AM Report 10/25/16: Bacterial Meningitis

Indications for CT before LP:

  • >60 years old
  • Immunocompromised state
  • History of CNS disease (mass lesion, stroke, focal infection)
  • Seizure within 1 week of presentation
  • Altered consciousness / focal neurological deficit

* Patients with suspected meningitis without the above findings are good candidates for LP without CT given their low risk for herniation.

CSF Studies: Normal Bacterial Meningitis Viral Meningitis Fungal/TB Meningitis
Opening Pressure (cm H20) <15 Normal/↑ Normal/↑
Protein (mg/dL) 15-45 Normal/↑
Glucose (mg/dL) 40-70 Normal
WBC Count (uL) 0-8 ↑↑ (>1000) ↑ (50-300)
WBC Differential Normal >80% PMNs >50% Lymphs, <20% PMNs 50-80% Lymphs

Common Signs/Symptoms:

  • Patient’s often present soon after onset of symptoms ~ 24 hours (range 1 hour – 14 days)

Classic Triad:

  • Fever (95-77% at presentation)
  • Nuchal Rigidity (94-83% at presentation)
  • Altered Mental Status (83-78% at presentation)
  • *Headache (94-79% at presentation)

*One review of 696 cases of community-acquired bacterial; only 44% had clinical triad, although almost all (95%) had at least 2 of 4 symptoms.

Laboratory Findings (besides CSF):

  • Routine blood work is often unrevealing, but leukocytosis can be present
  • Serum chemistry may reveal an AG metabolic acidosis or hyponatremia (30% in one study)
  • Blood cultures are often positive (50-90% of patients) and can help guide therapy

Common Pathogens:

1.jpg

  • Streptococcus pneumoniae (71%)
  • Neisseria meningitidis (12%)
  • Group B Streptococcus (7%)
  • Haemophilus influenza (6%)
  • Listeria moncytogenes (4%)

* Percentages based on CDC data of 1083 cases of bacterial meningitis from 2003-2007

Treatment for Suspected Bacterial Meningitis:

  • Empiric therapy should be directed at the most likely bacteria and must be started without delay

Typical empiric regimen:

  • 3rd generation cephalosporin (Ceftriaxone 2 g IV Q12H or Cefotaxime 2 g IV Q6H)
  • Vancomycin 15-20 mg/kg IV Q12H ~ goal trough 15-20 mcg/mL
  • Ampicillin in patients > 50 years old

Indications for Steroids:

  • Used in attempt to diminish the rate of neurological complications (seizures, hearing loss, cranial nerve deficits, etc.)
  • European studies showed a decreased mortality (7% versus 15% with placebo)
  • Only indicated for patients with suspected/confirmed S. pneumoniae
  • 15 minutes before administration of antimicrobial agents and continued for full course (0.15 mg/kg Q6H for 4 days)  in suspected/confirmed pneumococcal meningitis

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