Annals of B Pod - Necrotizing Fasciitis

HISTORY OF PRESENT ILLNESS

The patient is a female in her 50s who presents following an injury to her right ankle approximately one week prior. The patient was fishing for catfish, and the barb from one of the catfish caused a puncture wound in her right lower extremity. She reports worsening erythema, edema, and pain in this area since the injury. She initially presented to an outside hospital three days prior and was sent home on oral clindamycin. She returned to the outside hospital again on the day of presentation due to worsening pain and malaise, and was found to be hypotensive, tachycardic, and hypoxic. She received intravenous (IV) fluids and cefepime and was transferred to our tertiary care medical center. On arrival, the patient remains alert and oriented but is tachycardic and hypotensive, so she is triaged to the shock resuscitation unit for further management.

Past Medical History: Chronic obstructive pulmonary disease, coronary artery disease, congestive heart failure, hypertension

Past Surgical History: Left pleurodesis for spontaneous pneumothorax

Medications: Nitroglycerin, Atorvastatin, Carvedilol, Aspirin, Ticagrelor, Albuterol, Doxepin

Allergies: No known allergies

PHYSICAL EXAM

Vitals: T 97.5F HR 104 BP 82/70 RR 22 SpO2 91% on 4L NC

The patient is a female in no acute distress. She is alert and oriented. Pupils are equal, round, and reactive to light. Neck is supple and without meningismus. Auscultation of the heart and lungs is unremarkable. Her abdomen is soft and non-tender. The right lower extremity has a deep puncture wound above the lateral ankle with purulent drainage and surrounding bullae, erythema, and tenderness extending to the mid-thigh.

DIAGNOSTICS

WBC: 10.9 Hgb: 11.6 Hct: 33.8 Plt: 207

Na: 135 K: 5.3 Cl: 105 HCO3: 19 BUN: 60 Cr: 3.13 Glu: 99

Bedside soft tissue ultrasound: fluid along fascial planes and cellulitis

X-ray right femur, knee, tibia and fibula: soft tissue ulceration and swelling, subtle hyperdensities likely to represent foreign debris

HOSPITAL COURSE

Given concern for necrotizing fasciitis and sepsis, the patient was started on broad spectrum antibiotics including vancomycin, metronidazole, and clindamycin in addition to the cefepime she received at the outside hospital. Her systolic blood pressure dropped into the 70s, so IV fluids were administered and she was started on a norepinephrine infusion to maintain mean arterial pressure >65 mmHg. Acute care surgery was consulted to evaluate her right lower extremity for necrotizing fasciitis. The patient was emergently taken to the operating room (OR) with acute care surgery and podiatry for extensive debridement of the infected tissue from the lateral ankle wound up into the right thigh. Following the surgery, she remained intubated and was transferred to the surgical intensive care unit with a high vasopressor requirement including norepinephrine, epinephrine, and vasopressin. Antibiotic coverage was changed to meropenem and clindamycin to cover freshwater pathogens.

On post-operative day one, the patient developed oliguria, worsening acidosis, and elevation of her lactate to 14. Nephrology was consulted for renal failure, and the patient was started on continuous renal replacement therapy and a bicarbonate infusion. Blood cultures returned positive with growth of gram-negative rods, which later speciated as Edwardsiella tarda. She returned to the OR for further debridement and washout given concern for remaining infected tissue. Unfortunately, her clinical condition continued to deteriorate, and her family elected to pursue comfort care.

DISCUSSION

Epidemiology and Pathophysiology of Necrotizing Fasciitis

Table 1: Classification of necrotizing fasciitis according to microbial etiology

Necrotizing soft tissue infection (NSTI) is a rare, life-threatening, and therapeutically challenging disease affecting about 1000 patients annually in the United States. While diagnosis remains uncommon, the incidence of NSTIs has increased over recent decades, possibly due to emerging strains of resistant bacteria, increased bacterial virulence, and better reporting systems. [1,2] Necrotizing fasciitis (NF) is a type of NSTI that extends below the epidermis and dermis to infect fascia, adipose tissue, muscle, and tendons. Precipitating events typically include recent surgery or penetrating injury, however, there are also cases of NF after minor insult such as superficial abrasion. The clinical course of NF may be classified as subacute, with symptoms remaining localized for several weeks, or acute, with symptoms worsening within several days and involving large areas of tissue. [3] Patients with fulminant NF rapidly deteriorate and develop septic shock over the course of hours. The mortality rate associated with NF is up to 70%, primarily due to delay in diagnosis .[4] NF is classified into four subtypes based on microbial etiology (table 1). [4] Notable virulence factors for these microorganisms include the generation of α-toxin and θ-toxin by clostridium species, which facilitate tissue ischemia and inhibit neutrophil migration, and expression of M protein by streptococcus species, which bind T-cell receptors to induce massive inflammatory cascade. [1]

Risk factors for the development of NF include diabetes, obesity, advanced age, immunodeficiency, significant alcohol use, liver disease, intravenous substance use, and recent trauma. [1] Common locations of NSTIs include the extremities, perineum, and genitalia (known as Fournier’s gangrene when the perineum and genitalia are involved). Pathogens enter the subcutaneous tissue either via direct injury to the integument or hematogenous seeding from another site. [1] The associated inflammation and infection lead to cell death and tissue necrosis, which creates a nidus for microbial proliferation.

Catfish Injuries

Figure 1: Man with catfish caught by noodling. Public Domain via https://en.wikipedia.org/wiki/Noodling#/media/File:Noodling_champ.jpg

Catfish injuries, like the one sustained by the patient in this case, are fairly common both in the catfishing industry and in recreational activities. A particularly interesting recreational practice, common in the southern United States, is known as “noodling” and involves catching catfish with one’s bare hands (figure 1). Participants reach blindly into a hole or crevice where the catfish reside and grab hold of the fish by its mouth, pulling it to the surface. Catfish can exert a fair amount of force during this activity, putting the “noodler” at risk of blunt force trauma. In addition, catfish have dorsal and pectoral fins with spines that become erect and swordlike when they are disturbed, and some species even have venom that is released from the spines. The spines can cause puncture wounds and lacerations, and envenomation causes local reactions including pain, erythema, edema, local hemorrhage, tissue necrosis, and muscle contractions, thus predisposing the victim to infection from water-borne bacteria. [5]

Multiple case reports have been written on severe infections after catfish injuries, with numerous bacterial species implicated. The most common gram-negative bacteria seen in catfish-related infections is Edwardsiella tarda. [5] E. tarda is a motile anaerobic gram-negative rod and the causative organism of emphysematous putrefactive disease of catfish – also known as fish gangrene. Prior testing has isolated E. tarda from 75% of pond water samples in the US and almost 90% of channel catfish fillets. [6] Despite the extensive presence of this bacterium in the environment, the majority of catfish do not become ill. Catfish that do become infected by Edwardsiella develop abscesses and necrotizing cellulitis. While an unusual human pathogen, E. tarda can cause similar tissue infection in humans, with the dreaded complication of gram-negative bacteremia and sepsis. [7] E. tarda is typically pan-sensitive to the antibiotics used in gram negative infections, but unfortunately even with adequate antimicrobial regimens, mortality has been reported in up to 44% of cases of E. tarda bacteremia. There are no guidelines regarding antibiotic regimens for catfish-associated infections, but proper antibiotic selection should include coverage for waterborne bacteria. [5]

Figure 2: Early stage of necrotizing fasciitis [17] (figure via creative common license 4.0 via Joe doestch https://commons.wikimedia.org/wiki/File:Beginning_of_Necrotizing_Fasciitis_01.jpg)

Clinical Presentation

NF most commonly occurs on the extremities. The earliest symptoms of NF are non-specific and include erythema and edema that often appears similar to cellulitis or abscess formation. [3] Severe pain out of proportion to clinical appearance can be an important indicator of infection deeper in the fascial planes, and early diagnosis is crucial to improve mortality. [3] As NF infection progresses, the wound appearance may develop a grayish or purple discoloration with poorly demarcated borders. [8] (Figure 2) More specific signs of NSTIs include formation of bullae or blisters and palpable crepitus underlying the wound. [9] In late stages of disseminated infection, patients present with symptoms of sepsis, including tachycardia, hypotension, fever, and encephalopathy. [8] Symptoms that should alert the clinician to the possible presence of NSTIs are summarized in table 2.

Diagnosis

Early diagnosis is challenging due to overlapping symptoms with superficial cellulitis. Initially, many patients with NF are incorrectly diagnosed with cellulitis and discharged on oral antibiotics. The gold standard for diagnosis is surgical exploration based on clinical concern for NF. [9] Laboratory and imaging studies can provide further supporting evidence, although with limitations. The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score attempts to stratify patients with soft tissue infection into low, moderate, and high-risk groups (Table 3). [10] However, no prospective trials have been performed utilizing this tool, and validation studies have produced inconsistent results. [11] A meta-analysis comparison of clinical signs, LRINEC score, x-ray, and computed tomography (CT) found that only CT imaging has robust sensitivity for NSTI, nearly 95%. [12] (Table 4) Magnetic resonance imaging (MRI), which was not included in this meta-analysis due to lack of data, has variable sensitivity and specificity according to the criteria used (for example, the presence of gas has 100% specificity for NSTI but poor sensitivity, and abnormalities of the intermuscular fascia has 100% sensitivity for NSTI but poor specificity). [13]

Table 2: Clinical features of NSTIs [8]

Point of care ultrasound, which is quick to perform and readily available in the emergency department, may have a role in assisting the clinical diagnosis of NSTI. Ultrasonographic signs of NSTI include a “cobblestone” appearance of the soft tissue, irregularity and thickening of the fascia, abnormal fluid collection along the fascia, and hyperechogenic foci representing subcutaneous air. However, ultrasound evaluation of the deeper tissues can be quite difficult and differentiating cellulitis from NSTI is not always possible. [14] One small study estimated ultrasound to have a sensitivity of 88.2% and specificity of 93.3% in the diagnosis of NSTI in patients who were already suspected to have NSTI on clinical exam. [15] In practice, CT, MRI, or ultrasound imaging may aid the clinician in cases of diagnostic uncertainty if it is readily available, but should never delay prompt surgical evaluation.

Treatment

Unfortunately, the aggressive nature of the infection and resultant tissue hypoxia mean that IV antibiotics alone are rarely sufficient for treating NSTIs. Mortality without surgical intervention is greater than 90%. [7] Emergent surgical consultation for debridement and excision of infected tissue is the most important step following diagnosis, and it may be appropriate to consult surgery prior to any available test results if there is high clinical suspicion. Obtaining intraoperative tissue cultures is key for tailoring antibiotic therapy, which becomes more effective following surgery. Pending culture results, broad-spectrum antibiotics should include coverage for gram-positive (e.g. vancomycin), gram-negative (e.g. cefepime), and anaerobic microorganisms (e.g. clindamycin). [16] Clindamycin is frequently used since it has been shown to decrease clostridial toxin production, streptococcal M-protein expression, and lipopolysaccharide-induced tumor necrosis factor production by monocytes. [1] If fungal infection is suspected, treatment usually includes amphotericin or fluoroconazoles. [16] Patients also typically require intensive care including fluid resuscitation, vasoactive medications, and ventilator support. Limited evidence is available for other proposed interventions, including hyperbaric oxygen and intravenous immunoglobulin. [7]

SUMMARY

Necrotizing soft tissue infection is a rare, aggressive, and life-threatening disease with high mortality unless extensive surgical intervention is performed. Diagnosis can be challenging in the emergency department due to similarity to more innocuous infections such as cellulitis, but NSTI should be suspected in the case of pain out of proportion to exam, crepitus, bullae, or signs of systemic illness. Diagnosis in the ED is primarily clinical, but diagnostic imaging such as CT scan and ultrasound can be helpful, and the final diagnosis is made after surgical debridement. The mainstays of NSTI treatment in the ED are early surgical consultation and empiric antibiotic therapy for gram positive, gram negative, and anaerobic bacteria. Catfish-associated infections, including NSTI, have been reported in the literature and can be life-threatening.

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AUTHORED BY LOGAN RAMSEY, MD

Dr. Ramsey is a PGY-3 in Emergency Medicine at the University of Cincinnati

EDITING BY THE ANNALS OF B POD EDITORS

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REFERENCES

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5. Kaar CR, Nakanishi AK. Recreational and commercial catfishing injuries: a review of the literature. Wilderness & environmental medicine. 2017 Dec 1;28(4):348-54.

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10. Wong CH, Khin LW. Clinical relevance of the LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score for assessment of early necrotizing fasciitis. Crit Care Med. 2005;33(7):1677.

11. Neeki MM, Dong F, Au C, et al. Evaluating the laboratory risk indicator to differentiate cellulitis from necrotizing fasciitis in the emergency department. West J Emerg Med. 2017;18(4):684-689.

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13. Malghem J, Lecouvet FE, Omoumi P, Maldague BE, Berg BC. Necrotizing fasciitis: contribution and limitations of diagnostic imaging. Joint Bone Spine. 2013 Mar 1;80(2):146-54.

14. Magalhães L, Martins SR, Nogué R. The role of point-of-care ultrasound in the diagnosis and management of necrotizing soft tissue infections. The ultrasound journal. 2020 Dec;12(1):1-6.

15. Yen ZS, Wang HP, Ma HM, Chen SC, Chen WJ. Ultrasonographic screening of clinically‐suspected necrotizing fasciitis. Academic emergency medicine. 2002 Dec;9(12):1448-51.

16. Misiakos EP, Bagias G, Patapis P, Sotiropoulos D, Kanavidis P, Machairas A. Current concepts in the management of necrotizing fasciitis. Front Surg. 2014;1.

17. Beginning of Necrotizing Fasciitis. https://commons.wikimedia.org/wiki/File:Beginning_of_Necrotizing_Fasciitis_01.jpg. Photograph by Joe Doestch, distributed under a CC 4.0 International license