Bronchiolitis (part 2 of 2)

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Nebulised Hypertonic Saline… Everybody’s talking about it. Well, they should be. Is this finally the treatment for bronchiolitis that we’ve been waiting for? Could a cheap, simple medication like this be the answer to massive health-care costs?

Bronchiolitis is such a common condition, that saving a day (or even half a day) of hospital length of stay across the board, would result in major savings to healthcare costs, across the world.
If this was a new or patented drug, we would have heard all about it!
In this episode we discuss 4 original papers related to Hypertonic Saline for bronchiolitis, as well as the reviews riding on these original works.


Nebulised Hypertonic Saline for Bronchiolitis: Outline of this PEMcast

CP: welcome, disclaimer, overview

CP: Sarrell 2002: Nebulized 3% hypertonic saline solution treatment in ambulatory children with viral bronchiolitis decreases symptoms. [Chest 2002; 122: 2015-20]

SF: Mandelberg 2003: Nebulized 3% hypertonic saline solution treatment in hospitalized infants with viral bronchiolitis. [Chest 2003; 123: 481-7]

KB: Tal 2006: Hypertonic saline / epinephrine treatment in hospitalized infants with viral bronchiolitis reduces hospitalization stay: 2 years experience. [Israeli Medical Association Journal 2006; 8: 169-73]

CP: Kuzik 2007: Nebulized hypertonic saline in the treatment of viral bronchiolitis in infants. [Journal of Pediatrics 2007; 151: 266-70]

SF: Zhang 2008 Cochrane review: Nebulized hypertonic saline solution for acute bronchiolitis in infants. [Cochrane Database of Systematic Reviews 2008; CD006458]

KB: Horner 2009 BestBET: Nebulised hypertonic saline significantly decreases length of hospital stay and reduces symptoms in children with bronchiolitis. [Emergency medicine Journal 2009; 26: 518-9]

CP: summary / opinions of others

All: conclusions, goodbye

Thanks for joining us… Post a comment! Are you using hypertonic saline nebs for bronchiolitis?

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Traumatic LP for Meningitis

Special thanks to Reuben for inviting me to post this review from my teaching resident rotation.

Question:
Is a “corrected” CSF WBC count accurate for diagnosing meningitis for a traumatic LP?

Background:
Traumatic lumbar punctures may obscure accurate diagnoses. Many authors suggest correcting the WBC count by various methods — the most popular seem to be either 700 RBC = 1 WBC, or by using the actual patient’s RBC:WBC ratio in the blood. While this seems intuitive, does it work?
Answer:
Probably not.

Basically, no; the calculations are not helpful. But if the WBC count is MUCH higher than expected, it’s probably a positive tap.

Key points:

  • The sources I could find simply assert that correction is a viable method; I could not find any actual evidence that these corrections are valid.
  • Multiple small studies show that corrections are generally not accurate (including ref. 1), with ROC curves equivalent regardless of how — or if! — correction is applied
  • However, a few small studies also show that bacterial meningitis may be obvious despite a traumatic tap (refs 2 & 3):

If the “observed:predicted” ratio of CSF WBCs is >10, then some authors conclude that it indicates bacterial meningitis. Sensitivity & specificity are both around 80-90% with this method.

I think a higher threshold is probably better (ratio >100) — see images below.

Example:

CBC:
5 RBC (Hgb 15; Hct 45)
5 WBC

This is a predicted ratio of 1000:1 (RBCs are reported as 10^6/mcL and WBCs are 10^3/mcL)

A purely traumatic tap in this patient would be expected to look like this:

CSF
2000 RBC
2 WBC

If the CSF looked like this:
2000 RBC
20 WBC

than it is “likely” to be bacterial meningitis (Observed:Predicted = 10)

Looking at the data, I think we can all agree that this CSF is infected:
2000 RBC
200 WBC
(Observed:Predicted=100)

Here are the results from the Bonadio paper:

Bonadio data

Looking at their raw data, the ratio of 100 looks like a much better diagnostic cutoff, although it is probably best to still treat (i.e. antibiose & admit) pending more accurate tests (i.e. culture) if the picture is less clear.

Here is a ROC curve for their data, which looks pretty good altogether:

References:

  1. Greenberg RG, Smith PB, Cotten CM, Moody MA, Clark RH, Benjamin DK Jr. Traumatic lumbar punctures in neonates: test performance of the cerebrospinal fluid white blood cell count. Pediatr Infect Dis J. 2008 Dec;27(12):1047-51.
    There a number of similar small studies that all agree that adjustments are not useful.
  2. Bonadio WA, Smith DS, Goddard S, Burroughs J and G Khaja. Distinguishing cerebrospinal fluid abnormalities in children with bacterial meningitis and traumatic lumbar puncture. The Journal of Infectious Diseases. July 1990: 162(1): 251-254.
  3. Mayefsky, JH. Determination of leukocytosis in traumatic spinal tap specimens. The American Journal of Medicine. June 1987: 82(6): 1175.

NB I didn’t put references for any of the textbooks or papers (most of which refer to the same 2-3 textbooks) that simply assert that calculations are helpful.

How Timed Tweets Can Distract From Your Message

Originally Posted on 2010-Sept-18 (An old post but with events in the news as they are it still remains relevant, unfortunately.)

There are several software options for people to use to interact with Twitter and manage their posts.  Some of the more popular interfaces allow you to create Tweets and have time flagged for a delayed or a timed post.  While this is beneficial to prevent bursts of Tweets that can dilute the impact of the individual Tweets it can also have unintended consequences.

Recently there was a shooting at the Johns Hopkins campus that made national news.  There was a rash of erroneous information that was sent out over the net.  To the credit of the Hospital system they did utilize their Twitter stream, @JohnsHopkins, to distribute information for the public and the Johns Hopkins community.

However, they also had some timed tweets that were sent out during the incident and distracted from the messages about the tragedy.  There was even some outcry from followers.

@JohnsHopkins did respond that this was due to timed Tweets that were continuing to fire as they were placed prior to the incident.

Judging by the time stamps there were several Tweets that “escaped” during the ongoing events that were of national interest.  This dilution of the impact of the tragedy Tweets could have been avoided by canceling the timed Tweets and focusing the message on the ongoing events.

The first thing to be done would have been to eliminate the timed Tweets once the shooting occurred and the decision was made to use Twitter to distribute information.  However, there could have been a problem depending on the software that was used to create the timed Tweets.

I suspect that timed Tweets were stopped once they realized what was going on as there is a long gap in the timeline.  Once again this is a new area that organizations are moving into and processes and methods need to be refined.  Errors like this can serve to modify how we all use Twitter and other Social Media venues, but only if we pay attention and learn from them.  I am sure @JohnsHopkins has learned this valuable lessons, as have I.