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Study: It can be dangerous to guess a patient's weight
Estimates by ED nurses often are wrong
If you have estimated the weight of an adult patient recently, your guess was probably not accurate, says a new study. ED nurses and physicians estimated weights of 241 patients, and they were within 5% of the patient's true weight only 33% of the time, researchers found.1
"Our study found that our estimates are not that great, regardless of whether the estimator is a nurse or physician," says Christopher A. Kahn, MD, the study's lead author and clinical instructor of emergency medicine at University of California — Irvine. Previous researchers found that a patient's own report of his or her weight was more accurate than that estimates made by ED staff, notes Kahn.2 "Patient estimates are not perfect, but they are a bit better. So if possible, it's preferred to ask the patient rather than guessing," he says.
Many medications given in the ED are based on weight, so obtaining accurate weights is particularly important, says Mark Sargent, RN, clinical manager of the ED at Baylor Regional Medical Center at Plano (TX). "That being said, it is difficult to obtain weights on patients who are unable to stand or are unconscious. In the majority of EDs, stretchers with scales are not routinely used," he says.
If your patient requires cardiopulmonary resuscitation or emergent procedures for which a weight is not critical, the weight can be obtained after resuscitation has occurred, notes Sargent. Estimating weight is risky when using medications such as sodium nitroprusside, a very potent antihypertensive medication that requires very accurate weights, says Sargent. But if facing an emergent situation, an estimated weight may be needed to administer medications, he says. "It is airway, breathing, and circulation — not weight, airway, breathing, and circulation," says Sargent. "An accurate weight can be obtained upon arrival to the intensive care unit."
If you have to rely on your own estimate, keep in mind there is a good chance that it will be inaccurate, says Kahn. "Don't be surprised if something you are titrating per kilogram doesn't quite have the effect you intended," he says. "Be vigilant and ready to titrate to effect, rather than assuming the weight is accurate and that the dosing therefore must be correct."
Make every effort to weigh patients who might be receiving any weight-based medications with significant risk of poor outcomes, advises Kahn. "There is no 'set it and forget it' in emergency nursing," he says. "If you have someone whose pressure is a little bit high for a minute, chances are you are going to notice that and it is going to be OK."
However, if your next patient could require thrombolytics and you have one bed in the department with a built-in scale, then put the patient in that bed, says Kahn. "If you have a sling scale or weight-measuring gurney available, maybe you can have someone weigh the patient while you are working on getting the medication from the pharmacy," he says. "Take that minute and a half, if it's available, to weigh the patient."
Obese, underweight at risk
ED staff tended to overestimate the weight of underweight patients, Kahn says.
"If you look at someone and guess they are 50 kilos and they are only 40 kilos, that's a 25% error," he says. "And the last thing you want to do is overdose someone on thrombolytics by 25%. You are not going to get additional benefit, but you will certainly get additional risk."
Your ED should have stretchers with scales available, or floor scales that can weigh the patient and stretcher, says Dotty Kuell, RN, BSN, CEN, manager of the ED at FirstHealth Moore Regional Hospital in Pinehurst, NC. "The weight of each stretcher should be readily available for an easy computation of the weight." First Health Moore's ED uses stretchers with built-in scales manufactured by Kalamazoo, MI-based Stryker, and the stretcher weight is automatically deducted by zeroing the stretcher before patient placement. "You can also have scales built into your floor. In this case, the stretcher weight should be painted on the foot of the stretcher where anyone can easily see it," says Kuell.
Obese and underweight patients should be treated with sensitivity and appropriate equipment used, adds Kuell. "These individuals already have an image problem. Using under or oversized equipment will do more to damage that," she says.
However, just as obese patients have the right to compassionate care, ED nurses have the right to safely move patients, notes Kuell. "We have slide boards and lift teams right now, but are investigating the purchase of a lift for transferring patients from vehicle to stretcher," she reports.
For more information on estimating patient weights in the ED, contact: