Clinical study of a hematocrit (H)-based method to determine vascular access blood flow rates (QA) without saline injection (SI).
ASN 30th Annual Meeting, San Antonio
J Am Soc Nephrol (Sep) 8:174A 1997
Many of the methods of access recirculation (AR) detection rely on injection of saline into the venous (returning) bloodline. A sensor is placed on the arterial (inflow) bloodline and if the effects of venous line saline injection are not immediately detected by the arterial line sensor, then AR is absent. The sensor usually uses either ultrasound or optical methods to detect a hematocrit change in the arterial bloodline. The AR detection method was ingeniously adapted by Krivitsky to detect access blood flow: The access needle connections are reversed, such that the returning blood enters the access upstream to the inflow needle. AR is thereby induced, and the degree of induced AR is proportional to the ratios of the extracorporeal blood flow (which is known), and the access blood flow. Once AR is computed, one can solve the equation for the last unknown, namely, access blood flow. It would be advantageous to avoid the necessity of saline injection in using this method, whether to measure AR (normal line configuration), or access flow (reversed line configuration).
In this study, rather than diluting the venous line blood to detect AR in reversed line mode, and thereby access flow, the venous line blood is suddenly concentrated by acutely increasing the UF rate (from 0 to 30 ml/min) in the dialyzer. As before, an arterial line sensor looks for an almost immediate change in the arterial line hematocrit which would occur only if AR is present. Hematocrit was assessed using an optical method (CRIT-LINE), and results of saline injection dilution were compared with those for UF-hemoconcentration.
Access flow was similar using UF-hemoconcentration as with saline injection dilution (r=0.77), and similar mean access flows were determined (962 vs. 1100 ml/min). No standard error of the estimates are given, however.
Comment: These are interesting results, although Lindsay's work suggests that the optical hematocrit method of determining AR or access flow may be less accurate than thermal methods or when blood concentration is measured using ultrasound dilution. A correlation value of 0.77 is rather low when measurements are being made under nearly identical circumstances and almost at the same time, using the same detection technology. (John T. Daugirdas, M.D., University of Illinois at Chicago)
To go back use the BACK button on your browser. Otherwise click on the desired link to this article below:
ASN 30th Annual Meeting, San Antonio
Basic hemodialysis : Vascular Access: graft/fistula