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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

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