Obtaining an Accurate Body Weight Measurement in Adults and Children in Primary and Secondary Care Settings (Not Babies)

Overview

This Guidelines summary provides a clear step-by-step approach to ensure that an adult or child in a primary or secondary care setting is weighed using the required standard of calibrated weighing scales, at appropriate time intervals by competent staff. It includes background information and evidence and the weighing procedure.

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Introduction

• In an adult body weight should be recorded as part of the malnutrition screening process on admission for hospital in-patients, out-patients, people in care homes, and people attending GP surgeries
• Body weight should be repeated weekly for in-patients and when there is clinical concern for others, or on home visits if weight is relevant to purpose of visit, that is, person receiving nutritional support or weight management review
• An accurate body weight is required to:
  • assess and monitor fluid and nutritional status
  • calculate safe doses of medication and clinical therapies
  • calculate nutritional and fluid requirements so appropriate nutrition support plans can be devised
  • establish and monitor fluid and nutritional status, and to calculate safe doses of medication
  • when selecting supportive equipment such as pressure relieving beds, chairs, and mattresses.

Background/Evidence

• Weighing equipment are important diagnostic and monitoring tools
• A lack of consistent weight recordings in conjunction with the use of inaccurate or inappropriate weighing equipment hinders optimal care leading to potential errors in diagnosis, treatment, or medication dosage
• The Local Authorities Coordinators of Regulatory Services (LOCARS) and the Department of Health recommend that:
  • class III weighing scales should be used in healthcare premises:
    • where greater accuracy is required (for example, when weight is used to calculate medication doses or therapy or patients are being monitored for fluid retention)
    • for the calculation of weight for medication and ongoing treatment or monitoring
    • scales may be standing, sitting, hoist, wheelchair, or bed scales according to patient need
  • Class IV (less accurate domestic type scales) should only be used for monitoring/recording an individual's weight:
    • where weight is not required to calculate treatments or therapies
    • in GP consulting rooms, nursing or residential homes, and home visits
    • where there is no risk the scale will be used to weigh someone under the age of 18 years
• Maximum scale intervals:
  • maximum scale interval for adults is 0.5 kg and for children it is 0.2 kg
• Training and responsibilities:
  • basic training in the use of weighing equipment should be given to all healthcare professionals involved in weighing individuals
  • if the healthcare professional does not feel competent undertaking and recording body weight additional training should be sought
  • if the role of weighing is delegated to non-registered staff the Registered Nurse maintains accountability to ensure the non-registered staff are trained and competent in obtaining accurate weight measurements
• Changes in body weight:
  • short term changes in body weight, for example >0.25 kg per day, are likely to reflect changes in hydration rather than actual body weight
  • if recorded body weight is not as expected then the person should be re-weighed
• Using proxy measurements:
  • if it is not possible to weigh a patient a proxy measure of weight such as mid upper arm circumference may be used using the appropriate measurement tool and calculations
• Equipment needed to obtain body weight:
  • appropriate weighing scales placed on a flat even surface
  • cleaning equipment, as per local policy, to clean scales after use
  • weight conversion chart (to inform the person of their weight in stones/pounds if they prefer).

Procedure for Weighing an Individual

• Prior to use check:
  • the calibration date is still valid
  • scales have sufficient battery power to weigh the person (if appropriate)
  • for any signs of damage
• Position the scales for easy access, and to ensure privacy and dignity
• Place weighing equipment on a firm, solid surface or on the appropriate hoist equipment
• Apply brakes to scales (if appropriate)
• Ensure that no part of the scales is leaning against a fixed object (for example, a wall)
• If using:
  • stand on scales:
    • adjust the legs to ensure scales are level
    • check spirit level if present
  • wheelchair weighing scales:
    • weigh wheelchair
    • weigh individual in the wheelchair
    • calculate the individual's weight
  • hoist scales:
    • ensure scales are compatible with the type of hoist being used
    • ensure hoist slings are compatible and of an appropriate size for the person
• If unsure check manufacturers guidance
• Explain the procedure to the person being weighed
• Where the person has capacity to consent verbal agreement should be obtained
• Where the person does not have capacity, a risk assessment should be undertaken and decision regarding safe weight measurement made in the person's best interest
• The individual should be weighed:
  • wearing light indoor clothing (in community or out-patient settings)
  • night wear/hospital gowns (in hospital wards)
• Request the person remove shoes and outdoor garments as appropriate
• If weighing patients with stoma or catheter bags ensure they are emptied before weighing
• If weighing children they should be weighed wearing only a dry nappy or pants
• Where this is not possible or in older children the amount and type of clothing should be recorded
• Ensure that the weighing equipment records zero before the person is positioned on it or the hoist sling is attached
• If the weighing equipment does not show zero reset them before placing the patient onto them
• Following a risk assessment provide the appropriate level of assistance if the person cannot get on to the weighing equipment independently
• The person should remain still as possible while being weighed
• Monitor to ensure that:
  • clothing is not touching any fixed part of the scales or surroundings
  • body weight is not supported on an object, for example, a walking stick or wall, and the person does not have their feet placed on the floor (when using sitting scales) or on any part of the hoist
• Once the scales register a weight, record the reading on the scales and document in the appropriate documentation or nutrition screening tool
• Where necessary, or if requested, use a weight conversion chart to inform the person of their weight
• If possible check with the person and previous medical records that the weight reflects their expected weight and is similar to previous weights recorded
• If the weight is not as expected then the person should be re-weighed
• Also consider deliberate weight loss and fluid balance
• Once accurate weight is recorded assist the person to move away from weighing scales
• Ensure they are dressed appropriately and comfortable at end of procedure
• Routine cleaning of scales should be undertaken, in accordance with the manufacturer's instructions and local policy, after every patient use
• Return scales to storage position
• Record weight in kilograms (kg) in the appropriate noting system, including growth chart, screening tool, or medication chart (as appropriate)
• Record time of day patient was weighed and what clothing was worn
• Repeat weight should be recorded on the same scale, at the same time of day after urinating (if possible)
• Where weight is recorded as part of nutrition screening tool use it to calculate body mass index (BMI) and percentage body loss.