What are the key parameters and treatment options for interpreting lumbar punctures in suspected cases of meningitis?

From the Guidelines

Interpreting lumbar puncture results in suspected meningitis requires a comprehensive evaluation of CSF parameters, including opening pressure, appearance, cell count, protein, glucose, and microbiological studies, to guide treatment and improve patient outcomes. When interpreting lumbar puncture results, it is essential to consider the following key parameters:

• CSF opening pressure: Normal pressure is 10-20 cmH2O, with elevated pressure suggesting infection or increased intracranial pressure 1
• Appearance: Clear CSF suggests viral etiology, while cloudy or turbid fluid indicates bacterial infection
• Cell count: Neutrophil predominance (>1000 cells/μL) is typical of bacterial meningitis, while lymphocyte predominance (<500 cells/μL) is characteristic of viral meningitis
• Protein: Elevated protein (>100 mg/dL) is often seen in bacterial meningitis, while mildly elevated protein is typical of viral meningitis
• Glucose: Decreased glucose (<40 mg/dL or CSF:serum ratio <0.4) is characteristic of bacterial meningitis, while normal glucose is typical of viral meningitis

Treatment options for suspected meningitis include:

• Empirical antibiotic therapy with vancomycin (15-20 mg/kg IV q8-12h) plus ceftriaxone (2g IV q12h), adding ampicillin (2g IV q4h) for patients >50 years or immunocompromised to cover Listeria 1
• Dexamethasone (0.15 mg/kg IV q6h for 2-4 days) should be administered before or with the first antibiotic dose in suspected bacterial meningitis to reduce inflammation and improve outcomes 1
• Supportive care is typically sufficient for viral meningitis, though acyclovir (10 mg/kg IV q8h) should be given if HSV is suspected

It is crucial to note that cranial imaging before lumbar puncture is only recommended for patients with specific clinical characteristics, such as focal neurologic deficits, new-onset seizures, severely altered mental status, or severely immunocompromised state 1. In the absence of these features, lumbar puncture should be performed promptly to obtain CSF for analysis and guide treatment.

Key considerations when interpreting lumbar puncture results include:

• The potential for traumatic tap, which can contaminate the CSF with blood and affect the results 1
• The importance of considering the clinical context and other CSF parameters when interpreting the results 1
• The need for prompt treatment and adjustment of antibiotics based on culture results to improve patient outcomes 1

From the FDA Drug Label

For the treatment of meningitis, it is recommended that the initial therapeutic dose be 100 mg/kg (not to exceed 4 grams). Thereafter, a total daily dose of 100 mg/kg/day (not to exceed 4 grams daily) is recommended.

The key parameters for interpreting lumbar punctures in suspected cases of meningitis include:

• Cerebrospinal fluid (CSF) analysis: to confirm the presence of infection
• Dosing of ceftriaxone: initial therapeutic dose of 100 mg/kg (not to exceed 4 grams), followed by a total daily dose of 100 mg/kg/day (not to exceed 4 grams daily) Treatment options include:
• Ceftriaxone: a recommended antibiotic for the treatment of meningitis, with a dosage of 100 mg/kg/day (not to exceed 4 grams daily) 2
• Duration of therapy: usually 7 to 14 days, but may be longer in complicated infections

From the Research

Key Parameters for Interpreting Lumbar Punctures

• Cerebrospinal fluid (CSF) white blood cell (WBC) count: an elevated count can indicate meningitis 3, 4
• CSF-blood glucose ratio: a ratio of 0.4 or less can accurately diagnose bacterial meningitis 4
• CSF lactate level: a level of 31.53 mg/dL or more can accurately diagnose bacterial meningitis 4
• CSF WBC to red blood cell (RBC) ratio: a ratio of <or=1:100 can predict the absence of disease 3
• Observed to predicted (O:P) CSF WBC ratio: a ratio of <or=0.01 can predict the absence of disease 3

Treatment Options for Suspected Meningitis

• Empirical therapy: ceftriaxone and vancomycin for all patients, with vancomycin only added for patients with a higher likelihood of pneumococcal meningitis or reduced susceptibility to ceftriaxone 5
• Anti-Listeria agent: benzylpenicillin should be added to the treatment regimen for patients with risk factors for Listeria meningitis 5
• Dexamethasone: should be a routine component of empirical therapy due to its proven role in reducing morbidity and mortality from pneumococcal meningitis 5

Importance of Prompt Lumbar Puncture

• Early treatment is pivotal for favorable outcome in acute bacterial meningitis (ABM) 6
• Performing prompt lumbar puncture is associated with decreased mortality and increased favorable outcome 6
• Adherence to guidelines that prioritize prompt lumbar puncture, such as the Swedish guidelines, is associated with improved outcomes 6