What You Need To Know
Necrotizing fasciitis (nec fasc) is one of those dreaded boogeymen of emergency medicine; it thankfully doesn’t rear its ugly head too often, but when it does, boy is it scary. When that one big case of maybe rolls in, we all have the same thoughts: is this really nec fasc? Do I have any time to get some imaging? Would that even help? Do they need the operating room (OR)? Although the diagnosis itself is still fairly rare, there has been enough evidence in the past decade to help guide our hand in the management of this beast.
Necrotizing soft tissue infections (NSTI) are exceedingly difficult to recognize in their early stages, and can resemble a cellulitis . Just like in cellulitis, approximately 80% of patients will have swelling, another 80% will have pain, and 70% will have erythema. The key difference is PAIN OUT OF PROPORTION TO EXAM; if an angry red leg seems to hurt a lot more than it appears that it should, consider a NSTI!
- Blisters are a sign of skin ischemia, and point towards NSTI. Although they are fairly uncommon, only occurring in approximately 25% of case, their presence correlates with a higher rate of both amputations and mortality .
- The classic crepitus on palpation is actually very uncommon, only being seen in anywhere from 6% to 20% of cases [2,3]. If you find it, show your medical student, and they’ll owe you a beer later.
- Certain populations are more prone to NSTI; 50% of cases occur in diabetics, and another 50% occur in cirrhotics. Take extra care when seeing what looks like a simple cellulitis with these folks [2,3].
The LRINEC Score: In or Out?
The LRINEC score is a very powerful tool, having a negative predictive value of 96%. In fact, some of the literature has proposed integrating the LRINEC score into institutional clinical pathway guidelines to expedite the diagnosis of NSTI [4, 5].
- However, LRINEC is still not a be-all-end-all tool; there have been cases with LRINEC scores of 0, and given that NSTI secondary due Vibro infections have fewer lab abnormalities, they are less likely to be picked up by it. Clinical suspicion still trumps all .
Imaging: Yay or Nay?
- Plain Radiographs: Although seeing air in the soft tissue is pretty cool, they have little value. They are only positive in 25% of cases, and if non-diagnostic, can correlate with a delay in operative intervention [2,6].
- MRI: This study is highly capable of identifying inflammatory conditions within the fascial planes, but often overestimates the extent of fascial involvement, and takes a great deal of time [6,7]. Obviously, not a good go-to.
- CT: Highly sensitive, but poorly specific (100% and 81%, respectively), but with a negative predictive value of 100%, it can be a good choice to rule-out those unlikely cases if it can be done in a timely fashion in your shop .
Antibiotics: Best Choices ?
- Start broad spectrum antibiotics early and cover gram positive, gram negative, and anaerobes with specific consideration for group A Streptococcus and Clostridium species .
- Recommended multi-drug regimen:
- A carbapenem or beta-lactam + beta-lactamase inhibitor plus
- Clindamycin plus
- Antibiotic with activity against MRSA
Surgical Intervention: How Soon, Really?
- Although it is classically taught that the definitive treatment for NSTI is “early operative intervention”, the definition of “early” has not been clearly defined .
- Studies show that a delay more than 24 hours increases the likelihood of death by more than 9 times .
- A recent study has shown that taking a patient to the OR within 6 hours of diagnosis decreases the ICU and total hospital length of stay, but does not affect mortality . Keep in mind, however, this study looked at time from diagnosis, not time from symptom onset, which likely plays a bigger factor in the course of a patient’s illness .
As already described, it is difficult to discern a NSTI from a deep soft tissue infection. It is best to have a heightened suspicion, treat promptly and involve the experience of the surgical team. Although NSTIs requiring surgery are much rarer than deep soft tissue infections, given the need for a quick diagnosis and intervention, an emergency department practitioner should never feel uncomfortable requesting a surgical consultation.
A few important points to iterate and add:
- Because an NSTI can only be diagnosed following surgical debridement that demonstrates a necrotizing infection, a constellation of patient co-morbidities, lab values and physical exam findings are used to preoperatively diagnose a NSTI. Certain patient co-morbidities make a NSTI more likely including diabetes, obesity, hypertension, cirrhosis/chronic liver failure, peripheral vascular disease, HIV and immunosuppressive therapy. In the patient with peripheral vascular disease and a soft tissue infection of the extremity, an assessment of the blood supply to the limb is essential as this will help guide the decision of revascularization and debridement versus amputation.
- The initial diagnosis and treatment for both a NSTI and a deep soft tissue infection are relatively the same: early recognition, review of comorbidities, LRINEC score calculation, general overview of the SIRS/septic response, fluid resuscitation, blood cultures and broad spectrum antibiotic therapy. As a result, the major question of whether or not a patient needs debridement should be performed with a surgical team experienced in managing NSTIs. Together, with the emergency department and surgical teams, a finger fracture can be performed at the bedside in the emergency room to check for necrotic tissue, lack of bleeding, gross purulence or dishwater pus as an additional and quite helpful diagnostic tool. To do this, a portion of the wound centrally located in the erythema is sterilely prepped and draped and then locally anesthetized. With a scalpel, a several cm incision is made through the dermis. The soft tissues are then finger fractured. If the soft tissues fall apart too easily, there is gross purulence, a lack of bleeding or dishwater pus, the tissue should be debrided in the OR.
- As mentioned above, there is significant overlap between the physical exam findings for a deep soft tissue infection and a NSTI. While erythema, pain beyond the erythematous area and edema are concerning, skin anesthesia, bullae and a dusky coloration of the skin suggest necrosis of the underlying tissue and should prompt debridement in the OR.
- Necrotizing fasciitis is a small subset of NSTIs. Typically, the speed at which the soft tissue becomes necrotic, the pain and the overall septic state are more profound in necrotizing fasciitis. As opposed to other NSTIs, necrotizing fasciitis will proceed along the fascial planes at a rapid pace.
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How to cite this blog post
[Peer-Reviewed, Web Publication] Cunningham A, Pinchbeck C (2017, March 7). Necrotizing Fasciitis: Using EBM To Answer The Big Questions [NUEM Blog. Expert Commentary By Posluszny J]. Retrieved from http://www.nuemblog.com/blog/nec-fasc
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