Notes
Bacterial Meningitis Management
Sections
Overview
Here, we will walk through a guide to empiric, acute bacterial meningitis management. The purpose of this tutorial is to equip us with key, life-saving knowledge in suspected acute bacterial meningitis.
Topic
- Clinical Presentation
- Common Bacteria
- Therapeutic Rationale
- Standard Empiric Regimen
Clinical Presentation
Overview
We will specifically address:
- Key symptoms
- Key signs
- Key diagnostic tests
- Warning signs for lumbar puncture (signs of increased intracranial pressure – to avoid brain herniation)
Symptoms
Key symptoms
- Headache
- Photophobia
- Nausea/Vomiting
- Altered mental status (especially, confusion and depressed level of consciousness)
- Seizure
Mimickers
- Without going into a detailed differential diagnosis, it's helpful to consider that migraine and subarachnoid hemorrhage have similar symptom patterns. So, when we think of those diagnoses, we should also be thinking about bacterial meningitis (albeit far less common).
Physical Exam Signs
Key Signs
- Fever
- Focal neurological deficits (we can think of one-third of patients as having these).
- Meningismus. Two notable physical exam signs for meningismus (maneuvers that exacerbate meningismus):
- Kernig sign, which is positive if the patient has their hip flexed to 90 degrees but cannot fully extend the knee.
- Brudzinski sign is positive if with passive neck flexion, the patient automatically flexes the hip and knee.
- Rash occurs in meningococcal meningitis in roughly 60% of cases.
Waterhouse Friderichsen syndrome
- Waterhouse Friderichsen syndrome was first described in meningococcal sepsis and involves bilateral adrenal hemorrhage, petechial rash, purpura, DIC, in the setting of sepsis.
Index of Suspicion
It's helpful to be able to gauge a level of suspicion. Studies have shown that of the following 4 key symptoms: Headache, Fever, Stiff neck (meningismus), Altered mental status...
- Roughly 95% of patients will have at least 2 symptoms.
- Only roughly 20% of patients will have all 4 symptoms.
The take-home is that we need a high index of suspicion of this diagnosis to avoid missing it.
Diagnostic Testing
Testing
Basic diagnostic testing in suspected bacterial meningitis:
*All patients should be sent for a STAT noncontrast head CT to look for other culprits (eg subarachnoid hemorrhage) and to look for signs of increased intracranial pressure (ICP).
- Lumbar puncture for CSF evaluation (if no red flag features of ICP).
- Blood cultures.
- Note that blood cultures should be done prior to administering antibiotic therapy but antibiotics should not be delayed for lumbar puncture.
- Although blood cultures are not as reliable as CSF cultures for meningitis management, there are instances where LP cannot be performed.
- It is important to know when it is unsafe to perform a lumbar puncture due to the risk of brain herniation.
Risk of Brain Herniation (Warning for LP)
Brain herniation from lumbar puncture is a concern in the clinical setting of:
- Reduced level of consciousness
- Focal neurological deficits
- Papilledema.
- CT findings of increased intracranial pressure such as:
- Obliteration of CSF spaces, meaning compression (effacement) of the ventricles and obliteration of the cisterns and sulcal spaces.
- Loss of grey/white differentiation of the cerebral gyri.
- Signs of brain herniation
Common Bacterial Causes of Meningitis
Adults
All Adults
Let's start with the simplest, adults, include:
- Streptococcus pneumoniae (pneumococcal meningitis): the most common cause across all age groups.
- Neisseria meningitis (meningococcal meningitis)
They occur from blood stream invasion or direct leptomeningeal invasion of upper respiratory infection, most notably.
Older than 50 years old
- Listeria monocytogenes is also an organism that we need to routinely consider in adults older than 50 years old (as well as in compromised immune systems).
Pediatrics (3 months to 18 years old)
Now for pediatrics, less than 18 years old, include the same organisms but switch their order:
- Neisseria meningitis (the most common in this age group)
- Streptococcus pneumoniae
Newborn (less than 3 months)
For newborn, less than 3 months, include:
- Group B streptococcus (streptococcus agalactiae), which is the most common.
- Escherichia coli (E. coli), the most deadly.
- Listeria monocytogenes, another common microorganism (from food contamination).
Special Conditions
Now, let's turn to some important additional causes in special conditions.
The unvaccinated, the immune suppressed, and post-surgical patients.
Unvaccinated
- In the unvaccinated, we need to worry about haemophilus influenza (this is not the virual influenza, but the bacterial influenza). Prior to the introduciton of the hep. b vaccine, H. influenza was the most common cause of meningitis in children.
Immune-suppressed
For the immune suppressed, we need to think about (at the very least):
- Listeria monocytogenes
- Gram-negative aerobic organisms, most notably pseudomonas aeruginosa.
Post-surgical patients
Finally, for post-surgical patients (who will usually be treated by neurosurgery directly), there is a much wider-range of organisms, including (but, again, not limited to):
- Streptococcus species (not just strep pneumoniae)
- Staphylococcus aureus
- Gram-negative aerobic organisms, again, most notably pseudomonas aeruginosa.
- Gram-negative anaerobic organisms, most commonly bacteroides fragilis
Therapeutic Rationale
Ceftriaxone
- Ceftriaxone for streptococcus pneumoniae and neisseria meningitidis.
- You'll see that cefotaxime is sometimes used instead of ceftriaxone (but it's commonly considered to be more difficult to dose, so it's less commonly preferred).
- Ceftriaxone is responsible to knocking out the most common organisms in most individuals.
Vancomycin
- Vancomycin for double-coverage of streptococcus pneumoniae and also broad coverage of staph aureus: MRSA and MSSA, as well as other species of streptococci, and also enterococcus faecalis.
- Vancomycin doesn't cover the full extent of post-surgical organisms and it is not the treatment for the primary causes of community-acquired meningitis, but it does target some important additional organisms not captured by our 3rd generation cephalosporin.
Ampicillin
- In older adults, immune-compromised, and alcoholics, we use ampicillin to cover for listeria monocytogenes.
Cefepime
- Cefepime (a 4th generation cephalosporin) is often used to cover pseudomonas aeruginosa.
- Note that ceftazidime (a 3rd generation cephalosporin) has better pseudomonas a. coverage but worse step pneumoniae coverage.
- Note that meropenem also covers pseudomonas a.
Metronidazole
- Metronidazole covers for anaerobic bacteria (eg, bacteroides fragilis).
- Note that meropenem will cover for this, as well.
Meropenem
- Meropenem covers for a broad range of gram positive and gram negative aerobic and anaerobic organisms but not MRSA.
- Importantly, note that it is safe in penicillin (and cephalosporin) allergy (even severe (anaphylactic) reactions).
Acyclovir
- It's always important to remind ourselves of acyclovir for herpes simplex encephalitis (HSV encephalitis) -- bacterial meningitis is often suspected in the setting of cases that can turn out to be HSV encephalitis, and we can easily forget about acyclovir, since there are already so many drugs to consider.
Dexamethasone
- Importantly, it was shown that steroids at least 15 minutes prior to the initial dose of antibiotics will help preserve hearing in patients with pneumococcal meningitis.
Standard Regimen (Adult & Non-Newborn Pediatric)
Note that the blood-brain barrier reduces penetration of the antibiotics so higher doses of medication are required to treat meningitis than other systemic infections. Note that break-down of the blood brain barrier due to meningitis does impact penetrance (increasing penetrance) and steroid administration to reduce pathogenesis in strep pneumoniae will reduce drug penetrance.
All Individuals
Dexamethasone
Adult dose: 10 mg Q 6 hours IV (for 4 days)
Pediatric dose: 0.15 mg/kg IV (for 2 - 4 days)
Ceftriaxone
Adult dose: Ceftriaxone 2 grams Q 12 hours IV
Pediatric dose: Ceftriaxone 50mg/kg Q 12 hours IV
Vancomycin
Adult dose: Vancomycin 1 gram Q 12 hours IV
Pediatric dose: Vancomycin 15 mg/kg Q 6 hours IV
Older adults & immune-suppressed
Ampicillin
Adult dose: Ampicillin 2 g Q 4 hours IV
Pediatric dose: Ampicillin 75 mg/kg Q 6 hours IV
HSV Encephalitis Coverage
Acyclovir
Adult dose: Acyclovir 10 mg/kg Q 8 hours IV
Pediatric dose: Acyclovir 10-20 mg/kg Q 8 hours IV
Newborns
Newborns receive a different regimen, which we will not include in detail. For reference, it is typically recommended they receive a combination of vancomycin, an aminoglycoside, and cefepime or meropenem.