Combined electrosurgery/cautery system and method

Claims

What is claimed is:

1. A combined electrosurgery and cautery system for use with a patient, said system comprising

a combined heater and electrode element;

cautery power supply means for applying a first electrical current through said combined heater and electrode element to heat said element, said cautery power supply means including means for passing said first current through said element back to the cautery power supply means without passing through said patient so that tissue of said patient is necrosed by said first current in response to the element being positioned adjacent the tissue;

electrosurgical generator means for applying a second electrical current to said combined heater and electrode element, said electrosurgical generator means including means for passing said second current through said patient back to the electrosurgical generator means where said electrosurgical generator means produces a voltage on said element, the magnitude of which is sufficiently high to permit arcing from the element to the patient after said tissue has been necrosed by said first current.

2. A system as in claim 1 including current limiting means for limiting said second electrical current through said patient to an arcing only value at which desiccation of the patient's tissue is not likely.

3. A system as in claim 2 where said arcing only value is not more than about 200 ma.

4. A system as in claim 2 where said electrosurgical generator means includes power adjusting means for adjusting the output power delivered to said combined heater and electrode element and where said current limiting means includes feedback means for providing a feedback signal from said element, said power adjusting means being responsive to said feedback signal to thereby limit said second current to said arcing only value.

5. A system as in claim 2 including a first isolation transformer, the primary winding of which is connected to said electrosurgical generator meanns and the secondary winding of which is connected to said combined heater and electrode element and where the output impedance of said transformer is sufficiently high to limit said second current to said arcing only value.

6. A system as in claim 1 including a handpiece adapted for manual manipulation, said combined heater and electrode element being mounted on said handpiece and a current step-up transformer disposed within said handpiece, the secondary winding of said transformer being connected across said element and first and second wires connected from said cautery power supply means to the respective ends of the primary winding of said transformer whereby said wires may be of a fine gauge due to the current step-up effected by the transformer.

7. A system as in claim 6 where said cautery power supply means is an alternating current source, the frequency of which is high enough to avoid neuromuscular stimulation.

8. A system as in claim 7 where the frequency of said alternating current is about 120 KHz.

9. A system as in claim 8 including an isolating transformer, the primary winding of which is connected to said cautery power supply means and the secondary of which is respectively connected to said first and second wires.

10. A system as in claim 6 where said electrosurgical generator means is connected to one of said first and second wires.

11. A system as in claim 1 including means for isolating said cautery power supply means from ground.

12. A system as in claim 1 where said cautery power supply means is an alternating current source.

13. A system as in claim 1 wherre said combined heater and electrode element comprises a resistance wire wound about an electrically insulative core.

14. A system as in claim 13 where said core comprises glass fibers.

15. A system as in claim 1 where said combined heater and electrode element comprises a substrate of electrically insulating material, an electrically conductive wire deposited thereon, said wire being connected to said cautery power supply means and said electrosurgical generator means and a high resistivity, conductive covering disposed over said electrically conductive wire.

16. A system as in claim 15 where said substrate comprises a ceramic material, said wire comprises a nickel alloy and said cover comprises a carbon film.

17. A system as in claim 1 where said combined heater and electrode element has a loop configuration.

18. A system as in claim 17 including means for moving the loop in a predetermined direction whereby the loop may be encircled about a growth or the like on the patient to thereby effect electrosurgical removal of the growth.

19. A system as in claim 17 where said loop configuration is an elongated hairpin configuration.

20. A system as in claim 1 including means for regulating the amount of said first current passing through said combined heater and electrode element to thereby maintain the temperature of said element at a predetermined value.

21. A system as in claim 20 including means for establishing the predetermined value of the temperature of said combined heater and electrode element.

22. A system as in claim 21 where said temperature establishing means includes means for setting the temperature of said element to a value which will cause desiccation of the patient's tissue.

23. A system as in claim 22 where said temperature establishing means includes means for setting the temperature of said element to a value which will cause cutting of the patient's tissue.

24. A system as in claim 1 where said cautery power supply means is a direct current source.

25. A system as in claim 24 including a handpiece upon which is disposed said combined heater and electrode element and where said direct current source comprises a battery disposed within said handpiece.

26. A system as in claim 25 including means for recharging said battery.

27. A system as in claim 1 including a return electrode adapted for contact with said patient, said return electrode being connected to said electrosurgical generator means to thereby provide a return path for said second current to said electrosurgical generator means.

28. A system as in claim 27 where the surface area of said return electrode adapted for contact with said patient is no more than 60 square centimeters.

29. A system as in claim 28 where said surface area is no more than 10 square centimeters.

30. A system as in claim 27 including switching means having a first position in which said return electrode is connected to said electrosurgical generator means and a second position in which said electrosurgical generator means is disconnected from said return electrode and connected to ground so that, when no return electrode is employed, a return path for said second current is provided through said patient to said ground and then from said ground back to the electrosurgical generator means.

31. A system as in claim 1 including means for providing the intended return path for said second current through said patient to ground and then from said ground back to the electrosurgical generator means whereby a large area return electrode does not have to be applied to said patient to provide a return path for said second current.

32. A system as in claim 1 where said combined heater and electrode element comprises a cautery heater and an electrosurgical electrode.

33. A system as in claim 32 where cautery heater and said electrosurgical electrode are one and the same element.

34. An electrosurgical method comprising

placing a combined heater and electrode element adjacent tissue to a patient to be treated;

passing a first current through said combined heater and electrode element to effect necrosis of said tissue where said first current is passed through said element without passing through said tissue; and

passing a second current through said combined heater and electrode element and through said patient so that an arc is established between said element and said patient after the tissue is necrosed by said first current.

35. A method as in claim 34 where the magnitude of said second current is less than that which is needed to initiate said arc.

36. A method as in claim 35 where said magnitude of the second current is not more than about 200 ma.

37. A method as in claim 34 where said second current comprises a sine wave suitable for cutting said tissue.

38. A method as in claim 34 where said second current comprises bursts of high frequency electrical energy suitable for fulguration of said tissue.

39. A method as in claim 34 where said second current passes directly from said patient without passing through a return electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This invention is related to (1) a U.S. application filed Jan. 12, 1978 by Frank W. Harris entitled "Improved Multiple Source Electrosurgical Generator" (hereinafter Application No. 1) and (2) U.S. Application Ser. No. 852,431 filed by Frank W. Harris on Nov. 17, 1977 and entitled "Contact Area Measurement Apparatus and Method for Use with Electrosurgery and Cryosurgery". Both of the foregoing applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a unique electrosurgery/cautery system.

In the following specification and claims, a distinction is made between the terms electrosurgery and cautery. In electrosurgery, radio frequency current flows into the tissue being treated from a first electrode usually termed the active electrode. The current usually exits at a second electrode termed the patient or indifferent electrode although, as will be brought out in more detail hereinafter, the patient electrode does not necessarily have to be employed in accordance with one aspect of the present invention. Electrical interaction between the active electrode and tissue at the treated site may either be ohmic (to thereby effect a desiccation mode of operation) or by electrical arc (to thereby effect a cut or fulguration mode of operation). In cautery an element such as a wire is electrically heated by passing a current therethrough, the cautery element typically being used to seal bleeding blood vessels in hospital surgical procedures and in minor surgery performed in doctors' offices. Hence, in summary, an important distinction between electrosurgery and cautery is that in the former current flows through the patient's tissue while in the latter current is restricted to the heating element.

In electrosurgery there are three effects which may be produced by passing radio frequency current through tissue--namely, desiccation, cutting and fulguration. In desiccation, the active electrode is held in firm contact with the tissue with the current passing directly into the tissue and the heating effect being brought about by I.sup.2 R heating. Thus, the mode of operation is ohmic.

In cutting, the active electrode is not in good contact with the tissue and electric sparks jump from the electrode to the tissue. The voltage waveform used is generally a sinewave and the sparks are short in length but heat the tissue intensely. The cells burst into steam and the steam maintains the layer of gas between the electrode and the tissue as the incision proceeds. In order to produce a cutting effect without desiccation, the generator must be current limited to less than about 200 milliamperes.

In fulguration, the coagulation occurs by means of a high voltage spark which jumps from the active electrode to the tissue. Thus, an arcing mode of operation occurs in both cuting and fulguration. The spark produces intense heating at every point it strikes, but a high crest factor voltage waveform, called a COAG waveform, makes long sparks and distributes the spark widely. This keeps the energy density down and minimizes the cutting effect.

Of the three electrosurgical modes, desiccation is the primary threat to the patient in the event that a grounded patient electrode loses contact with the patient's body. The patient's body invariably has some electrical contact with ground, either by capacitive coupling or by direct contact with a grounded object. Even with a child, his body is large enough to produce a significant capacitance between his body mass and the grounded operating table. As a result of this relatively low impedance to ground, it is difficult for large voltage differences to exist between the patient's body and ground. Therefore, when RF leakage currents leave the patient's body and go to ground via small, grounded contact points, they do so by direct ohmic connection. In order for electric sparks to jump from the patient's body to ground a voltage difference of over 1000 volts is needed. As a result, a patient electrode related burn is almost always in the desiccation mode.

It is possible that if a small grounded contact were the only electrical connection to ground, then a burn at this location could proceed from desiccation to fulguration after the burn site acquired a high impedance because of the electrosurgical action at that point. However, even in this case, it is clear that the fulguration burn could not have occurred if the desiccation had not taken place first.

Unfortunately, desiccation is usually needed at the site of surgery even though the intention is to cut or fulgurate. That is, in most electrosurgery, desiccation is combined with cutting or fulguration because the surgeon usually starts his cut or fulguration with the electrode in firm contact with the tissue. Since, by definition, the starting mode is desiccation, the desiccation must be complete before the tissue in contact with the electrode will acquire a high enough impedance so that sparking can begin and cutting or fulguration will occur. A typical prior art generator produces over an ampere of desiccation current to necrose and dry the tissue at the active electrode so that the tissue impedance will rise to the requisite amount.

In aforementioned related Application No. 1, a feedback system is described which limits the electrosurgical current to less than 200 ma so that only arcing (only cutting or fulguration) can take place. When used by itself, a system such as this is safer than an ordinary monopolar electrosurgical system and could even be used without a patient electrode with comparative safety. However, as indicated above, a current limited system cannot be used for most surgery because there is no way to get the electrode started. That is, since the current is limited to less than 200 ma and since at least an ampere is needed to desiccate the tissue so that arcing can commence, the current limited, arc only system cannot be used by itself for most surgery. In the abovementioned related Application No. 1, the necessary tissue desiccation is effected by providing a separate desiccation generator capable of delivering at least 1 ampere of electrical current through the tissue. Thus not only is a capability provided for initiating current limited fulguration or cutting but also the advantages inherent in desiccation vis-a-vis fulguration in certain applications are realized. For example, neural tissue is so fragile that if one attempts to fulgurate a bleeder, the hard surface eschar seals the bleeder but in doing so shrinks and pulls the surface or the tissue so that bleeding may start at the periphery of the eschar. Desiccation does not dry and shrink the tissue as much as fulguration and thus this mode more effectively seals neural bleeders. Hence, the use of the separate desiccation generator is advantageous in this application as well as others. However, it is desirable in some situations to effect necrosis of the tissue to thereby permit the establishment the spark needed for fulguration or cutting without employing a high amperage current to do so and thereby avoid the problems associated with such currents as discussed above.

It is thus an object of this invention to provide a system capable of providing (a) desiccation-type tissue necrosis and (b) cutting and/or fulguration where the "desiccation" is effected by cautery and the cutting and/or fulguration is effected by electrosurgery.