Making A Fist Of Blood Taking - And Ending Up In Casualty
May 22nd, 2008 | by admin |A paper in the latest issue of the Annals of Clinical Biochemistry shows how the manner in which blood is collected from patients for some blood tests alters the results of those tests when it comes to analysis. Clenching the fist during blood taking could land some patients in their nearest A&E department being monitored for a heart emergency. When the test is repeated using correct blood collection technique, it may well be found to be a false alarm.
Researchers in the Bromley area of south east London noticed that if patients having blood taken were asked to clench and relax their fist during the procedure (a common practice in blood taking techniques), there was a significant increase in the likelihood of the test showing an apparently raised potassium level. Raised potassium levels in the blood can be an indicator of quite serious conditions, such as kidney or heart problems. The researchers found that if they asked the patient to give another blood sample, this time without their contracting and relaxing the fist, the sample indicated a normal level of potassium.
Vanessa Thurlow, a Consultant Clinical Scientist in Biochemistry and one of the authors, commented, “Some blood tests may not be affected by blood collection technique, but if you are having a serum potassium measurement and you get that late night call from your out of hours GP service to ask how you are feeling and suggesting a visit to A&E, think back - did you get asked to “pump up your vein” to help the blood collection?”
Cooler ambient temperatures and a delay between blood collection and analysis have both been known to cause false raised potassium levels (pseudohyperkalaemia). The effect of hand gripping and un-gripping (fist clenching) while blood is being drawn has been published previously and was documented in the Sixties, but the practice continues to be passed on from generation to generation of phlebotomists. Sometimes there is a gap in the training of the phlebotomists, but some patients are very difficult to bleed and the pressure on the phlebotomist to obtain some blood somehow, particularly with very nervous patients, can be high.
Notes:
‘Is suboptimal phlebotomy technique impacting on potassium results for primary care?’ is published in the current issue of Annals of Clinical Biochemistry.
Annals of Clinical Biochemistry is published by RSM Press, the publishing wing of the Royal Society of Medicine, on behalf of the Association for Clinical Biochemistry. It has full editorial independence of the RSM.
It is one of the leading journals in its field and is the official journal of a number of international clinical biochemistry organisations. Its editor is Julian H Barth MD FRCP MRCPath.
http://www.rsmpress.co.uk/acb.htm
Founded in 1805, the Royal Society of Medicine is an independent organisation that promotes the exchange of knowledge, information and ideas in medical science and continued improvement in human health. http://www.rsm.ac.uk Registered Charity No. 206219
Royal Society of Medicine
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