Calculating Ideal Body Weight: Keep It Simple

Authors: Olivier Moreault, M.D. et al

Anesthesiology 7 2017, Vol.127, 203-204.

To the Editor:

We read with much interest the editorial on protective ventilation by Hedenstierna and Edmark in the December issue of Anesthesiology.¹  We agree with most of the ideas put forward. However, as thoracic anesthesiologists, we strongly believe in the importance, during one-lung ventilation, of low tidal volume based on ideal body weight.^2,3 

Many authors still recommend using the gender-specific Acute Respiratory Distress Syndrome Network (ARDSnet) formulas to calculate ideal body weight.⁴  Ideal body weight is computed in men as 50 + (0.91 × [height in centimeters − 152.4]) and in women as 45.5 + (0.91 × [height in centimeters − 152.4]). A simple alternative would be to compute ideal body weight as the weight corresponding to an ideal body mass index of 22 kg/m². Ideal body weight is then simply calculated as 22 × ([the actual patient’s height in meters]^2) or by using body mass index charts available on our anesthesia cart.⁵  We chose 22 kg/m² as the ideal body mass index after comparing the ideal body weight corresponding to body mass indices ranging from 20 to 25 to ideal body weight calculated from ADRSnet formulas. For example, a 1.75-m man would have an ideal body weight of 67 kg (22 × [1.75^2]) compared to 71 kg if using ARDSnet; a 1.60-m woman would have an ideal body weight of 56 kg (22 × [1.60^2]) compared to 52 kg if using ARDSnet.

The method we propose is simple and easy to remember. The same computation applies for both men and women and involves simple arithmetic.

 

Olivier Moreault, M.D. Institut universitaire de cardiologie et de pneumologie de Québec – Université Laval, Québec City, Québec, Canada (J.S.B.). jbuss@criucpq.ulaval.ca

References

Hedenstierna, G, Edmark, L Protective ventilation during anesthesia: Is it meaningful? Anesthesiology 2016; 125:1079–82

Brassard, CL, Lohser, J, Donati, F, Bussières, JS Step-by-step clinical management of one-lung ventilation: Continuing professional development. Can J Anaesth 2014; 61:1103–21

Lohser, J, Slinger, P Lung injury after one-lung ventilation: A review of the pathophysiologic mechanisms affecting the ventilated and the collapsed lung. Anesth Analg 2015; 121:302–18

Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000; 342:1301–8

Moreault, O, Lacasse, Y, Bussières, JBody mass index chart 2016. Available at: http://bit.ly/2ikOtch. Accessed March 31, 2017