Gas gangrene overview

# Overview
Gas gangrene is a bacterial infection that produces gas in tissues in gangrene. It is a deadly form of gangrene usually caused by Clostridium perfringens bacteria. It is a medical emergency.
Myonecrosis is a condition of necrotic damage, specifically to muscle tissue. It is often seen in infections with Clostridium perfringens or any of myriad soil-borne anaerobic bacteria. Bacteria cause myonecrosis via specific exotoxins. These microorganisms are opportunistic and generally enter the body via significant skin breakage. In wartime particularly, the unhygienic conditions and frequent gross injuries meant that gangrenous infection of soil-borne bacteria was particularly prevalent. Indeed mankind has long suffered the ill-effects of gangrenous infections throughout history. Other causes of myonecrosis include ischemic necrosis, caused by vascular blockage (e.g. diabetes type II), tumours that block or hoard blood supply and disseminated intravascular coagulation (DIC) or other thromboses.

# Pathophysiology
Gas gangrene is caused by exotoxin-producing Clostridial species (most often Clostridium perfringens), which is mostly found in soil but also found as normal gut flora, and other anaerobes (e.g. Bacteroides and anaerobic streptococci). Staphylococcus aureus and Vibrio vulnificus can cause similar infections.

# Diagnosis

## History and Symptoms
Gas gangrene causes very painful swelling. The skin turns pale to brownish-red. If you press on the swollen area with your fingers, you may feel gas as a crackly sensation. The edges of the infected area grow so quickly that changes can be seen over a few minutes. The area may be completely destroyed.

## Laboratory Findings
Tissue and fluid cultures and Gram stain of fluid to test for Clostridium bacteria can be done. Blood cultures can be done to determine the bacteria causing the infection.

# Treatment

## Medical Therapy
Any significantly massive infection is a medical emergency. In cases of gangrene, the infection is so  severe by the time that a diagnosis is made that countering the bacterial load is impossible even with the strongest available antibiotics, for example gentamycin and vancomycin. Antibiotics alone are not effective because they don't penetrate ischemic muscles enough to be effective. However, penicillin is given as an adjuvant treatment to surgery. There are two major reasons for this; current antibiotics only prevent replication of bacteria and the production of toxins continues in pre-existing bacteria. Also, the extent of injury caused by the infection may leave the muscle tissues so damaged that the body will never be able to replace the lost structures (including vasculature).

## Surgery
Often the only available cure is amputation, which physically removes the source of infection. Understandably this is not the favoured option unless circumstances are particularly dire. In addition to surgery and antibiotics, hyperbaric oxygen therapy (HBOT) is used and acts to inhibit the growth of and kill the anaerobic C. perfringens.

## Primary Prevention
Clean any skin injury thoroughly. Watching for signs of infection (such as redness, pain, drainage, or swelling around a wound), and consulting health care provider promptly if these occur can help prevent gas gangrene.