Lone acute sudden Headache (LASH).... I still prefer the term "my head hurts" at least I can understand it 

Andres  

-----Original Message-----
From: Accident and Emergency Academic List [mailto:[log in to unmask]] On Behalf Of Adrian Fogarty
Sent: 26 February 2006 23:38
To: [log in to unmask]
Subject: Re: SAH

Not at all, I've no idea. I figure it must be Leicester slang for something!

AF

----- Original Message ----- 
From: "Paul Middleton" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, February 26, 2006 11:18 PM
Subject: Re: SAH


I might be behind the times but what's LASH?

Paul


------ Original Message ------
Received: Mon, 27 Feb 2006 04:54:46 AM EST
From: Coats Tim - Professor of Emergency Medicine <[log in to unmask]>
To: [log in to unmask]
Subject: Re: SAH




Paul,

I don't think that we have the data to give absolute answers to the 
interesting questions that you pose.

1) Role of LP when CT negative - depends on the pre-test probability of SAH. 
About 5% of the scans that we do for LASH show SAH (so we know that 
Emergency Physicians's threshold for CT scanning is about a 5% risk - you 
can work out your own threshold by looking back at what proportion of the 
scans you have recently ordered are positive). With this 5% pre-test 
probability and a negative likelihood ratio of 0.02 for CT scanning the 
post-test probability of SAH means that it is likely that about 1000 LPs 
will need to be performed to find each CT negative SAH. (Assuming that CT is 
as good a test in low probability patients as in high probability patients). 
(Article with the details due to be published in the European Journal, March 
edition). As CT scanning is a good test for SAH, we maybe should be talking 
to our patients about their post test probability, their attitude to risk 
and whether they wish to have any further investigations (LP is probably not 
to be undergone lightly).

2) CT angio has limited resolution and is answering a different question 
from a LP. If you want to know if there is an operable structural 
abnormality  CT angio may provide the answer, however the question usually 
is 'has the patient had an SAH'. If I was a patient I think that I would 
want to know if I had suffered a SAH, even if no structural abnormality 
could be found. (Maybe I would give up my hobby of bungee jumping and be 
just that bit more appreciative of life!).

3) The influence of new generation CT scanners is interesting - you are 
correct about technology running ahead of us. All of the published data (the 
98% sensitivity etc) seems to be from more than 5 years ago - therefore 
before the current generation of multi-slice scanners. How does this alter 
the negative likelihood ratio? Not sure, but it probably makes a CT scan a 
more sensitive test.

We risk stratify and accept 'low risk' rather than 'no risk' in many areas 
of emergency care (a PE can be just as fatal as a SAH). It is therefore a 
bit anomalous that we strive for 'no risk' in SAH.

My views on investigation of LASH come with a health warning - the dogma 
that every patient who has a CT for LASH must have an LP is very well 
entrenched. There is insufficient data to support any other approach, so 
deviate from the current 'norm' at your medico-legal peril. However, I will 
bet my hat that in 10 years time we will be risk stratifying and limiting 
the number of LPs that we perform.

Tim

Tim Coats.
Professor of Emergency Medicine.
Leicester University.


  -----Original Message-----
  From: Accident and Emergency Academic List 
[mailto:[log in to unmask]]On Behalf Of Paul Bailey
  Sent: 25 February 2006 03:44
  To: [log in to unmask]
  Subject: SAH


  I am beginning to wonder if I am still subscribed to the list as I 
haven’t heard much from you all of late.



  I wanted to bring up the topic of subarachnoid haemorrhage.



  I find myself, as time goes on, becoming increasingly interested in 
patient safety, uniformity in the delivery of emergency medicine (or 
complete lack thereof), the concept of ‘risk assessment’ as the core of 
our specialty, the concept of acceptable miss rates for particular 
conditions, and finally the approach to low prevalence high mortality 
conditions such as SAH.  In a lot of imaging related areas we have the 
additional problem of the wavefront of imaging technology being 
significantly ahead of the literature on most subjects – eg CTPA for PE 
and the role / sensitivity / accuracy of multislice CT – creating an 
evidence vacuum for a lot of the things that we do.



  With that out of the way I have been thinking a lot about SAH recently.



  In particular, two things:



  the role of LP when a high quality (ie no movement or artifact issues) 
multislice CT is negative.



  Why we aren’t just doing CT angiograms on everyone (and perhaps 
obviating the need for LP) given that this is what happens in a lot of 
centres when xanthochromia is positive.



  Out of interest, I am sure it occurs, but no-one in my institution has 
seen a 16 slice CT Head negative xanthochromia positive patient actually end 
up having a procedure – ie the CT angiogram / MR angiogram is always 
normal in this situation and no-one can really figure out where the blood 
came from.



  So, I’m opening it up to the collective wisdom of acad-ae-med.  What are 
all of your thoughts on the matter?

  Kind regards


  Paul Bailey

  Emergency Physician

  Western Australia






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