GANGRENE AND VARICOSE (STASIS) ULCERS

Necrosis due to primary blood circulatory disorders is referred to as gangrene.

Causes:

• extensive crushing;

• severe pressure on tissues;

• vascular injuries;

• organ compression (e.g. POP bandage);

• volvulus with compression of the vessels;

• leaving the tourniquet on a limb for a long time;

• vascular thrombosis and embolism;

• obliterating endarteritis;

• obliterating arteriosclerosis.

Most commonly acute and chronic arterial occlusion lead to gangrene.

Dry gangrene is caused by fast dehydration of the necrotic tissues without bacterial contamination.

This results in tissue mummification. In wet gangrene, colliquative tissue necrosis occurs, which is usually complicated by an ichorous infection, with subsequent disintegration of the devitalised tissue and severe intoxication. The tissue debris is dirty-green or black in colour and smells very offensive.

Gangrene resulting from acute ischaemia of an organ is accompanied by severe ischaemic pain that is normally felt below the level of vascular occlusion. The colour of the limb changes very fast from pale to marble-bluish; it becomes cold and skin sensations disappear.

In dry gangrene, the gradual drying up of the necrotic area is followed by a clear-cut demarcation between the intact and necrotic areas (fig. 126, colour inset). The skin becomes black, which is accompanied by minimum, if at all, intoxication. In wet gangrene the patient's condition is generally severe from the very onset (fever, tachycardia, chills, thirst, and dehydration) because of absorption of ichorous tissue disintegration products into circulation.

Over the areas of necrosis (often in the foot and the lower third of the leg) the skin becomes bluish with dark-red patches and haemorrhagic blisters. The extremity is oedematous, enlarged, and dirty-greyish tissues with offensive odour are visible (see fig. 126, colour inset).

Once the signs of necrosis appear, the limb is to be immobilised and an aseptic dressing applied.

The treatment of necrosis depends on its cause. The common strategy of the management of all types of necrosis is the removal of the necrotic tissue, or necrectomy.

Necrectomy requires that several parallel incisions be done in the necrotic area without anaesthesia and an antiseptic dressing be applied (see «Antiseptics»). This contributes to the removal of the degenerated necrotic tissues and, therefore, reduces the intoxication of the body.

Necrectomy can be performed with a scalpel or scissors (mechanical necrectomy), proteolytic enzymes (chemical necrectomy), physical factors - ultrasound or laser rays (physical necrectomy).

It is advisable:

• in progressive wet gangrene, to undertake above-knee amputation (without waiting for tissue demarcation) without delay;

• in dry gangrene, to first allow the demarcation line appear and then amputate the limb above it within the intact area.

As a form of necrosis a varicose ulcer is an intractable defect in the skin or mucous membranes (fig. 127, colour inset) which usually develops after the necrotic tissue has fallen off.

The aetiologic factors responsible for the development of varicose ulcers are as follows:

1. Traumas:

a) burns

— chemical;

— thermal;

— radiation;

— electric;

b) frost bite;

c) extensive degloving wounds of whatever origin.

2. Chronic blood or lymph circulatory disorders: chronic arterial and venous insufficiencies, elephantiasis.

3. Diseases of the nervous system:

a) injury to the peripheral nerves;

b) syringomyelia;

c) tabes dorsalis.

4. Metabolic disorders:

a) diabetes mellitus;

b) vitamin deficiency.

5. Systemic disease:

a) connective tissue disorders;

b) haematological conditions (anaemias, haemorrhagic and myeloproliferative disorders).

6. Infections:

a) tuberculosis;

b) syphilis;

c) leprosy;

d) erysipelas;

e) systemic fungal infections.

7. Tumours (disintegration of malignant tumours).

Whatever its cause, the signs of impaired tissue nutrition, or degeneration, and tissue decay, or necrosis, are evident in a varicose ulcer.

Degeneration can be classified as follows:

1. localized:

• vascular defect;

• the effect of trauma;

• tumour lysis;

2. generalised:

• systemic diseasel;

• metabolic disorders.

Types of varicose ulcers.

• Vasculogenic ulcers are commonly due to the cessation of blood or lymph flow into or out of the area.

• Post-traumatic, or scar-associated, ulcers, develop because the scar tissue affects circulation around the wound, which leads to degeneration.

• Neurotrophic ulcers result from defective sensory innervation.

In surgical practice, the commonest varicose ulcers are those caused by blood circulatory disorders of the extremities (chronic arterial or venous insufficiency).

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