EMCrit Podcast 28 – Severe CNS Infections

Severe CNS Infections are time dependent diagnoses! You must have a high index of suspicion, a good plan for your work-up, and rapid provision of treatment. After seeing a severely ill meningitis patient, I figured I would do a podcast on some tips and pearls on this topic.

When to Suspect

Here is the article I mentioned on establishing pretest prob:


What Antibiotics

Ceftriaxone 2g as empiric therapy in any suspected meningitis patient

If high risk or LP results are positive, also give

  • Vancomycin 1 G
  • Ampicillin 2g if age > 50 y/o
  • Acyclovir 10  mg/kg if high RBC count, obtundation, seizures, or focal neurologic deficit
  • Dexamethasone 10 mg
  • Cefepime or Imipenem if hospitalized or neurosurgery patient

listen to the podcast for more and see the EMCrit chapter for more.

photo by Lapoland

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  1. Mac says

    Assuming you are unable to get CSF after multiple failed attempts while the pt is laying down, don’t have the resources to call Neuro or Radiology to do the procedure for you, do you have any thoughts on getting the needle in w/ good CSF flow while the pt is sitting, and then laying the pt down to get the opening pressure?

    What is the numerical difference in opening pressures between laying and sitting?

    • emcrit says

      If I can’t get it lying down, I have never seen benefit from sitting the patient up. But that is just me, I know for some folks sitting the pt up makes things much easier. I usually grab ultrasound in this situation. Also, if I am hitting ligaments that feel like bones, I use para-median approach. To answer you question, the seated pressure will be changed by the height of the CSF column from the patient’s brain to you needle; you can’t correct for this. If you were able to support the needle and lay the patient down, it would be accurate, but I would be scared of the needle moving in the process. I think in this case you just accept that you will not get an opening pressure.

    • emcrit says

      i roll them on their side, move their legs way up in to fetal position and then put the bed rail back up. This keeps their knees from falling down. I then loop a sheet around their knees and tie it high up on the bed rail. Mech vent should not sig. affect the opening pressure, unless the PEEP is crazy high.

  2. Kurt says

    Can you comment on Academic Emergency Medicine Volume 10, Number 5 492-493, M Andrew Levitt Conclusion: Higher opening pressures are seen in the FSP compared to the LRP. However,the difference was not found to be of clinical significance and a conversion formula is developed to allow the FSP to be used and the pressure obtained to be converted to LRP.
    Lateral Recumbent position pressure equal = 0.7 Flexed seated position cm H2O-0.8

    • emcrit says


      I’d love to see the article when it is actually published, but I think the authors have only published the abstract. They derived the correction formula retrospectively; it needs to be prospectively validated before prime time use.

  3. jay says

    You mentioned an article in the podcast talking about minimal cross-reactivity between penicillin and 3rd generation cephalosporins in pen-allergic patients…do you have a reference for that?

    • emcrit says

      Studies of second- and third-generation cephalosporins show no increase in allergic reactions in patients who have a history of penicillin allergy (Ann Allergy Asthma Immunol 1995;74(2))

      AAP cephalosporins in the pen allergic patient (Pediatrics 2005;115(4):1048)

      From EMEDHome:
      Prescribing Cephalosporins in the Setting of a Penicillin Allergy: What is the Truth?

      Conventional wisdom holds that there is a significant risk of an allergic reaction if a cephalosporin is prescribed to a patient with a history of a PCN allergy (2007 PDR: “cross-hypersensitivity among beta-lactam antibiotics has been clearly documented and may occur in up to 10% of patients with a history of penicillin allergy”).

      Key Background Facts:

      * Early studies on this topic were very flawed because the penicillin test compounds had been contaminated with cephalosporins; until 1982, penicillin was produced commercially using the cephalsoporium mold (1,2). Furthermore, these early studies upon which the frequently quoted 10% cross-reactivity is based did not routinely confirm the allergy by skin testing, and at least some of the reactions were not immune-mediated (3).
      * When patients with a history of PCN allergy receive 1st generation cephalosporins – which share a side chain similar to penicillin – they may exhibit an increased risk of an allergic reaction. However, 2nd and 3rd generations cephalosporins are different enough structurally from PCN that they do not increase the risk of allergic cross-reactivity (1).

      Most patients who give a history of PCN allergy are not so allergic: The most frequent reactions are non-pruritic, non-urticarial rashes; for most the mechanism is idiopathic and not a contraindication to future use. The term “penicillin allergy” is often misused: although studies vary, perhaps 10% of patients who state they are truly “allergic to penicillin” are truly allergic (4-6).

      Much of the literature advises skin testing prior to administration of cephalosporins in a patent who describes a penicillin allergy, but skin testing is not practical in the ED. In fact, penicillin skin tests do not predict the likelihood of allergic reactions to cephalosporins in patients with histories of penicillin allergy (1,7). It is also important to note that extensive post-marketing studies of 2nd and 3rd generation cephalosporins showed no increase in the number of allergic reactions in patients with penicillin allergy (7). To further emphasize this point, it should be pointed out that the AAFP recently released an evidence-based clinical practice guideline on the treatment of acute otitis media recommending the use of 2nd/3rd generation cephalsoporins for patients allergic to penicillin (1).

      Several studies indicate that cephalosporin-induced anaphylaxis occurs no more frequently among patients with known PCN allergy than among those without such allergy (1,2). Furthermore, PCN allergy is most likely simply a marker for an allergic individual in general as opposed to a marker of cross-reactivity with cephalosporins: A recent retrospective study of a huge database of over 3 million patients who received penicillin revealed that 1.1% of the patients who had an allergic-like event (ALE) after penicillin also had an ALE after a cephalosporin BUT 1.6% of the patients who had an ALE after penicillin also had an ALE after a sulfonamide! (8)

      Conclusion: “For patients truly allergic to penicillin, the risk of reaction from a cephalosporin with side chains that differ from penicillin is so low that use is justified and medico-legally defensible by the currently available evidence” (1). A reasonable approach is that cephalosporins can safely be given to a penicillin-allergic patient who did not experience anaphylaxis to the penicillin.

      (1) Pichichero ME. Cephalosporins can be prescribed safely for penicillin-allergic patients J Fam Pract 2006;55(2):106-12.
      (2) Kelkar PS, Li JT. Cephalosporin allergy N Engl J Med 2001345: 804-9.
      (3) Gruchalla RS, Pirmohamed M. Clinical practice. Antibiotic allergy N Engl J Med 2006;354: 601-9.
      (4) Graff-Lonnevig V, et al. Penicillin allergy – a rare paediatric condition? Arch Dis Child 1988;63(11):1342-6.
      (5) Surtees SJ, et al. Allergy to penicillin: fable or fact? BMJ 1991;302: 1051-2.
      (6) Salkind AR, et al. The rational clinical examination. Is this patient allergic to penicillin? An evidence-based analysis of the likelihood of penicillin allergy JAMA 2001;285: 2498-2505.
      (7) Anne S, Reisman RE. Risk of administering cephalosporin antibiotics to patients with histories of penicillin allergy Ann Allergy Asthma Immunol 1995;74: 167-70.
      (8) Apter AJ, et al. Is there cross-reactivity between penicillins and cephalosporins? Am J Med 2006;119: 354.e11-19. (EMEDHOME.com)

  4. Michael says

    I have always been taught that adding acyclovir to someone with focal neurological signs and a meningitis picture was basically closing the barn door after the cows had gotten out, as it takes two days or so for the acyclovir to be incorporated into the HSV and kill the virus (time you obviously don’t have), and that the better solution was simply proper supportive care (fluids, pain management, etc). Have I just been getting bad advice?

    • emcrit says

      untreated, HSV encephalitis has a mortality of ~70%. With acyclovir it goes down to about 28%, see (N Engl J Med. 1986 Jan 16;314(3):144-9.
      Vidarabine versus acyclovir therapy in herpes simplex encephalitis.) As you allude to, the earlier the better, but I had not come across the 2 day timing at all. I don’t think you will find many folks who would just treat presumed or known HSV enceph with only supportive care. So I don’t want to say the advice is bad, but I would love to see some data. : )

      thanks so much for commenting. reply or email me if you have more.


  5. Mike Whiting says

    Just curious– what did this guy have? Certainly sounds suspicious for herpes, WNV or other meningoencephalitis……

    Just wondering. Love the podcast and catching up on back issues.

    Mike whiting
    Santa Fe NM

  6. J Kim says

    First of all, real nice blog. Great job!
    For ampicillin, age 50 (rather than 60) are recommended cut-offs for empiric tx for Listeria per IDSA guideline on bacterial meningitis.

    Also, rather than imipenem, meropenem is a better choice per IDSA, if you are going to use a carbapenem for pseudomonas coverage, given higher propensity for imipenem to cause seizures, in baterial meningitis where your brain is already inflamed and susceptible to seizures.


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