GAS GANGRENE

PREVENTION (1) Do a thorough wound toilet (54.1).(2) In high risk wounds (see above) give the patient penicillin 1.5 megaunits 4 hourly, or tetracycline. Start immediately after the injury.

DIFFERENTIAL DIAGNOSIS Gas gangrene is not the only cause of gas in the tissues. Air sometimes escapes into them in surgical emphysema. In ischaemic gangrene, there is no toxaemia, unless the gangrenous tissue becomes secondarily infected. Neither of these should cause difficulty. There are however two other conditions where the diagnosis is not so obvious. Both require drainage and penicillin or tetracycline but neither needs radical muscle excision.

Suggesting anaerobic cellulitis Infection is limited to the patient’s subcutaneous tissues. Spread may be rapid and there may be much subcutaneous gas. Sometimes his whole abdominal wall is involved. When you remove the affected tissue, the muscle underneath appears healthy, and bleeds and contracts normally. Remove the necrotic tissue, and drain the wound.

Suggesting anaerobic streptococcal myositis Spreading redness and swelling originating in a stinking discharging wound with Gram positive cocci and pus cells in its exudate. The patient’s muscles are boggy and pale at first, then bright red and later pale and friable. The characteristic toxaemia of gas gangrene does not develop. Make radical incisions through his deep fascia to relieve tension and provide drainage.

TREATMENT FOR GAS GANGRENE

NURSING Isolate him from other surgical patients. If possible, barrier nurse him. ANTIBIOTICS Give the patient 10 megaunits of benzyl penicillin daily for 5 days as four 6 hourly doses.

Or, give him tetracycline 0.5 g intravenously or 1 g orally every 6 hours.

Culture his wound, do sensitivity tests, and if necessary change his antibiotics.

Although clostridia are not sensitive to metronidazole (2.7), some other anaerobic bacteria are, so give it.

ANTITOXIN There should be no need to use this in most wounds. If you give it, do a skin sensitivity test first. Then give him pentavalent gas gangrene antiserum intravenously and repeat it after 4 to 6 hours.

RESUSCITATION Transfuse him rapidly, and keep a drip running during the operation. EXPLORATION Do this in a septic theatre, or even in the out-patient department, and not where clean cases go for operation.

Open the patient’s wound, enlarge it if necessary, lengthwise in his limb, and cut his deep fascia throughout the whole length of the skin incision.

Excise all infected muscle widely. Remove: (1) Any black crumbling muscle. (2) Any muscle which is swollen and pale and looks as if it has been boiled. (3) Any muscle which does not contract when you pinch it. (4) Muscle which does not bleed. (5) Muscle which contains bubbles of gas. If necessary, remove whole muscles from their origin to insertion, part of a large muscle, or a whole group of muscles. Close his wound later by secondary suture.

AMPUTATION If a patient’s limb is disorganized by injury or infection, amputate it, especially if he shows signs of severe toxaemia. X–ray it first to see how far the gas has reached. Amputate under a tourniquet. When you have amputated, his toxaemia should improve rapidly.

CAUTION! Close the stump by delayed primary suture, even if you think you are amputating through healthy tissue.

POSTOPERATIVE CARE He may develop septic shock if he has not already done so (53.4). Expect, and treat as best you can, the dehydration, vomiting, delirium, jaundice, and anuria (53.3) that he may develop.

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Figure 54.14: SEVERE GAS GANGRENE. This followed an intramuscular injection by an unqualified person, but it could equally well have followed a severely contaminated wound. Photograph by Dr. D. Fry, Cameroun. With the kind permission of the Editor of Tropical Doctor.