A study on accuracy and precision of fluid volume measurements by nurses, patients and healthy persons in a clinical setting.
Charlotte Frydenlund Michelsen, Morten Bo Søndergaard Svendsen, Marie Lommer Bagger and 1 others
PMID 34985207WHAT IT FOUND
Fluid volume estimates in a hospital setting were inaccurate and highly variable.
Nurses met the 10% error margin for only 50% of estimates of fluid removed or left, while patients met it for none.
Key findings
01Nurses were within a 10% error margin for 50% of mean estimates of fluid removed from or left in containers, while patients were within it for none.
02When pouring a 100 ml target, patients poured 26 ml less in a glass and 9 ml less in a cup, while nurses poured 17 ml less in a glass and 4 ml more in a cup.
03All groups had mean cup volumes poured within the 10% error margin, but only healthy participants had a mean glass volume within it.
STILL TO COME
How it was doneWhat they foundWhat it means for RNs
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What it does not show
The study was done at a medium-sized hospital in Denmark using a glass and a cup, so the results may not apply to other settings or containers. Only 25 people were in each group, and 92% of nurses had previously assessed fluid intake compared with 12% of patients and none of healthy people, so experience may have affected the results. Patients were cognitively able to consent but may have had pain, anxiety or other conditions that affected their ability to estimate volumes. Healthy people may not have been familiar with the hospital containers, while nurses and patients were, so familiarity could have affected the estimates. The 10% error margin used to judge accuracy is not well established and may vary between clinical contexts.
Declared interests
MBSS and MLB are affiliated with an organization with a non-financial interest in the subject matter.
The easy way to misread this
Do not conclude that nurses can reliably estimate fluid volumes by eye. Nurses were within the 10% error margin for only 50% of estimates of fluid removed or left, and patients were within it for none.