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Emphasizing The Urgency Of Soft Tissue Infections

By Zeeshan S. Husain, DPM, FACFAS, FASPS and Cody Ingram, DPM, MPH

Spanning from initial emergency department presentation, all the way through follow-up care, the podiatric foot and ankle team’s duty is to manage all foot and ankle pathologies. Some require emergent intervention. Others are less critical in timing. When it comes to soft tissue infections, however, the time between initial presentation and surgery may be limb- or life-threatening.

Certain buzz words often signal a need for urgent or emergent surgical intervention: sepsis; necrotizing fasciitis; gas gangrene; and compartment syndrome. Similarly, key clinical phrases from an initial evaluation will suggest urgency, including: dishwater-like drainage; soft tissue crepitus; and soft tissue emphysema on plain film X-rays. However, distinctions between severity levels of soft tissue pathologies may not always be clear. Most of us have had situations where we received a routine consult on a severely infected foot, triggering questions as to the apparent lack of urgency. Conversely, I know I have downplayed some cases, only to realize intra-operatively that a more aggressive, urgent approach would have been best.

Osteomyelitis seems to carry with it an intrinsic urgency. While there is an expected and typical devotion of resources to the patient with obvious osteomyelitis, a patient with poorly-controlled diabetes and soft tissue emphysema possibly not demonstrating a large immune response may not receive as much attention. Thus, there is placement of a routine consult the next day. It is incumbent upon all physicians to have an all-encompassing knowledge of the appropriate tests, imaging studies and prophylactic antibiotic regimens for any soft tissue infection encountered in the acute setting. Furthermore, adhering to the principles of antibiotic stewardship, as outlined in the Infectious Diseases Society of America (IDSA) in 2012, will align our medical and surgical management with the primary medical team.1 Although not comprehensive, we present here a systematic outline of approaches to a few soft tissue infectious pathologies, including antibiotic regimens as guided by literature and appropriate imaging modalities.

Necrotizing Fasciitis

Antibiotics: vancomycin + piperacillin/tazobactam + clindamycin2

Imaging: plain radiographs, magnetic resonance imaging (MRI) with contrast3

Summary: In general, MRI is very sensitive, but less specific for diagnosing necrotizing fasciitis. The literature shows the addition of contrast increases specificity.4 As a rule, contrast is indicated for infections or tumors. Computed tomography (CT) scan is better for gas gangrene. With respect to antibiotics, treatment should be prompt and aggressive. The initial empiric antibiotic regimen should combine broad-spectrum drugs including coverage for methicillin-resistant Staphylococcus aureus (MRSA) and gram-negative organisms. One should avoid vancomycin if the minimum inhibitory concentration (MIC) is greater than 1.5mg/mL. Daptomycin or linezolid are alternative choices for empiric MRSA coverage. Ceftaroline is another option. Clindamycin is applicable for clostridial myonecrosis and inhibits M-protein and exotoxin synthesis. Although expensive, linezolid exhibits significant effectiveness for necrotizing fasciitis. In our institution, our podiatric team has the discretion to start linezolid, but infectious disease must receive a consultation within 24 hours. Again, when in doubt, use broad-spectrum antibiotics for coverage. When suspecting necrotizing fasciitis, one should proceed with emergent surgical intervention. 

Here one can see a clinical picture of necrotizing fasciitis. Notice the necrotic wound, surrounding cellulitis, and generalized edema. On bandaging, brown malodorous fluid was noted.  This image shows an MRI of the same patient showing multiple pockets of abscess tracking along the medial calcaneal wall and on both sides of the talus.

Gas Gangrene (With Or Without Wet Gangrene) 

Antibiotics: vancomycin + piperacillin/tazobactam2

Imaging: plain radiographs, CT5

Summary: It is important to understand the incidence of community-acquired MRSA in your hospital’s area. In our geographic area, community-acquired MRSA is very high. Furthermore, a vast majority of patients with a soft tissue infection have been hospitalized within the previous three months that raises their risk for gram-negative bacteria.5 According to the IDSA guidelines1, only vancomycin and piperacillin/tazobactam are Food and Drug Administration-approved for diabetic foot infections involving MRSA with or without Enterobacteriaceae and anaerobes. The literature also supports the administration of vancomycin with the addition of ceftriaxone or cefepime.1 In our institution, the infectious disease team prefers vancomycin with linezolid. Similar to cases of necrotizing fasciitis, emergent surgical intervention is necessary for gas gangrene. CT is the imaging modality of choice, as the soft tissue emphysema is easily discernable. However, plain film radiographic evidence of localized soft tissue emphysema is often sufficient to justify taking the patient to surgery emergently instead of waiting for the CT.

This is a radiograph of gas gangrene demonstrating soft tissue emphysema on the dorsal and plantar aspect of the midfoot and possibly subcutaneous tissue just posterior to the Achilles tendon.  Typically, extensive infiltration of the soft tissue emphysema extending into the hindfoot often leads to lower leg amputation due to the extent of soft tissue necrosis making limb salvage unfavorable. We will often recommend guillotine amputation in the lower leg followed by definitive leg amputation with the general or vascular surgery team.

Dry Gangrene

Antibiotics: can be harmful, adhere to antibiotic stewardship1

Imaging: often unnecessary5

Summary: In the setting of dry, stable gangrene, we recommend allowing the tissues to demarcate and/or autoamputate. If there is no surrounding cellulitis, ulcerations or other reasons to suspect sepsis, prophylactic antibiotic usage is often discouraged. A simple plain film radiograph to rule-out osteomyelitis can be appropriate, but the use advanced imaging is rarely justified.5 

Here one can see a clinical picture of dry gangrene involving the first ray. Distally, the hallux is completely desiccated and necrotic, but there distal first metatarsal area has not fully demarcated and there is some localized erythema dorsally.

Compartment Syndrome 

Antibiotics: prophylactic (30 minutes pre-operatively)2

Imaging: often unnecessary and delays treatment6

Summary: The consequences of a missed compartment syndrome and delaying surgical fasciotomy can have debilitating consequences for the patient, resulting in ischemia, pain and irreversible neuromuscular injury.7 Although confirming compartment syndrome by using a Wicks catheter is appropriate, often clinical suspicion alone should be sufficient to take the patient to the operating room for emergent fasciotomy where the patient can be tested and treated without delay. General clinical physical findings include pain exacerbated by passive stretch, pallor due to vascular compromise, paresis due to nerve ischemia, paresthesias as a result of nerve ischemia, diminished or absent pedal pulses, and poikilothermia.6  

Suspicion for compartment syndrome alone by primary providers should be enough to trigger immediate consultation for further evaluation. There is often an underlying story of a crush or traumatic injury. 

Recently, we received a consultation for a patient with recent retrograde atherectomy from the midfoot due to severe infrapopliteal vascular disease. She subsequently developed severe swelling and pain to the midfoot. We emergently treated this patient in the operating room where we noted elevated pre-operative compartment pressures in the proximal first intermetatarsal space. This was the location of the atherectomy catheter from the previous vascular intervention. The emergent fasciotomy led to successful resolution of the compartment syndrome without any long-term consequences. In my experience, first-year residents should always have supervision during their first few months of emergency room call, as there are dire consequences if this diagnosis is missed.  

Clinical picture of a crush injury to the foot following an industrial injury and multiple comminuted metatarsal fractures.  Patient has severe pain and performing any further clinical examination would be excruciatingly painful.  Measuring compartment pressures in the emergency room setting is unnecessary as this case is assumed to have compartment syndrome and should be taken immediately for fasciotomy.

  

Cellulitis With Venous Stasis Dermatitis/Ulcerations

Antibiotics: cephalexin/cefazolin (amoxicillin/clavulanate if risk factors)1

Imaging: unnecessary2

Summary: It is important to differentiate venous stasis dermatitis, cellulitis and venous stasis ulcerations, because they are separate entities. Simple cellulitis is often caused by group A Streptococcus from a point of entry.1 This pathology warrants the lowest potency antibiotics in the form of first-generation cephalosporins.1 Amoxicillin/clavulanate can be a consideration if the patient has risk factors such as a chronic history of leg wounds, probable polymicrobial colonization and underlying medical conditions, such as diabetes, congestive heart failure (or other chronic cardiac or respiratory conditions) or chronic kidney disease. 

If venous stasis ulcers probe to bone, plain films are appropriate, but the majority of the time these wounds are superficial and do not warrant routine imaging. Although admission is often necessary to treat the underlying cause of fluid retention in the legs that resulted in cellulitis, aggressive anti-edema measures need to be a priority in coordinating care with the primary medical team. Although most patients begin antibiotics, simply confining the patient to bed rest and implementing anti-edema measures, such as elevation and compressive bandaging (if cleared by the cardiac team) results in resolution of the cellulitis. Topical treatment of the ulcer will also remove colonization and aid in wound healing. 

This image of venous stasis with cellulitis has outlined cellulitis that will be used to track improvement as patient was admitted on IV antibiotics and diuresis.This image shows a more complicated case with venous stasis ulcers that will also require topical wound care.

When taking emergency room call, soft tissue infections of the foot and ankle are some of the more frequently managed conditions. Having a good relationship with the emergency room and internal medicine teams is essential for optimizing patient outcomes, as well as efficient use of resources.  Differentiating emergent and urgent cases is critical in timely management of these conditions and can occur by maintaining an open line of communication with the triage team.

Dr. Husain is the Residency Director of the McLaren Oakland Hospital Podiatric Surgery and Medicine Residency Program in Pontiac, Michigan. He is a Fellow of the American College of Foot and Ankle Surgeons, and a Fellow of the American Society of Podiatric Surgeons. Dr. Husain is also the President-Elect of the Michigan Podiatric Medical Association and Chairman of the Michigan Podiatric Residency Consortium.

Dr. Ingram is a third-year podiatric resident at McLaren Oakland Hospital in Pontiac, Mich.

References

1) Lipsky BA, Berendt, AR, Cornia PB, et al. 2012 Infectious diseases society of America clinical practice guidelines for the diagnosis and treatment of diabetic foot infections, Clin Infect Dis. 2012;54(12):132-173.

2) Sartelli M, Guirao X, Hardcastle TC, et al. 2018 WSES/SIS-E consensus conference: recommendations for the management of skin and soft-tissue infections. World J Emerg Surg. 20118:13(58). 

3) Carbonetti F, Cremona A, Carusi V, et al. The role of contrast enhanced computed tomography in the diagnosis of necrotizing fasciitis and comparison with the laboratory risk indicator for necrotizing fasciitis (LRINEC). Radiol Med. 2016:121(2):106–21.

4) Yoon MA, Hye WC, Yujin Y, et al. Distinguishing necrotizing from non-necrotizing fasciitis: a new predictive scoring integrating MRI in the LRINEC score. Eur Radiol. 2019;29(7):3414-3423.

5) Hayeri MR, Ziai P, Shehata ML, et al. Soft-tissue infections and their imaging mimics: from cellulitis to necrotizing fasciitis. Radiographics. 2016:36(6):1888-1910.

6) Cook K.  Nonosseous injuries.  Chapter 90 in McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery. 4th edition.  Editors Southerland JT, Boberg JS, Downey MS, et al. pp 1350-60. Wolters Kluwer and Lippincott, Williams & Wilkins.  Philadelphia. 2013.

7) Elliott KGB, Johnstone AJ. Diagnosing acute compartment syndrome, J Bone Joint Surg. 2003:85B(5):625-632.

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