Residual Red Blood Cell Volume in Extracorporeal Blood Circuit after Hemodialysis: A Single-Center Study.

Introduction: The factors contributing to blood loss during hemodialysis (HD) procedures remain underexplored. This study aimed to quantify blood loss during HD and identify the potential factors associated with it.
Methods: The study included 70 ESRD patients undergoing HD. After dialysis, the extracorporeal blood circuits were rinsed with 1,000 mL of 0.05% NH3 solution in distilled water, and hemoglobin levels were measured. Univariate regression was used to assess the linear relationship between residual red blood cell (RBC) volume and various parameters, including HD mode, dialyzer surface area, ultrafiltration goal, hypotension during HD, blood flow rate, activated partial thromboplastin time, and C-reactive protein. Multivariate regression was also conducted to explore the relationships among these parameters.
Results: The mean RBC volume remaining in the extracorporeal blood circuit after HD was 1.6 ± 0.9 mL (mode: 1.0, range: 0.3-6.5 mL). When converted to whole blood volume per patient, the mean blood volume was 5.3 ± 3.0 mL (median: 4.1 mL, mode: 4.0 mL, range: 1.0-19.0 mL). Multivariate analysis identified the dialyzer surface area as the only significant determinant of residual RBC volume.
Conclusion: After HD, the remaining RBC volume in the extracorporeal blood circuit varies from 1.6 to 6.5 mL. When the RBC volume was converted to whole blood volume for each case, the blood loss ranged from 1.0 to 19.0 mL. Dialyzer surface area was the only significant determinant of residual RBC volume.
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