Total Body Water Determination: Have We To Adapt Its Determination To The Patient Clinical Status?

Abstract

The correct assessment of the total body water (TBW) is a crucial issue of the renal replacement therapy due to it represents the urea distribution volume, used for the determination of the dialysis adequacy Kt/V. Our objective was to study the correlation between the TBW estimated by Watson formula and with BCM-body composition monitor (Fresenius Medical care®). Methods: We study all the patients in hemodialysis in the Hospital La Paz Unit and Madrid El Pilar center, before the dialysis treatments. Results: Table 1 Weight ( kg) 70,05±13,12 ICW(l) 16,02±3,73 BMI( kg/ m2) 26,86±9,8 Albumin( g/dl) 3,87±0,48 FM(%) 37,97±10,52 Prealbumin ( g/dl) 28,22±8,18 FFM(%) 43,09±12,54 CRP 11,34±23 ECW(l) 16,8±3,51 TBW w(l) 35,76±6,15 TBW bcm(l) 32,92±7,31 Regarding the nutritional status, a 36.8% patients were undernourished by Chang criteria (19.3% sleigh, 15.8 % moderately and 1.8% severely). A 50.9% were obese by the %MG and a 61.4% had some criteria of muscle atrophy. We analyze the TBW differences by linear regression, adjusted by: BMI R2=0,076 p=0,038, %FFM R2=0,553 p<0,001, % FM R2=0,615 p<0,001 y CRP R2=0,228 NS. Conclusion: There is a good concordance between both methods in the determination of the TBW. The Watson formula overestimates the TBW in patients with high %FM and underestimates in those with high FFM. In the clinical practice, it is necessary to adapt the determination of TBW to the patient situation.