Electrosurgical instrument

A method of treating tissue using a bipolar electrode assembly, the assembly including an active electrode and a return electrode, the active electrode having an exposed treatment portion, and the return electrode having an exposed fluid contact surface spaced and set back from the exposed treatment portion, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid so that the conductive fluid defines an electrical path between the active and return electrodes,
• (c) applying sufficient radio frequency output power to the electrode assembly to increase the temperature of the conductive fluid adjacent to the active electrode treatment portion without creating a layer of vapour around the treatment portion;
• and
• (d) locally applying heat by means of the treatment portion to treat tissue while maintaining the return electrode fluid contact surface out of contact with the tissue.

A method of vaporising tissue using a bipolar electrode assembly, the bipolar electrode assembly including an active electrode and a return electrode, the active electrode having an exposed treatment portion, and the return electrode having an exposed fluid contact surface, and an insulating member positioned between and electrically insulating the active electrode and the return electrode and serving to space apart the exposed treatment portion of the active electrode and the exposed fluid surface of the return electrode, the fluid contact surface of the return electrode being set back in the direction of a treatment axis of the assembly from the active electrode exposed treatment portion, the dimensions and configuration of the exposed treatment portion, the exposed fluid contact surface and the insulation member being such that, when the electrode assembly is immersed in a conductive fluid medium, the ratio of (i) the length of the shortest conduction path (P1) through the fluid medium, between the exposed fluid contact surface and that part of the exposed treatment portion which is furthest from the exposed fluid contact surface, to (ii) the length of the shortest conduction path (P2) through the fluid medium between the exposed fluid contact surface and the exposed treatment portion, is greater than or equal to 2:1, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid;
• (c) applying sufficient radio frequency output power to the electrode assembly to vaporise the conductive fluid adjacent to the active electrode treatment portion to create a vapour pocket surrounding the treatment portion;
• and
• (d) positioning the treatment portion of the active electrode adjacent to the tissue with the vapour pocket in contact with the tissue while maintaining the return electrode out of contact with the tissue.

A method of vaporising and haemostatically treating tissue using a bipolar electrode assembly, the bipolar electrode assembly including an active electrode and a return electrode, the active electrode having an exposed treatment portion, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid;
• (c) alternating the application of sufficient radio frequency output power to the electrode assembly to (i) vaporise the conductive fluid adjacent to the active electrode treatment portion to create a vapour pocket surrounding the treatment portion, and (ii) to increase the temperature of the conductive fluid adjacent to the active electrode treatment portion without creating a layer of vapour around the treatment-portion;
• and
• (d) positioning the treatment portion of the active electrode adjacent to the tissue while maintaining the return electrode out of contact with the tissue.

A method of haemostatically treating tissue using a bipolar electrode assembly, the bipolar electrode assembly including an active electrode and a return electrode, the active electrode having an exposed treatment portion, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid;
• (c) applying maximum radio frequency output power to the electrode assembly to heat the conductive fluid adjacent to the active electrode treatment portion without creating a layer of vapour around the treatment portion;
• and
• (d) positioning the treatment portion of the active electrode adjacent to the tissue with the heated conductive fluid in contact with the tissue while maintaining the return electrode out of contact with the tissue.

A method of treating tissue using a bipolar electrode assembly, the assembly including a single active electrode having an exposed treatment portion, a return electrode having an exposed fluid contact surface, and an insulating member positioned between and electrically insulating the active electrode and the return electrode and serving to space apart the exposed treatment portion of the active electrode and the exposed fluid surface of the return electrode, the fluid contact surface of the return electrode being set back in the direction of a treatment axis of the assembly from the active electrode exposed treatment portion, the dimensions and configuration of the exposed treatment portion, the exposed fluid contact surface and the insulation member being such that, when the electrode assembly is immersed in a conductive fluid medium, the ratio of (i) the length of the shortest conduction path (P1) through the fluid medium between the exposed fluid contact surface and that part of the exposed treatment portion which is furthest from the exposed fluid contact surface, to (ii) the length of the shortest conduction path (P2) through the fluid medium between the exposed fluid contact surface and the exposed treatment portion, is greater than or equal to 2:1, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid so that the conductive fluid defines an electrical path between the active and return electrodes;
• (c) applying sufficient radio frequency output power to the electrode assembly to increase the temperature of the conductive fluid adjacent to the active electrode treatment portion without creating a layer of vapour around the treatment portion;
• and
• (d) locally applying heat by means of the treatment portion to treat tissue while maintaining the return electrode fluid contact surface out of contact with the tissue.

A method of vaporising tissue using a bipolar electrode assembly, the bipolar electrode assembly including a single active electrode having an exposed treatment portion, and the return electrode having an exposed fluid contact surface, and an insulating member positioned between and electrically insulating the active electrode and the return electrode and serving to space apart the exposed treatment portion of the active electrode and the exposed fluid surface of the return electrode, the fluid contact surface of the return electrode being set back in the direction of a treatment axis of the assembly from the active electrode exposed treatment portion, the dimensions and configuration of the exposed treatment portion, the exposed fluid contact surface and the insulation member being such that, when the electrode assembly is immersed in a conductive fluid medium, the ratio of (i) the length of the shortest conduction path (P1) through the fluid medium between the exposed fluid contact surface and that part of the exposed treatment portion which is furthest from the exposed fluid contact surface, to (ii) the length of the shortest conduction path (P2) through the fluid medium between the exposed fluid contact surface and the exposed treatment portion, is greater than or equal to 2:1, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid;
• (c) applying sufficient radio frequency output power to the electrode assembly to vaporise the conductive fluid adjacent to the active electrode treatment portion to create a vapour pocket surrounding the treatment portion;
• (d) positioning the treatment portion of the active electrode adjacent to the tissue with the vapour pocket in contact with the tissue while maintaining the return electrode out of contact with the tissue.

A method of vaporising and haemostatically treating tissue using a bipolar electrode assembly, the bipolar electrode assembly including a single active electrode having an exposed treatment portion, a return electrode having an exposed fluid contact surface, and an insulating member positioned between and electrically insulating the active electrode and the return electrode and serving to space apart the exposed treatment portion of the active electrode and the exposed fluid surface of the return electrode, the fluid contact surface of the return electrode being set back in the direction of a treatment axis of the assembly from the active electrode exposed treatment portion, the dimensions and configuration of the exposed treatment portion, the exposed fluid contact surface and the insulation member being such that, when the electrode assembly is immersed in a conductive fluid medium, the ratio of (i) the length of the shortest conduction path (P1) through the fluid medium between the exposed fluid contact surface and that part of the exposed treatment portion which is furthest from the exposed fluid contact surface, to (ii) the length of the shortest conduction path (P2) through the fluid medium between the exposed fluid contact surface and the exposed treatment portion, is greater than or equal to 2:1, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid;
• (c) alternating the application of sufficient radio frequency output power to the electrode assembly to (i) vaporise the conductive fluid adjacent to the active electrode treatment portion to create a vapour pocket surrounding the treatment portion, and (ii) increase the temperature of the conductive fluid adjacent to the active electrode treatment portion without creating a layer of vapour around the treatment portion;
• and
• (d) positioning the treatment portion of the active electrode adjacent to the tissue while maintaining the return electrode out of contact with the tissue.

A method of haemostatically treating tissue using a bipolar electrode assembly, the bipolar electrode assembly including a single active electrode having an exposed tissue treatment portion, a return electrode having an exposed fluid contact surface, and an insulating member positioned between and electrically insulating the active electrode and the return electrode and serving to space apart the exposed treatment portion of the active electrode and the exposed fluid surface of the return electrode, the fluid contact surface of the return electrode being set back in the direction of a treatment axis of the assembly from the active electrode exposed treatment portion, the dimensions and configuration of the exposed treatment portion, the exposed fluid contact surface and the insulation member being such that, when the electrode assembly is immersed in a conductive fluid medium, the ratio of (i) the length of the shortest conduction path (P1) through the fluid medium, between the exposed fluid contact surface and that part of the exposed treatment portion which is furthest from the exposed fluid contact surface, to (ii) the length of the shortest conduction path (P2) through the fluid medium between the exposed fluid contact surface and the exposed treatment portion, is greater than or equal to 2:1, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid;
• (c) applying maximum radio frequency output power to the electrode assembly to heat the conductive fluid adjacent to the active electrode treatment portion without creating a layer of vapour around the treatment portion;
• and
• (d) positioning the treatment portion of the active electrode adjacent to the tissue with the heated conductive fluid in contact with the tissue while maintaining the return electrode out of contact with the tissue.

A method of vaporising and haemostatically treating tissue using a bipolar electrode assembly, the bipolar electrode assembly including a single active electrode having an exposed tissue treatment portion, a return electrode having an exposed fluid contact surface, and an insulating member positioned between and electrically insulating the active electrode and the return electrode and serving to space apart the exposed treatment portion of the active electrode and the exposed fluid surface of the return electrode, the fluid contact surface of the return electrode being set back in the direction of a treatment axis of the assembly from the active electrode exposed treatment portion, the dimensions and configuration of the exposed treatment portion, the exposed fluid contact surface and the insulation member being such that, when the electrode assembly is immersed in a conductive fluid medium, the ratio of (i) the length of the shortest conduction path (P.sub.1) through the fluid medium between the exposed fluid contact surface and that part of the exposed treatment portion which is furthest from the exposed fluid contact surface, to (ii) the length of the shortest conduction path (P.sub.2) through the fluid medium between the exposed fluid contact surface and the exposed treatment portion, is greater than or equal to 2:1, the method comprising the steps of:

• (a) introducing the electrode assembly into a selected operation site;
• (b) surrounding the electrode assembly with a conductive fluid;
• (c) applying sufficient radio frequency output power to the electrode assembly to vaporise the conductive fluid adjacent to the active electrode treatment portion to create a vapour pocket surrounding the treatment portion;
• and
• (d) at least partially burying the treatment portion of the active electrode in the tissue while maintaining the return electrode out of contact with the tissue.

An electrosurgical system for the treatment of tissue, including:

• an electrosurgical generator which produces a radio frequency oscillating electrical output across a pair of output connections;
• an electrosurgical instrument having an active, tissue treatment electrode connected to one of the generator output connections, and a return electrode connected to another of the generator output connections, the return electrode being electrically insulated from the active electrode, and providing a path for the oscillating output from the generator to flow to and from the active electrode when a conduction path between the electrodes is completed by an electrically conducting fluid, wherein, when the electrodes are immersed in an electrically conducting fluid, the ratio of (a) the length of the shortest conduction path through the fluid between the return electrode and a part of the active electrode most distal from the return electrode, to (b) the length of the shortest conduction path through the fluid between the return electrode and a part of the active electrode most proximal to the return electrode is greater than 1.25:1;
• the generator controlling the power of the radio frequency oscillating output so that, in use, power can be dissipated into the electrically conducting fluid by current passing between the electrodes through the electrically conducting fluid, without creating a vapour pocket around at least a part of the active electrode.