An article in Metric Views in December 2009 discussed the LACORS survey on weighing scales in NHS hospitals, http://tinyurl.com/yao9kzb . This issue was also taken up on 25 February in Parliament by Lord Walton, http://tinyurl.com/y8m45z3.

Paul Trusten writes from the US:

At the risk of being called a meddling Yank, my answer to the question offered here – namely, should a totally metric culture be enforced by NHS – I say, emphatically and categorically YES!

The use of two different systems of measurement in healthcare must end. Only the SI metric system should be used in medical records and in verbal communications of a patient’s weight and height. 

I say this not just out of my commitment to metrication on my side of the pond as the Public Relations Director of the U.S. Metric Association, but, much more importantly, as a practicing pharmacist for the past 33 years. I agree completely with the statement that the use of customary units alongside metric units for height and weight in a hospital is a dangerous practice that should be ended as soon as possible, on both sides of the Atlantic.  The entire culture in hospitals must be metric, and conversion of any kind should be banned.  Ideally, weigh patients on scales that read in kilograms only, and measure height in meters or centimeters only.  I believe that the traditional romance of weighing babies in pounds and ounces must be exchanged for the peace of mind parents should enjoy from the enforcement a metric-only healthcare environment.  From a safety standpoint, their precious bundle’s weight in kilograms should be music to their ears.

My commitment to the goal of U.S. metrication began in 1974 when I was in pharmacy school.  When I was studying pharmaceutical calculations, I was horrified to learn that two, even three systems of measurement (apothecary, avoirdupois, and metric) were involved.  (Editor: It became illegal in the UK from 3 March 1969 to use any system of weights and measures other than the metric system for dispensing prescriptions).  Also, the decimal nature of the metric units made them so much simpler to manipulate mathematically.  Anyone who has ever tried to add apothecary weights denominated in ounces, drams, scruples, and grains vs. just adding up figures in grams will understand. My quest for one system of measurement in healthcare was easily extended to the goal of metric measurement for all purposes.  It just made sense.

Banish any thought that medication dosing is ever going to accommodate the old units by being stated in something like milligrams per pound. That is out of the question.  Medications can only be handled in the decimal metric system. Period. In the preparation of compounded sterile injectable products (intravenous and other injectables), use of only the decimal metric system is possible. Decimal calculations are the only safe ones.

For certain age groups (usually pediatric patients), medications are dosed on a milligram per kilogram of body weight basis.  The anticoagulant drug heparin is often dosed at the rate of units of heparin per kilogram per hour. Many drugs, especially anti-neoplastic agents (chemotherapy or anti-cancer drugs),  some antibiotics,  and other specialized drugs, are often dosed in micrograms or milligrams per square meter of body surface area (BSA), with BSA being calculated using the patient height and weight in metric units.  If, in the dose calculation, the patient weight in pounds were to be accidentally substituted for the weight in kilograms, a disastrous overdose could occur.  In this arena, well will not have metric martyrs. We will have customary ones.

U.S. healthcare safety officials made considerable progress in cultural metrication last year.  The Institute for Safe Medication Practices (ISMP),  a non-profit organization devoted entirely to medication error prevention and safe medication use, has recommended the total metrication of the medication delivery process, from prescribing to order entry to pharmacist counseling of the patient (see http://www.ismp.org/Newsletters/ambulatory/archives/200905_1.asp).

I want to suggest also that body temperature should be taken and recorded only in degrees Celsius, to allow for worldwide ease of communication. 

Be totally safe – be totally metric!  Let us all, UK and U.S., at long last, use only one system of measurement in healthcare.

The full text of the exchange is printed in Hansard and can be read here.  A video clip may also be viewed at this link.

The background to this exchange was covered in our recent article “NHS risking patients’ lives with imperial scales”, which gives links to the relevant documents.  Briefly, an official report found that, despite previous warnings, 30% of NHS hospitals were still using scales that are switchable between metric and imperial, and 10% were actually being used in imperial mode.  This risks wrong doses of drugs (which are calculated in metric) being administered to vulnerable patients – with possibly disastrous consequences.

The Minister’s statement is welcome as a public confirmation that it really IS Government policy “to move toward full metrication in time” (quoted from a letter from the Science Minister, Lord Drayson).  However, I do have reservations about her comment that “this is a matter that will solve itself in time”.  By this of course she was presumably echoing the widespread assumption that, since children are educated in metric units, as older people die out, metric units will gradually become the default for the general population, and imperial units will fall out of use.  If only this were true …

Unfortunately, the evidence suggests otherwise. The alternative view is that, after ca 35 years of metric education in schools, acceptance and use of metric units varies with occupation, educational standard and social class – and also with the mistaken  perception that metric units are “foreign”.  On this view, we have reached a stable but highly unsatisfactory situation of “two systems” with no prospect of resolution – without specific Government action.

The other reservation that one must have about the Minister’s statement – however welcome it may be – is that although she speaks for the Department of Health, the policy is not carried through to other aspects of Government – notably Transport.  We shall return to this point in a forthcoming article.

Going back to the exchange in the House of Lords, it is good that the Health Department is now committed to issuing an “alert” reminding all NHS hospitals of the importance of metric-only scales.  This will reduce the risk of a catastrophic accident resulting from confusion over measurement units.  So let us congratulate Baroness Thornton and hope that, with her support, stones, pounds and ounces can finally be eradicated from the NHS.

After a series of pilot studies in 2007 found some hospital staff using inaccurate or unsuitable scales to calculate dosages of medication for patients, including small children, LACORS (the Local Authorities Coordinators of Regulatory Services) set up the National Medical Weighing Project.

Interim Report – August 2008

Published in August 2008, the project’s interim report noted,

“Staff do not consider scales to be medical equipment”

“The amount of cheap bathroom scales in critical locations is astonishing”

“One of the most potentially harmful issues is that of switchable scales – those that can display metric, imperial and other units. The risk is that medication could be administered based on a readout that was assumed to be metric.”

LACORS made a series of recommendations to hospital trusts, which included:

• All scales used for medical applications should be accuracy Class III or higher.
• Any equipment that is found to be inaccurate should be immediately removed from service and either repaired or replaced.
• All scales used for medical applications should only display metric units. There should be no capacity for switching or dual readouts. Trusts should be aware of the pitfalls of using switchable scales and may wish to consider replacing them.

The report pointed out that implementing its recommendations would lead to significant improvements in patient care, and the ability for hospital trusts to demonstrate due diligence in relevant clinical negligence claims.

Final Report – June 2009

Commenting on changes observed in hospitals that had been previously visited in 2008, the Final report of the LACORS National Medical Weighing Project 2008/9, published in June 2009, reiterated the earlier report’s findings:

“The area with the most room for improvement (and potential to cause harm) is scales capable of showing metric and imperial units. While numbers have decreased, nearly one third of all scales in use are switchable. A staggering one in ten of these was set to imperial at the time of testing, despite no medicines or treatments having doses calculated in imperial units.”

Department of Health

The Department of Health has a system for issuing safety bulletins and procedure updates to hospital trusts known as Estates Alerts.

In early 2008, a series of bungled contradictory estates alerts were issued by the DH concerning medical weighing; all of which failed to recommend that all new scales should be metric-only.

The latest alert, issued 19 June 2008, countered advice given in previous alerts, but promised that “further guidance will be issued later in the year”. This advice has not been forthcoming.

In December 2009, the UK Weighing Federation announced that it is working with LACORS to push the Department of Health to issue the much-needed safety alert.

Background

Exclusively metric units are used for all medical purposes.

All drug doses are in metric, and are often calculated per patient body mass (mg/kg), or per surface area (mg/m²).

Tracking a patient’s weight is not straight-forward using imperial units. e.g. Calculating 10% of 75 kg is a trivial task, but finding 10% of 12 st 9 lb is more prone to errors because it is not so simple.

Babies have been weighed in kilograms for decades, although in recent years metric readings have been dumbed down to pounds and ounces for the ‘benefit’ of grandparents, sometimes without the mother being informed of the original metric weight.

References

LACORS

Interim report of the National Medical Weighing Project
http://lacors.gov.uk/LACORS/ContentDetails.aspx?id=20472
http://lacors.gov.uk/LACORS/upload/19736.pdf

Final report of the LACORS National Medical Weighing Project 2008/9
http://lacors.gov.uk/LACORS/ContentDetails.aspx?id=21837
http://lacors.gov.uk/LACORS/upload/21749.pdf

Department of Health Estates Alerts

DH (2008) 05 – Patient weigh scales
http://www.dh.gov.uk/en/Publicationsandstatistics/Lettersandcirculars/Estatesalerts/DH_085720
http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/documents/digitalasset/dh_085721.pdf

DH 2008/05U Patient weigh scales – update
http://www.dh.gov.uk/en/Publicationsandstatistics/Lettersandcirculars/Estatesalerts/DH_085050
http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/documents/digitalasset/dh_085058.pdf

DH (2008) 05(2U) – Patient Weigh Scales 2nd Updated http://www.dh.gov.uk/en/Publicationsandstatistics/Lettersandcirculars/Estatesalerts/DH_085724
http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/documents/digitalasset/dh_085722.pdf