Subarachnoid Hemorrhage, no LP


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Nurses Edition Commentary

Kathy Garvin, RN and Lisa Chavez, RN

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Lance M. -

Dr. Sachetti references another conversation about the topic. Would be nice to just link or show the issue so we could find it and compare. Thanks.

Chris Navarro: EM:RAP Production Team -

I've added the EM:RAP and EMA links to the written summary.

Carp27 -


The segment Al refers to was "Don't Feat the Stink" in June 2017 episode of EM:RAP with Evie Marcolini and Swami. There is also an EM Abstracts essay on the topic of post-CT LP for SAH in March 2017 episode of EMA that goes into greater detail on the ED-specific diagnostic evidence.

Chris Carpenter

Alfred S. -

Thankfully Chris has a much better memory than me.


Brian L. -

A mistake in the text.

LR 0.7, should read 0.07

Alfred S. -


Charles M. -

Beyond 6 hours, their meta-analysis shows fairly conclusive evidence that a modern generation CT scanner can accurately rule out aneurysmal subarachnoid with a likelihood ratio of 0.7 and tight confidence intervals.

The 0.7 should be .07 (as noted above) and the phrase needs to say it's the <<negative>> LR (word 'negative left out).

Yvonne K. -

Question: in the discussion of CTAs for subarachnoid hemmorage beyond 6 hours of sympton onset. if you do a CTA right after the CT head, why and who would follow up with an LP (ie the order may matter because we could spare an LP)

Alfred S. -

I guess you can sum this up this way.

1. CT within 6 hours with late generation CT negative for SAH then done.
2. CT at any time positive for SAH, then CTA.
3. CT > 6hrs after onset of symptoms is negative then offer patient option of CTA or LP.
4. If LP positive then need CTA
5. If CTA positive, with or without proceeding LP, then discuss with Neurosurgery / Interventional Radiology to see if meets high risk criteria based on age, location and size.

If it is me in your department, just do the CTA.


Michael L. -

I grew up in the era of doing an LP after every negative CT for SAH. The plus side of that practice is that you get really good at doing LPs. I've seen younger docs (can't believe I'm using the term "younger docs") who are less comfortable/facile with LPs given the change in practice with a lower threshold to send the patient to fluoroscopy. Neither here nor there, I suppose, but an interesting unintended consequence.

Alfred S. -


Yes, you are old. But there are many procedures that have changed with new technology. Landmark central lines, myleograms for epidural abscesses, and open abdominal surgeries are all some of the procedures that have disappeared.

Rick M. -

I have been dong CT/CTA for suspected SAH for what seems like decades now. My experience has been as follows: positive tap and negative CTA, the Neurosurgeon says, "what do you want me to exploratory brain surgery?" If the CTA is negative...what is the neurosurgeon or interventional radiologist going to do? If the LP was negative, but the CTA was positive...I am still going to call the neurosurgeon and/or the IR because the symptoms were suspicious, and the CTA shows an aneurysm. If the CTA is negative...the results of the LP (which may be traumatic) does not and never has changed the end result...a discussion with a neurosurgeon who says, "well there is no aneurysm for me to go fix." So, I get the CT/CTA.
I would like to know how many times a positive LP with a negative CTA has led to any further action, other than "follow-up?"

Alfred S. -

Your argument makes sense.


Steven P. -

Just to clarify: If patient presents greater than 6 hours since symptom onset and CT brain is negative and a CTA results as negative with no LP performed, am I done?

If so, are you aware of any evidence that supports this approach?

Than you.

Steve P. MD

Dean B. -

In Al’s segment, May 2020 EMRAP, who is reporting the CT scan & does this matter?
Academic/university centres are served by neuroradiologists, and these CTs are checked & reported by neuroradiologists. Smaller centres have in-house reporting by general radiologists till 7.00pm or so, and then the reporting is out-sourced, to a radiologist who is sometimes across the other side of the world. Does this discrepancy between reporting abilities in different centres change the recommendations made in this segment?

Alfred S. -

I am not aware of any data that suggest a neuroradiologist is required to read a plain CT looking for subarachnoid blood. I think this is a reading any radiologist should be capable of identifying.



Regina R. -

what is defined as a modern CT scanner?

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