LOCAL ANESTHESIA
Ethyl Chlorid
Ethyl chlorid is a colorless, mobile liquid, which boils at 52° F. This is furnished in thirty- and sixty-gram glass tubes, sealed with a metal screw cap or spraying device. As this cap is removed the liquid in the tube begins to boil, owing to the temperature of the room, or, better, the operator’s hand, and a fine vapor spray is ejected from the opening.
The tube end is held from six to eight inches from the part to be anesthetized. Immediately the skin is frosted over and the lanugo hairs become covered with snow. The skin turns white and becomes slightly elevated, appearing to be thickened; at the same time the patient feels a stinging pain in the area. This may be overcome greatly by first smearing the part with sterile vaselin. In a few moments the skin is frozen and rendered antalgic, and operations of short duration can be performed. The only disadvantage with this method is that the part to be operated on is frozen stiff, hence the skin cannot be neatly dissected away from the subcutaneous tissue as under other local anesthesia, nor can the tissues be moved about as readily, as in the case with flap operations, owing to this stiffness.
The parts thaw out quickly with a returning sensitiveness, and it may be necessary to apply the spray repeatedly until the operation has been completed. If elastic constriction can be employed, the antalgic effect is more quickly produced and more lasting.
As the parts thaw out there is considerable prickling, which can be mitigated by applying sponges soaked in hot sterilized water. More or less redness of the skin will be noted even for some time after the operation.
Cocain
(Methylbenzoylecgonin)
(Gädeke, Nieman, Bennett, Koller.) Cocain is the alkaloid derived from several varieties of Erythroxylon coca. It should appear as a permanent white crystalline powder in colorless prisms or flaky leaflets. The salt used for anesthetic purposes is the hydrochlorid; it is soluble in 0.4 part water, 2.6 parts alcohol, 18.5 parts of chloroform, and insoluble in ether.
Locally applied on mucous membranes and open wounds, it exerts an analgesic effect, but not of the unbroken skin. Punctures or abrasions are necessary to permit of absorption in this event. When locally applied it paralyzes the peripheral sensory nerves, and at first blanches the parts by reason of its active contraction on the arterioles, which is soon followed by marked congestion.