voltage level and resulting applied power are lower than in monopolar electrosurgical applications. This results in
less localized tissue heating and reduced “charring” of tissue. Bipolar electrosurgery is typically used in
neurosurgical and gynecological procedures, and in other procedures where there is concern due to implanted
pacemakers and automatic defibrillators. In general, bipolar electrosurgery is safer that monopolar
electrosurgery, and the subsequent risks of high frequency burns at the return electrode site are avoided.
Figure 3 Figure 4
Electrosurgery – Bipolar Mode Electrosurgery – Monopolar Mode
Monopolar electrosurgery (see Figure 4) is a more generalized and more frequently used mode. Monopolar
electrosurgery utilizes higher voltage levels than bipolar, resulting in higher power delivered at the surgical site.
The need for a well prepared and maintained patient electrode site is of paramount concern in monopolar
electrosurgical applications, in order to prevent high frequency burns at the patient return electrode site.
The high frequency waveform produced by the electrosurgical generator determines the physiological effect of the
application of this energy to the tissue in the body. The
Cut
mode of an electrosurgical generator creates a
continuous waveform, as shown in Figure 5. Different degrees of hemostasis (
coagulation
) can be achieved by
utilizing varying degrees of “
Blended
” waveforms as shown in Figure 6.
Figure 5 Figure 6
Pure Cut - Pure Sinusoidal Waveform Blended Waveforms
The
Coag
mode (see Figure 7) of an electrosurgical generator creates a waveform with large amplitude but short
duration “spikes” to achieve hemostasis (coagulation). The surrounding tissue is heated when the waveform
spikes and then cools down (between spikes), producing coagulation of the cells.
Fulguration
is achieved in the
Coag
mode of the electrosurgical generator, with the tip of the surgical “active electrode” held above (but not in
contact with) the tissue. Electrosurgical
Desiccation
is achieved in either the
Cut
or
Coag
modes of the
generator. The difference between
Desiccation
and
Fulguration
is the tip of the “active electrode” must contact
the tissue as in Figure 8 in order to achieve
Desiccation
. The more desired mode to achieve tissue
Desiccation
through direct tissue contact is the
Cut
mode.
Older electrosurgical generators (those produced prior to around 1968) are generally
ground-referenced
devices
and must be used with extreme care to avoid unwanted “current division” and possible resulting high frequency
burns at this site (or at multiple sites). This is illustrated in Figure 9 below. Current division can occur at any point
of contact with an earth grounded point, such as the frame of the surgical table or the outer chassis of another
medical device. For the most part, these types of devices are no longer used in surgical procedures, mainly due
to advances in electrosurgical generator technology and concerns over safety.
Copyright June, 2007 by BC Group International, Inc.
Author: Michael R. Erwine
4
Revision 1 – June 13, 2007