Bedside method to estimate actual body weight in the Emergency Department.

BACKGROUND: Actual body weight (ABW) is important for accurate drug dosing in emergency settings. Oftentimes, patients are unable to stand to be weighed accurately or clearly state their most recent weight. OBJECTIVE: Develop a bedside method to estimate ABW using simple anthropometric measurements. METHODS: Prospective, blinded, cross-sectional convenience sampling of adult Emergency Department (ED) patients. A multiple linear regression equation from Derivation Phase (n = 208: 121 males, 87 females) found abdominal and thigh circumferences (AC and TC) had the best fit and an inter-rater correlation of 0.99 and 0.96, respectively: Male ABW (kg) = -47.8 + 0.78 ∗ (AC) + 1.06 ∗ (TC); Female ABW = -40.2 + 0.47 ∗ (AC) + 1.30 ∗ (TC). RESULTS: Derivation phase: Number of patients (%) with a body weight estimation (BWE) > 10 kg from ABW for males/females were: 7 (6%)/1 (1%) for Patients, 46 (38%)/28 (32%) for Doctors, 38 (31%)/24 (27%) for Nurses, 75 (62%)/43 (49%) for 70 kg/60 kg convention, and 14 (12%)/8 (9%) using the anthropometric regression model. For validation phase (55 males, 44 females): Gold standard ABW mean (SD) male/female = 83.6 kg (14.3)/71.5 kg (18.9) vs. anthropometric regression model = 86.3 kg (14.7)/73.3 kg (15.1). R(2) = 0.89, p < 0.001. The number (%) for males/females with a BWE > 10 kg using the anthropometric regression model = 8 (15%)/11 (27%). CONCLUSIONS: For male patients, a regression model using supine thigh and abdominal circumference measurements seems to provide a useful and more accurate alternative to physician, nurse, or standard 70-kg male conventional estimates, but was less accurate for use in female patients.

Bedside estimation of patient height for calculating ideal body weight in the emergency department.

BACKGROUND: 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). OBJECTIVES: 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 male/60 kg female standard IBW. METHODS: 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; R(2) = 0.89, p < 0.001. Inter-rater correlation of tibial length was 0.94. RESULTS: Derivation set: percent within 5 kg of true height-based IBW for men/women = PATIENT: 91.1%:/85.7%; Physician: 66.1%/45.1%; Nurse: 65.7%/ 47.3%; tibial length: 66.1%/63.7%; and 70 kg male/60 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. All methods were more accurate than using the conventional 70 kg male/60 kg female IBW standard.