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Monday, October 13, 2008

Bacterial Meningitis-high yield facts

  • The classic triad of symptoms of bacterial meningitis includes
    •  fever,
    • stiff neck,
    • and alterations of mental status.
  • However, only two thirds of adults may present with all of these symptoms. Fever appears to be the most common symptom of this triad among adults with meningitis, and the presence of any of these symptoms is highly sensitive for detecting bacterial meningitis. The absence of any of the triad of symptoms should prompt an evaluation for other etiologies of patient symptoms.
  • Specific physical signs, such as Kernig's sign, Brudzinski's sign, and nuchal rigidity, carry a low sensitivity for detecting bacterial meningitis, but Kernig's and Brudzinski's signs are fairly specific. Rash is present in only a minority of cases of bacterial meningitis.
  • Clinicians may be concerned regarding the possibility of cerebral herniation following lumbar puncture among patients with suspected meningitis, and this may prompt the use of CT imaging prior to lumbar puncture and delay medical treatment. The current review suggests that the relationship between lumbar puncture and brain herniation is tenuous, but CT should be considered prior to lumbar puncture among a subset of patients with a possible cerebral space-occupying lesion or brain shift along with suspected meningitis. Such patients include those with new-onset seizures, moderate-to-severe impairment of consciousness, a history of immunocompromise, and evidence of space-occupying lesions such as papilloedema and focal neurologic signs.

Classic cerebrospinal fluid findings among patients with bacterial meningitis include

    • white blood cell count more than 1000 cells per microliter,
    • more than 80% neutrophils on white blood cell differential,
    • elevated protein levels,
    • and reduced glucose levels.
  • However, approximately 10% to 20% of adults with bacterial meningitis do not have typical laboratory findings.
  • For adults younger than 50 years, empiric treatment should consist of 2 g of ceftriaxone or 2 g of cefotaxime plus 1 g of vancomycin plus 10 mg of dexamethasone intravenously. [Empirical coverage with a third-generation cephalosporin (cefotaxime or ceftriaxone) at appropriate doses for meningitis is recommended, based on a broad spectrum of activity and excellent penetration into the cerebrospinal fluid when the meninges are inflamed. Because of the increasing prevalence of multidrug-resistant Streptococcus pneumoniae in many parts of the world ,most experts recommend adding vancomycin to initial empirical therapy in adult patients.]
  • Ampicillin 2 g intravenously should be added for patients at age 50 years or older for possible infection with L monocytogenes.
  • treatment with dexamethasone every 6 hours for 4 days for adults with bacterial meningitis. Dexamethasone should be initiated before or during the initial dose of antibiotics.
  • Pearls for Practice
    Classic cerebrospinal fluid findings among patients with bacterial meningitis include white blood cell count of more than 1000 cells per microliter, more than 80% neutrophils on white blood cell differential, elevated protein levels, and reduced glucose levels.
  • For adults younger than 50 years, empiric treatment of suspected bacterial meningitis should consist of 2 g of ceftriaxone or 2 g of cefotaxime plus 1 g of vancomycin plus 10 mg of dexamethasone intravenously. Ampicillin 2 g intravenously should be added for patients at age 50 years or older for possible infection with L monocytogenes.
  • "Bacterial Meningitis Score"=determined that patients had a very low risk for bacterial meningitis if all of the following were absent:
    • positive CSF gram stain,
    • CSF absolute neutrophil count (ANC) of ≥ 1000,
    • CSF protein of ≥ 80 mg/dL,
    • a circulating ANC of ≥ 10,000 cells/microliter (mcL),
    • or a seizure as part of the presentation.

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