Abstract

Introduction: In Chile in 2018 there were 22,310 patients under chronic hemodialysis (CHD) (1,260/1,000,000 inhabitants), with an annual increase of 2,152 patients/year and a global mortality of 10.9%. First cause of death is cardiovascular (CV) disease with 32.8%. Control of total body water (TBW) helps prevent CV damage. It is necessary to know TBW to program the ultra filtration rate at the beginning of HD. Methods for estimating TBW are invasive, complex and expensive, except for multi frequency electrical Bioimpedanciometry (BCM®).However, this device has certain limitations as the 20-40 minute preparation before HD and the restriction it has in some patients. Several equations have been proposed to estimate TBW but are difficult to calculate and neither of them are local. The aim of this study was to create a total body water equation (TBWE) to estimate TBW concordant with TBW by BCM®, easy and fast to use before each CHD session. Method: Observational, analytical, cross-sectional, bicentric study, from January 2011 to October 2013 in Santiago, Chile. This study was approved by the institution’s research ethics committee. Inclusion criteria were adults with more than 3 months of CHD, with at least 95% HD adherence, self-sufficient and who agreed to participate in the study signing the informed consent. Patients with pacemakers, metal prostheses, an amputated limb or hospitalized were excluded. TBW previous CHD was measured with BCM® during 1st and 3rd sessions of the week; gender, age, weight, height and BMI pre CHD were also measured. TBWE elaboration consisted on a series of statistical analysis such as: Comparison of categorical variables to know if a gender-adjusted equation was needed, Pearson correlation coefficient (r), multivariate generalized linear regression modeling with significant variables, model consistency evaluation, concordance between TBWE vs. TBWBCM® using Lin’s CCC and Bland Altman´s Diagram. Statistical significance was established with a p-value< 0.05. Stata12 statistical software was used. Results: The measurements of 88 pre CHD were analyzed, in 22 male and 22 female; median age 60 years (24-77) and 56 years (22-77) respectively (p = 0.493); height 1.67 meters (1.51-1.78) and 1.54 meters (1.14-1.66) (p = 0.001); previous HD weight 77.7 (55.7-132.5) and 58.7 (46.3-93.4) kgs, (p = 0.002); TBW pre CHD 35.2 (23.3-53.6) and 35.2 (23.3-53.6) liters (p = 0.001), respectively. Final TBWE male = -17.9 + 0.25x preHD weight + 0.19x height. TBWE female = -8.23+ 0.29x pre CHD weight + 0.10x height. CCC was 84% CI95% 78.4-91% p <0.001. Conclusion: A TBWE was created for Chilean CHD patients by gender, with daily measurement clinical variables, quick and easy calculation and 84% concordant (CI95% 78.4-90%) whit BCM®. Its use will be feasible after validation with a larger sample.