Wound Infection(GAS GANGRENE)

This is a dreaded concequence of inadequately treated crushing injury and high voltage electrical injury . It is a rapidly progressive , potentially fatal condition , characterised by wide spread necrosis of muscles and subsequent soft tissue destruction . The common causative organism is Clostridium perfringens , a spore forming gram positive saprophyte that florishes in anaerobic condition . Other organisms are Cl. bifermentans , Cl. septicum ,Cl.sporogens . Clostridium perfringens produce many exotoxin but their exact role is unclear . Alpha toxin, the most important is a lecithinase which destroy red and white cells , platelates , fibroblast and muscle cells The Phi –toxin produces myocardial supression whereas the Kappa toxin is responsible for the destruction of the connective tissue and blood vesseles .

  Wounds become contaminated with clostridial spores and the devitalise tissue , foreign bodies and premature wound clossure provide the anaerobic conditions necessary for spore germination . The incubation period is < 24 hours but it can range from 01hr.to 06 weeks The tissue destruction is initiated by rapidly multiplying bacteria and locally and systemically acting exotoxins This results in spreading necrosis of the muscle and thrombosis of blood vessels while progressive oedema further compromise blood suply . The typical feature of this condition is the production of gas ( N2 ,H2S& CO2) that spread along the muscle planes . Systemicallythe exotoxin cause severe haemolysis , and combined with local effects , this lead to rapid progression of the disease , hypotension , shock , renal failure acute respiratory distress syndrome (ARDS) .

  The earliest symptom is acute onset of pain that increases in severity as the myonecrosis progresses .The limb swells up and the exudes a sero-sanguinous discharge . The skin is involved due to underlying muscle necrosis turning brown and progressing blue black colour with appearance of haemorrhagic bullae . The soft tissue crepittus caused by gas production appear with established infection . The local signs are pyrexia , tachycardia disproportionate to body temperature , tachyapnoea and alteration to mental status . THe diagosis is made by history and  clinical features .A gram stain of the exudate reveals large gram positive bacilli . Radiological examination can visualise gas in the soft tissue .

 Patients should be admitted to ICU and treated agressively with careful monitoring . High dose penicillin G and clindamycin along with third generation cephalosporin should be given I/V untill the patients toxicity abates .The mainstay of management is early surgical excision of the necrotic tissue . The muscle planes are opened through generous longitudinal incision and all devitalised tissue is removed . In established gas gangrene with systemic toxicity amputation of the involved extremity is life saving . Wound is lightly packed with saline soaked gauze & dressed .