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From: Rod on 27 Jul 2008 07:37
Given the recent posts concerning potassium, I thought this story to be
of particular interest. Please note, however, that blood serum potassium
levels can be normal even when tissue levels are low. So blood tests are
not much use for detecting problems of insufficency. They have their
place in detecting problems with control of blood potassium levels.

At least, that is how I understand it at the moment. :-)

Fist clenching has usually been part of the process when I have had
blood taken for tests. So I guess it is pretty widespread. Wonder if it
affects anything else? And what other things might also affect results?

======

Warning over blood-taking method

Unexpectedly high levels of potassium were found in the blood

People who take blood have been warned not to get the patient to tightly
clench their fist during the procedure.

UK researchers who examined 200,000 blood test results found clenching
then relaxing the fist could raise potassium levels, potentially
confusing results.

Raised potassium levels can indicate kidney or heart problems, the
Annals of Clinical Biochemistry study said.

A UK expert said clenching was an outdated practice and staff taking
blood should not ask patients to do so.

'Hit or miss'

Vanessa Thurlow, a biochemistry expert and co-author of the report,
first noticed a problem when GPs were questioning test results for a
small number of patients.

When she retested them, their potassium levels were normal - but they
had all started to clench their fists before the test.

It seems to be hit or miss whether they get trained to avoid using this
procedure
Vanessa Thurlow, report author

It led Ms Thurlow to speak to managers of the phlebotomy - blood-taking
- services in her trust, which then instructed staff not to use the
clenching method.

Her study looks at 200,000 results from blood tests requested by GPs
between 2002 and 2005. The updated training was offered in September 2003.

The percentage of tests showing worryingly high potassium levels fell
significantly after the change.

The impact of fist-clenching while giving blood has been known since the
1960s, but she said procedure was being passed on from generation to
generation of phlebotomists.

"It seems to be hit or miss whether they get trained to avoid using this
procedure," she said.

She said other factors such as exposure to cooler temperatures have been
known to cause false raised-potassium levels, but she believes the
impact of this hand-gripping is underestimated.

"We think that as a result patients might have to have their medication
adjusted. We don't know how widespread a problem this is in other parts
of the country."

Blood flow

Ms Thurlow admitted some patients were very difficult to bleed.

"The pressure on the phlebotomist to obtain some blood somehow,
particularly with very nervous patients, can be high.

"Clenching and relaxing the fist does improve the blood flow and makes
veins stand out, making it easier to get a sample."

Jackie Hough, president of the National Association of Phlebotomists
(NAP), agreed clenching the fist could alter the blood test results.

"But best practice advocates that patients don't tightly clench but
gently close their hand during needle insertion and that the hand is
loosened prior to the collection of blood.

"Also the tourniquet should not be tightened on the arm for longer than
60 seconds or during the collection of the sample."

< http://news.bbc.co.uk/go/em/fr/-/1/hi/health/7525932.stm >

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>
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