Fluid cooled electrosurgical cauterization system

An electrosurgical probe is disclosed which provides the ability to both cut and cauterize tissue. The probe includes at least one cauterization electrode mounted upon a distal portion of the electrode and adapted to deliver electrosurgical energy to tissue. Further, a central lumen is disposed within the probe. The lumen is adapted to accommodate the flow of fluid from a remote source to tissue through an outlet port in the distal end of the probe. Also, the lumen houses a cutting electrode which is selectively deployable. Both cauterization and coagulation can be conducted in a bipolar mode. The flow of fluid through the lumen serves to limit the heat transfer from the cauterization electrode to adjacent tissue to an extent sufficient to prevent the sticking of tissue to the probe. A feedback system is also provided to optimize the electrode temperature.

BACKGROUND OF THE INVENTION 
The present invention relates generally to the field of electrosurgery. 
More particularly, the present invention relates to a system for 
controlling heat transfer from surgical electrodes to adjacent tissue. 
During the course of surgical procedures it is often necessary to cauterize 
or coagulate tissue to control bleeding. Electrosurgical devices are known 
which utilize electrical current for tissue cauterization. U.S. Pat. Nos. 
1,983,669 and 4,637,392 disclose electrical cauterization devices in which 
electrodes are disposed about the surface of a probe. Tissue is heated and 
coagulation is effected by delivering electrosurgical energy to tissue 
through the electrodes. Among the drawbacks of such devices is the 
potential that the electrodes will become overly heated, thus prematurely 
dessicating the tissue and causing the tissue to stick to the electrodes. 
This can result in further bleeding upon disengagement of the electrodes 
from the tissue, and the need to remove tissue from the electrode before 
continuing to use the device. Moreover, it can be inconvenient to use such 
cauterization devices during certain surgical procedures because cutting 
and cauterization must be performed with separate instruments. 
Various electrosurgical probes exist for transferring energy to a 
biological site. Typically these probes dispose a metallic electrode along 
the outer surface of a rigid shaft. When the probe is positioned within 
the patient, the probe is in contact with the tissue at the surgical site. 
As energy is transferred through the electrode, electrical currents are 
established within adjacent tissue. As current passes through the tissue, 
some energy is absorbed into the tissue causing tissue temperature to 
rise. The rising temperature of the tissue denatures tissue protein 
molecules and facilitates coagulation. 
Among the drawbacks of such devices is the potential that the electrodes 
will become overheated, and the denatured proteins will weld to the 
electrode on the outer surface of the probe. This can result in tissue 
searing or dessication, or in tissue being torn from the surgical site as 
the probe is removed from the patient. Such a tear can result in bleeding 
or the reopening of a wound. A further problem results from tissue 
collecting over the probe. Tissue stuck to the probe interferes with the 
delivery of energy to the surgical site. This interference limits the 
depth of penetration of energy into the tissue and thereby limits the 
depth of cauterization. Because of these drawbacks these devices are 
impractical for certain surgical procedures. 
Surgical systems exist that attempt to limit the sticking of tissue to 
surgical probes. Some thermal cauterizing probes have placed a non-stick 
coating of TEFLON (a fluorocarbon polymer) around the thermal electrode. 
However, because teflon does not conduct electricity the use of this 
technique for electrosurgical probes is impractical. Some electrosurgical 
systems monitor the temperature of the electrodes at the probe and reduce 
the energy being transferred to the site in order to control the 
temperature of the probe. This process results in a fluctuating energy 
density being delivered to the surgical site and a resulting uncertainty 
as to the depth of cauterization being effected. 
There is a need for an electrosurgical device and system that can perform 
tissue cutting procedures and tissue cauterization procedures without 
overheating and causing tissue to stick or weld to the electrode. Such a 
device would be useful in that it would eliminate the need for the surgeon 
to scrape tissue and/or coagulant from the probe during the cauterization 
or cutting procedure. A device of this type would be well suited to 
general surgical procedures as well as to microsurgical procedures. 
Accordingly, it is an object of the present invention to provide a surgical 
device and system that controls the transfer of heat from the device to 
tissue at the surgical site. A further object of the invention is to 
provide such a device that is adapted to control the temperature of an 
electrode mounted on an electrosurgical device. Yet another object of the 
invention is to provide an electrosurgical device that controls the 
transfer of heat from the electrode to adjacent tissue without limiting 
the electromagnetic energy delivered to the tissue. It is also an object 
of the invention to provide an electrosurgical device that prevents tissue 
and/or coagulant from welding to an energy delivering electrode. Other 
objects of the invention will be apparent upon reading the description 
which follows. 
SUMMARY OF THE INVENTION 
In one embodiment the present invention comprises an electrosurgical device 
that includes an elongate surgical probe member having disposed about a 
portion of its outer surface dual cauterization electrodes that are 
electrically isolated from each other. In one embodiment the cauterization 
electrodes may be helically oriented about the outer surface of the probe 
member. A longitudinally oriented lumen extends through the member and is 
adapted to deliver a fluid through the member from a fluid source. The 
lumen has at least one outlet port, preferably at the distal end of the 
member, through which the fluid can be discharged. The device also 
includes a selectively deployable cutting electrode that is able to be 
retracted within the lumen when not in use, and to be extended from the 
lumen upon deployment. The fluid delivered through the lumen serves both 
to cool the cauterization electrodes during cauterization, and to irrigate 
the surgical site. 
The device is used in conjunction with an electrosurgical generator that 
supplies electrosurgical energy to the cauterization electrodes and to the 
cutting electrode. Switches are provided to enable a surgeon to switch 
easily between the cutting and coagulation modes, and to selectively 
deliver fluid through the lumen at desired flow rates. 
When used for cauterization the device can function in a bipolar mode with 
the dual cauterization electrodes being electrically isolated from each 
other. The device also may be used as a bipolar surgical device for 
performing cutting procedures with the cutting electrode serving to cut 
tissue, and one or both of the cauterization electrodes serving as return 
electrodes. 
In another embodiment the device serves only as a cauterization probe and 
does not include a cutting electrode. 
A control system associated with the device facilitates the control 
temperature of the energy delivering electrode (especially in the 
cauterization mode) to prevent excess heating of the electrode and/or the 
delivery to the electrode of excess energy. In one embodiment the 
temperature of the energy delivering electrodes is monitored and compared 
to a predetermined maximum temperature value. The flow rate of fluid 
delivered through the lumen is controlled, based upon the compared 
temperature values, to maintain electrode temperature at or below the 
predetermined value. Flow rate can be increased if the measured 
temperature exceeds the predetermined value. Similarly, flow rate can be 
maintained or decreased if the measured temperature equals or is below the 
predetermined value. 
The energy output by the generator to the probe may also be controlled 
based on measured tissue impedance, in conjunction with the monitoring of 
electrode temperature. Upon delivery of energy to tissue, the impedance 
value is then compared to a predetermined maximum impedance value. If the 
measured impedance exceeds the predetermined impedance value, a signal is 
generated and transmitted to the generator to prevent further delivery of 
energy by the generator. This system serves as an added safety measure to 
prevent injury to a patient as a result of delivering too much energy 
through the probe or excessively heating tissue. The measured tissue 
impedance value may also be used to control the fluid flow rate, 
independent of temperature monitoring. 
The device is useful for general surgical applications in which the cutting 
and cauterization probe directly accesses a target site through a 
percutaneous incision located proximal to the target site. In addition, 
the probe may be manufactured in dimensions suitable for use in 
microsurgical procedures where the probe can be delivered to the target 
during arthroscopic, endoscopic, or laproscopic surgery.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 illustrates the electrosurgical cutting and coagulation system 10 of 
the present invention. The system 10 comprises a radio frequency energy 
source 12, a control unit 14, in electrical communication with the energy 
source, and an electrosurgical probe 16. The control unit 14 is in 
electrical communication with probe 16 through electrode leads 18, 20, 22. 
Further, a fluid source 24 communicates a fluid to probe 16 through 
conduit 26. 
The electrosurgical cutting and cauterization probe 16 is further 
illustrated in FIGS. 2 through 3C. As illustrated, probe 16 has a handle 
portion 28 at its proximal end and an elongate member 30 that extends from 
the handle portion. The distal end of elongate member 30 is somewhat 
tapered and includes a cauterization tip 32 and a retractable cutting 
electrode 34. Cutting electrode 34 is able to extend from, or to be 
retracted within, a substantially circular orifice 36 which preferably is 
disposed in the distal end of cauterization tip 32. The exposed outer 
surface 33 of the cauterization tip 32 includes dual cauterization 
electrodes 38, 40. Preferably, cauterization electrodes 38, 40 are 
helically oriented about the surface 33 of cauterization tip 32. However, 
other orientations for electrodes 38, 40 are possible as well. 
The handle portion 28 of probe 16 includes a fluid inlet port 42 that 
communicates with fluid source 24 through conduit 26. Electrode leads 20 
and 22 emerge from a cuff 44 on the handle portion 28 of the probe. The 
proximal ends of leads 20, 22 have connectors 46, 48, which are matable 
with control unit 14. The distal ends of leads 20 and 22 connect to 
cauterization electrodes 38 and 40, respectively. 
Cutting electrode 34 extends throughout the length of probe 16, and 
preferably has a length greater than the probe itself so that it is able 
to emerge both from the distal end of member 30 and the proximal end of 
handle 28. An electrode lead 18, having connector 50, connects the 
proximal end 34A of cutting electrode 34 to control unit 14. Cutting 
electrode 34 preferably is coated with an insulating material over its 
entire length, except for its extreme distal end which is uncoated so as 
to deliver electrosurgical energy to tissue. Suitable insulating materials 
include polymers such as polyvinylidene fluoride, polytetrafluoroethylene, 
fluorinated ethylene-propylene polymers, polyethylene, and others known to 
be suitable for use in medical applications. 
Referring to FIGS. 4, 5, and 6, lumen 52 preferably is centrally located 
within probe 16 and extends throughout the length of the handle portion 28 
and elongate member 30, along the longitudinal axis of the probe. The 
inlet port 42 provides a passageway for fluid to be communicated from 
conduit 26 to lumen 52. A fluid from source 24 is thus able to be 
communicated to inlet port 42 to enable fluid to be delivered through the 
lumen to the orifice 36 where it is discharged from the probe to contact 
tissue. 
In an alternative embodiment, illustrated in FIG. 7, a side-mounted orifice 
60, in fluid communication with lumen 52, may be used to discharge fluid 
to adjacent tissue. Orifice 60 may be used alone, or in combination with 
orifice 36. Also, orifice 60 may, if desired, be paired with one or more 
additional side-mounted orifices (not shown). 
As noted, cutting electrode 34 is positioned within and extends over the 
entire length of lumen 52. The selectively deployable nature of cutting 
electrode 34 is advantageous in that electrode 34 can be deployed for a 
cutting procedure and retracted during cauterization. 
Deployment of electrode 34 can be controlled by a suitable mechanism 
preferably mounted on the handle portion 28 of probe 16. FIG. 4 
illustrates a thumbscrew 54, mounted upon the proximal end of handle 28, 
which can be used to control the retraction and extension of the cutting 
electrode 34. Alternatively, as shown in FIG. 1, an excess length of 
electrode 34 may extend from the proximal end of handle 28 so as to be 
manually manipulated to regulate the length of electrode 34 extending from 
orifice 36. A variety of other length controlling mechanisms may be 
utilized as well. 
In one embodiment cutting electrode 34 may be biased either to an extended 
or retracted position. The biasing force may be overcome by the mechanism 
used to control the extension/retraction of electrode 34. 
The dimensions of the probe 16 are such that it is suitable for use in 
arthroscopic, endoscopic, laproscopic, and general surgery. Preferably, 
the length of the probe is approximately 10 to 18 inches. The diameter of 
member 30 can vary within a range of dimensions known in the art to be 
suitable for the intended use of the probe. In a preferred embodiment, the 
diameter is not constant along the entire length of member 30. Member 30 
preferably has approximately three distinguishable but integral sections 
which have slightly differing diameters. As illustrated in FIG. 2, a 
proximal section 30A of the member 30 is the longest segment and has the 
largest diameter D.sub.1. Adjacent this section is portion 30B of member 
30, having a slightly smaller diameter D.sub.2. The diameter of region 30C 
tapers over its entire length, terminating in cauterization tip 32 which 
has a diameter D.sub.3. Generally, the diameter D.sub.1 ranges from 
approximately 10 to 20 French (0.13 to 0.26 inch). Diameter D.sub.2 ranges 
from 7 to 15 French while D.sub.3 ranges from about 5 to 12 French. 
The diameter of cutting electrode 34 can also vary, and its size depends to 
a large extent upon the diameter of lumen 52. One requirement of the lumen 
diameter is that it be sufficient to accommodate the flow of fluid while 
electrode 34 is disposed within the lumen. Generally, the lumen diameter 
is in the range of 3 to 7 French, while the diameter of electrode 34 
ranges from 1 to 3 French. 
The probe 16 of the present invention can be manufactured of a variety of 
materials, including polyolefins and nylons, that are known to be suitable 
for use in medical applications. The outer wall 58 of member 30 preferably 
is manufactured of an insulating polymeric material of the type well known 
in the art and suitable for use in medical applications. 
The cutting electrode 34 and cauterization electrodes 38, 40 preferably are 
made from a highly conductive material such as gold, silver or platinum. 
The conductive material from which the electrodes are made can be a solid 
material or, alternatively, a plating which is deposited upon an 
insulating material such as a polymer. The cutting electrode should have 
sufficient rigidity, tensile strength and compressive strength to enable 
it to be extended from and retracted within the probe 16. 
As noted, the probe 16 of the present invention is useful in general 
surgical procedures as well as in laproscopic, arthroscopic, and 
endoscopic surgical procedures. A significant advantage of probe 16 is 
that it represents a single instrument which can perform both 
cauterization and cutting procedures in a bipolar mode. Moreover, 
cauterization with probe 16 is more effective because the fluid flow 
through lumen 52 prevents electrodes 38 and 40 from transferring excessive 
thermal energy to tissue. 
In operation, the probe may be inserted through an incision and directed to 
the location at which the surgical procedure is to be performed. Cutting 
electrode 34 can be extended from within lumen 52 once the probe reaches 
the surgical site. Thereafter, electrosurgical energy can be delivered 
between electrode 34 and one or both of electrodes 38, 40 (serving as 
return electrodes) to cut tissue. Control of bleeding can be effected 
utilizing cauterization tip 32 and cauterization electrodes 38 and 40. To 
do so, tip 32 is positioned in contact with tissue requiring cauterization 
and electrosurgical energy is delivered between electrodes 38 and 40 upon 
changing the mode of operation from cutting to coagulation, using, for 
example, switch 56 on control unit 14. This cauterization procedure can be 
bipolar in that one of electrodes 38 and 40 serves as an active, energy 
delivering electrode, while the other serves as a return electrode. 
FIGS. 8 through 10 illustrate an alternative embodiment of the invention in 
which system 10 serves only to cauterize tissue. The probe is similar in 
construction to that illustrated in FIGS. 1 through 7, but it does not 
include a cutting electrode. Although lumen 52 is illustrated as being 
centrally disposed within member 30, it is understood that the lumen need 
not be disposed within member 30, but instead can be appended to member 
30. 
During cauterization procedures, and optionally during cutting as well, 
fluid is delivered through lumen 52 at a desired rate. The delivery of 
fluid serves two purposes. First, the fluid acts to limit the heat 
transfer from cauterization electrodes 38, 40 to adjacent tissue to an 
extent that tissue does not become overly heated by the electrodes, 
causing tissue and/or coagulant to stick to tip 32. This enables more 
effective and convenient cauterization. The fluid delivered to tissue can 
also serve as an irrigant to improve the visibility in the area subject to 
surgery and to remove any debris from the surgical site. 
The fluid flow rate may be constant or variable. Preferably, the flow rate 
is variable and occurs only when energy is delivered to effect 
cauterization and preferably ranges from approximately 1 to 50 ml/minute. 
One skilled in the art will readily appreciate that it may be desirable to 
use a somewhat higher flow rate. 
One of ordinary skill in the art will appreciate that the fluid flow rate 
depends on a number of variables, including the temperature of the fluid 
and the amount of power delivered to the cauterization electrode. The flow 
rate should be effective to control the temperature of the cauterization 
electrode, but should not be so high as to destroy tissue. The electrode 
temperature should be maintained below about 60.degree. C., and more 
preferably below about 46.degree. C. The temperature of the fluid may 
range from quite cold (e.g., about 4.degree. C.) to about room temperature 
or higher (e.g., about 27.degree. C.). 
Flow rate can be manually adjusted or can be controlled by one or more 
feedback mechanisms that monitor temperature impedance and/or electrode 
temperature. A suitable feedback mechanism is described below. 
One skilled in the art will readily appreciate that certain surgical 
procedures will be able to tolerate more fluid flow while others will be 
able to tolerate less. The fluid flow rate can be adjusted to accommodate 
the requirements of a variety of surgical procedures. 
The fluid source 24 may communicate with a valve or pump mechanism (not 
shown) which controls the flow rate of fluid through lumen 52. The flow 
rate can be constant at a predetermined rate, such as about 30 ml/minute, 
which generally is sufficient to limit the temperature of electrodes 38, 
40 and cauterization tip 32. 
The flow rate preferably is variable and is controlled through a feedback 
system that monitors electrode temperature and/or tissue impedance. The 
delivery of energy through electrodes 38 and/or 40 to cauterize tissue 
causes the temperature of the electrodes to rise significantly. Excess 
heating of the electrodes (e.g., above about 60.degree. C.) can damage 
tissue and result in the buildup of excess coagulant on the cauterization 
tip 32 of probe 16. Such coagulant can impede the flow of current from tip 
32 to tissue and thus must be removed to enable effective energy delivery 
to tissue. 
The present invention utilizes a feedback system 100, illustrated in FIG. 
11, that monitors electrode temperature and/or tissue impedance to control 
the flow rate of fluid through lumen 52. The fluid passing through the 
lumen serves to cool electrodes 38, 40, and flow rate of the fluid affects 
electrode temperature. FIG. 11 is a block diagram that illustrates the 
operation of feedback system 100. As illustrated, generator 102 delivers 
electrosurgical energy to probe 104 which, in turn, conveys the energy to 
tissue 106. Impedance of the tissue is measured through a circuit 108, 
preferably associated with the generator, based on the energy applied to 
the tissue. Circuit 108 compares the measured impedance with a 
predetermined maximum impedance value. If the measured impedance exceeds 
the predetermined maximum impedance a disabling signal 110 is transmitted 
to generator 102 to cease further delivery of energy to probe 104. 
Alternatively, the measured impedance, as compared to a predetermined 
desired impedance value, can also be used to control the fluid flow rate 
through the probe 104 to avoid excessive heating of energy delivering 
electrodes. 
Feedback system 100 preferably monitors electrode temperature 
contemporaneous with the monitoring of tissue impedance. In a preferred 
embodiment the tissue impedance monitoring circuit is used to disable the 
generator (if necessary) while a temperature monitoring function 
facilitates control of fluid flow rates. 
As electrosurgical energy is delivered to tissue 106 from probe 104, the 
electrode temperature is monitored by element 112, which may be a 
thermistor, thermocouple, or the like. Comparator 114 compares the 
measured electrode temperature value with a predetermined maximum 
temperature value. Flow control element 116 regulates the fluid flow rate 
to achieve optimal electrode temperature based on the measured electrode 
temperature in relation to the predetermined maximum temperature. For 
example, if the measured electrode temperature exceeds the predetermined 
maximum temperature, flow rate will be increased. Similarly, if the 
measured temperature is low, flow rate will be maintained or decreased. 
Further, output 117 from the temperature comparator 114 can be input to 
generator 102 to regulate the amount of power delivered by the generator, 
thus controlling temperature. Similarly, output 119 from impedance monitor 
and comparator 108 can be inputted to flow regulator 116 to regulate fluid 
flow and thus control electrode temperature. 
Although one having ordinary skill in the art will appreciate that the 
feedback system of the invention can be implemented in a variety of ways, 
an exemplary feedback circuit is illustrated in FIG. 12. 
FIG. 12 depicts an exemplary circuit to effect the system described in FIG. 
11. An energy delivering means, such as RF generator 102, is transformer 
coupled to the probe 104, to apply a biologically safe voltage to a 
patient's tissue. In this embodiment, the probe is represented as a 
bipolar cauterization probe 104 having an energy delivering electrode 38 
and a ground electrode 40. Both electrodes 38, 40 are connected to the 
primary side of the transformer windings 1,2. The common primary winding 
1,2 is magnetically coupled via a transformer core to the secondary 
windings 1',2' so that the current and voltage of the primary side is 
reflected to the secondary windings 1',2'. 
According to a preferred aspect of the invention, the primary windings 1 of 
the first transformer t.sub.1 couple the output voltage of the probe 104 
to the secondary windings 1'. The primary windings 2 of the second 
transformer t.sub.2 couple the output current of the probe 104 to the 
secondary windings 2'. Those of ordinary skill in the art will appreciate 
that the two transformers act as step-down transformers and further serve 
as means of isolating the high voltage between the electrosurgical probe 
102 and the secondary windings or measuring circuit 1',2'. 
The measuring circuits determine the root mean square (RMS) values or 
magnitudes of the current and voltage and these values, represented as 
voltages, are inputted to a dividing circuit D to geometrically calculate, 
by dividing the RMS voltage value by the RMS current value, the impedance 
of the body tissue at the probe electrode 104. Those of ordinary skill in 
the art will understand that the voltage presented at the output of the 
divider circuit D is representative of and a function of the impedance of 
the tissue adjacent to the probe electrodes 38, 40. 
The output voltage of the divider circuit D is presented at the positive(+) 
input terminal of comparator A. A voltage source V.sub.o supplies a 
voltage across the variable resistor R.sub.v, thus allowing one to 
manually adjust, via a knob, the voltage presented at the negative input 
of comparator A. This voltage represents a maximum impedance value beyond 
which power will not be applied to the probe 104. Specifically, once the 
tissue is heated to a temperature corresponding to an impedance value 
greater than the maximum cut-off impedance, the RF generator 102 will stop 
supplying power to the probe 104. Comparator A can be of any commercially 
available type that is able to control the amplitude or pulse width 
modulation of the RF generator. 
In one aspect of the invention, the flow rate of the coolant can be 
controlled by either the tissue impedance, as represented by signal 115, 
or by the probe temperature, as represented by signal 120. In one 
preferred embodiment, the switch S is activated to allow the impedance 
signal 115 to enter the positive(+) input terminal of comparator A. This 
signal along with the reference voltage applied to the negative(-) input 
terminal actuates the comparator A to produce an output signal. If the 
tissue is heated to a biologically damaging temperature, the tissue 
impedance will exceed the selected impedance value seen at the negative(-) 
input terminal thereby generating a signal 110 to disable the RF generator 
102, ceasing the power supplied to the probe 104. 
The output signal of comparator A can further be communicated to pump 125. 
If the temperature of the probe 104 is high, despite the tissue impedance 
falling within acceptable limits, the pump 125 will adjust the rate of 
flow of the cooling fluid subsequently applied to the probe electrodes 38, 
40 to decrease the probe temperature. Thus, the output signal of 
comparator A may either disable the RF generator's 102 power output 
(depending on the tissue temperature as reflected by its impedance) or 
cool the probe or perform both operations simultaneously. 
In another aspect of the invention, the rate of flow of the cooling fluid 
is controlled by the temperature measured at the catheter tip. The switch 
S is actuated so as to transfer to the positive(+) input terminal of 
comparator A the comparator B output signal 120. The temperature sensor is 
a thermistor T, and is preferably disposed longitudinally along the 
outside body of probe 104. The thermistor T senses temperature and reacts 
to differential temperature changes in a predictable manner. Thus, the 
thermistor actively reflects through varying resistance the temperature it 
is exposed to. 
Both leads of the temperature sensitive thermistor T are inputted to the 
positive(+) and negative(-) terminals of comparator B to produce a signal 
120 indicative of the catheter temperature. This signal 120 works in 
conjunction with the reference voltage inputted at the negative(-) 
terminal to activate the comparator A to produce an output signal that is 
electrically communicated to the pump 125. The pump 125 in response to the 
signal selectively varies the flow rate of the cooling fluid as it travels 
through a lumen 52 disposed within the probe 104 to the energy delivering 
electrode 38. 
It is understood that the temperature of the electrode can be continuously 
monitored or randomly sampled to ensure against excessive heating of the 
tissue. Moreover, the pump employed can be a valve, or series thereof, 
rather than an electrical-mechanical apparatus. The valve can adjust the 
rate of flow of the cooling liquid from the fluid supply source in the 
same manner as a pump. 
Virtually any generator able to provide electrosurgical energy for medical 
applications may be used with the present invention. Preferably, the 
generator 12 is a voltage determinative, low source impedance generator 
that provides radio frequency energy. A preferred generator is able to 
supply up to 3 amps of current and has an impedance value of less than 10 
ohms. 
The energy supplied by the generator to the control unit 14 and to probe 16 
is preferably in the radio frequency (RF) range. Although virtually any 
frequency in the RF range may be supplied to probe 16, the preferred range 
is about 500 to 700 KHz, and most preferably about 550 KHz. 
As illustrated in FIG. 1, RF energy is provided to a control unit 14 from a 
generator 12. The control unit 14 includes switching mechanism 56 which 
enables a surgeon to control to mode of operation of the probe. Moreover, 
additional switches (not shown) mounted on or remote from unit 14 may be 
used to control the delivery of energy and the magnitude of the delivered 
energy. 
The energy requirements of the probe are dynamic and will vary upon the 
impedance value of tissue which is being treated, and upon whether the 
tissue is being coagulated or cut. The impedance of tissue varies among 
tissue types and the amount of blood present in or around the tissue. The 
amount of current delivered by the probe to tissue thus depends on the 
impedance of the tissue. Where the tissue contacted has a lower impedance 
value, more current will be delivered to the tissue through the clip, and, 
conversely, less current will be delivered where the tissue has a higher 
impedance value. The current delivered during cutting procedures utilizing 
electrode 34 generally ranges between 0.2 amps and 3 amps. The voltage 
applied to tissue for such cutting procedures is between about 60 and 
1,000 volts rms. Current delivered during coagulation is generally in the 
range of 0.25 to 1.0 amp., and coagulation voltages is in the range of 
about 10 volts to about 50 volts rms. 
It is understood that various modifications may be made to the invention 
described above without departing from the scope of the claims. For 
example, rather than operating in the bipolar mode, the cutting and 
coagulation each may be performed in a monopolar mode with the use of a 
remote ground pad. Also, the mode of operation may be controlled by the 
use of a foot pedal rather than a switch mounted on control unit 14.