Height and weight are routinely measured for most patients during admission to a health care facility. An accurate record of the patient's height and weight is essential for calculating dosages of drugs, anesthetics, and contrast agents; assessing the patient's nutritional status; and determining the height-weight ratio. Because body weight provides the best overall picture of fluid status, monitoring it daily proves important for patients receiving sodium-retaining or diuretic medications. Rapid weight gain may signal fluid retention; rapid weight loss may indicate diuresis.
Weight can be measured with a standing scale, chair scale, or bed scale; height can be measured with the measuring bar on a standing scale or with a tape measure for a supine patient. (See Types of scales, page 20.)
Equipment
Standing scale (with measuring bar) or chair or bed scale • wheelchair (if needed to transport patient) • tape measure if needed.
Preparation of equipment
Select the appropriate scale—usually, a standing scale for an ambulatory patient or a chair or bed scale for an acutely ill or debilitated patient. Then check to make sure the scale is balanced. Standing scales and, to a lesser extent, bed scales may become unbalanced when transported.
Implementation
  • Explain the procedure to the patient.
Using a standing scale
  • Place a paper towel on the scale's platform.
  • Tell the patient to remove his robe and slippers or shoes. If the scale has wheels, lock them before the patient steps on. Assist the patient onto the scale and remain close to him to prevent falls.
  • If you're using an upright balance (gravity) scale, slide the lower rider to the groove representing the largest increment below the patient's estimated weight. Grooves represent 50, 100, 150, and 200 lb. Then slide the small upper rider until the beam balances. Add the upper and lower rider figures to determine the weight. (The upper rider is calibrated to eighths of a pound.)
  • If using a multiple-weight scale, move the appropriate ratio weights onto the weight holder to balance the scale; ratio weights are labeled 50, 100, and 200 lb. Add ratio weights until the next weight causes the main beam to fall. Then adjust the main beam poise until the scale balances. To obtain the weight, add the sum of the ratio weights to the figure on the main beam.
  • Return ratio weights to their rack and the weight holder to its proper place.
  • If you're using a digital scale, make sure the display reads 0 before use. Read the display with the patient standing as still as possible.
  • If you're measuring height, tell the patient to stand erect on the platform of the scale. Raise the measuring bar beyond the top of the patient's head, extend the horizontal arm, and lower the bar until it touches the top of the patient's head. Then read the patient's height.
  • Help the patient off the scale, and give him his robe and slippers or shoes. Then return the measuring bar to its initial position.
Using a chair scale
  • Transport the patient to the weighing area or the scale to the patient's bedside.
  • Lock the scale in place to prevent it from moving accidentally.
  • If you're using a scale with a swing-away chair arm, unlock the arm. When unlocked, the arm swings back 180 degrees to permit easy access.
  • Position the scale beside the patient's bed or wheelchair with the chair arm open. Transfer the patient onto the scale, swing the chair arm to the front of the scale, and lock it in place.
  • Weigh the patient by adding ratio weights and adjusting the main beam poise. Then unlock the swing-away chair arm as before, and transfer the patient back to his bed or wheelchair.
  • Lock the main beam to avoid damaging the scale during transport. Then unlock the wheels and remove the scale from the patient's room.
Using a multiple-weight bed scale
  • Provide privacy, and tell the patient that you're going to weigh him on a special bed scale.
  • Position the scale next to the patient's bed and lock the scale's wheels. Then turn the patient on his side, facing away from the scale.
  • Release the stretcher frame to the horizontal position, and pump the hand lever until the stretcher is positioned over the mattress. Lower the stretcher onto the mattress, and roll the patient onto the stretcher.
  • Raise the stretcher 2″ (5 cm) above the mattress. Then add ratio weights and adjust the main beam poise as for the standing and chair scales.
  • After weighing the patient, lower the stretcher onto the mattress, turn the patient on his side, and remove the stretcher. Be sure to leave the patient in a comfortable position.
Using a digital bed scale
  • Provide privacy, and tell the patient that you're going to weigh him on a special bed scale. Demonstrate its operation if appropriate.
  • Place the protective plastic covering over the stretcher, and confirm that the scale is balanced.
  • Release the stretcher to the horizontal position; then lock it in place. Turn the patient on his side, facing away from the scale.
  • Roll the base of the scale under the patient's bed. Adjust the lever to widen the base of the scale, providing stability. Then lock the scale's wheels.
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  • Center the stretcher above the bed, lower it onto the mattress, and roll the patient onto the stretcher. Then position the circular weighing arms of the scale over the patient, and attach them securely to the stretcher bars.
  • Pump the handle with long, slow strokes to raise the patient a few inches off the bed. Make sure the patient doesn't lean on or touch the headboard, side rails, or other bed equipment, and that nothing is pulling on the scale (such as I.V. or catheter tubing) because these types of pressure will affect the weight measurement.
  • Depress the operate button, and read the patient's weight on the digital display panel. Then press in the scale's handle to lower the patient.
  • Detach the circular weighing arms from the stretcher bars, roll the patient off the stretcher and remove it, and position him comfortably in bed.
  • Release the wheel lock and withdraw the scale. Dispose of the protective plastic covering and return the stretcher to its vertical position.
Special considerations
  • Reassure and steady patients who are at risk for losing their balance on a scale.
  • Weigh the patient at the same time each day (usually before breakfast), in similar clothing, and using the same scale. If the patient uses crutches, weigh him with the crutches. Then weigh the crutches and any heavy clothing and subtract their weight from the total to determine the patient's weight.
  • Before using a bed scale, cover its stretcher with a drawsheet. Balance the scale with the drawsheet in place to ensure accurate weighing.
  • When rolling the patient onto the stretcher, be careful not to dislodge I.V. lines, indwelling catheters, and other supportive equipment.
  • Bed and dialysis scales, with platforms that are placed under the castors of the bed, are useful if frequent weights are needed or the patient is too critically ill to move.
Documentation
Record the patient's height and weight on the nursing assessment form and other medical records, as required by your facility.