How to manage central nervous system infections in the ICU

Empiric management of bacterial meningitis

The completion of empiric treatment should occur when CSF lab reports and clinical presentations are in line with the diagnosis. Treatment may last from 7-14d depending on the pathogen & clinical response.

In immunocompetent adults <50y, S. pneumoniae & N. meningitidis are the most common causes of community-acquired bacterial meningitis. Given this, treatment should be: third-generation cephalosporin (cefotaxime or ceftriaxone) with vancomycin.  

L. monocytogenes is common in adults ≥50y, immunosuppression, pregnant people, & patients with significant alcohol use. Treatment should be high-dose ampicillin (if penicillin sensitive use meropenem or IV trimethoprim-sulfamethoxazole) with IV gentamycin.

On suspicion of health-care associated meningitis caused by staphylococcal spp., & MDR-GNBs (P. aeruginosa & A. baumannii), start the following: vancomycin + antipseudomonal cephalosporin (ceftazidime or cefepime) or meropenem.

Adjuvant dexamethasone (0.15mg/kg IV q6h for 2-4d) should be started within 4h of antibiotic initiation for all patients with presumed bacterial meningitis beyond the neonatal age.    

Worsening CSF lab analysis indicate resistant bacteria, pathogens more typically associated with subacute meningitis syndrome, or non-infectious conditions.

Empiric treatment of brain abscess

In situations where the source of infection can’t be determined or the metastatic spread from a distant focus, treatment should include: vancomycin, third-generation cephalosporin, & metronidazole.

Antipseudomonal cephalosporin should be substituted for postneurosurgical infections or abscess arising from an area within the ear.  Meropenem should be an alternative when either cephalosporin or metronidazole is contraindicated.

Antibiotic therapy should be coupled with open or stereotactic drainage for better outcome if it permits. Antibiotic therapy may last 6-12wks depending on whether surgical drainage is used.

Empiric management of encephalitis

Encephalitis is clinically defined as a major criterion of altered mental status longer than 24h & at least two of the following: fever; seizures not attributable to a previously identified seizure disorder; new focal neurologic findings; CSF white cell count >5/mm³ &; neuroimaging or EEG abnormalities suggesting inflammation.

Routine adult testing include: CBC with differential; kidney & liver function test; blood cultures; HIV testing &; treponemal testing &; CSF analysis. In addition to this, Mycoplasma pneumoniae antibodies, & EBV serologies (VCA IgG & IgM & EBNA IgG) should be obtained in children.    

CSF analysis should include: cell count & differential; protein; glucose; oligoclonal bands; IgG index; gram stain & bacterial cultures; HSV-1/2 PCR; VZV PCR; VZV IgG & IgM; enterovirus PCR; cryptococcal antigen &; VDRL

Treat all patients with encephalitis using IV acyclovir pending CSF PCR result for HSV. Patients with confirmed HSV 1 or 2 & VZV infection are treated with IV acyclovir, while most other viral encephalitides are managed with supportive care. 10mg/kg acyclovir IV q8h (duration of 14-21d minimum for HSV encephalitis, & 10-14d for VZV encephalitis).

First-line treatment of anti-NMDAR encephalitis include: tumor removal (when present); corticosteroids; IV immunoglobulin (IVIg) or; plasmapheresis. One method is to combine Ig (0.4g/kg/d) & IV methylprednisolone daily for 5-7d with plasma exchange (1 vol. every other day for 5 sessions).

The Second-line treatment of anti-NMDAR includes rituximab &/or cyclophosphamide. Use rituximab or cyclophosphamide if improvement isn’t observed within 10d. Detection of anti-NMDAR antibodies in serum and/or CSF confirms the diagnosis of anti-NMDAR encephalitis.

Acute disseminated encephalomyelitis can be treated with: high-dose 20-30mg/kg/day methylprednisolone IV to 1g/d max for 3-5d, followed by oral prednisone tapered over 4-6wks.  0.4mg/kg/day IVIg for 5d should be considered if patient is unresponsive to steroids.

Antimicrobial doses

• Ampicillin: 30mg/kg IV q4h

• Ceftazidime: 30mg/kg IV q8h

• Cefepime: 30mg/kg IV q8h

• Ceftriaxone: 30mg/kg IV q12h

• Meropenem: 40mg/kg IV q8h

• Metronidazole: 7.5mg/kg IV/PO q6h

• Penicillin G: 60,000-70,000U/kg IV q4h

• Gentamycin: 1.7mg/kg IV q8h

• Trimethoprim-sulfamethoxazole: 5mg/kg IV q6h

• Vancomycin: 15mg/kg IV q6h