Related Experiment Videos
Measurement of blood access flow rate during hemodialysis from conductivity dialysance
F A Gotch1, R Buyaki, F Panlilio
1Department of Dialysis Treatment and Research, Davies Medical Center, San Francisco, California, USA.
Insights
This study introduces a new method using an online clearance monitor to accurately measure blood access flow rate (cnQac) during hemodialysis, improving patient safety by detecting unexpected stenosis.
Area of Science:
- Nephrology
- Biomedical Engineering
- Medical Devices
Background:
- Accurate measurement of blood access flow rate (cnQac) is crucial for effective hemodialysis.
- Current methods may have limitations in detecting critical issues like stenosis.
Purpose of the Study:
- To develop and validate an automated method for measuring cnQac during hemodialysis using an online clearance monitor.
- To assess the reliability of this method in detecting vascular access complications.
Main Methods:
- Utilized an online clearance monitor for conductivity dialysance (Dcn) measurements.
- Derived mathematical equations based on transport analysis to calculate cnQac.
- Validated the method through in vitro and in vivo studies, comparing results with volumetric measurements and urea dialysance.
Main Results:
- Demonstrated excellent correlation between the new method and volumetric measurements (r=0.98) and urea dialysance (r=0.97) in vitro.
- Showed comparable agreement in in vivo studies (r=0.97).
- Successfully identified unsuspected severe midgraft stenosis in two patients, revealing access flow rates of 89 and 202 ml/min.
Conclusions:
- The automated online clearance monitor provides a reliable and accurate method for measuring blood access flow rate during hemodialysis.
- This technique can effectively detect critical vascular access problems, enhancing patient safety.
- The derived equations offer a valuable tool for real-time monitoring and management of hemodialysis access.
Abstract:
An on line clearance monitor automated for measurements of conductivity dialysance (Dcn) was used to measure blood access flow rate (cnQac) during hemodialysis. From mathematical analysis of transport, it was shown that cnQacc = [(Dcn*Decn)/(Dcn - Decn)] [1/bwf], where Dcn is measured with standard cocurrent flow of dialyzer blood (Qb) and Qac; Decn is measured with countercurrent Qb/Qac; and bwf is fractional blood water content. An identical equation was derived to measure Qac from urea dialysance (uQac, Du, Deu). In vitro studies showed excellent correlation between volumetric measurement of Qac (vQac) and cnQac, r = 0.98, n = 29, and between uQac and cnQac, r = 0.97, n = 28. In vivo studies showed comparable agreement between uQac and cnQacc, r = 0.97, n = 14. In two of the patients studied, there was unsuspected severe midgraft stenosis (no recirculation in cocurrent flow) with a Qac of 89 and 202 ml/min disclosed by both cnQac and uQac measurements. Mathematical analysis also showed that when Qb is greater than Qac and there is recirculation in cocurrent flow, the above equations always return the value Qac = Qb. An equation was derived to calculate cnQac without reversal of blood lines in this case, using Dcn calculated from the dialyzer transport coefficient and flow rates.