Surgery, with Special Reference to Podiatry Part 32

+Technic.+ Various methods of accomplishing the insensitization of a part may be employed. Thus, if the skin alone is to be incised, it alone will require injection and by careful insertion of the end of the needle it may be kept just under the epidermis, thus injecting the anesthetic endermatically in and about the papillae of the papillary layer.

+Endermic Method.+ This method is an end-organ anesthesia, and the solutions employed are strong and act because of their drug content.

It is not in any sense a pressure anesthesia. The skin should be picked up and pinched hard for the better insertion of the needle directly into the skin substance. It is therefore endermic and the skin is seen to become blanched as the needle advances delivering its solution on the way. But little of the fluid is pressed out as the needle advances. When the syringe is empty or the needle has advanced to the limit of its length, refill and insert just inside of the last blanched spot and proceed in a line until the end of the contemplated line of incision is reached.

Pressing out too much of the solution at one time causes a burning sensation and should therefore be avoided as the only pain should be that of the initial p.r.i.c.k of the needle. Care, however, should be taken to inject just sufficient of the solution to penetrate beyond the zone of operation laterally, to insure sufficient s.p.a.ce for the insertion of sutures into anesthetized tissues. Only a small quant.i.ty of fluid is necessary in this procedure as it comes in direct contact with nerve terminals. By touching the injected line with the needle in several places along its length and inquiring of the patient if it is felt, we may make sure of the completeness of the anesthesia before making the incision which should begin and end inside the anesthetized area.

+Subdermic Method.+ An appreciable area of skin and subcutaneous tissue may be incised by anesthetizing as previously described, together with depositing the fluid well under the skin, thus affecting many terminal nerve branches before they reach their final distribution in the skin, and widening the anesthetized area considerably.

This method is applicable to such work as the removal of small growths, and the deep incision of a carbuncle. Beneath the skin in the loose connective tissue the fluid is deposited and causes anesthesia by acting upon the nerves just before their emergence into the skin.

The two methods may be combined. It is not possible to inject directly into thin skin or mucous membrane and it is therefore employed in such operations as circ.u.mcision, where the nerve terminals must be anesthetized by the diffusion of the anesthetic from its position under the skin. A little time should be allowed before beginning the operation to permit of the diffusion of the drug. This applies also to such operations as that for ingrown toe-nail where the deeper tissues down to the root of the matrix are involved.

+Edemitization Method.+ This is the method of Schleich and it is to him that the credit must be given for a procedure which has done more to encourage the use of local anesthetics in operative surgery than any other. He employed weak solutions of cocaine and other local anesthetics in great volumes of water in order to gain the combined action of both drug and of pressure. The method is described under the heading of "Cocaine." It was designed to obtain anesthesia with cocaine with the elimination of the toxic effects of the latter.

There are decided disadvantages to the filling up of the tissues with fluid; healing is delayed; relations are distorted and coaptation of the edges is difficult. This is probably the method of selection where an indefinite amount of manipulation is expected and where the length and depth of the incision may need to be augmented. A large quant.i.ty of a very weak solution is employed and the tissues in all directions are injected until visibly distended.

+Nerve Blocking Method.+ By injecting a small quant.i.ty of a fairly strong anesthetic solution either directly into a nerve or beneath its sheath, the entire area supplied by it will be anesthetized. This method of nerve blocking may be spoken of as _endoneural_ when the injection is made directly into the nerve trunk, and _perineural_ when made into its sheath or immediately outside of the nerve. The injection of fluid around nerves too small to inject directly is also spoken of as perineural nerve blocking. (Hertzler).

+DRUGS EMPLOYED+

The essential qualities of a good local anesthetic are:

1. Reliability in producing anesthesia.

2. Const.i.tutional and local harmlessness.

3. Non-irritating qualities.

4. Ability to be rendered aseptic by boiling.

No one local anesthetic can be exclusively relied upon to fulfill all of these requirements at all times. Each one has its advocates and from the large number offered, it is possible to select several which, while not being perfect, are preferable to cocaine in that they obviate the disagreeable train of symptoms peculiar to that drug.

By local anesthetics are understood certain chemical compounds, weak solutions of which, when brought in contact with sensory nerves paralyze them without lastingly injuring them. This effect is dependent upon the presence in these agents of certain atom groups which Ehrlich named _anesthiferous_. It is possible that just these atom groups enter into certain chemical combinations with the nerve substance and that the nerve thus remains paralyzed until the newly formed compounds are split up and the poison is washed away by the circulating blood.

Cocaine is the original type of a local anesthetic. Einhorn has made possible its synthetic production and has also opened the field for a great number of experiments of scientific and practical importance leading to the discovery of new local anesthetics obtained by exchanging the non-anesthiferous atom groups of cocaine for other groups different for each of the various new agents; thus eucaine, orthoform, anesthesine, alypin, and others have been obtained.

+Cocaine+ occurs as a white, crystalline powder, readily soluble in water and in alcohol. It is an alkaloid which effects all living protoplasm. It first excites, then paralyzes. In greater concentrations it paralyzes immediately. Its effect is very ephemeral, producing no lasting harm to the cocainized protoplasm. Its effect is most readily understood by a.s.suming that cocaine poisons the protoplasm by entering with it into combinations which are easily broken up. The products of decomposition, among which cocaine cannot be recovered, are slightly or not at all poisonous and are carried away by the circulation.

+Effect on the Mucous Membrane.+ The external application of cocaine in solutions of varying strengths has been of great service since its introduction by Roller in 1884, and many operations on the eye and on its coverings are now greatly facilitated, by reason of its use. Small quant.i.ties only are required, hence there is little fear of its toxicity. Its anesthetic qualities by contact are also made use of in operations in and about the nose and throat. Here comparatively mild solutions are used liberally but care must be exercised against its noxious effects; it is usually employed in freshly prepared solutions which are held to be less toxic. Where extensive areas of mucous membranes are to be anesthetized, as in the r.e.c.t.u.m or urethra or bladder, one of the less toxic drugs is preferable.

+Strength of Solutions.+ In the eye, it is customary to employ a 4 per cent. solution. For work in the nose, 2 per cent. is generally considered sufficient. In the latter connection, it is often combined with adrenalin solution in small amounts to mitigate its depressing effects as well as to control bleeding. The latter effect is but transient and is omitted by many as unsatisfactory because of the more profuse subsequent hemorrhage. In this respect cocaine and adrenalin are similar. They both cause constriction of the minute superficial vessels and immediate blanching of the membrane; work in the nose is hence greatly facilitated, the field of operation being clear and enlarged by the shrinkage of the encroaching membrane, but it is inc.u.mbent upon the operator to keep his patient under observation at least an hour after the completion of the operation that he may be certain of the degree of hemorrhage after the effects of the drugs have pa.s.sed away. For the above reason many operators prefer a general anesthetic or one of the local anesthetic drugs which exert no constrictor action so that they may know, _ab initio_, the exact degree of bleeding.

Whatever drug is used, strong solutions are seldom necessary for application to the mucous membranes but the necessary time for its absorption is a prime requisite. To secure anesthesia of the conjunctiva and cornea, the solution is dropped into the eye at the outer canthus and as it flows off with the tears, it must be replenished three or four times until anesthesia is accomplished. In the nose, a spray over the site of incision or a pledget of cotton saturated with the anesthetic solution and allowed to rest in contact with that locality, will suffice. The flow of mucus from the nasal mucosa is stimulated by the presence of the cotton pledget and it soon becomes entirely coated with a thick mucus which no longer is able to impart to the membrane its anesthetic solution and must therefore be renewed several times before complete insensibility of the part is a.s.sured. The topical application of a strong solution on a cotton wound applicator to a limited area or spot is also efficient.

+Application by Injection.+ In order to bring the anesthetic in contact with the nerves, it is necessary, where a skin surface is to be incised, to inject the solution as already described. The technic, previously detailed, applies here, and any of the methods may be employed for the injection of solutions of cocaine, some preferring a single method to the exclusion of all others. The locality to be treated will also influence the operator as to method.

+Endermically.+ The endermic method is the one most generally employed in securing cocaine local anesthesia by injection. The papillary layer of the skin is well infiltrated with a mild solution (one-eighth per cent. to one-half per cent.), frequently with adrenalin 1-1000, in the proportion of 15 to 20 drops to the ounce of the solution. The strongest of the formulas of Schleich may also be used for endermic infiltration.

The skin is injected to a fair degree of tension and a white ridge marks the line of injection which should be sufficiently extensive to permit the manipulation of the cut edges.

+Edemitization.+ Schleich's solutions are here of extreme value because large amounts of solution are necessary to produce the degree of distention required because of the minute quant.i.ty of cocaine present, though the added salt and morphine a.s.sist considerably.

+Nerve Blocking and Perineural Blocking.+ Here a stronger solution must be employed; 1 per cent., or even stronger, is injected in small quant.i.ties, either into the substance of the nerve or under its sheath, as already described.

+Strength of Solution.+ Schleich has worked out a method whereby very weak solutions of cocaine may be used advantageously. His plan is to enhance the action of the drug by the admixture of morphine in minute quant.i.ties and of sodium chloride in proper strength. These substances, in themselves, were found to possess anesthetic powers.

Large quant.i.ties of Schleich's solutions may be injected-even several ounces, without ill effects as they contain so little cocaine. The formulas used by him are:

1. Cocaine hydrochlorate 0.2 Morphine hydrochlorate 0.02 Sodium chloride 0.2 Distilled water 100.

2. Cocaine hydrochlorate 0.1 Morphine 0.02 Sodium chloride 0.2 Distilled water 100.

3. Cocaine hydrochlorate 0.01 Morphine 0.005 Sodium chloride 0.02 Distilled water 100.

It will be seen that the strength of cocaine in the respective solutions is from one-fifth to one-hundredth of a gram.

The solutions used in the early days of cocaine anesthesia were much stronger than were found necessary afterward and it has now become the rule to employ weak solutions and to give them time to penetrate the tissues. The less toxic action of mild solutions, even when like amounts of the drug are employed, makes it inc.u.mbent upon the operator to follow this plan and the element of time is so important in the matter of securing a perfect local anesthesia that it is customary to wait fifteen or twenty minutes after the completion of the injection before making the incision. The weakest solution possible is the one of choice in the use of this anesthesia.

+Toxicology.+ The repeated use of cocaine in the same patient should be avoided on account of the danger of establishing the cocaine habit.

The drug should be given with the greatest care, especially in operations about the head, neck, face, and urethra, as several deaths and many alarming cases of syncope, delirium and paralysis or tetanic fixation of the respiratory muscles have followed its use. Because of its marked depressing effect upon vital organs, it should never be given unless the patient is in the rec.u.mbent position. The administration of one drop of a one per cent. solution of trinitrin given at the first onset of the const.i.tutional effects and repeated if necessary every five minutes, will entirely prevent any unpleasant effects as it is a true physiologic antidote.

If the surgeon has a case in which he intends to use large amounts of cocaine, it is best to have at hand and ready for use the following agents: a hypodermic and a rectal syringe, a battery, cardiac and respiratory stimulants, oxygen, and a catheter.

If the patient becomes very delirious and is in no way depressed, chloral or hyoscine should be given. In all cases of cocaine poisoning the patient should be catheterized to prevent re-absorption and should then be treated symptomatically.

Strong solutions should never be employed for any purpose except in cases where, by previous experience with the mild ones, it is known that no idiosyncrasy exists.

The central nervous system, and next the sensory and motor nerves, are affected by cocaine. Respiratory paralysis follows the introduction of appreciable amounts of cocaine into the circulation and respiratory depression may follow the introduction of smaller quant.i.ties. A given quant.i.ty of the drug in great dilution will, under normal conditions, give no toxic symptoms, whereas the use of the same amount in a more concentrated form will give rise to pallor, cyanosis and even syncope and collapse. It is said that a maximum dose of cocaine can never be fixed; this, however, seems of less importance than knowing the minimum dose, for while it is true that many bear it well, this drug so frequently gives rise to toxic symptoms, and the idiosyncrasy for it is so common, that one can never be certain of an exact dosage.

Various pharmacopias place the maximum dose at 0.05 grm. (about seven-eights of a grain).

Bearing in mind that a great dilution of a given amount makes for safety, we are astonished to learn that 7 c. c. (about 2 drams), of a 1 per cent. solution introduced into the urethra has caused death.

(Czerny).

Hertzler cites numerous instances in which a few drops of a more concentrated solution (2 per cent. to 4 per cent.) have caused death.

It is therefore obvious that the use of this drug must be guarded by a technic so perfect that but the smallest quant.i.ty of a very weak solution shall be permitted to enter the circulation.

+Adjuvants, Subst.i.tutes and Safeguards.+ The numerous disadvantages in the general use of this most efficient but most treacherous local anesthetic have operated so strongly that efforts have constantly been made to find a substance which, when used with it, would correct its toxic effects.

The desirability of employing large quant.i.ties of an anesthetic solution so as to enable the operator to infiltrate large areas of tissue has led to the method of preparing very dilute solutions and mixing them with various chemical substances which in themselves would act as mild anesthetics and at the same time increase the diffusibility of the cocaine. With any of these substances, cocaine still remains toxic and the quant.i.ty injected must be kept account of when an operation of any extent is being performed even though the solution be never so mild.

A valuable preventive to this absorption is found in the application of a constricting band or tourniquet to impede the return circulation and allow the washing out of much of the drug before the obstruction is removed. It is evident that no method has yet been devised whereby the use of cocaine is rendered safe and it is for this reason that chemists throughout the world have sought to produce either a new anesthetic drug or to evolve a drug synthetically, from cocaine, minus its toxicity. This has been done, but cocaine still has its adherents because of its superior qualities.

Quinine and urea hydrochloride is one of the new subst.i.tutes which has found much favor. Among the synthetic derivatives may be mentioned alypin, novocaine, stovaine, betaeucaine, tropacocaine, anesthesin, subcutin and many others. Each of these has its advocates and all of them have some advantage over cocaine; they have disadvantages as well, which, however, in the hands of skilled operators, may be overcome.

+Quinine and Urea Hydrochloride.+ Among the quinine salts and combinations, the above has found most favor. It consists of a molecule of quinine hydrochloride and one of urea. It occurs as a fine crystalline powder and is readily soluble in water, forming an acid solution.

This substance is one of the most recent and best subst.i.tutes for cocaine, being capable of a wide range of usefulness and practically devoid of any toxicity. It causes redness on being injected and, in strong solutions, may delay healing considerably, this const.i.tuting the main disadvantage to its use. After the use of this anesthetic, primary union is not usual.

In a one per cent. solution, anesthesia is accomplished by any of the methods already described. Weaker solutions require a more perfect technic, and are therefore not generally employed. They, however, are indicated where it is imperative to secure primary union and when for some reason no other local anesthetic is available. The scar formation which almost always follows the use of this anesthetic would indicate that some other drug be employed in operations about the face and neck. This anesthetic is preferred by many because of its safety in large quant.i.ties and because of the length of insensibility following the injection of solutions of from 1 per cent. to 2 per cent.

strength.

Notwithstanding knowledge of the facts above enumerated as to the difficulty of primary union and the likelihood of scar formation in connection with the use of urea and urea-hydrochloride for purposes of local anesthesia, this drug is still considered a most valuable and useful one for providing local anesthesia for operative purposes.