Necrotising Fasciitis - Advances in diagnosis and management

Necrotising Fasciitis – Advances in diagnosis and management

A 40 year old man underwent a minor elective day case lower limb soft tissue operation. 72 hrs later he began to feel unwell and developed fevers and rigors. He was seen first thing in the morning with increasing pain and inflammation extending up from the foot to the knee. Intravenous antibiotics were started on admission. He was in theatre having a debridement by late morning, by which time the inflammation had spread to the inner thigh. He was in profound septic shock with disseminated intravascular coagulopathy. During the debridement, it was noted that the inflammation had spread to his pelvis. He had a laparotomy and it was determined that the resection he would require was unsurvivable. Treatment was withdrawn and he died on the operating table.

How is necrotising fasciitis diagnosed and how is it managed?

Prad Shanmugasundaram

Necrotising fasciitis (NF) is a rare soft tissue infection with an estimated incidence of around 500 new cases per year in the UK.(1) Necrotising fasciitis typically has a polymicrobial aetiology with mixed anaerobic and aerobic organisms.(1) Streptococcal species and other gram positive cocci are most often responsible for monomicrobial infection.(2) NF usually presents acutely with a rapidly progressive course over hours or days, often in immunocompromised patients such as IV drug users, patients with diabetes, end-stage renal failure, malignancy or in the puerperium.(3)

Diagnosis remains one of the most difficult challenges in the management of NF. A clinical diagnosis is based on signs which typically include inflammation around a (often pre-existing) break in the epidermis, pain disproportionate to the local inflammation and signs of systemic toxicity. Imaging that may be helpful includes plain x-ray, CT, ultrasound and particularly MRI. These can reveal soft tissue gas, thickening of the fascial layer with or without enhancement and often need to be compared to the contralateral uninvolved site. In necrotising fasciitis, clinical examination and imaging tests are usually of high sensitivity but low specificity.(4)

More recently, a diagnostic tool has been validated which identifies 6 independent variables which are associated with necrotising soft tissue infections. These laboratory based variables form a scoring system, the Laboratory Risk Indicator for Necrotising Fasciitis score (LRINEC), which is able to stratify the likelihood of diagnosis of NF into low, intermediate and high. For intermediate and high risk patients the LRINEC has a positive predictive value of 92% and negative predictive value of 96%.(5)

Treatment of necrotising fasciitis should be instituted immediately. Management includes appropriate broad-spectrum antimicrobial administration, usually a regime including clindamycin, with appropriate resuscitation and supportive measures. Clindamycin has a particular role in necrotising infections as its protein synthesis inhibitory properties help prevent further toxin production. This can limit the inflammatory response, particularly in those infections caused by streptococcal and clostridial species.

Crucially, aggressive and early source control (within 24 hours) remains the mainstay of treatment often necessitating extensive surgical debridement or amputations, and frequently repeat surgical exploration 24-48 hours later. Management of the severe sepsis and its sequelae are a particular challenge in the critical care unit and several novel or experimental therapies have been reported. (6)

Use of hyperbaric oxygen therapy (HBOT) has been investigated in necrotising soft tissue infections, but has produced conflicting results with some studies suggesting improved mortality and reduced number of debridements to achieve source control, whereas others have failed to show beneficial effect.(7) Further quality randomised controlled trials are necessary and logistical difficulties in providing HBOT to the critically ill patient would need to be overcome before HBOT could be recommended.

The role of intravenous immunoglobulins (IVIG) has been investigated, particularly in severe infections resulting from group A streptococci, such as necrotising fasciitis or toxic shock syndrome. A randomised controlled trial in 2003 showed lower SOFA scores at days 2 and 3 in patients with streptococcal toxic shock syndrome treated with IVIG versus those that weren’t. The 28 day mortality was 3.6 fold higher in the placebo group, but this did not reach statistical significance (P=0.3) because of the small sample size. The trial was terminated early due to slow recruitment.(8) A small case series showed that aggressive medical therapy, including IVIG therapy, with a conservative surgical approach in severe Group A streptococcal soft tissue infection. All seven patients (six of whom had toxic shock syndrome) survived with no surgery or only limited exploration (9). Further work is required to clearly delineate the role of IVIG, but its use is generally advocated in current practice.


Lessons learnt

Severe necrotising soft tissue infections are a potentially horrific illness which can progress extremely quickly. As such, management must be instituted without delay. Implementation of severe sepsis bundles and early surgical exploration are mandatory. Imaging and diagnostic tools may help, but diagnosis is usually confirmed at surgery or after microbiological confirmation. A regime of broad spectrum antibiotics, including clindamycin, is usually commenced to cover the most likely causative organisms. Although the evidence for its use is not strong, IVIG is usually used in these types of severe infection.


References

1. Hasham S, Matteuchi P, Stanley PRW, Hart NB. Necrotising Fasciitis. BMJ 2005; 330:830-833
2. Wong CH, Chang HC, Pasupathy S, Khin LW, Tan JL, Low CO. Necrotizing fasciitis: clinical presentation, microbiology, and determinants of mortality. J Bone Joint Surg Am 2003; 85:1454–60
3. Elliott DC, Kufera JA, Myers RAM. Necrotizing soft tissue infections: Risk factors for mortality and strategies for management. Ann Surg 1996;224: 672-83
4. Anaya D, Dellinger P. Necrotizing soft tissue infection: diagnosis and management. Clin Infect Dis 2007; 44:705-710
5. Wong CH, Khin LW, Heng KS, Tan KC, Low CO. The LRINEC (laboratory risk indicator for necrotizing fasciitis) score: a tool for distinguishing necrotizing fasciitis from other soft tissue infections. Crit Care Med 2004; 32:1535–41
6. Stevens DL, Bryant AE, Hackett SP. Antibiotic effects on bacterial viability, toxin production, and host response. Clin Infect Dis 1995; 20(Suppl 2):S154–7
7. Jallali N, Withey S, Butler PE. Hyperbaric oxygen as adjuvant therapy in the management of necrotizing fasciitis. Am J Surg 2005; 189:462–6
8. Darenberg J, Ihendyane N, Sjolin J, et al. Intravenous immunoglobulin G therapy instreptococcal toxic shock syndrome: a European randomized, double-blind, placebo-controlled trial. Clin Infect Dis 2003;37:333-40
9. Norrby-Teglund A, Muller MP, McGeer A, et al. Successful management of severe group A streptococcal soft tissue infections using an aggressive medical regimen including intravenous polyspecific immunoglobulin together with a conservative surgical approach. Scand J Infect Dis 2005;37:166-72.

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