- It is an infective gangrene caused by clostridial organisms involving mainly skeletal muscle as oedematous myonecrosis.
- Earlier it was called as malignant oedema.
- Source and Predisposing Factors
Contaminated, manured or cultivated soil, intestines are the sources. Faecal fl ora commonly contains clostridial organisms enters the wound; in presence of calcium from blood clot or silica (silicic acid) of soil, it causes infection.
It is common in crush wounds, following road traffi c accidents, after amputations, ischaemic limb, gunshot wounds, war wounds. Injury or ischaemia or necrosis of the muscle due to trauma predisposes infection.
Anaerobic environments in the wound—initial infection with aerobic organism utilises existing oxygen in tissues creating anaerobic environment to cause clostridial sepsis.
- Gram-positive, central spore bearing, nonmotile, capsulated organisms, most common—60%.
- Clostridium oedematiens.
- Clostridium septicum.
- Clostridium histolyticum.
- Various strains include—A, B, C, D, E. ‘A’ strain is most common.
Note: Nonclostridial gas producing organisms like coliforms can also cause gas gangrene.
- Lecithinase is important toxin which is haemolytic, membranolytic and necrotic causing extensive myositis. It splits lecithin into phosphocholine.
- Haemolysin causes extensive haemolysis.
- Hyaluronidase helps in rapid spread of gas gangrene.
- Proteinase causes breaking down of proteins in an infected tissue.
- Spores enter through the devitalised tissues commonly in road traffic accidents, crush injury → Spores germinate → Released bacteria will multiply → Exotoxins are released. cause their effects
- Extensive necrosis of muscle with production of gas (hydrogen sulphide; nitrogen; carbon dioxide) which stains the muscle brown or black anaerobic myositis/myonecrosis.
Usually muscle is involved from origin to insertion.
- Often may extend into thoracic and abdominal muscles.
- When it affects the liver it causes necrosis with frothy blood—foaming liver, is characteristic.
- Rapidly spreading infection which is also often fatal.
- Limbs are commonly involved; but organs like liver can also be affected.
- Muscle glycogen is broken down into lactic acid, CO2 and hydrogen. Proteinase released by organism forms amino acids which further releases ammonia and hydrogen sulphide.
- Acid released earlier is neutralised by ammonia and calcium to progress further multiplication of organisms.
Incubation period is 1-2 days.
- Features of toxaemia, fever, tachycardia (out of proportion
to fever) pallor.
- Wound is under tension with foul smelling discharge (sickly
sweety/decaying apple odour).
- Khaki brown coloured skin due to haemolysis.
- Crepitus can be felt.
- Jaundice may be ominous sign and also oliguria signifi es renal failure.
Frequent sites are adductor region of the lower limb and buttocks and subscapular region in upper limb.
- Clostridium welchii can infect limbs, abdominal wall, appendix, gallbladder, common bile duct, intestine, uterus (during septic abortion).
- Fulminant type causes rapid progress and often death due to toxaemia, renal failure or liver failure or MODS or ARDS.
- Massive type involving whole of one limb containing fully dark coloured gas fi lled areas.
- Group type: Infection of one group of muscles, extensors of thigh, fl exors of leg.
- Single muscle type affecting one single muscle.
- Subcutaneous type of gas gangrene involves only subcutaneous tissue (i.e. superfi cial involvement). It is mainly of anaerobic cellulitis type without muscle involvement
usually caused by less virulent clostridial organisms other than clostridial welchii. It is usually superfi cial but may spread and involve fascial planes. It causes necrosis with
foul smelling seropurulent discharge.
Complications of Gas Gangrene
- Septicaemia, toxaemia.
- Renal failure, liver failure.
- Circulatory failure, DIC, secondary infection.
- Death occurs in critically ill patients.
- X-ray shows gas in muscle plane or under the skin.
- Liver function tests, blood urea, serum creatinine, total count, PO2, PCO2.
- CT scan of the part may be useful especially in chest or abdominal wounds.
- Gram’s stain shows Gram-positive bacilli.
- Robertson’s cooked meat media is used which causes meat to turn pink with sour smell and acid reaction.
- Clostridium welchii is grown in culture media containing 20% human serum in a plate.
- Antitoxin is placed in one-half of the bacteria grown plate sparing the other half. Zone of opacity will be seen in that half of the plate where there is no antitoxin. In the other half part of the plate where there is antitoxin there is no opacity—Nagler reaction.
Prevention of gas gangrene
- Proper debridement of devitalised crushed wounds
- Devitalised wounds should not be sutured
- Adequate cleaning of the wounds with H2O2 and normal saline Penicillin as prophylactic antibiotic.
- Injection benzyl penicillin 20 lacs 4th hourly + Injection metronidazole 500 mg 8th hourly + Injection aminoglycosides (if blood urea is normal) or third generation cephalosporins or metronidazole.
- Fresh blood transfusion.
- Polyvalent antiserum 25,000 units given intrav enously after a test dose and repeated after 6 hours (Welchii 10,000 IU, oedematiens 10,000 IU, and septicum 5,000 IU).
- Hyperbaric oxygen is very useful.
- Liberal incisions are given. All dead tissues are excised and debridement is done until healthy tissue bleeds.
- Rehydration and maintaining optimum urine output (30 ml/ hour) (0.5 ml/kg/hour).
- In severe cases amputation has to be done as a life-saving procedure—stump should never be closed (Guillotine amputation).
- Often ventilator support is required.
- Once a ward or operation theatre is used for a patient with gas gangrene, it should be fumigated for 24-48 hours properly to prevent the risk of spread of infection to other
patients especially with open wounds.
- Hypotension in gas gangrene is treated with whole blood transfusion.
- Therapy should be concentrated in managing dehydration, hypotension, infection, toxaemia by hydration, fresh whole blood transfusion, passive immunisation, antibiotics, and hyperbaric oxygen, doing radical wound excision with removal of all dead tissues with foreign body or amputation with critical care.