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Screening dehydration in elderly possible from routine bloods

  • 15 Comments

Routine blood testing for sodium, potassium, urea and glucose could be used to detect dehydration in older people, following new research that has found a “universal” approach to this form of screening.

Academics at the University of East Anglia, who led the research, have found the most accurate way of using results from these tests in an equation to screen for the condition.

After looking at a series of “osmolarity equations” currently being used to predict dehydration, they found one – developed by Khajuria and Krahn – showed the best results across all different groups of older people in the trial.

“Using routine blood tests in older people to screen for dehydration… would enable healthcare professionals to provide appropriate support in older people”

Study paper

The study, published in the British Medical Journal, looked at 595 people over the age 65, including those who were healthy and lived independently, frail people living in residential care, and those in hospital.

The group also included men and women at a range of dehydration levels and spanned several European countries and took into account those with poor renal function and diabetes.

Those behind the research indicated this form of testing could in most cases replace the need for serum osmolality testing – a direct measurement taken in laboratories, which is costly and not available for widespread NHS screening of dehydration.  

Lead researcher Lee Hooper from UEA’s Norwich Medical School, said: “A serum osmolality test measures the freezing point of blood serum to show how concentrated a sample of blood is. People’s blood becomes more concentrated as they become dehydrated.

“But it is an expensive and time consuming procedure – and clinical laboratories would not be able to handle routine screening,” she said.

Simpler tests such as urine measurements, which appear to work well in children and young adults, do not work in older adults, she noted.

“We wanted to find a universal equation which would be accurate for a broad range of elderly people including people with conditions such as diabetes”

Lee Hooper

“When our blood becomes more concentrated, as we become dehydrated, concentrations of serum sodium, potassium, urea and glucose rise. Many blood tests routinely measured in older people already check for all of these, and assess them independently,” added Ms Hooper.

She said a number of equations were already being used that included these blood test results but that they “vary considerably” and it wasn’t previously clear which ones worked for older people.

“We wanted to find a universal equation which would be accurate for a broad range of elderly people including people with conditions such as diabetes,” she said. 

The research paper stated: “Using routine blood tests in older people to screen for dehydration using the Khajuria and Krahn formula for serum osmolarity would enable healthcare professionals and carers to provide appropriate support in older people by increasing fluid intake and improving and maintaining good hydration and thereby prevent associated poor health.

“This information could be provided  automatically on  the  reports  from  pathology laboratories where serum sodium, potassium, urea and glucose have been measured, although to improve sensitivity (though increasing costs) positive results from this screening could be followed by assessment of directly measured serum osmolality,” it said.

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Readers' comments (15)

  • Pussy

    Is this NEW?

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  • I agree with Pussy above...is this new?...and the ultimate in cost effectiveness...fluid in versus fluid out...commonly referred to in the olden days as 'fluid balance'...not to mention the clinical signs of dehydration...loads to do before you have to subject frail, elderly, and possibly difficultly in gaining consent patients to having a needle stuck in them...routine blood tests or not....just a thought or two

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  • ''Using routine blood tests in older people to screen for dehydration… would enable healthcare professionals to provide appropriate support in older people''...quote from the article...stable door and bolted horse here...if patients had (had) the appropriate support they would not be at risk of being dehydrated....

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  • michael stone

    I didn't find the article on BMJ. Although I didn't spend long looking.

    But it looks as if the authors are claiming 'a proven refinement' - in answer to Pussy's question, my impression is that the authors claim to have come up with a better equation to use in assessing the blood test results.

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  • Pussy

    Anon. 1:39. Indeed trying to get blood from some ropey old vein on some poor elderly person and often with nothing to show for it but a bruise. As you say other measures first. Anon 1:43 Spot on,it's a stable door job! We shall see.......!

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  • yeh, the state of the skin and veins as well as other very obvious observations will tell you whether or not a patient is dehydrated - no need to cause them further suffering and treat them like a pin cushion! this has always worked in the past!

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  • michael stone | 22-Oct-2015 2:58 pm

    perhaps you like to offer your services as a guinea pig! just hope you are tame and house trained! :-)

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  • michael stone

    Anonymous | 22-Oct-2015 8:10 pm

    No, I'm not 'tame'.

    Anonymous | 22-Oct-2015 8:07 pm

    'no need to cause them further suffering and treat them like a pin cushion!' - I completely agree.

    Presumably, this is about 'less than immediately obvious' dehydration, though ? Or, perhaps, 'preventing dehydration from developing into something serious' ?

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  • Stone. Perhaps you should tend to your own hydration. It improves cerebral functionality!

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  • To all those who suggest first using observing and responding to the person's clinical signs before resorting to any potentially distressing intervention, I wholeheartedly agree.

    To Michael Stone- (must you respond to that irksome fool commenting at 8.10 and 7.22 ?) Yes, maybe there is a reason why the finer detail may be important but it is not explained here.

    If blood were taken quickly by doctors certifying death would it mean that hospitals and care homes where dehydration was normal and an unreported causative factor in death, management would be held accountable at last?

    IN RESPONSE TO THE ARTICLE- Does "routine blood testing" for dehydration simply mean that when a blood sample has been taken for a reason other than dehydration that blood would be routinely checked for dehydration? Unclear reporting.

    IF IT DOES NOT MEAN THAT.. Has anyone thought of just offering sufficient quantities of preferred drinks to the person? and often enough? and in containers that are appropriate for physical needs, e.g. in the slanting beakers for those with restricted neck movements who cannot tilt their heads back enough to get all the drink out, and in larger mugs to those with shaky hands who often get deprived of a cup full as it would get spilt?

    Should drinks be offered in cups at all, unless the person clearly states that as a preference and can access extra fluids as required? Yes, it looks so much prettier but how pretty is the less obvious scenario where the person cannot get all the drink out of the cup because neck movement is restricted and some gets spilt and it's a long time to the next drinks round assuming that they don't get missed out of that; then the longterm dehydration perhaps accompanied by constipation, a fall with joint pain, possibly a UTI, etc etc results in delirium with aggression which results in inappropriate use of anti psychotics which can impair kidney function and probably should not be used anyway for debilitated people- and of course, reduced ability to ask for a drink or drink independently...

    I've been told that if we feel thirsty we already are dehydrated.

    There is an unacceptable level of dehydration going on for staff and service users (and fizzy drinks machines are not the answer).

    I suppose that this easier/cheaper form of testing dehydration in blood samples taken anyway for another reason might help to pinpoint and hold accountable any organisations which recklessly and negligently deprive people of one of the most basic needs for life…….water. If this is the case, I am 100% behind it.

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