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|Typical Number in Hospital: 2||Cost Bands: 4||References: 3,4|
As an alternative to the conventional (monopolar) surgical diathermy, in which the electrical current flows from a small active probe through the body to a large indifferent electrode, the path of the current can be constrained to pass only through the tissue being treated. This is achieved using a special forceps in which the two halves of the instrument are insulated from one another and in effect one half becomes the source of the current and the other the destination, thus replacing the active and indifferent electrodes mentioned above.
Bipolar diathermy has the advantage that electric currents do not pass through parts of the body which are not being treated and also it is possible to be much more precise with the quantity of tissue being coagulated. For instance, a small blood vessel gripped between the jaws of the forceps will be coagulated, whereas tissue next to other parts of the forceps will not be heated at all. It is useful in microsurgery, but is often called for in other applications, particularly where there may be interference with the action of a cardiac pacemaker by the stray diathermy currents arising with monopolar systems.
Most modern diathermy machines can support the use of bipolar probes without modification. Older types are generally unsuitable since the indifferent connection to the machine is at earth potential, or is capacitively coupled to earth. An ideal bipolar diathermy current generator should be fully isolated from earth so that there will be no tendency for diathermy currents to circulate in the body to find other routes to earth. This is difficult to achieve at the frequencies used (1-3 MHz).
Content and Design Copyright 2000 Dr. Malcolm C Brown. See Title Page for more details