Flashcards in Necrotizing Fasciitis (Jamal & Teach, Pediatr Emerg Care 2011) Deck (24):
Nec fasc is more common in which population: adults or children?
What is the most common monomicrobial cause of nec fasc?
Where is the location of the infection in nec fasc?
Superficial fascia and subcutaneous cellular tissue
How quickly can a lesion progress to necrosis/ulceration/bullae?
Within several hours
Why is there a high mortality rate from NF?
Usually due to a delay in the initiation of treatment since it is tough to diagnose clinically and is hard to differentiate from other soft tissue infections
What are the two types of NF?
-which is more common?
Based on causative organism:
-Type 1: polymicrobial (gram-positive cocci, gram-negative rods, anaerobes). Most commonly isolated organisms together: strep, staph, bacteroides, gram negative enterobactericeae (E coli, Kleb pneumonia, pseudomonas, proteus)
-Type 2: monomicrobial infection, classically caused by GAS either alone or in association with staph aureus
***Type 1 is far more common in adults (76%) but type 2 tends to occur in otherwise healthy, young immunocompetent hosts
Which type of NF is commonly known as "flesh eating disease"?
What is the incidence of MRSA in NF?
In a review from 2001-2006, found a 39% prevalence of MRSA and 93% of these cases were monomicrobial in nature
How common is NF in kids?
Rare!! Annual incidence of 0.08 per 100,000 children
What are the pediatric risk factors for the development of NF?
1. Chronic illness
4. Recent infection with varicella
***A portion of patiets are found to have no identifiable risk factors!
Is NF more common in older children or younger children?
Younger! Substantially higher in children < 5 yo
Fill in the blank: Recent infection with varicella has been associated with a _____ fold increased risk of invasive GAS disease in children.
58-fold increased risk!
-60% occur within 1 month of a varicella infection
What are the clinical manifestations of NF?
1. Severe pain out of proportion to physical examination findings
2. Tenderness, erythema, warm skin
****Commonly, these are the only signs of early NF
5. Altered mental status
****These signs typically develop during the first 24-48 hours of disease progression but are often absent at presentation
According to the Canadian Pediatric Surveillance Program study, what were the most common presenting symptoms of NF?
-97% had localized pain
-73% had rash
-only 4% had confusion, 19% had hypotension
***Lack of dramatic skin manifestations at disease presentation is a major factor in inaccurate initial diagnoses
What is the pathophysiology of NF?
Infection is in the subcutaneous and deep soft tissues (this is why the overlying skin is initially minimally affected)
-usually starts with inoculation of bacteria from a disruption in the epithelial barrier from minor trauma, cuts, abraions, needle punctures or other underlying skin conditions.
-bacteria then spread subcutaneously along the fascial planes that separate adjacent muscle groups
-get severe tisse damage from the combined action of bacterial toxins and tissue damaging enzymes
-get rapid invasion and thrombosis of the vessels coursing through the fascia resulting in tissue hypoxia and necrosis
***This is why you get extremely painful lesions without impressive outward appearance
-only with disease progression do you see vesiculation, necrosis and crepitus
-the extent of the involved area is often larger than appreciated on physical examination and only apparent on intraoperative debridement
-extensive tissue damage and toxin release into the circulation may lead to septic shock and multiorgan failure
What are potential lab findings with NF?
1. Elevated WBC with left shift
4. Elevated lactate
5. Elevated CK
6. Elevated Cr
***Currently there are no specific guidelines or clinical decision rules available for NF in children
What are the recommendations for imaging in NF?
There are no current recommendations for obtaining specific imaging studies to diagnose NF
-Plain radiographs: show gas in soft tissues in only 57% of non-GAS-associated NF and are not useful in the diagnosis of NF
-one study found a correlation between nondiagnostic radiographs and delay in definitive surgery, increasing morbidity and mortality
-MRI = imaging modality of choice and can show the extent of soft tissue infection
-problem with MRI: can be overly sensitive and cannot always distinguish NF from cellulitis or inflammation
-CT: not as sensitive as MRI but can be useful in excluding a diagnosis of NF and in correctly identifying the disease with high likelihood
How do you make the definitive diagnosis of NF?
Findings on surgical exploration - operative findings consistent with NF ("dishwasher" discharge, lack of bleeding from necrosis, loss of normal resistance to dissection of the fascia)
What are the most common causes of neonatal NF?
Secondary infection of omphalitis (most common), balanitis, mammitis, fetal scalp monitoring, postop complications
What type of NF is most common in neonatal NF?
Where are the most common locations of NF in a neonate who does not have a known inciting factor (ie. post op, omphalitis, balanitis, etc.)?
Lower back and lateral abdominal wall
What is the mortality rate from NF in adults vs. peds?
What is the most significant modifiable contributor to increased mortality in NF?
Delay in surgical debridement
-in adult review: delay of > 24 hours from admission to surgery was the only independent predictor of mortality after adjusting for age, sex, diabetes, hypotension on admission
-in peds case series: all survivors underwent surgical debridement within 3 hours of admission to the hospital; all 5 patients with delayed initial management died