LOCAL ANÆSTHESIA.
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.
Cocaine.
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
¾ 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.
Novocaine.
This drug is immensely superior to cocaine for ordinary surgical
purposes. It is the hydrochloride of a synthetic base, its chemical
formula being C_{13}H_{20}N_{2}O_{2}, 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.”
Tropacocaine.
This drug was first isolated from the leaves of the coca plant of Java,
but is now prepared synthetically. Its formula is C_{15}H_{19}NO_{2}.
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.
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.
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.
Quinine and Urea Hydrochloride.
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.
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.
Induction of Local Anæsthesia
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 100·0 (·45 per cent. NaCl)
strength)
[Illustration: 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.
Regional Anæsthesia.
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.
Methods of Application of Infiltration and Regional Anæsthesia.
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.
Operations on the Upper Extremity.
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.
[Illustration: 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.
Operations on the Neck.
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.
Operations on the Thorax.
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.
Operations on the Abdomen.
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.
Analgesia from the Application of Cocaine to the Eye or to
a Mucous Surface.
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.