good morning! thursday, february 2, 2011. csf shunts used in the setting of hydrocephalus to divert...
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GOOD MORNING!
Thursday, February 2, 2011
CSF Shunts
Used in the setting of hydrocephalus to divert CSF to another part of the body for absorption Proximal portion is placed in one of the
cerebral ventricles Distal portion can be internalized or
externalized VP- ventriculoperitoneal VA- ventriculoatrial
Shunt Infection
Rate of infection is 5 to 15% Highest rates of infection
Initial month after placement Patients requiring several revisions Patients undergoing revision after
treatment of infected shunt
Microbiology and Pathogenesis Most commonly via colonization with skin flora
Occurs at time of surgery or post-op via breakdown of the wound or overlying skin
Most predominant pathogen Staphylococci
50% are coag-negative Staph 30% are Staph aureus
Direct contamination of distal end of shunt Bowel perforation or peritonitis Variety of organisms: streptococci, gram-negative
bacteria (including Pseudomonas), anaerobes, mycobacteria, and fungi
Hematongenous seeding
Clinical Manifestations
Can present with few or no symptoms Sometimes symptoms only develop when
shunt obstruction and malfuntion occurs Clinical signs of increased intracranial
pressure Headache Nausea/vomiting Lethargy Mental status changes
Meningeal signs may not be observed Fever +/-
Clinical Manifestations
Symptoms may localize to distal or internal end of shunt VP
Peritonitis (fever, abdominal pain, anorexia) VA
Fever, bacteremia Subsequent endocarditis
Diagnosis
CSF Direct aspiration of the shunt is preferred WBC count and diff, glucose, protein, Gram
stain, culture Results can be challenging
Less inflammation than bacterial meningitis Cell count abnormalities may be subtle
White cell diff can be useful >10% neutrophils has 90% sensitivity for predicitng
infection
Culture results are critical for organism indentification and directing antibiotic therapy
Diagnosis (cont’d)
Blood cultures Should be obtained Higher yield in VA shunts
Imaging To look for evidence of ventriculitis or CSF
obstruction Abdominal imaging may be useful to
identify loculations at the distal end of VP shunts CT or ultrasound
Treatment
1) Removal of the device If not feasible, intraventricular antibiotics
2) External drainage
3) Parenteral antibiotics
4) Shunt replacement once CSF is sterile
Antibiotic Therapy
Guided by CSF gram stain and culture Empiric therapy
Vancomycin + gram-negative coverage For kids, cefotaxime
Intraventricular antibiotics No controlled trials Potentially toxic Most experience with Vanc and Gent
Candida
Shunt infection usually occurs within several months of the surgical procedure Results from implantation rather than
hematogenous seeding Most patients had received antibiotics, had
previous bacterial meningitis, or had abdominal complications (intestinal perforation)
Symptoms and signs similar to bacterial shunt infection Fever and shunt malfunction
Incidence is up to 17% in one study Clinical manifestations are subtle and slowly
progressive
Candida
Yeasts that reproduce by budding Non-albicans Candida species now
account for more than half of invasive infections Candida parapsilosis can cause serious
infections, especially in immunocompromised and debilitated hosts
Treatment of Candida CNS Infection
First line therapy Amphotericin B
Lipid formulation achieves higher concentrations in the brain +/- Flucytosine *Side effects
Fluconazole Excellent CNS penetration, however treatment
outcomes vary Use as step down treatment
Voriconazole Excellent CSF concentrations Limited clinical experience
Treatment of Candida CNS Infection (cont’d)
Posaconazole Does NOT achieve adequate CSF levels
Echinocandins (caspofungin, micafungin, anidulafungin) Do NOT achieve adequate CSF
concentrations
Antibiotic Duration
No controlled trials to determine optimal duration
Suggested approach (UpToDate): 1) If device removed, CSF chemistries are
normal, and culture is positive for coag-negative staph → shunt may be replaced on 3rd day after removal if culture is negative
2) Coag-negative staph and abnormal CSF chemistries → antibiotics for total time device remains in place and for 1 additional week following removal. CSF should be sterile prior to replacement
Antibiotic Duration (cont’d)
3) Shunt infections with more virulent pathogens (S. aureus, gram-negative, etc) warrant at least 10 days (14 to 21 for gram-negative). CSF should be sterile for 10 days prior to shunt replacement
4) If device is not removed, antibiotics for 7 to 10 days after sterilization of CSF
Prevention
Careful adherence to sterile technique Antibiotic prophylaxis
Warranted in the intial 24 hours after device placement
Vancomycin is drug of choice due to predominant role of coag-negative staph
Antibiotic-impregnated catheters Prophylactic catheter exchange
Not effective for preventing infection
Male GU, Dr. Nass
Noon Conference