Hannan et al used bio-impedance analysis (BIA) to estimated body water in surgical patients. The authors are from Western General Hospital and Royal Infirmary of Edinburgh in Scotland.
Patient selection: adult surgical patient
Method of analysis: BIA
Parameters:
(1) height in centimeters
(2) R50 (resistance at 50 Hz) in Ohms
(3) antero-posterior thickness in centimeters (APT, maximum thoracic thickness along the length of the sternum as measured with calipers)
(4) X50 (reactance at 50 Hz) in Ohms
(5) weight in kilograms
(6) R500 (resistance at 50 Hz) in Ohms
(7) X500 (reactance at 500 Hz) in Ohms
total body water in liters =
= (0.497 * ((height)^2) / R50) + (0.5 * APT) + 0.275
total body water in liters =
= (0.45 * ((height)^2) / R500) + (0.46 * APT) + (0.0119 * ((height)^2) / X50) - (0.0106 * ((height)^2) / X500) -1.04
total body water in liters =
= (0.446 * ((height)^2) / R50) + (0.126 * (weight)) + 5.82
where:
• Equation 1: r=0.957, SEE=2.37 liters. coefficient of variation 6.5%.
• Equation 2: r=0.967, SEE=2.17 liters. coefficient of variation 6.0%.
• Equation 3: r=0.951, SEE=2.54 liters. coefficient of variation 7.0%.
