Gas Gangrene

This is a life-threatening bacterial infection with gangrene which has the following three features

1. Muscle necrosis
2. Sepsis
3. Gas production - usually a mixture of hydrogen, carbon dioxide, nitrogen and oxygen

Gas gangrene can be broadly grouped in to

1. Traumatic
2. Nontraumatic or Spontaneous - more rare and commonly there is an underlying malignancy

Previously common in the setting of war but now much less common.

• Clostridium species (found in soil and normal gastrointestinal tract flora of humans and animals) e.g. C. perfringens, C. septicum, C. novyi , C. histolyticum
• Bacteroides spp.
• Anaerobic streptococci

The pathogens enter through wounds usually after contact with soil e.g. soil contaminated with faeces (not always so). However, in patients with colonic neoplasm GIT C. septicum can pass via the blood to muscle (associated with a very poor prognosis).

The destruction caused by the pathogen is from the release of exotoxins and not from the bacteria itself. C. perfringens releases alpha toxin - which requires anaerobic surroundings to survive and thrive. This probably explains why hypoxic or poorly perfused tissue is attractive to these organisms.

Risk factors for gas gangrene include

• Chronic alcohol abuse
• Malnourishment
• Trauma e.g. burns, crush injuries, open fractures, large muscle involvement e.g. thigh
• Diabetes mellitus¹
• Corticosteroid use
• GIT malignancy e.g. infection of perineum or scrotum from colonic seeding
• Haematological disease with immunosuppression
• Has been reported to follow intramuscular injections²
• Features relating to the wound e.g. contamination with dirt or shrapnel
• Abortion (especially criminal abortion) and Caesarian section³

The incubation period varies from 1 to several days but symptoms may progress within hours.

• Initially - no skin changes just pain
• Systemic symptoms e.g. fever,dehydration
• Once nerves damaged anaesthesia occurs
• Paralysis
• Skin changes - cellulitic progressing to dark purple; develop vesicles and bullae⁴
• Subcutaneous air on palpation (may not be present early on)
• Foul smelling discharge
• Oedema
• Necrotic or haemorrhagic tissue
• Patients may also present in septicaemic shock with tachycardia, hypotension, fever, stupor

This includes

• Necrotising fasciitis in the early stages
• Anaerobic cellulitis with myonecrosis

• FBC
• Renal function
• Liver function
• Creatine kinase
• Specimens from skin for culture e.g. vesicle exudate
• Immunological methods - provide more rapid diagnosis⁵
• Blood cultures
• ABG - patients may be acidotic
• Urine dipstick - ? myoglobinuria
• Plain X rays - will show gas in soft tissues⁴

• Supportive therapy - e.g. analgesia, oxygen, intravenous fluids and good nourishment
• Surgical - radical debridement of necrotic tissue (may require amputation if limb involved)
• Antibiotics - these do not work alone as they are unable to penetrate the necrotic tissue. Cover Gram negative, Gram positive and anaerobes e.g. combination of penicillin, gentamicin and metronidazole.
• Hyperbaric oxygen therapy - kills anaerobic C. perfringens; but efficacy not proven⁶
• Tetanus toxoid may also be indicated⁷

• Multi-organ failure
• Spread to involve bone marrow⁸
• Disseminated intravascular coagulation

Mortality approaches 25% in conditions associated with trauma and up to 100% in nontraumatic cases. This can be improved with better and more rapid recognition of the disease followed by early treatment of gas gangrene.