Full text of DOI:10.1089/089277903322518545

JOURNAL OF ENDOUROLOGY
Volume 17, Number 8, October 2003
© Mary Ann Liebert, Inc.
Electrocautery: Principles and Practice
M. BARBA, M.D.,1 K. FASTENMEIER, Ph.D.,2 and R. HARTUNG, M.D.1
ABSTRACT
We explain the basic physics of transurethral resection of the prostate (TURP). Modifications of electrodes
or high-frequency units that should improve TURP are discussed. Finally, we introduce Coagulating Inter-
mittent Cutting (CIC), which is a TURP using a modified high-frequency generator. Results of in vitro ex-
periments and the first data from a multicenter trial are demonstrated.
in the patientis heating the tissue. The amount of heat produced
depends on the current flowing per unit area; i.e., the current
density. More exactly,the dissipatedheat energy is proportional
to the current density squared. The current density is high only
in the tissue neighboring the current loop and, therefore, only
here does the temperature increase significantly. If the applied
power is high enough, the fluid in the cells near the cutting loop
will be vaporized. As a result, the steam pressure bursts the
cells, and the cutting loop can be moved through the tissue al-
most without mechanical force.
The described cutting effect depends only on the magnitude
of the current density, not on the frequencyof the current. How-
ever, if sufficient cutting or coagulating is to be achieved, the
magnitudes of the high-frequency currents and voltages have
to be enough to avoid massive nerve and muscle stimulation
that would occur at direct current or at low frequencies.In 1908,
Nernst5 found that all effectsof an electricshock can be avoided
if the frequency of an electric signal exceeds 100 kHz. There-
INTRODUCTION
IGH-FREQUENCY SURGERY as used in transurethral
resection (TUR) has proved its advantages and reliability
H
for many years. Nevertheless, there are hazards, which can be
caused by the high-frequency power applied to the patient:
burns, strictures of the urethra, and nerve and muscle stimula-
tion have been reported. To avoid these hazards, the surgeon
needs at least a minimum understandingof the basic physics of
the high-frequencycurrentused for cuttingand coagulatingdur-
ing TUR.1–4
ELECTRIC BASICS OF TUR
In Figure 1, the principal electric arrangements for TUR are
shown. On the right-hand side is a schematic cross-section of
the patient with the resectoscope in the urethra. On the left-
hand side is the electrosurgical unit or, more technically, the fore, high-frequencyvoltages and currents are necessary for bi-
ologic cutting and coagulating. A typical generator voltage for
cutting is presented in the oscillogram of Figure 3. The voltage
has a sinusoidal dependence on time. The distance between
maximum and maximum is about 1 msec. Therefore, there are
1 million maximums in 1 second, and the frequency is
high-frequency generator. This generator is connected to the
patient through the groundingplate, normally fixed to his thigh,
and through the cutting loop. Inside the resectoscope, the elec-
trical connection from the generator to the cutting loop is care-
fully insulated. When activated, the generator produces a high-
u
U
frequency voltage (t) with a magnitude . This voltage drives 1,000,000 Hertz (5 1 MHz). The magnitude of the voltage is
i
I
about 300.
To produce coagulation without (or with only small) cutting
effects, the heat produced in the tissue has to be less than dur-
ing cutting. Therefore, the applied power has to be reduced.
This is done by pulsing the output signal of the electrosurgical
a high-frequencycurrent (t) (magnitude ) through the patient.
A closer look at the cutting loop is given in Figure 2. The
left side shows the loop removing a piece of tissue, and the
right side represents a cross-section along the dashed line. The
I
high-frequencycurrent, , spreads from the cutting loop into the
tissue and leaves the patient at the patient plate. Thus, the pa- unit. The oscillogram of Figure 4 is an example, but great dif-
ferences can be found in the signal forms of different types of
tient is part of the electric circuit. The current flowing within
1Department of Urology, Technische Universität München, Munich, Germany.
2Institute of High-Frequency Technology, Universität der Bundeswehr München, Munich, Germany.
541

542
BARBA ET AL.
u
Þ u
U f t i Þ i
I
f t
FIG. 1. Schematic electricaldiagram of TUR: (t): voltage
(t) < ?cos(2?p? G? ) and (t): current: (t) < ?cos(2?p? G? 1
f
u
i P
R
Z
w), where G 5 generator frequency; w 5 phase shift between and ; 5 power; 5 patient resistance; 5 patient impedance.
electrosurgical units. It is typical, however, that the maximal ditional effects with increasing current density in the urethra,
output voltage is as high as, or even higher, than during cut- burns can occur, resulting in stricturesand stenoses. In the past,
ting, but only for a few high-frequency periods. Thus, the pro- the influence of the current on stricture formation was often
duction of heat is stopped before cutting can occur.
overestimated, in that most of the strictures following TUR are
caused mechanically or by postoperative inflammation. With
excessive generator settings, the hazards of burns are appre-
ciable, however.
CURRENT PATHWAYS THROUGH
THE PATIENT
In Figure 5, the lines with arrowheads inside the patient in-
dicate the currentpathwaysthroughthe patient.These pathways
were determined with the help of phantoms of a human body.4,6
Most of the current is flowing from the cutting loop to the pa-
INFLUENCE OF ELECTRICAL
CONDUCTIVITY OF LUBRICANT
An additional effect to keep in mind is the influence on the
tient plate directly. Nonetheless, in the case of a resectoscope electricconductivityof the lubricationjelly appliedto the sheath
with a metal sheath, part of the current is flowing to this sheath of the resectoscope. If its electric conductivity is as high as or
first and then from the middle of the instrument to the patient higher than that of the tissue, the current is flowing from the
plate. In this way, there is current flowing through the urethra. sheath to the tissue over the whole surface of the resection in-
Normally, the current density along the instrument is low strument, and the current density is low. If the electric con-
enough that no dramatically effects occur, but if there are ad- ductivity of the lubricant is much less than that of the tissue,
FIG. 2. Cutting loop in urethra.

543
ELECTROCAUTERY: PRINCIPLES AND PRACTICE
u
fG
FIG. 3. Typical voltage (t) frequency for cutting. < 1
U
MHz magnitude; < 300 V.
there is the effect shown schematicallyin Figure 6. In this case,
most of the sheath is insulated by the lubricant jelly, with poor
electric conductivity. However, the layer of lubricant is not
equally thick over the whole surface. For instance, at the tip of
the instrument, the lubricant is washed away by the irrigation
fluid, and at narrow passages in the urethra, the lubricant will
be pressed away. The current flowing from the resectoscope to
the tissue concentrates at those spots where the layer of lubri-
cant is thin or absent. Because of the quadratic dependency of
the heat produced from the current density, tissue heating will
increase rapidly, and burns can occur. So for use with resecto-
scopes with metal sheaths, the lubricant jelly needs an electric
conductivity almost as high as or higher than that of muscular
tissue.
We have measured many lubricants gathered from hospitals
on all continents (Table 1). Figure 7 shows a histogram of the
electricalconductivity[dimension:mmho/cm] of 20 of the most
popular lubricant jellies. The measured range of electrical con-
ductivity of these materials is between 0.1 mmho/cm and 9
mmho/cm. In comparison, the electric conductivity of muscu-
lar tissue is about 4 mmho/cm, and that of blood is 7 mmho/cm.
The cross-hatchedsamples (1 to 7) have conductivitymuch less
than that of human tissue, and these lubricants should not be
used with resectoscopeswith metal sheaths. We measured only
the electric properties of the lubricants, and therefore, nothing
can be said about the medical aspects or the mechanical prop-
erties (i.e., for how long the material has sufficient lubrication
effect during TUR).
FIG. 5. Measurement of current pathways in patient and cur-
rent density along urethra.
power is needed to start a cut and also when the cut is forced
through an artery.
But one cut lasts only about 1 to 3 seconds: there is no time
to adjust the generator setting manually to match the momen-
tarily needed setting. The only way is to choose a generatorset-
ting from experience such that the cutting loop will not stick.
At other times, the power needed, and therefore the required
generator setting, could be less.
There are risks associated with excessive generator settings.
All hazards of burns are increased. Additionally, there is ex-
tended necrosis,and, as will be shown later, the hazards of mus-
cle and nerve stimulation increase, too.
ELECTRIC POWER APPLIED DURING TUR
Naturally, the power applied to the patientshould be as small
as possible, just high enough for cutting, but this cannot be
achieved easily. Figure 8 schematically expresses the dilem-
matduring TUR. The appropriate generator setting depends on
many parameters; e.g., cutting speed and depth and the electri-
cal and mechanical properties of the tissue. Normally, high
Output characteristics of standard generator
Now, let us have a closer look at the dependencies of the
generator output power on the generator setting (Fig. 9). If the
generator is a standard one, the power flowing from the gener-
ator to the patient is fully determined by the generator setting
and the electric resistance, R, which is formed for the electric
current by the patient.
With low resistance, almost no power is flowing to the pa-
tient. With increasing resistance, the output power increases.
There is one characteristic resistance, RQ, at which the power
has a maximum. In this measurement, the RQ is 500 V. Above
this point, the power decreases. With the generator setting, the
characteristicform of the curve does not change, but at a higher
setting, more power is available at each patient impedance. It
u
FIG. 4. Typical voltage (t) for coagulation.

544
BARBA ET AL.
FIG. 6. Metal sheath with low-conductive lubricant.
is important what resistance, R, or, better what impedance, Z
(the impedance Z is an electrical expression for the electric re-
sistance summarizing ohmic, capacitive, and inductive effects),
is formed by the patient and therefore what power is applied to
the patient during TUR.
The patient is connected to the measurement adapter in the
same way he is normally connected to the generator. For the
surgeon, the procedure does not differ in any way from a nor-
mal TUR. The measurement adapteris passive without any sep-
arate power supply. Its circuits are insulated from the patient
circuit, so there is no additional hazard to the patient as a con-
sequence of the measuring.
Measuring the electric parameter of TUR
In Figure 11, a statistic can be seen that was generated from
the data measured during a prostatectomy with a standard gen-
erator. It is a diagram of the compound probability of genera-
tor power, P, and patient impedance, Z, and shows the proba-
bility of the coincidenceof a destined impedance and the power
delivered to the patient at the same time. Dark areas mark those
combinations of P and Z most frequently found in the mea-
In order to address this problem, we developed a measure-
ment system (Fig. 10).8 With it, the electric voltage, current,
and power applied to the patient during whole TURs can be
measured, and the data can be stored for offline analysis. There,
additional data processing can be done. The results are either
statistical diagrams of a whole TUR procedure (Fig. 11) or the
time dependenciesfrom every cut done during a TUR (Fig. 12)
A schematic of the measurement equipment is shown in Fig-
ure 10. In the connectionlines between the high-frequencygen-
erator and the patient, a measurement adapter is placed. From
it, signals proportional to generator voltage and current are led
to an analog signal-processing system. The processed signals
are read by a computer with analog-digitalconverterinputs and
stored on floppy disks.
TABLE 1. LUBRICATING GELS TESTED
Sample
no.
Brand name
1
2
3
4
5
Miro, Lubricante Urologico, Organon Espanola S.A.
Lubrajel, Guardian Chemical Corporation
Lubrajel HC, Guardian Chemical Corporation
Hafinol, Johnson u. Johnson, Best. Nr. 4160
Sterile Lubricating Jelly, Holland Rantos
Hafinol, Johnson u. Johnson, Best. Nr. 4110
Lubafax, Wellcome
6
7
8
Surgilube, E. Fougera and Co.
9
Lubricating Jelly, Johnson and Johnson
K-Y Sterile Lubricant, Johnson and Johnson, S. Africa
Xylocain, Astra Chemicals
Instillagel, Farco Pharma
Lube Jelly, Badger Laboratories
Cathejell, Montavit/Paul Hartmann
Lubrajel 7, Guardian Chemical Corporation
Lubricating Jelly, Kenwood
Lubricating Jelly, Will Ross Inc.
Aristamid Gel, Nordmark-Werke
10
11
12
13
14
15
16
17
18
19
20
Endosgel, Farco Pharma
K-Y Lubricating Jelly, Johnson and Johnson
For metal sheath sample No. . 7 should be preferred.
FIG. 7. Electric conductivity of lubricants used for TUR.

545
ELECTROCAUTERY: PRINCIPLES AND PRACTICE
FIG. 8. Power necessary for cutting.
surements. The patient impedance during this TUR was usually
between 500 and 900 V and the power delivered to the patient
between 100 and 200 W. The curve formed by the measure-
ments is very similar to that of the calculated output charac-
teristic of Figure 9, except that it is not a single line but a band.
This is because the generator in use had a rectifier with an only
partially smoothed output signal. This can be seen in Figure 12,
too, where the time dependence of one cut of this resection is
shown. Using output signals partly modulated with the net fre-
quency is a technique often used with standard generators. For
cutting, there are some very useful side effects of this kind of
output signal.
The measurement shows that the power applied to patient is
fully determined by the output characteristic of the generator
and the patient impedance. But the necessary power for cutting
has quite a different dependence on the patient impedance: It
FIG. 9. Dependence of output power (P) of standard generator on patient resistance (R).

546
BARBA ET AL.
FIG. 10. System for measuring electric parameters during TUR.
is known from other measurements (and can be seen in Fig. 12) cuit, we looked for a parameter showing in every moment the
that low impedances, with values about 100 O, exist in the in- right power setting for best cutting without excessive power.
terval between generator activation and the time cutting actu-
Physical effects during cutting
ally starts. During this time interval, the tissue of the patient is
heated from 37°C to 100°C. Additionally, the vaporizing en-
ergy of the cell fluid has to be applied. Much power would be
needed there, but the power available is low: ,100 W. There-
fore, during this TUR, cutting often started with a delay of as
long as 1 second, as in the cut of Figure 12.
Having so much trouble in initiatingcutting, normally, a sur-
geon would increase the generator setting. This time, however,
the generator setting was not changed in order have a sample
for a TUR done with the lowest possible setting.
We found a very easy-to-use parameter with the nonlinear
effects produced by the electric arc generated during every cut-
ting with high-frequency currents. Figure 14 gives the basic
physical model for cutting and Figure 15 the related output
properties of the high-frequency generator.
The circle in the three panels of Figure 14 is a cross-section
through the wire of the cutting loop. The white arrow indicates
the cutting direction and the black arrows and lines the current
density in the tissue neighboring the cutting loop. Three cases
can been distinguished:
Influence of the irrigation flood
In Figure 13, the compound probability function of P and Z
is shown for a second prostatectomy performed by the same
surgeon with the same generator. Some minor but important
changes can be seen. First, there is a smaller probability of low
impedances; the cutting has started faster. Second, the imped-
ance is higher and, because of the output characteristic of the
generator, the output power applied to the patient is lower. The
important difference in the operating parameters causing these
desirable effects is the irrigation fluid. In this case, an indus-
trial deionized irrigation fluid was used. The TUR in Figure 12
was performed with sterilized tap water. This is an important
result: the output power applied to the patient can be decreased
if deionized irrigation fluid is used.
1. In Figure 14 on the left-hand side of the lower row, the gen-
erator setting is very low or the generator was stopped after
cutting and has just been started again. The current is flow-
ing from the wire of the loop to the tissue along the whole
surface of the wire.
2. With sufficient power applied, the tissue is heated, and a
short time later, vapor is produced. Most of the vapor is
within the cells; another part is between the tissue and the
wire. It is important that both parts of vapor form an insu-
lating layer between the normal tissue and the wire. This
layer is thin, with its narrowest extension in the cutting di-
rection. When the output voltage of the generator is high
enough, the insulating layer does not stop the current. The
gap between the conductive parts, the tissue and the wire, is
bridged by an electric spark or a small electric arc. Now, as
shown at the top of Figure 14, all of the current is flowing
through the small area where the electric arc burns. This
changed contributionof the current density is very useful for
cutting. The energy produced by the flowing current con-
centrates where it is needed, directly at the cutting loop in
AUTOMATICALLY CONTROLLED
GENERATOR
The output power can be reduced further with more sophis-
ticated methods. To construct an automatic power control cir-

547
ELECTROCAUTERY: PRINCIPLES AND PRACTICE

548
BARBA ET AL.
FIG. 12. Cut 100 of 366 measured during prostatectomy.
hand side). There are several serious disadvantages in this
case. For example, the arc burns a relatively wide hole in
the cutting direction, and the narrowest place is no longer in
the cutting direction. Also, the arc burns to tissue already
cut and can create extended necroses with their disadvan-
tages: a reduced possibility of differentiating the tissue and
the cutting direction. It can be shown with a rough compu-
tation that cutting without spark, if this were possible, would
require ten times as much power as is needed with a small
electric arc.
3. If the applied power is too high, the small electric arc grows
rapidly to an extendedelectric arc (Fig. 14, lower row, right-
FIG. 13. Compound probability of power (P) and impedance (Z) of whole prostatectomy. Removed tissue 5 35 g; 122 cuts;
13,402 samples. Electrosurgical unit was standard generator. Irrigation fluid was deionized water.

549
ELECTROCAUTERY: PRINCIPLES AND PRACTICE
FIG. 14. Cutting and electric arc. (Top) Optimal cutting. (Lower row, left) Generator setting too low. (Lower row, right)
Generator setting too high.
slower healing. Additionally, the arc can produce low-fre-
quency currents out of the high-frequencycurrents. This ef-
fect can cause severe muscle and nerve stimulation, espe-
cially if the cutting is done near the obturatornerve.8 Finally,
with very high electric arcs, albumin and the irrigation fluid
can be dissociated into explosive gases. Gas explosions in
the bladderare reportedin the literature.9 Thus, this extended
electric arc has to be avoided.
FIG. 15. Output spectrum of electrosurgical unit during cutting.

550
BARBA ET AL.
FIG. 16. Schematic of generator automatically controlled by extent of electric arc.
In Figure 15 is shown the way the three cases can be dis-
tinguished with electronic means. As long as the wire of the
cutting loop is in electric contact with tissue, in the high-fre-
. . . ) are growing too. The harmonic frequency with n 5 0 de-
scribes a rectifying effect of an electric arc. The generated low-
frequency signals cause nerve and muscle stimulation, which
should be avoided as much as possible. The signals at the ad-
ditional frequencies can be measured very easily and can form
the criteria for a control circuit. If there is no signal at the ad-
ditional frequencies, then the generator setting is too low, and
the output voltage has to be increased. If the magnitudes of the
signals at the additional frequency are growing too much, then
f
quency current, only the generator frequency, G, can be found.
If there is an electric spark or arc, additional signals with fre-
f
quencies n? G (n 5 0, 1, 2, 3, 4, . . . ) are generated. With a
small arc especially, frequencies with an odd value for n (n 5
3, 5, . . . ) are generated. With a growing arc, the magnitudes
of the signals at frequencies with even values of n (0, 2, 4, 6,
FIG. 17. Compound probability of impedance (Z) and power (P) performed with automatically controlled high-frequencygenerator.

551
ELECTROCAUTERY: PRINCIPLES AND PRACTICE

552
BARBA ET AL.
the output voltage of the generator has to be reduced. In Fig- rigation fluid was sterilized tap water. The applied power in-
ure 16, the schematic of a generator including this control cir- creased, and there were more measurements at low impedance
cuit is presented.
than in Figure 15. The start of cutting was more difficult than
Figure 17 shows a statistic of a whole TUR as before but before. Once more, it is demonstrated that only deionized irri-
performed with a generator having the described control cir- gation fluid should be used for TUR.
cuit. The statistic looks very different from the statistic shown
In Table 2 and Figure 19, four complete TURs are compared,
for the standard generator.Most of the time, the power is about two performed with the standard generatorand two with the au-
60 W. The average power to the patient is reduced. Addition- tomatically controlled generator. With the automatically con-
ally, there is almost no probability of low impedance values be- trolled generatorand deionizedwater, the applied power is only
cause this generator has a very high available power at low about one third that with a standard generator and sterilized tap
impedances, so cutting starts at once without a problem. Para- water. This is the best combination for TUR. The high-fre-
doxically, if high power is available, it is seldom used, as the quency current through the patient is minimized and so are all
applied average power is decreased.
hazards for the patient.
In Figure 18, the characteristic electric parameters (voltage,
There is a problem in selecting the best generator: More and
U, current, I, power, P, and impedance, Z) of a typical cut from more high-frequencygeneratorsare said to have automatic con-
a prostatectomy performed with an automatically controlled trol circuits, but many of them control only characteristic out-
high-frequency generator are shown. The cut has lasted about put values such as output power or output voltage, without re-
3 seconds. During the first milliseconds, the maximum, almost gard to the physical effects at the cutting loop. Therefore, these
350 W, was applied to the patient to start the cut very rapidly. generators have the same problems with the setting as do the
Then the power was reduced by the control circuit to ,100 W. standard generator without control circuits.
Between 2.1 and 2.3 seconds, an artery was cut: more power
was needed and therefore was delivered by the generator. Af-
ter 3 seconds, the loop left the tissue and was, for about 0.1
Modification of shape of electrode
seconds,in the irrigationfluid beforethe generatorwas stopped.
The development of thicker resection loops with modified
Because of the low conductivity of the irrigation fluid, the shapes (wedge resection,11,12 vapor-cut,12 band electrode,13 wing
power was low, in spite of the fact that the output voltage was electrode14) improves surgical vision during resection.15 The tis-
high. This holds true as long as the irrigation fluid has low con- sue removal of the standard loop is combined with the hemosta-
ductivity. If there are ions in the fluid; e.g., with use of steril- tic effect of higher current densities. Our own data show that the
ized tap water, the power can be high at that moment, too. This current density to the patient increases depending on which loop
can be seen in the measurement of Figure 19. Once more, the is used (Fig. 20). The clinical importance of this fact is still un-
impedance–power statistic of a TUR performed with an auto- known. A problem with these thicker resection loops may be ob-
matically controlledhigh-frequencygenerator is shown. The ir- taining accurate resection at the apex of the prostate.
FIG. 19. Compound probability of patient impedance (Z) and output power (P) with automatically controlled generator and
sterilized tap water.

553
ELECTROCAUTERY: PRINCIPLES AND PRACTICE
TABLE 2. MEAN POWER AND CURRENT APPLIED DURING FOUR TURS TO COMPARE STANDARD AND AUTOMATICALLY
CONTROLLED GENERATORS
Generator
Irrigation fluid
Power (W)
Current (mA)
Standard
Standard
Auto. controlled
Auto. controlled
Sterilized tap water
Deionized water
Sterilized tap water
Deionized water
141.2
110.9
113.6
65.2
483.4
350.5
393.7
251.3
developed. During each cut, phases with predominant cutting
effect alternate with coagulating phases of defined duration. A
disadvantage was that operative time increased because of the
lower cutting speed. Subsequent studies were aimed at in-
creasing resectionspeed and maintainingthe reductionof blood
loss. As the second step, cutting combined with coagulation
effect with high-voltage pulses (“coagulating intermittent
cutting”) (August 1996–June 1997) was developed. In this
technique, the output signal consists of a pulse-modulated si-
nusoidal voltage with high amplitudes. To reduce the mean
power, the output signal is pulsed. The amplitude of the volt-
age during the pulse periods is not constant but rather is tuned
for optimal cutting. Because of the high-voltage pulses and the
resulting spark, the surgeon’s vision was impaired by the ap-
pearance of significantly more gas bubbles in the irrigation
fluid. Thus, another coagulating cutting method had to be de-
veloped that would maintain the cutting speed as well as the
coagulation effect. This work finally resulted in the “coagu-
lating intermittent cutting” (CIC) with constant voltage
pulses and control of pulse intervals (from July 1997 to now).
Again, in this generator, the coagulating effect is achieved by
Transurethral vaporization of the prostate
Many clinical trials have compared TURP and transurethral
vaporizationof the prostate (TUVP). The latter seems to be as-
sociated with a relative decrease in intraoperative and postop-
erative blood loss, and many authors feel that electrovaporiza-
tion is as effective as TURP while bleeding is less.16–22 The
greater likelihood of persistent irritative voiding symptoms af-
ter TUVP than after TURP is believed to result from the in-
flammatory reaction of the prostatic bed to coagulation necro-
sis. Postoperative stress incontinence is seen in some series
(5.7%).21 Intravesical extension and bulky glands limit
TUVP.22 Own data show the high current densities applied to
the patient with TUVP. Long-term data on the morbidity of this
effect are still lacking. Accurate resection at the apex of the
prostate is difficult, so some authors use the standard loop to
complete the resection.21
COAGULATING INTERMITTENT CUTTING
Searching for a new high-frequencyprocedurethat would al-
low a blood-sparingcut without significantlyhigher current ap- a pulsed output signal using voltages with high amplitudes.
plied to the patient, we developed “coagulatingcutting.”23 This However, the pause between pulses is not fixed but controlled.
If the necessary power decreases, the lag between pulses in-
creases, and less power is delivered to the patient. The differ-
ent time periods between the single pulses are shown in Figure
21. Considering the signals of an entire cut, a virtually constant
technique can be performed using standard resectoscopes to-
gether with an electronically modified standard high-frequency
generator and can be done using either direct or video en-
doscopy. As a first step, “coagulating cutting” with coagu-
lating and cutting periods (October 1994–August 1996) was voltage amplitude can be seen.
FIG. 20. Electrical parameters in TUVP and TURP.

554
BARBA ET AL.
FIG. 21. “Coagulating intermittent cutting” with constant pulses and control of pulse intervals. Oscillogram represents voltage
and electrical current, with interval between two pulses being determined by electric arc control. Our first determinations of cur-
rent flow showed increased energy load applied to patients, with estimated values between those of band electrode and Vapor-
cut electrode. To date, no disadvantages have been seen as a result.
kidneys were dissectedand freed of coagula by means of a hep-
arin solution and perfused with porcine blood via a catheter
placed in the renal artery. The perfusion pressure was adjusted
to 120 to 140 mm Hg, and perfusion continued until the pa-
renchyma showed a normal color. The kidneys were then fixed,
and four parallel cuts 1 cm deep and 10 cm long were created
through the parenchyma. This process was repeated with both
generator types at 200 W (Fig. 22). The amount of blood loss
could not be measured exactly, but semiquantitative data were
obtained by weighing six cotton swabs before and after they
IN VITRO EXPERIMENTS
To validate the clinically observed improved coagulation
characteristics with a constant cutting effect, CIC was evalu-
ated semiquantitatively on a perfused cadaver porcine kidney.
These studies were performed in cooperation with the Depart-
ment of Urology, Mannheim, Germany. In these experiments,
we compared the blood loss during the resection of a light arc-
controlled high-frequencygeneratorwith those of our modified
generator (CIC cocut BMP). The vessels of 10 cooled porcine
FIG. 22. Bleeding of porcine kidney during resection with light arc-controlledgenerator (left) as well as with Storz Cocut BMP
(right) at 200 W output power.

555
ELECTROCAUTERY: PRINCIPLES AND PRACTICE
5. Nernst W. Zur Theorie des elektrischen Reizes. Pflügers Arch
1908;122:275–315.
had been pressed on the resection site for a total time of 2 min-
utes. For statistical analysis, the Wilcoxon test for paired sam-
ples was used.
Using this model, a blood-sparing cut using CIC was dem-
onstrated. The coagulation zone of the resected tissue was
deeper than that obtained using a standard high-frequencygen-
erator. Nevertheless, there was no carbonization, as is well
known from vaporization experience. The comparison of the
modified generator (CIC cocut BMP) with a standard light arc-
controlled generatorrevealed a significantreduction in with the
6. Flachenecker G, Fastenmeier K. High frequency current effects
during transurethral resection. J Urol 1972;122:336–341.
7. Gminder F. Bestimmung der elektrischen Parameter bei der
Hochfrequenzchirurgie [dissertation]. München: Universität der
Bundeswehr, 1987.
8. Prentiss RJ, Harvey GW, Bethard WF, Boatwright DE, Penning-
ton RD. Massive adductor muscle contraction in transurethral sur-
gery: Cause and prevention; development of new electrical cir-
cuitry. J Urol 1965;93:263–271.
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transurethral surgery. J Urol 1975;114:536–539.
P
CIC ( 5 0.002).
10. Flachenecker G, Fastenmeier K. Hochfrequenzgenerator mit au-
tomatischer Stromregelung für optimalen Schnitt. Urologe B
27:1–4.
11. Perlmutter A. Advances in electrosurgical techniques. Curr Opin
Urol 1997;7:21–24.
12. Perlmutter AP, Vallancien G. Thick loop transurethral resection of
the prostate. Eur Urol 1999;35:161–165.
13. Doll HA, Black NA, McPherson K, Flood AB, Williams GB, Smith
JC. Mortality, morbidity and complications following transurethral
resection of the prostate for benign prostatic hypertrophy. J Urol
1992;147:1566–1573.
Multicenter trial: CIC improvement of TURP
A series of 457 consecutive patients suffering from sympto-
matic bladder outlet obstruction underwent TURP using CIC.
The rate of blood transfusion was compared with the retro-
spective data of 1000 consecutivepatients who underwent clas-
sical TURP between 1990 and 1994.To evaluate the effective-
ness of CIC, the International Prostate Symptom Score (IPSS)
and uroflometry data were analyzed preoperatively and after a
median postoperativefollow-up of 22 days. For analysis,a non-
parametric statistical test was used.
14. Talic RF. Transurethral electrovaporization-resection of the
prostate using the “wing” cutting electrode: Preliminary results of
safety and efficacy in the treatment of men with prostatic outflow
obstruction. Urology 1999;53:106–110.
The median weight of tissue resected was 33 g. The IPSS
and peak flow rate, which ranged from 8 to 35 and 1 to 23
mL/sec before surgery, respectively, were significantly better
15. Perlmutter AP. Advances in electrosurgical techniques. Curr Opin
Urol 1997;7:21–24.
P
postoperatively (IPSS 6–22, peak flow rate 5–49 mL/sec;
,
0.001). The minimum and maximum hemoglobin values were
7.7 to 18.1 g/dL preoperativelycompared with 6.6 to 16.7 g/dL
postoperatively.The postvoidingresidualurine volume was 151
mL preoperatively (range 10–1500 mL) and 63 mL postopera-
tively (range 0–450 mL). Only 4.6% of the patients needed
blood transfusion intraoperativelyor postoperativelycompared
with 16.5% in our own historicalseries. Looking at the last 100
consecutive patients treated by CIC, only 1 required a blood
transfusion. Only 1.8% of the patients showed clinical signs of
irrigation fluid absorption, which could be managed with so-
dium substitution and diuretics.
16. Desautel MG, Burney TL, Diaz PA, Austria A, Badlani GH. Out-
come of Vaportrode transurethral vaporization of the prostate us-
ing pressure-flow urodynamiccriteria. Urology 1998;51:1013–1017.
17. Kuepeli B, Yalcincaya F, Topaloglu H, Karabacak O, Guenluesoy
B, Uenal S. Efficacy of transurethral electrovaporization of the
prostate with respect to standard transurethral resection. Urology
1998;12:591–594.
18. Cetinkaya M, Ulusoy E, Adsan O, Saglam H, Oezt¸rk B, Basay S.
Comparative early results of transurethral electroresection and
transurethral electrovaporisation in benign hyperplasia. Br J Urol
1996;78:901–903.
19. Hammadeh MY, Madaan S, Singh M, Philip T. Two-year follow-
up of a prospective randomised trial of electrovaporisation versus
resection of prostate. Eur Urol 1998;34:188–192.
20. Kuepeli S, Baltaci S, Soygur T, Aytac S, Yilmaz E, Budak M. A
prospective randomized study of transurethral resection of the
prostate and transurethral vaporization of the prostate as a thera-
peutic alternative in the management of men with BPH. Eur Urol
1998;34:15–18.
21. Gallucci M, Puppo P, Perachino M, et al. Transurethral electrova-
porization of the prostate vs. transurethral resection: Results of a
multicentric, randomized clinical study on 150 patients. Eur Urol
1998;33:359–364.
22. Weiner DM, Kaplan SA. Electrosurgery: VaporTrode. Eur Urol
1999;35:166–172.
23. Barba M, Hartung R, Fastenmeier K, Leyh H. Koagulierendes In-
termittierendes Schneiden (KIS cocut BMP): Eine neue Technolo-
gie für die transurethrale Hochfrequenzchirurgie. Minim Inv
Chirurg 1999;8:108–112.
CONCLUSION
Coagulating intermittent cutting lowers the rate of blood
transfusion and maintains the effectiveness of TURP. Further
investigationis needed,but the preliminaryclinicalresultsshow
improvement of the gold standard TURP.
REFERENCES
1. Fastenmeier K, Flachenecker G. Hochfrequenztechnische Aspekte:
Wirkungsweise and Gefahren. In: Mauermayer W (ed): Trans-ure-
thrale Operationen. Berlin: Springer, pp 51–66.
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3. Fastenmeier K, Flachenecker G. Elektrische Sicherheitsrisiken bei
der Hochfrequenzchirurgie und deren Vermeidung Biomed Tech
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Address reprint requests to:
Mathias Barba, M.D.
Ismaningerstr.22
D-81675 Munich, Germany
4. Flachenecker G, Fastenmeier K. Die transurethrale Prostataresek-
tion mit Hochfrequenzströmen aus elektrotechnischer Sicht. Urologe
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E-mail:
Mathias.Barba@t-online.de