The weighing process in patients on hemodialysis: an opportunity to improve volume management

Background
Hemodialysis relies on accurate body mass (BM) assessment to determine ultrafiltration volumes, but we have not identified published practice patterns disclosing how to handle clothing mass. Here we investigated the potential impact of clothing mass on predialysis BM determination, hypothesizing that a standardized template for clothing mass estimation enhances accuracy, compared with conventional practice.

Methods
Measurements included dressed and undressed BM predialysis. A pre-established template for average clothing mass was used to approximate undressed BM from clothed measurements. Differences from undressed BM were compared using Bland–Altman plots and tested for statistical significance using Wilcoxon signed rank tests.
Results
After excluding erroneous results, data from 48 patients were analyzed. Thirty-six patients (75%) did not habitually estimate clothing mass, but used their dressed BM as the predialysis BM, while the other 12 patients (25%) reported deducting a self-estimated clothing mass from their clothed predialysis BM. The differences from undressed BM were 0.819 ± 0.462 kg and 0.342 ± 0.321 kg in these two groups, respectively, indicating that patients underestimated clothing mass. Using the template to deduct clothing mass from clothed predialysis BM, these differences could be reduced to 0.197 ± 0.220 kg and 0.133 ± 0.135 kg, respectively. The average differences using the patient-reported BM and the template-based BM made up 39.4% and 8.6% of the average subsequent ultrafiltration volume, respectively, suggesting that potential overestimation of the actual ultrafiltration volume could be reduced.

Conclusion
A standardized template for clothing mass may be useful to derive representative predialysis BM, leading to more precise ultrafiltration calculation. Exact BM determination might improve volume management in hemodialysis.