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Michael M., M.D. -

where is this link to SAH risk factors that Scott mentioned?

Michael M., M.D. -

Found it in the written summary. Thanks.

Spiro T -

Thanks guys, Take home message I got from this was: "watch this space"; BUT "don't hold your breath". We still need to be prepared to stab the back!

Len U., D.O. -

Do we need to worry about the 1%? If the initial CT is negative what is the likelihood of finding an aneurysm on CTA or DSA?
Negative CT angiography findings in patients with spontaneous subarachnoid hemorrhage: When is digital subtraction angiography still needed? Agid R - AJNR Am J Neuroradiol - 01-APR-2010; 31(4): 696-705
This study indicates that all 32 patients with xanthrochromic LPs (negative initial CT) had no identifiable aneurysm on CTA and DSA. The only positive finding was vasculitis on one DSA. All delayed imaging was similarly negative.
Cerebral aneurysm exclusion by CT angiography based on subarachnoid hemorrhage pattern: a retrospective study. Kelliny M - BMC Neurol - 01-JAN-2011; 11: 8
In this study, all 35 patients with a negative or perimesencephalic hemorrhage pattern on initial CT had negative CTA and DSA.
Is there recent evidence indicating the rate of surgical disease with negative initial CT (latest generation)?

EMCrit -

Len--very interesting question. 9% of the patients in this study had a lesion with negative CT. (Ann Emerg Med. 2008 Jun;51(6):697-703) You'd need a pretty big study to convince me it is not worth the time to get a CTA in these folks.


Peter W. -

It is the New Year and Mel's statement about CT and then LP being the standard of care still bugs me. The LP is still the "Gold Standard" for those patients with the rare sentinel or sub-massive SAH. Advocating an initial CT which will be negative for most patients just adds one layer of usually needless testing. If I am concerned enough about a patient's story that SAH is high enough in my differential to warrant a test, I'll be doing the best test (LP) right away.

Hussein E., M.D. -

I am very much surprised that low hematocrit could lead to false negative CT finding(especially when considering moderate multi-sliced CT machines) in someone who is presenting with complaints of SEVERE headache to the ED: I am talking about someone who is alert, oriented, walking and talking would have a hematocrit so low that it would not show up while they are having active SAH bleed. I am sorry but to me this possibility is so remote and unlikely as be considered impossible. May be I am missing something; Please clarify what it is I am missing here. Dr. Weingart would you be so kind to comment on this please? Thanks
H. W. Egal

Jon F. -

Two comments:
First, this idea of targeting 0% miss rate for SAH is flawed and inconsistent with ED research standards in other potentially lethal conditions, e.g. ACS, PE. It is an impossible standard and leads to all kinds of contortions in headache workups.

Second, I feel the approach that diagnosis focused SAH studies take toward "CT miss rate" is also problematic. In reality, what we are hoping to achieve with these tiny SAH's is to find an aneurysm and fix it before it rebleeds (i.e. the sentinel hemorrhage idea). Remember when CT PA for PE was first starting to pick up steam? There was all this debate about finding peripheral PE's and its relative sensitivity to angiography. But just like SAH, what we really care about with tiny SAH's and tiny PE's is preventing the next "big" one. What contributed to CT PA going mainstream was studies looking at whether a negative study accurately PREDICTED a repeat event in a defined time frame. In my mind, the best study on CT and SAH is: "How many people go on to have a clinically significant aneurysmal SAH within a defined time frame after a negative head CT." I suspect the negative PPV of head CT for this parameter would be fantastic - ESPECIALLY for the undifferentiated headache population in a community ED.

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Episode 123 Full episode audio for MD edition 236:44 min - 99 MB - M4AC3 Project Written Summary: Aortic Dissection 225 KB - PDFEM:RAP December 2011 Written Summmary 4 MB - PDF