Les, in answer to your questions:

1: Penumbra IS related to the solar eclipse analogy. In an eclipse, the 
umbra is the central shadow of the moon on the earyh's surface where a 
total eclipse is seen, while the penumbra ('pen' meaning 'almost', as in 
peninsula & penultimate but not penis) is the surrounding shadow on the 
earth's surface where a partial eclipse is observed. Where this is used as 
an analogy for a stroke the umbra equates to the area of brain completely 
and irreversibly damaged by the loss of blood supply. The penumbra is the 
surrounding part of the brain which is suffering from reduced blood supply, 
but might recover if oxygenation and blood pressure are optimised. However, 
the distinction between the two areas cannot be made prospectively - you 
can only tell umbra from penumbra retrospectively, and only if you treated 
the stroke optimally (ie. the umbra is the bit that didn't get better.)

2: Dopplars is very much to do with length of sound waves. It is to do with 
the change in length of sound waves when sound is reflected from a moving 
object. In the clinical setting (I presume you are talking about carotid 
dopplars as you were just asking about strokes) high frequency sound waves 
are directed at the carotid arteries and bounced back off the moving blood. 
Where the blood is moving towards the probe, the wavelengths are compressed 
slightly, producing a higher frequency - where the blood is moving away, 
the wavelength is extended and the frequency is lower. Where the flow is 
turbulent a random frequency is generated, like a hiss. These changes in 
frequency can be turned into an audible sound (like the hand-held dopplar 
machines) or into a colour picture if the information is processed on a 
screen to give a cross sectional picture.

3: Fat coming out of the broken ends of the bone is probably too 
simplistic. Fat emboli tend to occur after several days rather than 
immediately after the injury, which counts against that idea rather. It is 
probably more to do with the body mobilising fats as a response to the 
injury (in nature you can't catch your next meal very easily with a broken 
leg, so metabolically you are going to have to get an overdraft and draw on 
your reserves). Quite why some people have fat emboli and others don't 
remains a mystery, but putting metalwork in after a few days seems to make 
it a lot worse - presumably nature didn't reckon on orthopaedic surgeons.

4: The ischaemic cascade is not really a term used clinically. I presume 
you mean (or that other people have meant) that reduced blood supply in a 
tissue, or more correctly a reduced oxygen supply, starts a cascade or an 
escalating sequence of events which form a 'vicious circle'. This includes 
production of lactic acid, vasodilatation, capillary leakage, tissue 
oedema, and thus even further tissue hypoxia.

5: Your man on CCU with complete heart block (CHB or 3rd degree AVB) may 
have (a) converted spontaneously, (b) benefited from atropine or (c) 
generated his own adrenal stimulation. Shock from reduced cardiac output of 
any cause will produce an adrenal response in any patient, so I doubt 
whether the threat of a pacemaker would have done it. Don't think 
adrenaline is the treatment of CHB, although isoprenaline (not dissimilar, 
but definitely not the same stuff) is sometimes used (sometimes even 
successfully) to increase the heart rate in CHB. Isoprenaline is not used, 
however, to convert someone from CHB back into sinus rhythm. You'll never 
know why this man converted back to sinus rhythm - it is only an anecdote. 
It's only with large, well conducted studies that we can ever know with any 
degree of certainty what actually causes what, and more importantly which 
component of our intervention actually make a difference.

On the subject of making a difference, do your medical secretaries really 
need to know about all this?

Also, most of this information could easily be obtained from a short spell 
down the medical library - I presume AMSPAR pay you to teach them. This 
forum is really designed to air the greyer areas of emergency medicine, not 
really to save you homework.

Howard Simpson
A&E consultant, North Hampshire Hospital, Basingstoke.




-----Original Message-----
From:	Les King-Smith [SMTP:[log in to unmask]]
Sent:	16 October 2000 09:39
To:	[log in to unmask]
Subject:	Any Answers Please.

Dear List,
As another list lurker I hope you will indulge me the occasional comment or
question and oblige me with a reply or three.
I am currently lecturing to a group of would be medical receptionists on 
the
AMSPAR ( Association of Medical Secretaries, Practice Managers,
Administrators and Receptionists) course. My brief is principally mecical
terminology. However there are some interesting questions which have arisen
both in my own mind and those of my students.
1.    In relation to stroke's-is does Penumbra have a similar meaning as in
solar eclipse i.e. umbra              when the sun begins to pass from
behind the sun.
2.    Doplar Test? Is this to do with different lenghtsof sound wave?
3.    I have conveyed in the past a number of elderly clients to hospital
with fractured bones. I                understand the reason for some of
these people dying is possibly due to a fat embolism. I also        beleive
I understand this correctly as being a case of fat being liberated into the
blood stream        from the open ends of the bone, is this fact or 
fiction.
4.    What is the ischaemic cascade?
Slightly different, when I undertook my paramedic training in 1991 I was as
part of my placement working in CCU at Chesterfield Royal. I witnessed a 
man
in 3rd degree block treated with Atropine revert to NSR all supposedly due
to his apparent fear of being fitted with a pacemaker. He did go on to have
unifocal ventricular ectopics, all this took place over a period of about 
36
hours. Was it likely that the Atropine was responsible for this dramatic
change or did the brown Adrenaline have something to do with it.

Les King-Smith
Training Consultant FAFL Training Services Limited

Lecturer Macclesfield College of Further and Higher Adult Education

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