By the term local anæsthesia, or more correctly local analgesia, is meant the loss of sensibility to painful stimuli without loss of general consciousness. It may be induced in a considerable number of ways, but for practical purposes there are only four methods of value:—(1) by infiltration of the tissues to be operated upon by a solution of the drug, (2) by injecting the solution into or around the nerve trunks supplying the part, (3) by painting the solution on a mucous surface, and (4) by the application of intense cold. The last method has only a limited application. The method of injecting the anæsthetic into the blood vessels of the part is still in the experimental stage and is not to be recommended for general use.
It is advisable first to consider the behaviour of the principal drugs which are employed.
This was the first drug to be widely used for the production of local anæsthesia. It is an alkaloid occurring in the leaves of Erythroxylon Coca. It is only slightly soluble in water—about 1 in 1300, but the hydrochloride of cocaine is freely soluble, and it is this salt that is commonly used for aqueous solutions. The solutions do not keep well, and should be made up shortly before being used. The drug is decomposed by boiling.
Action.—When a solution of cocaine is injected into the tissues, the sensory nerve endings become anæsthetic over the area into which the drug penetrates, direct paralysis of the nerve terminals being produced. When it is injected into or around a nerve trunk it blocks the transmission of nerve impulses. When it is applied locally to a mucous membrane, it produces, besides a loss of sensation, a feeling of constriction and a distinct pallor and contraction of the vessels, which point to a local action on the vessel walls. The drug is very frequently applied to the eye. There it produces not only local anæsthesia, but also contraction of the conjunctival vessels, and this is followed by dilatation of the pupil and often by partial loss of the power of accommodation.
Cocaine Poisoning.—Certain patients show an idiosyncrasy to the action of cocaine, and the greatest care must be exercised in its use. Absorption of small quantities usually causes mental excitement. The patient becomes restless and garrulous, and a feeling of happiness may be produced, but in other cases the patient becomes anxious and confused. In some patients a small dose is followed by a calm languorous state, resembling that produced by morphia, but with less tendency to sleep. The pulse is accelerated, the respiration is quick and deep, and the pupils are dilated. When poisonous doses have been administered, the heart becomes extremely accelerated, powerful tonic or clonic convulsions supervene, the breathing becomes rapid and shallow, and may be finally arrested during a convulsion. In some cases a different set of symptoms are observed, fainting and collapse occur, and convulsive seizures are almost entirely absent. The heart is slow and and weak, the respirations are slow and shallow, the skin is cyanotic and cold, and death takes place from gradual arrest of respiration.
Treatment.—The treatment consists in endeavouring to encourage the action of the heart by every possible means. The patient is placed flat on his back, if he is not already in this position, hypodermic injections of ether and strychnine are administered, and hot coffee given by the mouth; warmth is of great importance. Artificial respiration is commenced if respiration begins to fail. There is no specific antidote to cocaine.
Dosage.—The maximum dose of cocaine that can be given with safety is 3/4 of a grain. The amount of solution that may be employed depends upon the strength. To make a 1 per cent solution, 1 gr. of cocaine hydrochloride is dissolved in 110 minims of distilled water or half strength normal saline; from these proportions the amount of cocaine in a given solution can be calculated. It will be seen that the amount of cocaine solution, even with strengths as weak as ½ or ¼ per cent, that can be used with safety is small and insufficient to anæsthetise an area of any great extent. Owing to its toxicity cocaine has largely fallen out of use for the production of infiltration or regional anæsthesia, though it is still widely used in ophthalmic surgery and in the surgery of the ear, nose and throat.
This drug is immensely superior to cocaine for ordinary surgical purposes. It is the hydrochloride of a synthetic base, its chemical formula being C13H20N2O2, HCl. It is soluble in water 1 in 1, and can be heated to 120°C without decomposition. Its solutions possess slight antiseptic properties, and are capable of repeated boiling without affecting their strength. They may be kept for several months without suffering any change in their action, a quality not possessed by any other anæsthetic agent.
The toxicity of novocaine is one-fifth or one-seventh of that of cocaine. When used in conjunction with adrenalin, its anæsthetic activity is equal to that of cocaine. When injected into the tissues it produces no irritant effects like certain other local anæsthetics, notably stovaine. For the production of local anæsthesia it is used in ½ per cent. solution with the addition of three or four minims of 1 in 1000 solution of adrenalin chloride to each ounce. Several ounces of this preparation may be used with the greatest safety.
Allen makes the following statement regarding this drug:—“After a rather extended experience, including a large number of cases embracing the entire field of surgery, in which this agent has been almost exclusively used, we have failed to note a single case in which there has been any unpleasant local or constitutional action. We, therefore, feel thoroughly justified in unqualifiedly recommending it as the safest, most reliable, and satisfactory of any local anæsthetic agent yet introduced.”
This drug was first isolated from the leaves of the coca plant of Java, but is now prepared synthetically. Its formula is C15H19NO2. Its action is exactly the same as that of cocaine, except that it is one-half as toxic and the duration of anæsthesia is shorter. The hydrochloride is freely soluble in water, and can be boiled without fear of decomposition. It is the agent which is most suitable for spinal anæsthesia, as fewer unpleasant effects have followed its use than that of any other drug.
Stovaine is the hydrochloride of a synthetic compound of the benzoyl group. It occurs as a white crystalline powder, soluble in water, 1 in 14. Its solutions withstand boiling, but are decomposed when heated to 120°C. Its action is the same as that of cocaine, except that it is slightly less toxic and less powerful. It has a distinct irritant effect locally. When injected in dilute solution, it produces a slight burning pain before anæsthesia appears, and very often a distinct inflammatory reaction persists for some time after the operation. It is therefore unsuited for local anæsthesia. It has been widely used for the production of spinal anæsthesia, especially by the French school, but since its injurious effects on nerve tissues have become more apparent, it has been less used than formerly.
Eucaine was introduced as a substitute for cocaine, and, before the introduction of novocaine, was extensively used. It has a similar action to cocaine, and although it is less toxic, it is by no means free from danger unless it is used in very dilute solutions. It is a vaso-dilator, and must therefore be used in combination with adrenalin. It can be boiled without undergoing decomposition, and is practically non-irritant. It has been largely superseded by novocaine.
The use of this drug for purposes of local anæsthesia is still in the experimental stage. It is made by adding urea to a solution of quinine in hydrochloric acid. The crystals are soluble in their own weight of water. For the production of local anæsthesia it is used in strengths of ·25 to 1 per cent. It is free from toxic effects, and its solutions can be sterilised by boiling.
The striking feature about this drug is the extraordinary duration of the anæsthesia, this being from one to six days. It has therefore been used by Crile and other American surgeons to prevent pain during the first few days after operation. The great drawback to its use, however, is that it causes a persistent indurated condition of the tissues which interferes with primary union, and which is sometimes followed by actual sloughing. In addition, it is now established that its use has been followed by tetanus in several cases, and it is recommended that a dose of antitetanic serum should be given immediately before or after the injection of quinine.
Although the action of this drug is of great interest, it cannot be recommended at present for ordinary purposes.
Adrenalin is obtained as an extract from the suprarenal glands of animals. It is a greyish white powder, slightly soluble in water, and readily so in weak acids. The usual preparation is a 1 in 1000 solution of adrenalin chloride in normal saline. It contains ·5 per cent. of chloroform as a preservative. The drawback to the animal extract is that the solution does not keep well, decomposition being indicated by a brownish colour. Of late a synthetic preparation has been introduced, which appears to have the same action, and which can be sterilised by boiling.
The action of the drug is to cause marked vaso-constriction by direct action on the vessel walls. It has no analgesic action, and is used as an addition to solutions of anæsthetic drugs. The advantages of its use are that the action of the anæsthetic is concentrated and prolonged, owing to the delay in absorption, and that the field of operation is rendered practically bloodless. In large doses it may produce toxic symptoms in the form of palpitations and breathlessness, or even actual syncope, so that care is necessary in its use. For purposes of local anæsthesia, it is added to the solution of the anæsthetic drug in the strength of 3 drops to the ounce, and large injections of this dilute solution may be made without risk. At least twenty drops may be safely given.
Local anæsthesia may be induced by the use of anæsthetic drugs in three ways—(1) infiltration anæsthesia, (2) regional anæsthesia, and (3) by application to a mucous surface or to the surface of the eye.
Infiltration Anæsthesia.—In this method anæsthesia is induced by injection of the drug directly into the tissues to be operated upon. This method acts by paralysing the sensory nerve-endings. Although the term anæsthesia is constantly used, it is, strictly speaking, an operative analgesia that is aimed at; it is a paralysis of the pain-conducting fibres, and not of those which conduct purely tactile sensations, the patient being often able to feel the contact of the fingers and instruments during the operation. True anæsthesia can be secured, but it is necessary to use considerably stronger solutions than those that are required for the production of analgesia.
Solution of the Drug.—Novocaine is far superior to any other drug for infiltration anæsthesia. The strength for most purposes is ½ per cent., though some operators find ¼ per cent. quite satisfactory. In specially sensitive parts, such as the nose, throat, or mouth, 1 or even 2 per cent. solutions may be preferable. Sufficient sodium chloride should be added to prevent osmosis of the solution into the tissue cells. The most satisfactory preparation is:—
| Novocaine | 0·25, 0·5, 1 or 2 (¼ to 2 percent.) |
| Normal salt solution (half strength) | 100·0 (·45 per cent. NaCl) |
Fig. 51. All-Metal Syringe for Infiltration Anæsthesia.
Adrenalin is added to the solution in the proportion of 3 drops of 1 in 1000 adrenalin chloride to the ounce, and as much as 6 ounces of this preparation may be safely given. The novocaine solution can be boiled before use, but the adrenalin must not be added until after boiling.
For private practice it is sometimes convenient to procure the novocaine in tabloid form of definite strength combined with sodium chloride. These tabloids are added to the necessary amount of water, and the whole boiled. The adrenalin can then be added.
Choice of Syringe.—The best form of syringe for infiltration anæsthesia is the all-metal syringe illustrated in Fig. 51. It ought to have a capacity of at least 10 c.c. The advantage of the all-metal syringe over glass syringes is that it can be safely sterilised by boiling, and does not get broken. Between the syringe and the needle is a metal segment which is curved so that the needle is set at an obtuse angle to the syringe. This renders the infiltration of the tissues at the proper depth much easier. The needles employed are the ordinary hypodermic needles which are sold in small tubes. The sizes which should be selected are 1 inch, and 3 or 3½ inches. The needle fits into a hole in a small metal mount, which screws on to the intermediate metal portion. This section also is attached to the syringe by a screw, and these screw attachments have the advantage of rendering leakage impossible.
Failing the syringe described, a 10 c.c. Record syringe will be found to be quite efficient, if suitable needles can be obtained. The syringe, needles, and glass measure for the solution should be boiled in plain water or normal saline, as soda interferes with the action of the drug.
Technique of Injection.—The needle is introduced into the subcutaneous tissue, and pushed on slowly to its full length, the fluid being injected as the needle advances. The needle is then partly withdrawn, and pushed in in a different direction so as to infiltrate a fresh area. This procedure is repeated, and as wide an area as possible infiltrated from the one puncture. The needle can then be completely withdrawn and introduced at a fresh point which has already been rendered analgesic. The deeper tissues can nearly always be infiltrated from the surface, but if large blood-vessels traverse the region to be infiltrated, it may be necessary to defer the deeper injection until these have been exposed. It is wise to infiltrate wide of the intended line of the incision, since it is not possible to anticipate with certainty the extent of an operation until it has been commenced. The secret of successful anæsthesia is to employ plenty of the solution, and make the injection thorough.
The skin over the area becomes blanched within a few minutes of the injection owing to the action of the adrenalin. Anæsthesia is not usually complete until ten minutes have elapsed, and the operation should not be commenced until it has been made certain by suitable tests that the anæsthesia is complete. The duration of the anæsthesia is usually at least an hour and a half.
It will be seen that the injection in the manner described above is entirely subcutaneous, the pain-conducting nerves from the skin being caught up by the drug as they traverse the superficial fascia in the area infiltrated. This method usually gives complete satisfaction, but some surgeons advise that the infiltration should be commenced with an intra-dermal injection so as to reduce the pain of the needle punctures to a minimum. A fine needle is employed, the prick of which is practically painless. If the skin at the selected point is pinched up between the finger and thumb, and held firmly, this lessens its sensibility. The needle is advanced beneath the epidermis with a quick but light thrust. The injection into the substance of the skin causes a distinct wheal, which stands out from its surroundings like an urticarial wheal. From this starting-point a long needle can be introduced into the deeper tissues without pain. The intra-dermal injection may be carried along the whole length of the area to be infiltrated, each fresh puncture being made in the margin of the wheal-like area already anæsthetised.
Precautions.—The most careful asepsis is essential throughout. Infiltration with novocaine causes no interference with the healing of the wound, and although cases of sloughing of the tissues have been reported after its use, these are almost certainly due to infection of the wound. Care must be exercised also to avoid injecting the drug into a vein. When this accident takes place, the drug is carried at once into the general circulation, and may reach the higher nerve centres in such quantity as to produce serious toxic results. The use of adrenalin calls for special care and thoroughness in securing all bleeding-points, as, after the effect of the adrenalin passes off, even a slight ooze may increase and give rise to a hæmatoma which may jeopardise the healing of the wound.
In this method of producing anæsthesia, the sensory nerve paths are blocked by injecting the anæsthetic drug into, or around, a nerve trunk. By this procedure complete anæsthesia is produced in the area of distribution of the nerve, and the effect corresponds to a temporary physiological section of the nerve trunk. A temporary motor paralysis is also produced in a mixed nerve.
Technique.—The solution of the drug must be stronger than that employed for infiltration anæsthesia. A 2 per cent. solution of novocaine in half-strength normal saline with the addition of adrenalin is employed. The injection may be paraneural or intraneural.
A paraneural injection is made by passing a needle through the tissues to the known position of a nerve trunk and injecting the anæsthetic around it. The solution gradually diffuses into the nerve tissue, and anæsthesia of the nerve is produced. This method is open to the objection that unless the anæsthetic is accurately placed, no anæsthesia will result, and that in the case of certain nerves there is considerable risk of making the injection into a vein. The latter risk can be avoided by using a glassbarrelled syringe and applying a little suction before the injection is made; if a vein has been pierced, blood will enter the syringe.
The intraneural method is more accurate but requires the expenditure of considerable additional time and trouble, and is only employed where other methods of anæsthesia are not feasible. The tissue over the nerve having been infiltrated, the nerve is exposed by open dissection. It must not be pinched by forceps or other instruments, as such manipulations cause severe pain referred to its peripheral distribution. The injection should be made with the nerve lying in its bed by inserting a fine needle in the long axis of the nerve, first into the sheath, which is infiltrated, and then into the nerve itself. The infiltration of the nerve is continued until it presents a fusiform swelling and this may require from 5 to 15 minims of the solution. Complete anæsthesia of its entire distribution usually results in from five to ten minutes.
A third method of inducing regional anæsthesia—first recommended by Hackenbruch—which is worth mention, is by the production of a ring of infiltration around a peripheral part, such as a finger, or around and underneath a tumour. By this means the nerve fibres are caught up by the anæsthetic and their conductivity interrupted as they enter the area to be operated upon. In dealing with such conditions as a large lipoma, or an umbilical hernia, it may be possible to avoid the use of an excessive amount of anæsthetic solution by employing this method.
It is sometimes stated that local anæsthesia should be limited to small and superficial operations, but with a knowledge of anatomy and of the correct technique, there are few operations which the surgeon cannot undertake with this form of anæsthesia. If we remember that the mortality from the anæsthetic is practically nil, it is obvious that it is often the duty of the operator to give the patient the choice of local anæsthesia. In urgent conditions in which the administration of a general anæsthetic would be attended with great danger, it is often a life-saving measure. Either infiltration or regional anæsthesia may be used alone; in some cases it is convenient to combine the two methods.
Regional anæsthesia is sometimes employed in operations on the upper extremity in conditions, such as diabetic gangrene or advanced cardiac disease, where a general anæsthetic is contra-indicated. In similar conditions in the lower extremity, spinal anæsthesia is usually preferred, though it is quite possible to anæsthetise the lower limb by blocking the sciatic, femoral, and lateral cutaneous nerves with a local anæsthetic. Crile lays great stress on the blocking of nerves with a local anæsthetic during operations on the limbs as a means of preventing shock, even where a general anæsthetic is being employed. The effect of the local anæsthetic is to prevent the impulses which produce shock from passing up to the higher centres. Only those methods which are applied to the upper extremity need special description.
Anæsthesia of the Whole Arm.—The nerves of the upper extremity are all derived from the brachial plexus except the intercosto-brachial. This nerve, which is the lateral cutaneous branch of the second intercostal, crosses the axilla and pierces the deep fascia on the medial side of the arm. It supplies the skin on the dorsal part of the medial aspect of the upper arm. The lateral cutaneous branch of the third intercostal nerve sometimes crosses the axilla also, and reaches the medial side of the arm. Injection of the brachial plexus produces complete analgesia of the shoulder and entire arm, and is particularly suited to high amputations and disarticulations at the shoulder. If the area supplied by the intercosto-brachial is encroached upon, this can be anæsthetised by infiltration with a few drams of solution injected subcutaneously along the floor of the axilla from its lateral and posterior borders.
Method.—The injection may be intraneural or paraneural. The intraneural is made after exposing the plexus by an incision under infiltration anæsthesia from the junction of the middle and lower thirds of the sterno-mastoid to the union of the middle and lateral thirds of the clavicle. It is found lying on the scalenus medius and each of its branches is separately injected with a few drops of 5 per cent. solution of novocaine containing a few drops of adrenalin to the ounce.
The paraneural injection is less satisfactory, since the nerves are too large to be readily penetrated in effective quantities by the anæsthetic solution, and since there are numerous veins in the neighbourhood into which the solution may be accidentally injected with dangerous results.
The injection is usually made above the clavicle. In this region the plexus lies mainly above and to the lateral side of the third part of the subclavian artery, the lowest trunk lying directly behind the vessel as it rests on the first rib. The position of the artery is first localised with the finger by its pulsations, and the skin and subcutaneous tissue infiltrated immediately above the mid-point of the clavicle. From this point a long fine needle, unattached to the syringe, is passed downwards, backwards, and medially in the direction of the second or third thoracic spine. The distance to which the needle penetrates varies from 2 to 4 c.m. When the plexus is reached a slight radiating pain is felt down the distribution of the radial or median nerve. At this point the needle is held stationary, the syringe attached, and the injection made. The reason for not attaching the syringe earlier is that should the artery be entered, blood will flow. This accident is of little consequence, the needle being withdrawn slightly and introduced a little more laterally. About 10 c.c. of a 2 per cent. solution of novocaine and adrenalin is injected; the needle is then slightly withdrawn and a further 10 c.c. injected in the neighbourhood. Anæsthesia occurs in from three to fifteen minutes.
Fig. 52.—Point at which the needle is introduced in paraneural injection of brachial plexus.
The individual nerves of the upper limb can be readily injected. The median can be exposed at the bend of the elbow for an intraneural injection, or a needle may be passed under the tendon of the palmaris longus at the wrist for a paraneural injection. The ulnar can be easily reached as it lies on the posterior aspect of the medial epicondyle of the humerus for a paraneural or intraneural injection. The superficial radial can be reached for a paraneural injection about two inches above the wrist to the lateral side of the tendon of the brachio-radialis (supinator longus). The injection is made into the deep fascia, and carried across the lateral border of the forearm for about an inch, to ensure reaching all the branches of the nerve.
The medial antibrachial (internal) cutaneous can be blocked on the front of elbow by a paraneural injection about half an inch medial to the biceps tendon, and the lateral antibrachial cutaneous (musculo-cutaneous) at a corresponding point on the other side of the tendon.
Anæsthesia of the Arm below the Elbow.—In operations below the elbow, in conditions in which a general anæsthetic is not permissible, as in diabetes, nephritis or advanced cardiac disease, a full anæsthesia can be obtained by intraneural injection of the median, ulnar, and radial (musculo-spiral) nerves, combined with paraneural injection of the medial and lateral antibrachial cutaneous. The median and radial are each exposed by an incision under infiltration anæsthesia, the radial being exposed in the groove between the brachialis and brachio-radialis. The infiltration to expose the median nerve usually blocks the anterior branch of the medial antibrachial cutaneous. To make certain that the posterior branch is also anæsthetised, it is advisable to inject a little anæsthetic solution over the front of the medial epicondyle. The intraneural injection into the ulnar nerve can often be made without exposing it.
Anæsthesia of Finger.—The paraneural method applied to the digital nerves at the root of the finger gives perfect results. A circle of anæsthetic solution is first injected round the root of the finger. The needle is then passed through the infiltrated skin on each side of the finger, and a few drops of ½ per cent. novocaine solution injected around the nerves. Complete anæsthesia of the finger results in a few minutes.
In the Lower Limb injection of individual nerves is rarely employed, as anæsthesia is easily obtained by the method of spinal analgesia. The lateral cutaneous can be injected as it lies immediately medial to the anterior superior iliac spine emerging from under cover of the inguinal ligament. This procedure may be useful in obtaining skin grafts, the grafts being taken from the antero-lateral aspect of the thigh. Amputations in the middle third of the thigh have been performed by injecting the sciatic, the posterior cutaneous (small sciatic), the femoral (anterior crural), and the lateral cutaneous at the root of the limb. The obturator nerve is difficult to find and anæsthetise in such cases. Operations below the knee can be painlessly performed by this method of anæsthesia.
Tracheotomy.—This operation is conveniently and safely performed under infiltration anæsthesia. The anæsthetic solution is injected in the usual way in the line of the incision down to the trachea but not into it, as the trachea itself is insensitive to pain.
Goitre.—A parenchymatous or adenomatous goitre can be readily removed under local anæsthesia, though the administration of ether by intra-tracheal insufflation is usually to be preferred. The principal nerve supply to the field of operation is derived from the cervical plexus, whose branches become superficial about the middle of the posterior border of the sterno-mastoid. An intradermal injection may be made first at this point, and a longer needle then passed down to the posterior border of the muscle, and an area of infiltration produced. From this point the needle is directed first upwards and then downwards round the margin of the goitre so as to produce a zone of infiltration. The same procedure may be repeated on the opposite side, so that the whole gland is surrounded with a zone of infiltration with a special depot of solution around the branches of the cervical plexus. Where only one lobe is involved, it is sufficient to carry the injection down in the middle line after one side has been encircled. When the sheath has been incised and the surface of the gland exposed, the isthmus is infiltrated and divided. The affected half of the gland is then rolled outwards, and the attachments between the posterior aspect of the gland and the larynx and trachea are infiltrated, special attention being paid to the upper pole. The rest of the operation can then be carried out painlessly.
Exophthalmic Goitre may also be operated upon under local anæsthesia after a preliminary hypodermic injection of morphia and scopolamin, though many operators prefer a general anæsthetic on account of the nervous state of the patient. In bad cases a procedure which is often of great value is ligature of the superior thyroid artery on both sides under local anæsthesia. After ligature of the vessels a colloid degeneration takes place in the gland, and the symptoms of hyperthyroidism subside. After a delay of two or three months it may be possible to carry out the radical operation with little or no danger. The incision is two and a half inches in length, and crosses transversely the central part of the thyroid cartilage. The line of the incision is infiltrated with novocain solution in the ordinary way, and both superior thyroid arteries exposed and ligatured.
The greater part of the wall of the thorax is supplied by the intercostal nerves. In front the supraclavicular nerves come down as far as the second intercostal space or sometimes as far as the nipple, and the lateral and medial anterior thoracic nerves supply the pectoral muscles, sending a few twigs to the overlying skin. The long thoracic nerve extends down the side of the chest, supplying the serratus anterior. The intercostal nerves can be blocked in the region of the angles of the ribs and the supraclavicular by carrying a line of infiltration along the clavicle. The anterior thoracic can be blocked by deeper injections. In this way the greater part of the chest wall and the pleura can be anæsthetised.
Acute Empyema.—This operation should always be performed under local anæsthesia. Exhaustion from septic absorption and from the antecedent pneumonia or other disease, with the dyspnœa from the pressure of the pus on the lung may render a general anæsthetic highly dangerous. The method of producing local anæsthesia is simple and easily carried out. A point is selected on the rib which is to be resected a short distance behind the line of the incision and an intra-dermal injection made with a fine needle. A long needle is then substituted and passed down to the upper border of the rib until it reaches the plane between the external and internal intercostal muscle, the injection being continued lightly as it advances. When the desired point is reached one or two drams of the solution are injected. The needle is then slightly withdrawn and passed to the lower border of the rib to reach the same plane and the same procedure carried out. The infiltration is then carried along the line of the incision or it may be made to pass obliquely upwards to the rib above and obliquely downwards to the rib below so as to catch up the nerves coming from behind into the area of operation. The anæsthesia of soft parts, bone, and pleura is perfect after the above injection.
The anterior abdominal wall, including the anterior parietal peritoneum, is supplied by the lower six intercostal nerves, the last thoracic nerve, and the ilio-hypogastric and ilio-inguinal nerves from the first lumbar. It is a very interesting and important fact that, although the parietal peritoneum is exceedingly sensitive to touch and pain, the visceral peritoneum and the viscera themselves are insensitive. When operations are performed under local anæsthesia of the abdominal wall, the viscera can be freely handled or incised without the patient experiencing the slightest discomfort, provided that the parietal peritoneum is not put upon the stretch by traction on the mesentery or other peritoneal attachment. Thus the colon can be opened twenty-four or forty-eight hours after being brought outside the abdominal wall without any anæsthetic in the operation of colostomy. Local anæsthesia is therefore well adapted to cases in which a small amount of manipulation of the viscera is required, and where a general anæsthetic would be dangerous, as in grave cases of intestinal obstruction and in cases of carcinoma of the œsophagus with weakness and loss of flesh from starvation.
Gastrostomy.—This operation is commonly performed under local anæsthesia and may be taken as an illustration of the procedure employed. The incision is made through the middle of the left rectus and is about two and a half or three inches long, beginning about an inch below the costal margin. An intradermal wheal is established at the middle of the proposed incision. A long needle is entered at this point and passed first upwards and then downwards in the line of the incision, infiltrating the subcutaneous fat as it goes. The needle is then passed in through the anterior wall of the rectus sheath, this being easily recognised as a plane of decided resistance. The needle is advanced a little inside the sheath, the injection being continued as it advances. The same procedure is repeated at various points along the line of the incision. The extra-peritoneal fat may be infiltrated in the same way, the posterior wall of the sheath being identified as a deeper plane of resistance and gently pierced. This step may be deferred until the posterior wall of the sheath has been exposed. The infiltration may be completed by forming a line of intradermal infiltration along the line of incision, though this last step can often be omitted.
The abdomen can then be opened painlessly. The only step in the operation which may cause a little discomfort is the traction which may be necessary to bring the shrunken stomach down from under cover of the ribs. The incision into the stomach is quite painless.
Gastro-enterostomy can be performed under local anæsthesia, the only special step required being infiltration of the meso-colon before it is perforated.
Appendicectomy is not suitable, as a rule, for local anæsthesia. If the cæcum is fixed or the appendix bound down by adhesions, the traction necessary to bring the appendix to the surface causes considerable pain.
In Acute Obstruction, when the procedure of enterostomy has been decided upon owing to the gravity of the patient’s condition, local anæsthesia is often of great value. The abdominal wall is infiltrated in the manner described, and a distended loop of bowel brought to the surface and sutured to the parietal peritoneum. A Paul’s tube can then be introduced.
Inguinal Hernia. Local anæsthesia is specially suited to cases of strangulated hernia, but it may be employed in the ordinary case. It should be pointed out that spinal anæsthesia gives equally good results and is less troublesome to carry out.
The injection is commenced with a fine needle a little beyond the lateral end of the proposed incision. An intradermal wheal is produced at this point, a long needle introduced into the subcutaneous tissue, and about half-an-ounce of anæsthetic solution injected in this position. The needle is then passed downwards and medially, and the subcutaneous fat infiltrated in the line of the incision. The needle is then partly withdrawn and again advanced until it reaches the resistance of the aponeurosis of the external oblique. This is gently pierced and about half-an-ounce of solution injected underneath so as to block the ilio-hypogastric and ilio-inguinal nerves. In most cases this is all that is necessary. As additional precautions the line of incision may be infiltrated intradermally, and an injection may be made around the neck of the sac after it is exposed.
Femoral Hernia.—A femoral hernia may be anæsthetised by infiltration along the line of the incision, or by injecting around the circumference of the hernia after the method of Hackenbruch. After the sac has been exposed and defined, it is necessary to inject some novocaine solution around the neck, care being taken to avoid the femoral vein which lies on the lateral side.
Umbilical Hernia.—Local anæsthesia is sometimes of great value in dealing with umbilical hernia, especially if it is strangulated, in stout patients who are bad subjects for a general anæsthetic. The injection is best made around the circumference of the hernia. Several intradermal injections are made at points around the swelling, and through these the long needle can be introduced and the deeper tissues infiltrated. If the muscles are fairly well defined and can be felt, they may be infiltrated at the commencement, but it may be advisable in fat subjects to inject only the subcutaneous tissues to begin with, and to delay the injection of the muscles and extra-peritoneal fat until the sac has been opened and a protecting finger can be introduced to guard the intestines. Omental adhesions can be divided without causing pain. If the intestines are extensively adherent to the sac it is better to infiltrate the points of adhesion, as extensive manipulation may cause cramp-like pains.
After the circumferential injection has been made in these cases, it is best to wait for ten or fifteen minutes before making the incision in order to allow the anæsthetic solution to diffuse.
Suprapubic Cystotomy.—In operations for drainage of the bladder local anæsthesia is highly successful. The skin and subcutaneous tissues are infiltrated in the line of the incision. The needle is then carried between or through the recti muscles and several drams injected into the layer of fat in front of the bladder. It is unnecessary to inject the wall of the bladder itself.
Hæmorrhoids.—In patients in whom there is some contra-indication to the use of a general anæsthetic the removal of hæmorrhoids can be carried out quite safely and painlessly under local anæsthesia. A circumferential injection is first carried out round the muco-cutaneous junction. It is best to start the infiltration about an inch out from the anus as the skin immediately around the anal orifice is extremely sensitive. The infiltration is made subcutaneously, and each re-insertion of the needle is made just short of where the previous injection stopped. When the circumferential injection has been completed, a finger is passed into the rectum, and the long needle introduced through the anæsthetised area, injecting as it advances, to a depth of about 2½ inches, keeping just outside the sphincters. Four such injections are made, one on each side of the bowel, one in front and one behind, from 5 to 10 c.c. being injected in each position.
Anæsthesia results almost immediately and the anal canal can be readily dilated.
The Tongue.—For the Whitehead operation of removal of one half of the tongue, complete anæsthesia can be obtained by the infiltration method. A long needle is introduced at the tip of the tongue, and the injection carried in the middle line to a point behind the tumour. The mucous membrane of the floor of the mouth and the glosso-palatine fold are infiltrated, and a last injection made across the affected half of the tongue well behind the tumour.
The tongue can be anæsthetised also by blocking the lingual nerve with a paraneural injection. The nerve lies under the mucous membrane of the mouth opposite the last molar tooth. If the tongue is drawn well over to the opposite side, the nerve can be felt and the injection made around it. The only drawback to this method is that it does not anæsthetise the posterior third, which is supplied by the glosso-pharyngeal nerve.
Operations on the Skull and Brain can be readily performed by infiltration of the scalp. In the later stages of the recent war, a large proportion of operations on the skull and brain were performed under local anæsthesia. The brain itself is insensitive to touch and painful stimuli, and infiltration of the scalp is all that is necessary. A 1 per cent. solution of novocaine with adrenalin has been commonly employed, and is injected into the subaponeurotic space so as to surround the field of operation with a wall of anæsthetic solution—the method of Hackenbruch. The advantages are that hæmorrhage is reduced to a minimum, and the head can be conveniently and safely elevated and the intra-cranial tension thus reduced.
For Operations on the Eye.—Analgesia is obtained by the instillation of a few drops of a 4 per cent. solution into the conjunctival sac. This is repeated two or three times, and analgesia is obtained in five or ten minutes. It may be necessary to repeat the instillation during the course of the operation.
For Operations on the Nose, Pharynx, or Larynx cocaine is commonly used. A 5 or 10 per cent. solution is employed and is merely painted on the surface. Care must be taken that such strong solutions are not swallowed.