Bedside Estimation of Patient Height for Calculating Ideal Body Weight in the Emergency Department

Ideal body weight IBW, which can be calculated using the variables of true height and sex, is important for drug dosing and ventilator settings. True height often cannot be measured in the emergency department ED. Determine the most accurate method to estimate IBW using true height-based IBW that uses true height estimated by providers or patients compared to true height estimated by a regression formula using measured tibial length, and compare all to the conventional 70 kg male60 kg female standard IBW. Prospective, observational, double-blind, convenience sampling of stable adult patients in a tertiary care ED from September 2004 to April 2006. Derivation set 215 patients had blinded provider and patient true height estimates and tibial length measurements compared to gold-standard standing true height. A validation set 102 patients then compared the accuracy of IBW using true height calculated from the regression formula vs. IBW using gold-standard true height. Regression formula for men tibial length-IBW kg 25.83 1.11 tibial length for women tibial length-IBW 7.90 1.20 tibial length R2 0.89, p 0.001. Inter-rater correlation of tibial length was 0.94. Derivation set percent within 5 kg of true height based IBW for menwomen Patient 91.185.7 Physician 66.145.1 Nurse 65.7 47.3 tibial length 66.163.7 and 70 kg male60 kg female standard 46 75. Validation set tibial length-IBW estimates were within 5 kg of true height-ideal body weight in only 56.2 of men and 42.2 of women. Conclusions Patient-reported height is the best bedside method to estimate true height to calculate ideal body weight. Physician and nurse estimates of true height are substantially less accurate, as is true height obtained from a regression formula that uses measured tibial length.