Page 29 - World Journal of Laparoscopic Surgery

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Perspective of Electrosurgical Sources in Minimal Access Surgery
waveform is used in either contact or noncontact mode,
yielding desiccation or vaporization respectively. Cut
waveform is a continuous sinusoidal waveform with
current flowing 100% of the time (duty cycle), coagulation
waveform is an intermittent or “damped” waveform where
the duty cycle is reduced, and blend waveforms are also
intermittent waveforms, but with interrupted duty cycle.

Conventional Bipolar Electrosurgery Fig. 3: Pathway of current in bipolar energy
In bipolar electrosurgery (including advanced bipolar
modalities), the active and return electrodes are the two density and pressure applied. As the current density
jaws of the energy source placed at the target tissue. In cannot be concentrated at a single focal point in bipolar
1974, scientist introduced bipolar electrosurgery as a electrode, it is unable to produce cutting effect. To battle
means of eliminating the risk of complications that had this hindrance, the progressive bipolar devices have a
been observed with monopolar electrosurgery, while at mechanical cut mechanism along in form of blade.
the same time a means of sealing larger vessels. 5
In bipolar electrosurgery, electrical current passes Waveform
through the tissue held between the jaws of the instru-
ment, not through the patient, and results in tissue The waveform applied is similar to that applied during
desiccation and vessel coaptation. Alternating current is monopolar “coag” mode. It is a high-voltage interrupted
standard output for ESUs, and it is this physical property duty cycle current. Best permutation and combinations
that results in efficient sealing of vessels with bipolar are incorporated in the device to achieve a high vessel-
electrosurgery, via change of direction of current flow sealing capacity.
through the tissue compressed between the instrument Advanced Bipolar Electrosurgery
jaws, as orientation of the active and return electrodes
6
rapidly alternates. A major advantage of conventional In addition to the features of conventional bipolar electro-
bipolar over monopolar electrosurgery is the ability to surgery, advanced bipolar energy sources are progressive
seal vessels up to ~5 mm in diameter. The dissection in many ways. Main advance is computer-controlled
capability of the bipolar forceps is good, especially in the tissue feedback system. Newer products floating in the
grasping configuration. Bipolar electrosurgery is gener- market are LigaSure (Fig. 4; Covidien), EnSeal (Fig. 5;
ally available and relatively inexpensive. Disadvantages Ethicon), and Lyons Dissecting Forceps (Fig. 6; Gyrus
of bipolar electrosurgery include lateral thermal spread ACMI). The tissue impedance is monitored with continu-
that will continue until device activation is ceased; no ous adjustment of the generated voltage and current to
audio signal from the ESU to inform the surgeon when maintain the lowest possible power setting to achieve the
desiccation or coaptation is complete, which increases the desired tissue effect, at which time an audio signal alerts
risk of injury from lateral thermal spread as well as tissue the specialist that the terminal point has been achieved.
charring and tissue adherence to the instrument jaws; and In this way, the risk of lateral thermal spread as well
the need for another instrument, such as a laparoscopic
scissor, for tissue cutting. 6

PRINCIPLES OF BIPOLAR ENERGY
Current Pathway

A high frequency electrical current flows from one tong to
the other tong of the surgical pencil, through the interven-
ing tissue (Fig. 3). The tissue within the forceps completes
the circuit. An indifferent electrode is not required as the
patient is not part of the circuit. So, no risk of SCI is seen.

Current Density
The tissue effects of bipolar energy are identified as
desiccation and coaptation depending upon the current Fig. 4: Ligasure
World Journal of Laparoscopic Surgery, September-December 2016;9(3):130-137 133