Heat, moist or dry, is the simplest of all sterilizing methods. It is used in dry and in moist form. The most resistant spores are those of anthrax, which is supposed to be a laboratory germ, one not seen in practice. Most of the imported catgut is made from the intestines of sheep, and sheep die frequently (on the Continent) of anthrax; it will thus be seen that the danger of an anthrax infection is not so remote as might first appear, and that no precautions are sufficient which do not include a degree of heat and length of exposure sufficient to kill these germs. In the operating-room, as in the laboratory, has been introduced the method of “fractional,” i. e., repeated sterilization. Most of the materials thus exposed may be left in superheated steam under pressure from thirty to sixty minutes. They are then exposed once or twice more to the same heat at intervals of twenty-four hours. In order to make heat thoroughly useful its effects should permeate everything which it is expected to so sterilize; hence the addition of steam under pressure, especially when dressings, towels, etc., are folded. It is well to have a form of sterilizer that permits steam to be turned off and drying to be accomplished slowly by the aid of dry heat.
Next to steam thus utilized is boiling water, in which nearly everything can be sterilized. Silk sutures and silkworm-gut may also be sterilized in this way; animal suture does not permit of it unless previously hardened. The effectiveness of boiling water is increased by adding to it 1 per cent. of sodium bicarbonate, by which its boiling point is raised.
Dry heat is employed in an oven, or its equivalent, preferably in some apparatus by which temperature can not only be measured but maintained. In such a mechanism it is well to have the temperature raised to 300° F. for at least half an hour, and then let its contents cool slowly.
Another method of sterilization is by using volatile or easily volatilized chemicals, such as formalin in its fluid form, or its equivalent called paraform, which comes in crystals or may be had in tablets ready for use. Formalin is a powerful bactericidal agent, and if used in such form as to be sure of its penetration, good results may be expected. Some materials and instruments which are injured by steam or dry heat may be kept in an atmosphere of paraform, or sterilized by exposure to formalin vapor, being then subsequently protected against exposure in a sealed package. Catheters which have been boiled or cleansed can be thus exposed, as Hutchings has shown, and can be regarded as safe for use. They can, moreover, be resterilized in the same way. Naphthalene has similar properties, but is not quite so strong. The writer is accustomed to use one or the other of these in jars or receptacles containing dry dressings, catheters, and rubber gloves.
If aseptic methods are practised there will be but little use for the employment of any antiseptic, either in solution or in any other form.
Boiled water and sterile salt solution should be available for all purposes. It is customary, however, to have a solution of mercuric chloride on hand, which is colored in order that it may not be mistaken for any other, in which to rinse the hands, especially after they have been in alkaline solution.
The first thing to be sterilized should be that part of the body upon which operation is to be made. In some cases, as about the feet, the mouth, etc., this preparation should be begun two or three days beforehand; in other cases twelve to twenty-four hours will suffice. Preparation should be begun with soap, nail-brush, and razor, the parts being thoroughly cleansed and shaved. It is then customary with most operators to keep a moist and antiseptic dressing applied upon surfaces thus cleansed, which should be protected from drying by a covering of oiled silk or rubber tissue. Green soap is usually employed, which may have added to it a small percentage of carbolic acid or lysol. The mercurial preparations are too irritating to the skin. Carbolic acid has the reputation of being absorbed rapidly. On tender skins and in certain parts of the body it is impossible to make such applications, especially of soap poultices. Under these circumstances repeated washings and some protection should be practised. Feet upon which operations are to be made should be soaked repeatedly and scrubbed. Twenty-four hours previously to operating on the head the scalp should be shaved—preferably forty-eight hours—and prepared as above. For operations in the mouth the tooth-brush and antiseptic mouth-washes should be frequently used. For those in the vagina, douches, etc., should be frequently administered.
The preparation of the field of operation includes a final scrubbing, with a washing of alcohol or alcohol and ether. The hands and external clothing of the surgeon and his assistants should be sterilized, also the towels, suture materials, instruments, and dressings.
Lawson Tait was the first to teach the great value of absolute and mere cleanliness. This applies in large degree to the hands of the chief operator and of the assistants. With a large amount of scrubbing and cleansing of the hands it is not possible to put them into a condition of ideal sterilization. This is perhaps more true of the hands of some than those of others. A realization of this fact has led to the introduction of gloves, either thin rubber or cheap cotton. The former may be used repeatedly. The latter are sterilized by repeated boiling and may then be used again. Rubber gloves may be sterilized by steam or boiling water, and may be cleansed with soap and water or one of the stronger antiseptic solutions. The introduction of rubber gloves has brought great improvement in results. The gloves, however, constitute an impediment to some of the finer work and the easy recognition of tissue. Not the least important of the advantages of rubber gloves is the protection they afford to the surgeon’s hands and to other patients. Many accidental infections may be saved the operator if his hands can be kept out of pus, while the use of gloves permits the operator to pass from a pus case to a clean one without exciting fear. A snugly fitting glove is best drawn upon the dry hand by the aid of sterilized talcum. But the hand which it encloses should have been previously thoroughly sterilized so that it will not be a source of danger should the glove be pricked or torn. The operator can keep his hands in more favorable condition by using gloves dry in this way than by macerating his hands inside of wet ones.
The question of hand sterilization is an important one, whether the gloves are to be worn by some or all of the operating staff. There are occasions when it is important to make the hands absolutely clean because no gloves can be procured. Even the hands encased in gloves should be thoroughly prepared, as there is no knowing when the glove may tear and the surgeon’s bare hand come into contact with the patient’s tissues. Running water is preferable to a basin filled with it, for while it runs it carries away such material as may be detached by soap or nail-brush. If it be not possible thus to wash the hands, then repeated basins of sterilized water should be used, and all the crockery or metal ware used in the process should be sterilized, so that the hands will not be contaminated by handling unsterilized material. Nail cleaners are essential agents, to be vigorously used, and nail-brushes should be sterilized after each using, and there should be a separate brush for each operator. The common soaps and even the officinal green soap are not sterile. The former should be relied on only for the first cleaning, and the latter should be sterilized before use. A dirty hand should not be thrust into a receptacle containing freshly sterilized green soap. The outside coating of dirt should first be removed by an ordinary soap. Vegetable fiber has been recommended by many, but it is not as good as ordinary corn-meal, which should be sterilized before using. It is not as gritty nor as keen as sand, and yet it is sufficiently rough to serve admirably the purposes of a curry-comb. A first scrubbing with common soap and a nail-brush, followed by green soap with corn-meal, and this by a thorough use of the nail cleaner and a clean nail-brush, will ordinarily serve to put the hands in a reliable condition. It is the practice of some to add antiseptics to the soap, e. g., lysol and thymol. A number of years ago I introduced ordinary mustard flour for this purpose, basing its use upon the fact that the essential oil of mustard is one of the most potent of the vegetable antiseptics, in addition to its power as a deodorizer. (Parenthetically it may be said that when unpleasant odor attaches to the unprotected hands after making a postmortem examination, or opening an offensive collection of pus, the use of mustard will quickly remove the taint.) Even mustard is not absolutely reliable, nor is anything else which can be tolerated by the human skin. A method much in vogue a few years ago was to wash the hands in a solution of potassium permanganate, and then to decolorize the skin in another strong solution of oxalic solution. This method was at one time regarded as an effective one, but it is severe upon the skin. Another method in use at present combines commercial chloride of lime with saleratus; here free chlorine is supposed to be the active agent.