B44 - meningitis, encephalitis Flashcards by Olivia Brownlee

Meningitis most common causative organisms age>3m

Neisseria meningitidis (meningococcus) - a gram-negative, aerobic diplococcus
Streptococcus pneumoniae (pneumococcus) -a gram-positive, anaerobic bacteria with a lancet shaped diplococcus structure.
Haemophilus influenzae type b

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Immediate Mx suspected meningitis

ABCDE

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Treatment given in community for suspected meningitis

Benzylpenicillin sodium IV/IM in IV unavailable

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Benzylpenicillin sodium doses based on age

<11m - 300mg
1-9y - 600mg
>10y (&adults) - 1.2g

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Benzylpenicillin drug class

Beta lactam antibiotics (penicillins)

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Beta-lactam pen ab MOA

bind to penicillin-binding proteins and inhibit synthesis of the peptidoglycan layer of the cell wall

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Benzylpenicillin particularly effective against..

aerobic gram-positive bacteria, with some activity against gram-negative cocci and anaerobic organisms and no activity against gram-negative bacilli.

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Benzylpenicillin indications (7)

Meningitis
Endocarditis
Intrapartum prophylaxis against group B streptococcal infection
Tonsillitis/otitis media/pneumonia/cellulitis

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Benzylpenicillin CI

Hypersensitivity to penicillins

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Benzylpenicillin SE (6)

Hypersensitivity
GI disturbance
CNS toxicity
Interstitial nephritis
Blood disorders
Antibiotic associated colitis

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Benzylpenicillin interactions (2)

Warfarin

Methotrexate (risk of toxicity)

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What drug (& class/dose) is offered immediately following LP in suspected meningitis (adult)

3rd generation cephalosporin: Ceftriaxone or Cefotaxme IV

8g daily in 4 daily doses, increased if necessary to 12g daily in 3-4 divided doses

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Alternative initial drugs offered immediately following LP in suspected meningitis

Penacillin (if cephalosporin anaphylaxis)

Chloramphenicol: Used ONLY in life-threatening conditions, because of its toxicity. Biggest unwanted effect is bone marrow toxicity (aplastic anaemia, reversible anaemia).
Can cause “grey baby” syndrome

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Why are Third generation cephalosporinsare usually the empirical antibiotic of choice for bacterial meningitis

Known bactericidal activity for both pneumococci and meningococci
Increased ability to cross the blood-brain barrier

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How are beta-lactam cephalosporins classified

Classified by generations, with succeeding generations having enhanced activity against gram-negative bacilli at the expense of gram-positive activity and increased ability to cross the blood-brain barrier.

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cefotaxime indications (3)

Meningitis
Haemophilus epiglottitis
Sexually transmitted infections

cefotaxime CI (2)

Hypersensitivity to cephalosporins

Immediate hypersensitivity to penicillin

Cefotaxime SE (6)

Hypersensitivity
GI disturbance
Skin reactions (including Stevens-Johnson syndrome)
Cholestatic jaundice
Blood disorders
Antibiotic associated colitis

Cefotaxime interactions

Ibuprofen
Aminoglycosides
Methotrexate (nephrotoxicity)

What can be given to help prevent/treat cerebral oedema and act as an adjunct treatment of bacterial meningitis?

Dexamethasone

dexamethasone indications (4)

Cerebral oedema and adjunct treatment of bacterial meningitis
Rheumatic disease
Suppression of inflammatory and allergic disorders
Symptom control in a palliative care setting

(Potential uses within a palliative care setting include pain due to nerve compression, nausea and vomiting, dyspnoea due to bronchospasm/obstruction, anorexia and dysphagia.)

dexamethasone contraindications (3)

Systemic infection (except bacterial meningitis as benefits outweigh risk)
Live vaccines (if high dose)
Many associated cautions

Dexamethasone SE

Cushings syndrome

Infections
Myopathy
Osteonecrosis/porosis
Neuropsychiatric symptoms
HPA insufficiency
Weight gain, oedema, impaired glucose metabolism, insulin resistance, beta cell dysfunction
Gastric ulcer (w concomitant NSAIDS)
Hirsutism, skin thinning
Cataract, glaucoma
^ Cardiovascular risk

Consequences of abruptly stopping dexamethasone

acute adrenal insufficiency, hypotension and death

due to HPA surpression

Drugs which interact with dexamethasone to cause hypokalaemia (9)

``` Citalopram & venlafaxine Amiodarone Antipsychotics Lithium Clarithromycin & erythromycin Sildenafil Ondansetron Furosemide Methadone ```

Drugs which interact with dexamethasone to produce GI effects (2)

NSAIDs (bleeding) | Nicorandil (perforation)

Drug toxicity interactions with dexamethasone (4)

Digoxin (digoxin toxicity) Warfarin  (increased anticoagulant effect) Clarithromycin (increased exposure to steroid) Ketoconazole (increased steroid exposure)

Suspected meningitis (w/o signs of shock, severe sepsis or brain shift) immediate Ix/Mx (5 steps)

``` Blood cultures Lumbar puncture Dexamethasone 10mg IV Ceftriaxone or Cefotaxime 2mg immediately following LP, or if LP can't be done within 1 hour immediately after blood cultures taken (penicillin 2nd line) Careful fluid resus (avoid overload) ``` CT scan usually NOT indicated

Suspected meningitis with signs suggestive of shift of brain compartments secondary to increased ICP immediate Ix/Mx (7 steps)

Get critical care input Secure airway, high flow O2 Take bloods including cultures Dexamethasone 10mg IV Give ceftriaxone of cefotaxime 2mg IV immediately after blood cultures taken DELAY LP Arrange neurological imaging once patient stabilised

Susepected meningitis with signs severe sepsis or a rapidly evolving rash (with or without signs or symptoms of meningitis) 7 steps Ix/Mx

``` Get critical care input Secure airway and give high flow O2 Fluid resus Blood cultures Ceftriaxone or cefotaxime 2mg immediately after blood cultures taken DELAY LP Follow surviving sepsis guidelines ```

Differences in presentation between viral meningitis and encephalitis

Viral Meningitis - Symptoms of headache, neck stiffness,photophobia. GCS normal unless unresponsive. Caused by enteroviruses and herpes viruses. Encephalitis - Flu-like symptoms, headache, psychiatric symptoms. (triad headache, fever, altered GCS/confusion) Caused by herpes simplex.

Viral encephalitis 1st line Mx

Aciclovir

Aciclovir MOA

Guanosine analogue which inhibits synthesis of viral DNA. Requires phosphorylation by viral enzymes that are not present in uninfected host cells, preventing cytotoxic effects on human cells. Aciclovir targets viral DNA polymerase terminating viral DNA synthesis and thus replication. Most active against HSV

Aciclovir indications

Herpes simplex and varicella zoster infections

Aciclovir cautions

Elderly patients (risk of neurological reactions)

Aciclovir SE (6)

GI disturbance (nausea, vomiting, diarrhoea, abdominal pain), Skin reactions and photosensitivity Blood disorders (anaemia, leucopenia, thrombocytopenia), Renal impairment CNS effects (agitation, coma, confusion, ataxia, dizziness, encephalopathy, psychosis) Hepatic disorders

Aciclovir administration route for encephalitis

IV only Not available as oral treatment for encephalitis Available as oral tablet for chickenpox/shingles/labial or genital herpes

Aciclovir length of treatment encephalitis

Min 14 days Min 21 days if immunocompromised Repeat LP to confirm CSF is negative before stopping