Gangrene
Gangrene implies death with putrefaction of
macroscopic portions of tissue. It is commonly seen affecting the distal part of
a limb, the appendix or a loop of small intestine, and sometimes organs such as
the gallbladder, the pancreas or the testis. Note that the term necrosis applies
mainly to the death of groups of cells, although it is extended to include bone,
i.e. a sequestrum. A slough is a piece of dead, soft tissue, e.g. skin, fascia
or tendon.
Secondary to arterial obstruction from
disease, for example:
•
thrombosis of an atherosclerotic artery;
•
embolus from the heart in atrial fibrillation or after coronary
thrombosis;
• arteritis with neuropathy in diabetes;
• Buerger’s disease;
• arterial shutdown in Raynaud’s disease or ergotism;
•
effect of intra-arterial injections — thiopentone and cytotoxic
substances.
Infective:
boils and carbuncles, gas gangrene, gangrene of the
scrotum (Fournier’s gangrene).
Traumatic:
direct, such as crushes, pressure sores and the constriction groove of
strangulated bowel; or indirect, due to injury of vessels at some distance from
the site of gangrene, e.g. pressure on the popliteal artery by the lower end of
a fractured femur.
Physical, e.g.
burns, scalds, frostbite, chemicals, irradiation and electricity.
Venous
gangrene: see Chapter 16.
Clinical features of gangrene
(Fig 15.4
and Fig 15.5)
A gangrenous part lacks arterial pulsation,
venous return, capillary response to pressure (colour return), sensation, warmth
and function. The colour of the part changes through a variety of shades
according to circumstances (pallor, dusky grey, mottled, purple) until finally
taking on the characteristic dark brown, greenish black or black appearance,
which is due to the disintegration of haemoglobin and the formation of iron
sulphide.
Clinical types
Dry gangrene occurs when the tissues are desiccated by gradual
slowing of the bloodstream; it is typically the result of atherosclerosis. The
affected part becomes dry and wrinkled, discoloured from disintegration of
haemoglobin and greasy to the touch.
Moist gangrene occurs when venous as well
as arterial obstruction is present, when the artery is suddenly occluded, as by
a ligature or embolus, and in diabetes. Infection and putrefaction are always
present, the affected part becomes swollen and discoloured, and the epidermis
may be raised in blebs. Crepitus may be palpated, owing to infection by
gas-forming organisms. Moist gangrene is manifest also in such conditions as
acute appendicitis and strangulated bowel.
Separation of gangrene
Separation by demarcation
A zone of
demarcation between the truly viable and the dead or dying tissue appears first.
It is indicated on the surface by a band of hyperaemia and hyperaesthesia.
Separation is achieved by the development of a layer of granulation tissue which
forms between the dead and the living parts. These granulations extend into the
dead tissue until those which have penetrated farthest are unable to derive
adequate nourishment. Ulceration follows and thus a final line of demarcation
(separation) forms which separates the gangrenous mass from healthy tissue.
In dry
gangrene, if the blood supply of the proximal tissues is adequate, the
final line of demarcation appears in a matter of days and separation begins to
take place neatly and with the minimum of infection (so-called separation by
aseptic ulceration). Where bone is involved, complete separation takes longer
than when soft tissues alone are affected, and the stump tends to be conical as
the bone has a better blood supply than its coverings.
In moist
gangrene, there is more infection and suppuration extends into the
neighbouring living tissue, thereby causing the final line of demarcation to be
more proximal than in dry gangrene (separation by septic ulceration). This is
why dry gangrene must be kept as dry and aseptic as possible, and why every
effort should be made to convert moist gangrene• into the dry type.
Vague
demarcation; spread of gangrene; skipping and die-back. In many cases of
gangrene from atherosclerosis and embolism, the line of final demarcation is
very slow to form or does not develop. Unless the arterial supply to the living
tissues can be improved forthwith, the gangrene will spread to adjacent tissues
or toes, or will suddenly appear as ‘skip’ areas further up the limb. Signs
of skipping should always be carefully looked for. Black patches suddenly
appear, perhaps on the other side of the foot, on the heel, on the dorsum of the
foot or even in the calf. Infection, another cause of the spread of gangrene,
may spread upwards beyond the line of separation along the lymphatic vessels or
cellular tissue into healthy parts; extensive inflammation then results. Except
in diabetic gangrene without concomitant atherosclerotic obstruction, these
forms of spread do not usually respond to efforts to save the limb and an
above-knee amputation becomes necessary. To attempt local amputation in the
phase of vague demarcation is to court failure, as gangrene reappears in the
skin-flaps (‘die-back’).
Treatment of gangrene
General
principles
A
limb-saving attitude is needed in most cases of symptomatic gangrene affecting
hands and feet. The surgeon is concerned with how much can be preserved or
salvaged3. With arterial disease all depends upon there being a good
blood supply to the limb above the gangrene, or whether a poor blood supply can
be improved by such measures as percutaneous transluminal angioplasty or direct
arterial surgery. A good or an improved blood supply indicates that a
conservative excision is likely to be successful and a major amputation may be
avoided. A life-saving amputation is required for a badly crushed limb, rapidly
spreading symptomatic gangrene and gas gangrene.
General treatment
includes that of cardiac failure, atrial fibrillation and anaemia, to improve
the tissue oxygenation. A nutritious diet, essential in all forms of gangrene,
and the control of diabetes, when present, are additional items of care. Pain,
especially night pain, may be difficult to relieve. Nonaddictive drugs should be
used whenever possible.
Local
treatment
Care of
the affected part includes keeping it absolutely dry. Exposure and the use of a
fan may assist in the desiccation and may relieve pain. The limb must not be
heated. Protection of local pressure areas, e.g. the skin of the heel or the
malleoli, is required otherwise fresh patches of gangrene are likely to occur in
these places. A bed-cradle, padded rings, foam blocks and air beds are useful
preventive aids. Careful observation of a gangrenous part will show whether the
lifting of a crust, or the removal of hard or desiccated skin, will assist in
demarcation, the release of pus and the relief of pain.
Varieties of gangrene
Diabetic
gangrene
Diabetic
gangrene is due to three factors. These are:
•
trophic changes resulting from peripheral neuritis;
• atheroma of the arteries resulting in ischaemia;
•
excess of sugar in the tissues which lowers their resistance to infection
(Fig. 15.33), including fungal infection.
The
neuropathic factor impairs sensation and thus favours the neglect of minor
injuries and infections, so that inflammation and damage to tissues are
ignored. Muscular involvement is frequently accompanied by loss of reflexes
and deformities. In some cases, the feet are splayed and deformed (neuropathic
joints). Thick callosities develop on the sole and are the means whereby
infection gains entry, often following amateur chiropody. Infection involving
fascia, tendon and bone can spread proximally with speed via subfascial planes.
Clinical
examination and investigations include those on the urine and blood for
diabetes. Palpable dorsalis pedis and posterior tibial pulses, and the absence
of rest pain and intermittent claudication, imply that there is no associated
major arterial disease. A bacteriological examination is made of any pus. A
radiograph may help to reveal the extent of any osteomyelitis.
Treatment.
The diabetes must be brought under control by diet and appropriate drugs. The
gangrene is treated along the
Direct
traumatic gangrene is due to local injury and may arise as a result of crushes,
pressure (as in the case of splints or plasters) or bedsores. Gangrene following
severe injury, e.g. a street accident in which a vehicle passes over a limb, is
of the moist variety and excision without delay is usually indicated. Amputation
may be performed as close to the damaged part as will leave the most useful
limb.
Bedsores
(syn. decubitus ulcers) are predisposed to by five factors — pressure, injury,
anaemia, malnutrition and moisture. They can appear and extend with alarming
rapidity in patients with disease or injury of the spinal cord and other
patients with debilitating illness. It is important to recognise patients at
risk and take adequate prophylactic measures. These measures include the
avoidance of pressure over the bony prominences, regular turning of patients and
nursing on specially designed beds, which reduces the pressure to the skin.
These beds include the high air loss Clinitron bed, low air loss Mediscus bed
and the very low air loss OSA 1000. There are advantages in not blowing large
quantities of air around the ward, and also advantages in being able to
articulate the patient, yet removing the increased pressure and sheer forces
produced by such articulation (Chapter 33). Preventive measures are of the
utmost importance. Thus pressure over bony prominences is counteracted by a
2-hourly change of posture and protection by foam blocks. A water bed or a
ripple bed is sometimes desirable. Injury due to wrinkled draw-sheets and
maceration of the skin by sweat, urine or pus is combated by skilled nursing and
the use of an adhesive film such as Opsite (Fig. 15.34).
A
bedsore is to be expected if erythema appears which does not change colour on
pressure. The part must be kept dry. An aerosol silicone spray may be used.
Actual bedsores may be treated either by lotions or by exposure to keep them as
dry as possible. Once pressure sores develop, they are extremely difficult to
heal. They should be kept clean and débrided, and the use of rotation flaps
should also be considered. The haemoglobin of the patient should be maintained
at a normal level by transfusions of packed cells if needed. If the patient is
young and otherwise healthy, excision of the dead tissue and flap pedicle skin
grafting is often successful.
•
from pressure by a fractured bone in a limb or by strangulation (Fig.
15.35) (strangulated hernia, Chapter 62);
•
thrombosis of a large artery following injury;
•
ligation of the main artery of a limb, as after division by injury;
•
poor technique for local digital anaesthesia. The combination of a
tourniquet and an adrenaline-containing local anaesthetic solution can lead to
permanent occlusion of all the arteries (Chapter 30).
Treatment
directed to the cause, e.g. closed or open reduction of a fracture
together with direct arterial surgery for the damaged vessel, will usually
prevent the onset of gangrene. The limb must be kept cool, so as to reduce
metabolism to the minimum. When gangrene is slow to develop, a line of
demarcation will indicate the level of vitality. If moist gangrene occurs and
spreads rapidly, amputation may be needed to save the patient’s life.
Ergot
Ergot,
a cause of gangrene among dwellers on the shores of the Mediterranean Sea and
the Russian steppes who eat rye bread infected with Claviceps purpurea, also
occurs in migraine sufferers who, for
Physical
and chemical causes of gangrene
Frostbite
is due to exposure to cold, especially if accompanied by wind or high altitude
(e.g. climbers and explorers). It is also encountered in the elderly or the
vagrant during cold spells (Fig. 15.37). Pathologically, there is damage to the
vessel walls, which is followed by transudation and oedema. The sufferer notices
severe burning pain in the affected part, after which it assumes a waxy
appearance and is painless. Blistering and then gangrene follow.
Treatment.
Frostbitten parts must be warmed very gradually. Any temperature higher than
that of the body is detrimental. The part should be wrapped in cottonwool and
kept at rest. Friction, e.g. rubbing with snow, may damage the already
devitalised tissues. Warm drinks and
clothing
are provided and powerful analgesics are required to relieve the pain which
heralds the return of circulation. Paravertebral injection of the sympathetic
chain may be helpful in relieving associated vasospasm. Amputations should be
conservative. Hyperbaric oxygen (Chapter 4) may help.
Trench
foot is due to cold, damp and muscular inactivity; it is predisposed to
by tight clothing, such as garters, puttees and ill-fitting boots. Prophylaxis
is of paramount importance. Numbness is followed by pain, which is excruciating
when boots are removed. The skin is mottled like marble and, in severe cases,
blisters containing bloodstained serum develop; moist gangrene follows. The
pathology is similar to that of frostbite and the treatment is essentially the
same.
Inadvertent
intra-arterial injection of thiopentone can happen when a high division
of the brachial artery results in one of its two terminal branches, usually the
ulnar, passing superficially downwards in the antecubital fossa. The
appreciation by palpation of pulsation of the vessel and of the withdrawal of
bright red blood prior to injection should prevent this calamity. Injection
causes immediate and severe burning pain, with blanching of the hand. The needle
should be left in position, and 5 ml of I per cent procaine and/or 2 per
cent papaverine sulphate injected to reduce vascular spasm. Dilute heparin
solution may also be given intra-arterially if the needle is in position.
Intra-arterial thrombolysis and intravenous low molecular weight dextran may be
employed. Brachial block should also be performed and repeated as necessary.
Even so, gangrene of one or more fingers may occur.
Drug
abuse. Inadvertent arterial injection of drugs is becoming common in
many countries with significant numbers of drug addicts. usually the femoral
artery in the groin is involved, and presentation is with pain and mottling
distally in the leg. Often all pulses down to ankle level are retained. If
pulses have been lost, angiography and intra arterial thrombolysis may be
considered (possibly with dextran and heparin in addition). If pulses are
retained, dextran and heparin may be given but there is no firm evidence of
their efficacy in this condition. Many cases are self-limiting and resolve
spontaneously. It should be remembered that many of these patients carry the
human immunodeficiency virus (HIV) or have frank acquired immunodeficiency
syndrome (AIDS).
Chemical
gangrene. Carbolic acid (phenol) is the most dangerous, as anaesthesia
masks the pain which occurs before the onset of gangrene. Carbolic compresses
should never be used, for fingers have been lost by application of
compresses even as dilute as 1:80. The gangrene is due to local arterial spasm.
In addition, there is danger of severe systemic effects from absorption of
phenol. Local bicarbonate soaks should be applied. Later, excision of the slough
and skin grafting are necessary.
Ainhum
(Fig. 15.38), a disease of unknown aetiology, usually affects
black males (but some females) who have run barefoot in childhood.
Venous
gangrene is discussed in Chapter 16.