.8 sq. in.) which contains in its center a crimped stainless steel snap. The conductor is lightly smeared with 15 percent sodium sulfate gel (Example II) prior to placing the electrode on the skin.

d. Ground electrode D consists of a 1.86 inch radius stainless steel (316) disc (surface area = 10.8 sq. in.) which contains at its center a crimped stainless steel (316) snap. A 1.86 inch radius (surface area = 10.8 sq. in.) polyetherurethane foam matrix (188 mils thick) which is saturated with 15 percent sodium sulfate gel (Example II) is placed on top of the metal conductor.

__________________________________________________________________________ GROUND CSV BOVIE ACTIVE GROUND TIME OF ELECTRODE SUBJECT SETTINGS AMP. AMP. ACTIVATION __________________________________________________________________________ C Male III #1 Cut/50 -- 1.30 17.0 sec. D Male III #1 Cut/50 -- 1.30 30.0 sec. __________________________________________________________________________

Example xii

the following data demonstrate that a variety of geometrical configurations of both electrolyte composition and metal conductor can be used:

1. Elliptical Configuration

a. The construction of the active electrode is the same as that described in Example VIII(2a).

b. The ground test electrode consists of an elliptical stainless steel (316) conductor (major axis = 37/8 inch; minor axis = 2 3/16 inch) which contains at its center a crimped stainless steel (316) snap. An elliptical (major axis =4 3/8 inch; minor axis = 21/2 inch) polyether-urethane foam matrix (188 mils thick) which is saturated with 15 percent sodium sulfate gel (Example II) is placed on the metal conductor.

______________________________________ CSV BOVIE ACTIVE GROUND TIME OF SUBJECT SETTINGS AMP. AMP. ACTIVATION ______________________________________ Male IV #1 Cut/45 0.86 0.97 75.0 sec. Male V #1 Cut/45 0.86 0.98 >90.0 sec. Male VI #1 Cut/45 0.84 0.95 >90.0 sec. ______________________________________

c. The ground test electrode consists of a 1 inch .times. 1 inch square stainless steel (3 mils thick) (316) conductor which contains at its center a crimped stainless steel (316) snap. A 3 inch .times. 3 inch square polyether-urethane foam matrix (188 mils thick) which is saturated with 15 percent sodium sulfate gel (Example II) is placed on top of the metal conductor.

______________________________________ CSV BOVIE ACTIVE GROUND TIME OF SUBJECT SETTINGS AMP. AMP. ACTIVATION ______________________________________ Male III #1 Cut/43 -- 1.18 34.0 sec.* Male IV #1 Cut/43 -- 1.20 26.0 sec.* Male V #1 Cut/43 -- 1.20 47.0 sec.* Male II #1 Cut/43 -- 1.20 24.0 sec.* ______________________________________ * In all cases the active electrode became much hotter than the ground electrode.

d. The ground test electrode connsists of a 1 inch .times. 1/2 inch rectangular stainless (316) steel conductor (3 mils thick) which contains at its center a crimped stainless steel (316) snap. A 4 inch .times. 1 inch polyether-urethane foam (188 mils thick) matrix which is saturated with 15 percent sodium sulfate gel (Example II) is placed on top of the metal conductor.

______________________________________ CSV BOVIE ACTIVE GROUND TIME OF SUBJECT SETTINGS AMP. AMP. ACTIVATION ______________________________________ Male IV #1 Cut/42 0.80 0.92 73.0 sec. Male V #1 Cut/42 0.82 0.86 94.0 sec. ______________________________________

Example xiii

the following data demonstrate that a non-conductive material (insulator) can be placed either between the conductor and electrolyte, between the skin and electrolyte, or between both the conductor-electrolyte interface and the skin-electrolyte interface:

a. The active electrode is that of Example VIII(2a).

b. Ground test electrode A consists of a 2.25 inch diameter stainless steel (316) disc (3 mils thick) which contains at its center a crimped stainless steel (316) snap. The disc is completely covered (FIGS. 8 and 9) with a 3 mil thick piece of saran (polyvinylidene chloride) film. A 2.25 inch diameter (310 mils thick) polyether-urethane matrix which is saturated with 15 percent sodium sulfate gel (Example II) is placed on top of the polyvinylidene chloride film.

c. Ground test electrode B consists of a 2.25 inch diameter stainless steel (316) disc (3 mils thick) which contains a crimped stainless steel (316) snap. A 2.25 inch diameter (310 mils thick) polyether-urethane matrix which is saturated with 15 percent sodium sulfate gel (Example II) is placed on top of the disc. A 3 mil thick film of saran (polyvinylidene chloride) film (FIGS. 10 and 11) which completely covers the foam matrix is placed on top of it.

d. Ground test electrode C consists of a 2.25 inch diameter stainless steel (316) disc (3 mils thick) which contains at its center a crimped stainless steel (316) snap. The disc is completely covered with a 3 mil thick film of saran (polyvinylidene chloride) film. A 2.25 inch diameter polyether-urethane matrix which is saturated with 15 percent sodium sulfate gel (Example II) is placed over this film of polyvinylidene chloride. A second 3 mil thick film of saran (polyvinylidene chloride) is then placed over and completely covers the foam matrix (see FIG. 12).

e. Ground test electrode D consists of a 2.25 inch diameter stainless steel (316) disc (3 mils thick) which contains at its center a crimped stainless steel (316) snap. A 10 mil thick piece (2.25 inch diameter) of non-woven cotton fabric which is saturated with 15 percent sodium sulfate gel (Example II) is placed over the disc. A 3 mil thick film of polyvinylidene chloride is placed over and completely covers the non-woven fabric.

______________________________________ GROUND CSV BOVIE GROUND TIME OF ELECTRODE SUBJECT SETTINGS AMP. ACTIVATION ______________________________________ A Male III #1 Cut/27 0.75 >120.0 sec. B Male III #1 Cut/25 0.74 61.0 sec. C Male III #1 Cut/25 0.74 93.0 sec. D Male III #1 Cut/22 0.74 41.0 sec. ______________________________________

It should be noted that the insulator can be any material which is commonly used as an insulator in electrical capacitors. However, it must be of such a nature that at the alternating current frequencies encountered in electrosurgery, the skin and electrolyte, and also the electrolyte and metal conductor can be capacitively coupled.

Of course, the experimental procedure of EXAMPLE VIII is followed in each of EXAMPLES IX through XIII.

The following Table I gives the ages and weights of each of the males (I - VI) referred to in the above experiments:

MALE AGE WEIGHT ______________________________________ I 38 195 II 35 170 III 28 183 IV 40 170 V 33 180 VI 36 133 ______________________________________

As is evident from the above experiments, the small size electrodes of the present invention and the unique electrolytes with which they are assembled provide a very effective, disposable biomedical instrument. This is a finding which flies in the teeth of the suggestions and teachings of the art of patient ground plates, not to mention the many, many advantages insuring its immediate success.

Pursuant to statutory requirements, there are described above the invention and what are now considered its best embodiments. It should again be understood, however, that the invention can be practiced otherwise than as specifically described, within the scope of the appended claims.

Claims

What is claimed is:

1. An indifferent electrode for use in electrosurgical procedures and easily contoured to body surfaces which comprises an electrode-electrolyte assembly including an electrode and an electrolyte composition in which the electrode is an electrically conductive means having at least 0.038 square inch surface thereof in essentially complete contact with said electrolyte composition having at least 2.0 square inches of its conductive surface adaptable to be applied in essentially complete conductive contact with the skin of a patient and having a thickness of at least 10 mils to thus space any part of said conductive means from the skin, said thickness being at least about 165 mils when the conductive element surface area is between about 0.038 and 0.10 square inch, said electrically conductive means, in turn, having a means for electrically connecting said electrode.

2. The indifferent electrode of claim 1 wherein the electrically conductive means is a disc.

3. The indifferent electrode of claim 1 wherein the electrically conductive means is a wire.

4. The indifferent electrode of claim 1 wherein the electrically conductive means is a flexible sheet of stainless steel and the electrolyte is an alkali metal sulfate.

5. The indifferent electrode of claim 4 wherein the electrolyte is an aqueous composition containing, by weight, from about 0.5 percent to about an aqueous saturated solution of alkali metal sulfate.

6. The indifferent electrode of claim 5 wherein the electrolyte is an aqueous composition containing, by weight, from about 5 percent to about 20% alkali metal sulfate.

7. The indifferent electrode of claim 6 wherein the alkali metal sulfate is sodium sulfate.

8. The indifferent electrode of claim 4 having means defining a low profile cup shaped non-conductive cavity which opens to the body surface and having said flexible sheet of conductive metal electrode at the base of the cavity and coplanar to said base, said electrolyte composition being contained in said cavity and completely overlying and in contact with the surface of the electrode away from said base.

9. The indifferent electrode of claim 8 wherein the electrolyte comprising an alkali metal sulfate and a sponge-like cellular matrix is an aqueous highly viscous semisolid composition comprising, by weight, from about 3 percent to about an aqueous saturated solution of alkali metal sulfate, and a small but effective amount of a water-soluble, water-swellable mucilage, said sponge-like cellular matrix containing said sulfate-mucilage blend uniformly distributed throughout its interstices.

10. The indifferent electrode of claim 9 wherein the mucilage is a neutralized, water-soluble water-swellable carboxypolymethylene present in the concentration of about 0.2 percent to about 5.0 percent, based upon the total weight of the electrolyte composition.

11. The indifferent electrode of claim 8 wherein the electrode is a flexible sheet of stainless steel which is in electrical contact with a conductive means passing through the base of the cup-shaped member and to a ground external to the cup.

12. The indifferent electrode of claim 11, wherein the aqueous highly viscous semisolid electrolyte composition substantially fills the interior of said cup member and has a thickness at least as great as the depth of said cup member.

13. The indifferent electrode of claim 12 wherein the thickness of said aqueous highly viscous semisolid electrolyte composition exceeds the depth of said cup member.

14. The indifferent electrode of claim 13 wherein a removable protective covering overlies the open end of the cup member, said covering being a sheet material having a raised portion overlying the semisolid electrolyte protruding from the cup member.

15. The indifferent electrode of claim 14 having an apertured flexible and resilient sheet carrying said cup member, the surface of said flexible and resilient sheet in coplanar relationship to the outer surface of the base of the cup member being substantially greater than that of the outer surface of the base member and having a pressure sensitive adhesive coating thereon for adhering to a body surface.

16. The indifferent electrode of claim 15 having conductive securing means projecting through the aperture in said flexible and resilient sheet, through the base of said cup member, and securely attached to the flexible sheet of conductive metal.

17. The indifferent electrode of claim 16 wherein the conductive securing means is securely attached to the flexible sheet of conductive metal by projecting through said thin flexible sheet, and the said securing means is a conductive metal snap fastener.

18. The indifferrent electrode of claim 17 wherein the stud portion of said snap fastener passes sequentially through the flexible sheet of conductive metal, the cup member and the flexible, resilient adhesive-bearing sheet and terminates in locking engagement with the mating socket of said snap fastener.

19. The indifferent electrode of claim 18 wherein the aqueous highly viscous semisolid composition has an aperture therein through which a non-conductive rivet passes and terminates in locking engagement in the hollow neck portion of said stud of said snap fastener, thus mounting the semi-solid composition on the flexible sheet of conductive metal and in immediate contact therewith.

20. The indifferent electrode of claim 15 further including a cover sheet releasably secured to said adhesive coating and means securing said protective covering to said cover sheet.

21. The indifferent electrode of claim 1, wherein the electrolyte composition has on its skin an electrical capacitor insulator capable of capacitively coupling under electrosurgical conditions.

22. The indifferent electrode of claim 21, wherein said insulator is at the interface of the electrically conductive means and the electrolyte composition.

23. The indifferent electrode of claim 21, wherein, in addition, a similar insulator is at the interface of the electrolyte composition and the electrically conductive means.

24. The indifferent electrode of claim 23, wherein the insulator is a thin polymer film.

25. The indifferent electrode of claim 24, wherein the insulator is a saran film.

26. The indifferent electrode of claim 1, wherein the electrolyte composition is an electrolyte-containing fabric.

27. The indifferent electrode of claim 26, wherein the fabric is unwoven cotton fabric.

28. The indifferent electrode of claim 1, wherein the electrolyte composition contains an inert filler.

29. The indifferent electrode of claim 28, wherein the inert filler is powdered talc.

30. In surgical diathermy, a method of conducting high frequency radio waves to ground which comprises placing against and coplanar to the body surface a flexible sheet of conductive metal electrode, said sheet surface opposite and nearer said body surface having an area in the range of about 0.5 square inch to about 10 square inches, and interposing in direct and essentially complete contact with said opposed surfaces of electrode and body an electrolyte composition of substantially uniform thickness, said thickness being in the range of about 62 mils to about 500 mils.

31. The method of claim 30 wherein the said sheet surface opposite and nearer said body surface has an area in the range of about 2 square inches to about 5 square inches.

32. The method of claim 30 wherein the flexible sheet of conductive metal is stainless steel and the electrolyte is an alkali metal sulfate.

33. The method of claim 32 wherein the alkali metal sulfate is sodium sulfate.

34. The method of claim 33 wherein the electrolyte is an aqueous composition containing, by weight, from about 0.5 percent to about an aqueous saturated solution of alkali metal sulfate.

35. The method of claim 34 wherein the electrolyte is an aqueous composition containing, by weight, from about 5 percent to about 20 percent alkali metal sulfate.

36. The method of claim 26 wherein the alkali metal sulfate is sodium sulfate.