Methods and apparatus for dispersing current flow in electrosurgery

• US 20050101947A1
• Filed: 11/06/2003
• Published: 05/12/2005
• Est. Priority Date: 11/06/2003
• Status: Active Grant

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Scimed Life Systems Incorporated (Boston Scientific Corporation)
• Inventors: Behl, Robert S., Jarrard, Jerry W.
• Granted Patent: US 7,566,332 B2
• Time in Patent Office: Days
• US Class Current: 606/35
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: A61B 2018/165 Multiple indifferent electrodes

Abstract

Methods and apparatus for delivering, monitoring, balancing, and/or dispersing high-frequency current flow in monopolar electrosurgery. The methods generally include positioning an active electrode in or on target tissue, positioning at least two dispersive electrodes on tissue remote from the target tissue, establishing electrical current flow from the active electrode through the dispersive electrodes, and individually adjusting the current through at least one of the dispersive electrodes to balance the current through the dispersive electrodes. By adjusting and balancing the current through two or more dispersive electrodes, safety of electrosurgical systems may be enhanced by preventing unwanted patient burns.

Claims

1. A method for delivering electrical energy to a target site in human tissue, the method comprising:

positioning at least one active electrode in or on tissue at a target site;

positioning at least two dispersive electrodes on tissue at sites remote from the target site;

establishing electrical current flow from the active electrode through each of the dispersive electrodes; and

individually adjusting the current through at least one of the dispersive electrodes to balance the current through the dispersive electrodes.

2. A method as in claim 1, further comprising:

monitoring resistance through each of the dispersive electrodes; and

comparing resistances through the dispersive electrodes to detect one or more dispersive electrodes having a higher resistance than one or more other dispersive electrodes.

3. A method as in claim 2, further comprising adding resistance to one or more dispersive electrodes that have lower resistances than one or more other dispersive electrodes.

4. A method as in claim 2, further comprising repositioning at least one dispersive electrode on the tissue, wherein the at least one dispersive electrode has a higher resistance than at least one other dispersive electrode.

5. A method as in claim 1, further comprising:

monitoring current in each of the dispersive electrodes; and

comparing current in the dispersive electrodes to detect one or more dispersive electrodes having a higher current than one or more other dispersive electrodes.

6. A method as in claim 5, further comprising adding resistance to one or more dispersive electrodes that have higher currents than one or more other dispersive electrodes.

7. A method as in claim 5, further comprising repositioning at least one dispersive electrode on the tissue, wherein the at least one dispersive electrode has a lower current than at least one other dispersive electrode.

8. A method as in claim 1, further comprising monitoring the current through each of the dispersive electrodes and signaling an alarm when the current through any single dispersive electrode exceeds the current through another dispersive electrode by a predetermined amount.

9. A method as in claim 8, wherein the alarm is signaled when the current through any single dispersive electrode exceeds the current through another dispersive electrode by fifteen percent (15%) or more.

10. A method as in claim 1, further comprising monitoring the electrical resistance in each of the dispersive electrodes and signaling an alarm when the resistance in any single dispersive electrode exceeds a predetermined maximum resistance.

11. A method as in claim 10, wherein the alarm is signaled when the resistance in any single dispersive electrode exceeds twenty five ohms.

12. A method an in claim 1, further comprising positioning at least a third dispersive electrode on the tissue.

13. A method as in claim 12, further comprising positioning at least a fourth dispersive electrode on the tissue.

14. A method as in claim 1, wherein each dispersive electrode has a conductive surface area of about one hundred twenty square centimeters (120 cm²) or larger.

15. A method as in claim 1, further comprising producing analog signals representative of the current through each of the dispersive electrodes, converting the analog signals to digital signals, and comparing the digital signals.

16. A method as in claim 1, wherein the target site is a liver in a patient and wherein at least one dispersive electrode is positioned on the right leg of the patient and at least one dispersive electrode is position on the left leg of the patient.

17. An improved method for ablating tissue at a target site, the method being of the type wherein at least one subcutaneous active electrode is positioned at the target site beneath a patient'"'"'s skin and electrical current is delivered between the subcutaneous active electrode and a dispersive electrode positioned on the patient'"'"'s skin, the improvement comprising delivering the current with at least two dispersive electrodes on the patient'"'"'s skin and balancing the amount of current passing through each dispersive electrode.

18. A method as in claim 17, wherein balancing the amount of current passing through each dispersive electrode comprises adding resistance to at least one dispersive electrode having a higher current than at least one other dispersive electrode.

19. A method as in claim 18, wherein adding resistance comprises adding resistance across at least two bipolar transistors in series.

20. A method as in claim 17, wherein the balancing the amount of current passing through each dispersive electrode comprises adding resistance to at least one dispersive electrode having a lower resistance than at least one other dispersive electrode.

21. A method as in claim 20, wherein adding resistance comprises adding resistance across at least two bipolar transistors in series.

22. A method as in claim 17, further comprising monitoring the current through each of the dispersive electrodes and signaling an alarm when the current through any single dispersive electrode exceeds the current through another dispersive electrode by a predetermined amount.

23. A method as in claim 18, wherein the alarm is signaled when the current through any single dispersive electrode exceeds the current through another dispersive electrode by fifteen percent (15%) or more.

24. A method as in claim 17, further comprising monitoring the electrical resistance in each of the dispersive electrodes and signaling an alarm when the resistance in any single dispersive electrode exceeds a predetermined maximum resistance.

25. A method as in claim 18, wherein the alarm is signaled when the resistance in any single dispersive electrode exceeds twenty five ohms.

26. A method an in claim 17, further comprising positioning at least a third dispersive electrode on the patient'"'"'s skin.

27. A method as in claim 26, further comprising positioning at least a fourth dispersive electrode on the patient'"'"'s skin.

28. A method as in claim 17, further comprising producing analog signals representative of the current through each of the dispersive electrodes, converting the analog signals to digital signals, and comparing the digital signals.

29. A method as in claim 17, wherein the target site is a liver in a patient and wherein at least one dispersive electrode is positioned on the right leg of the patient and at least one dispersive electrode is position on the left leg of the patient.

30. A method as in claim 17, wherein delivering the current comprises delivering current between about one and three amperes.

31. A method for balancing current through two or more dispersive electrodes, the method comprising:

monitoring resistance in each of the dispersive electrodes;

comparing resistances in the dispersive electrodes to detect a dispersive electrode having a lower resistance than one or more other dispersive electrodes; and

adding resistance to a dispersive electrode detected as having a lower resistance than one or more other dispersive electrodes.

32. A method as in claim 31, wherein the adding step comprises adding resistance across at least two bipolar transistors in series.

33. A high-frequency power supply comprising:

an electrical energy source;

an active electrode connector for removably attaching an active electrode to the energy source;

at least two dispersive connectors for removably connecting at least two dispersive electrodes to the energy source; and

current balancing circuitry for balancing current from the active electrode through the at least two dispersive electrodes.

34. A high-frequency power supply as in claim 33, further comprising a monitor for monitoring individual current through the at least two dispersive electrodes.

35. A high-frequency power supply as in claim 34, further comprising an alarm for signaling when the current through any single dispersive electrode exceeds the current through another dispersive electrode by a predetermined amount.

36. A high-frequency power supply as in claim 33, further comprising a monitor for monitoring individual resistance in the at least two dispersive electrodes.

37. A high-frequency power supply as in claim 36, further comprising an alarm for signaling when the resistance in any single dispersive electrode exceeds a predetermined maximum resistance.

38. A high-frequency power supply as in claim 33, further comprising a third dispersive connector for removably attaching a third dispersive electrode to the energy source.

39. A high-frequency power supply as in claim 38, further comprising a fourth dispersive connector for removably attaching a fourth dispersive electrode to the energy source.

40. A high-frequency power supply as in claim 33, wherein the energy source is configured to provide current between about one and three amperes.