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In critically ill patients, how often is their weight estimated and how accurate is that estimate?

Introduction

Weight is frequently required to determine the dose of many medications and is important in quantifying treatments such as haemofiltration and calorific requirement. We present the findings of an audit to determine how frequently a patient's weight is estimated in one ICU and the results of a pilot study to determine the accuracy of an estimated weight in the critically ill patient.

Methods

A prospective audit of 100 admissions to an ICU was undertaken over a 6-week period. Data were collected from observation charts and hospital notes. Following data analysis a pilot study was undertaken to assess the accuracy of the estimated weight of patients in the ICU. Urine bags and drains were emptied before weighing and the same number of pillows and blankets was ensured on each bed. Due to a short loan period of scales, only 18 patients could be weighed.

Results

Audit The median (IQR) patient weight was 75 kg (64 to 85). Ninety-four ICU observation charts had a weight recorded, and of these 38 (40.4%) were estimated. Sixteen out of 20 (80%) medical patients and 22/74 (29.7%) surgical patients had an estimated weight. Sixty-three per cent of patients had a recent accurate weight recorded in the notes and only 43 (68.3%) had the same weight recorded on the ICU observation chart. Seventy per cent of patients required a weight for cardiac output monitoring and 54% for drug dose calculation. Pilot study The median (range) measured weight was 92 (66.8 to 137.4) kg. Twelve out of 18 had an estimated weight on the ICU chart. The mean (precision) of estimation was 10.1 (± 21.4) kg. Seven out of 12 (58%) had a greater than 10% difference between the estimated and true weights. Of the six patients who had a recent accurate weight documented in the notes, the mean difference (precision) between that and the true weight was 5.8 (± 4.0) kg. Two out of six (33%) had a greater than 10% difference between estimated and true weights.

Conclusion

A patient's weight is an important parameter in guiding therapy. A large proportion of ICU patients have their weight estimated. In some cases this is unnecessary as a recent weight can be found in the notes. A more comprehensive study is required to assess the clinical impact of weight estimation on the ICU.

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Mathew, D., Kirwan, C., Dawson, D. et al. In critically ill patients, how often is their weight estimated and how accurate is that estimate?. Crit Care 13, P460 (2009). https://doi.org/10.1186/cc7624

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Keywords

  • Pilot Study
  • Medical Patient
  • Dose Calculation
  • Weight Estimation
  • Patient Weight