It is imperative in the application of endothermy that no
alcohol, ether, or other inflammable liquid be used on or near the area to be
treated, as the spark will set fire to any such liquid. Inflammable or
explosive anesthetics must also be avoided.
Cosmetic
desiccation of superficial lesions usually requires no anesthesia. For the
epilation of hypertrichosis, no anesthesia is used. For all other lesions a
solution of procaine is administered by injection. Instillation of a few drops
of 1 per cent procaine should be made before operations on or near the eye. Anesthesia is often obtained by infraorbital
or inferior dental nerve block with 2 per cent procaine solution.
It is
advisable to test the size and character of the spark upon a metal instrument
before using it for treatment. The spark for most lesions should be clean,
cold, regular, and should not feather.
The
desiccating current may be applied to the lesion by a sewing needle directly
connected with the generator by a cable. Another method is to have the patient
grasp an indifferent electrode so connected, while the operator draws the
current from the lesion with a sewing needle. The operator's fingers are placed
in contact with the patient, and by increasing or lessening the amount of this
contact, the intensity of the spark drawn from the lesion by the sewing needle
may be regulated.
Coagulation
and cutting generally require that the patient be in the recumbent position and
receive local or general anesthesia by sodium pentothal or other noncombustibles.
The use of a
bipolar current requires an indifferent electrode. This is conveniently
attached by a cable to an aerial. Various forms of indifferent electrodes are
used. The most satisfactory is a metal plate, measuring about 6 by 8 inches,
with rounded corners. This is covered with two thicknesses of a towel soaked in
hot saline solution. It is important that a strong solution of not less than 10
per cent should thoroughly saturate the towel, as weaker solutions offer
resistance to the current and may induce scalding, especially if the patient is
unconscious. A strong soap solution may be substituted for the saline.
The flat
electrode is placed upon the trunk and so bandaged in position that the
moistened towel interposed between it and the skin makes contact with the body
at all points. It may be bandaged over the chest or abdomen or placed under the
back or hips, where the weight of the body holds it in place. Modifications of
this form of electrode may be strapped on the upper arm or hand. In minor
operations a tubular electrode may be held in the patient's hand. Much loss of
time and annoyance are caused by patients dropping the tubular electrode at
critical moments during operations; therefore firm fixation of
the indifferent electrode to the patient is advisable. The
electrodes must always be in position prior to the diathermy current being
turned on, and must not be removed from contact until it is turned off. If
these precautions are not taken, sparks between the body surface and the
electrode will occur and are likely to burn adjoining parts. Moreover, contact
by any one with the indifferent electrode or the exposed end of the active
electrode or the skin of the patient may produce burns from the sparks.
The active electrode is screwed into
the end of a holder connected by a flexible cable to the instrument. It is very small and may be of various shapes and sizes. For coagulation it may be the shape of a disk or ball, a knife blade, or a needle. When the lesions are superficial and small, a ball or a flat circular disk-shaped electrode is preferable to a needle. This placed in contact with the lesion, with the current turned on, causes destruction to a depth of 2 Or 3 cm., depending on the time and the strength of the current. This method avoids any traumatism from the insertion of a needle. The length of the knife blade or needle to be used as the active electrode depends upon the thickness of the area under treatment. The point of the electrode is inserted into the lesion as deeply as necessary to coagulate the entire mass thoroughly. Unless the electrode is promptly applied to the tissue, sparks from it will produce undesirable charring. Enough current should be used sufficiently long to blanch the entire mass and the marginal tissue to a dark gray. Care should be exercised in coagulating tissues close to bone or cartilage because if the periosteum or perichondrium is destroyed, healing is delayed. When indicated, however, the bony structure can be completely destroyed and removed.
The cutting
current may be applied with a needle, a small knife blade, or various sized
wire loops. The large wire loops are useful for the snaring of papillomatous
growths, and the smaller ones make possible the making of biopsies without
bleeding. The needle and small knife blade are specially adapted to the removal
of portions of the tongue, or for the circumvallation of local malignant
growths of the skin or mucous membrane. The technique for building a barrier of
a coagulated, impermeable wall in the healthy tissues around and beneath
malignant growths is described under the terms "circumvallation."
Before any application to the cancer is made directly, a wall of coagulation
and necrosis is made surrounding the growth completely. The wall of coagulated
tissue seals the blood and lymph channels about the lesion, as well as beneath
it, thus isolating the growth from the surrounding structures and mechanically
preventing the dissemination of viable cells and subsequent metastasis. After
the lesion has been isolated, as outlined, tissue may be safely taken for
microscopic examination since all blood and lymph drainage from the affected
part has been cut off. The tumor itself is then coagulated, after which the destroyed
mass is removed.
When large
blood vessels are encountered in the use of the cutting current, the electrode
may be pushed directly into the bleeding vessel, or the vessel may be grasped
with forceps and the electrode applied to the forceps at any place between the
fingers and the bleeding. The current then courses down the forceps and
extensively coagulates the bleeding vessel.
Secondary
hemorrhages do not often occur, but have happened in isolated instances. When
work is done in close proximity to large blood vessels a preliminary ligation
is advisable.
Pain and
charring are proportionate to the heat of the spark. After-pain is minimal due
to the blocking of the sensory nerve supply by the cutting current. Observance
of the rules of asepsis and the use of isotonic solutions for injection
decrease postoperative edema and the chances of infection, which sometimes is
responsible for after-pain. Charring is invariably objectionable, as it forms a
superficial carbon barrier over the treated area which restricts the deep
action of the current and later delays healing.
As a measure of precaution it is best to
remove the desiccated, coagulated, or charred areas because they favor secondary infection, except where the destruction is very superficial. In this case, for cosmetic purposes less scarring seems to result if the thin, desiccated layer is left in place, and kept soft by the application of creams. For removal of the destroyed areas, the curet, forceps, and scissors or the cutting current is used. The purpose of dressings is to keep the wound clean, relieve after-pain and swelling, and keep the edges soft. For immediate postoperative use borated Vaseline is desirable. Treated lesions should be cleansed morning and night, or oftener, with pieces of cotton soaked in boric acid solution. The frequency is indicated by the amount of discharge. Hemor-rhage may be caused by dry, sticky dressings. Collodion dressings should never be employed, as the oozing which usually follows treatment makes them ineffective and favors secondary infection. The formation of hard crusts should be prevented. Occasionally, as a complication of healing, exuberant granulation tissue develops. It should be removed by silver nitrate.