Flashcards in Bacterial Meningitis Deck (30)
What is bacterial meningitis?
inflammation of meninges with increased intracranial pressure and pleocytosis (increased WBCs) in cerebrospinal fluid secondary to bacteria in the pia-subarachnoid space and ventricles
What is the classic triad of bacterial meningitis?
fever (95%), neck stiffness/nuchal rigidity (88%), and altered mental state (78%) - more common with pneumococcal meningitis - absence of all three essentially excludes bacterial meningitis
What are additional common symptoms of bacterial meningitis?
headache (severe and generalized), lethargy, vomiting, nausea, photophobia, seizures, coma, rash (purpura fulminans), myalgia, unilateral cranial nerve abnormality, papilledema, nonreactive pupils, decorticate (damage to corticospinal tracts - arms adducted and flexed)/decerebrate (damage to upper brain stem - arm adducted and extended) posturing
What is Kernig's sign?
positive when the thigh is flexed at the hip and knee at 90 degree angles, and subsequent extension in the knee is painful (leading to resistance)
What is Brudzinski's sign?
severe neck stiffness causes a patient's hips and knees to flex when the neck is flexed
What are the most common causes of bacterial meningitis?
S. pneumoniae (most common in adults), N. meningitidis (most common in children and young adults), L. monocytogenes, for patients with HIV - invasive meningococcal disease
How is bacterial meningitis diagnosed?
STAT lumbar puncture as soon as the diagnosis suspected
What aspects of CSF examination are consistent with bacterial meningitis?
opening pressure (> 100- 200), WBCs (> 1000/mm3), neutrophilic predominance (> 80%), Gram stain +, protein (> 50 mg/dl), glucose (< 40 mg/dl), culture +, bacterial antigen (50% to 100% sensitivity)
What is the workup for bacterial meningitis?
blood cultures, WBC with differential, CSF examination
When is empiric IV Abx treatment necessary for bacterial meningitis?
purulent CSF fluid at time of lumbar puncture, PT is asplenic, PT has signs of DIC or sepsis
What is the treatment for bacterial meningitis in adults?
vancomycin: 15-20 mg/kg IV q8 to 12 h PLUS 3rd generation cephalosporin (ceftriaxone - 2 g IV q12h or cefotaxime - 2 g IV q4 to 6 h) for 10 to 14 days - for adults over age 50, add ampicillin (2 g IV q4h) to cover Listeria (given for 21 days)
What is the treatment for bacterial meningitis in immunocompromised adults?
vancomycin plus ampicillin plus cefepime or meropenem to cover Pseudomonas
When should corticosteroids be used in bacterial meningitis?
first 4 days of therapy (dexamethasone 0.15 mg/kg q6h) - main indication is for known or suspected pneumococcal meningitis (only continue if CSF Gram stain or blood cultures reveal S. pneumoniae)
What is pleocytosis?
elevated CSF WBC concentration - does not necessarily diagnose an infection
What is a normal protein concentration in the CSF?
< 50 mg/dL - proteins are largely excluded from the CSF by the blood-CSF barrier (may be mildly elevated in DM, subarachnoid hemorrhage, or traumatic lumbar puncture)
What is a normal glucose concentration in the CSF?
normal ratio of CSF-to-serum concentration is > 0.6 (can take hours for serum glucose to equilibrate with CSF glucose) - concentrations < 18 mg/dL are strongly predictive of bacterial meningitis
What are the normal CSF findings in viral meningitis?
WBC < 250/microL (predominance of lymphocytes), protein < 150 mg/dL, glucose > 50% serum concentration
What are the normal CSF findings in bacterial meningitis?
WBC > 1000/microL (neutrophilic predominance > 80%), protein > 200 mg/dL, glucose < 40 mg/dL
How is severe hypoglycorrhachia defined?
severe reduction of glucose concentration in CSF (< 10 mg/dL)
When is rifampin added in the treatment for bacterial meningitis?
in the setting of treatment with dexamethasone because entry of vancomycin into the CSF may be reduced by the decrease in inflammation with treatment by dexamethasone
What are the treatment recommendations for N. meningitidis?
3rd generation cephalosporins for 7 days and droplet precautions for first 24 hours
When can outpatient antimocrobial treatment be initiated in patients with bacterial meningitis?
after inpatient Tx for > 6 days, afebrile 24-48 hrs, no neurological dysfunction, clinical stability, able to take fluids by mouth, access to home health nurse/physician, reliable IV line, established plan of care, patient/family adherence, safe environment
What are clinical features associated with a poor outcome in bacterial meningitis?
hypotension, altered mental status, seizures
When is a CT scan of the head recommended prior to lumbar puncture in suspected bacterial meningitis?
age > 60 years, immunocompromised state, Hx of CNS disease (lesion, stroke, or focal infection), new onset (within 1 week) seizure, papilledema, abnormal level of consciousness, focal neurological deficit
What are relative contraindications to lumbar puncture in patients with suspected bacterial meningitis?
evidence of increased intracranial pressure, thrombocytopenia, spinal epidural abscess, skin infections at site, abnormal respiratory pattern, bleeding disorders
What is the mean opening pressure in a patient with bacterial meningitis?
350 mm H2O
What is a normal lactate concentration in the CSF?
< 3.5 mEq/L
What is the advantage of Gram stain in evaluation for bacterial meningitis?
can suggest the bacterial etiology 1 day or more before culture results are available: Gram+ diplococci (pneuococcal), Gram- diplococci (meningiococcal), Gram- coccobacilli (Hib), Gram+ rods/coccobacilli (listeria)
What is the jolt accentuation of headache test?
patient rotates head horizontally 2-3 times per second - test is positive for bacterial meningitis if patient reports exacerbation of headache with maneuver