Tissue Oxygen Saturation Monitoring in Diagnosing Necrotizing Fasciitis of the Lower Limb: A Valuable Tool but Only for a Select Few

To the Editor:

I read with interest the article by Wang and Hung1 published in the September 2004 issue of Annals. Necrotizing fasciitis is perhaps the deadliest soft tissue infection known to humankind, and early diagnosis and aggressive debridement have been proven to improve survival.2, 3, 4 I think this article would contribute to the development of a focused and targeted approach in the management of necrotizing fasciitis by helping in the detection of early cases of necrotizing fasciitis. While I applaud this effort, I would like to raise some points that I hope will help in the potential application of this work.

The first matter is regarding terminology. The authors used the term fasciotomy as a treatment of necrotizing fasciitis. Fasciotomy is a treatment for compartment syndrome where there is acute or chronic elevation of intracompartment pressure. It is doubtful that increased intracompartment pressure has any role in necrotizing fasciitis. The authors themselves mentioned this in passing in their discussion. The pathological process in necrotizing fasciitis is liquefactive necrosis with thrombosis of the perforating vessels supplying the skin. Although the authors mentioned that several factors may be responsible for their clinical observation, I believe that this is the primary reason for their observation of decreased tissue saturation. The correct term should be excisional debridement of the necrotic fascia. Aggressive removal of all infected tissue, especially the superficial fascia, not fasciotomy, is the only way to halt and control the infection.

Another issue that critically compromised the utility of this article clinically is the patient selection for the study. All patients with chronic venous stasis, peripheral vascular disease, shock, and systemic hypoxia were excluded from the study. This is understandable because most patients with these conditions would have impaired tissue perfusion and oxygen saturation and, thus, would give a false-positive result. However, most patients who develop necrotizing fasciitis have underlying predisposing conditions that make them susceptible to the development of this condition. In my review of 89 consecutive patients, predisposing conditions such as diabetes, peripheral vascular disease, or chronic liver disease were present in 87% of patients. In addition, patients presenting with necrotizing fasciitis with multi-organ failure and shock (eg, streptococcal toxic shock syndrome) would not have interpretable results. Therefore, a majority of patients susceptible to necrotizing fasciitis would have been excluded from this study. This is a pity, because this is a group of patients in whom early diagnosis would profoundly affect outcome. Still, in the select group of patients (namely healthy patients), tissue oxygen saturation monitoring may potentially be a valuable diagnostic adjunct.

Our group has been interested in the early recognition of necrotizing fasciitis. We compared laboratory tests for patients with necrotizing fasciitis and severe soft tissue infections and analyzed routinely performed tests for the assessment of severe soft tissue infections (ie, CBC count, electrolytes, erythrocyte sedimentation rate, C-reactive protein). A numeric score based on the relative significance of the laboratory parameters called the laboratory risk indicator for necrotizing fasciitis (LRINEC) score was devised.5 We think this is capable of detecting even nascent cases of necrotizing fasciitis and can potentially be a valuable diagnostic adjunct in the assessment of potential necrotizing fasciitis.