Relative blood volume changes during haemodialysis estimated from haemoconcentration markers

Area of Science:

• Nephrology
• Biomedical Engineering
• Physiology

Background:

• Relative blood volume (RBV) monitoring aids fluid management and cardiovascular stability in hemodialysis patients.
• RBV is typically estimated using haemoconcentration markers like haematocrit (HCT), haemoglobin (HGB), or total blood protein (TBP).
• The initiation phase of hemodialysis, involving extracorporeal circuit filling, presents dynamic circulatory changes.

Purpose of the Study:

• To quantitatively assess the impact of measurement timing on RBV monitoring accuracy.
• To evaluate how the start of RBV tracking influences observed changes, particularly concerning saline priming.

Main Methods:

• Utilized a mathematical model to simulate RBV changes during hemodialysis.
• Assessed the effect of varying measurement start times relative to saline infusion.

Main Results:

• Model simulations show that delayed RBV measurement start times can substantially alter observed RBV changes, especially with large priming volumes.
• Infusing priming saline to the patient, rather than discarding it, exacerbates timing-dependent RBV variations.
• The highest overestimation of actual RBV changes occurred when measurements began within minutes after completing saline infusion.

Conclusions:

• The precise timing of initiating RBV monitoring is critical for accurate fluid management during hemodialysis.
• Careful consideration of saline priming protocols and measurement initiation is necessary to avoid misleading RBV estimations.