Effective blood flow and recirculation rates in internal jugular vein twin catheters: measurement by ultrasound velocity dilution.

The ultrasound dilution technology (Transonic Systems, Ithaca, NY) is a reliable method to assess blood flow (Qb) and recirculation rates (R) in vascular access during hemodialysis. However, the information available on these parameters for central venous dialysis catheters remains scarce at this point. Real Qb and R were evaluated in 33 well-functioning TwinCath (Medcomp, Harleysville, PA) inserted as mid- or long-term hemodialysis vascular access (mean duration since insertion, 270 +/- 253 days); all were implanted into the right internal jugular vein with their multiperforated distal tips located in the superior vena cava or right atrium. Several types of dialysis machines were used (Monitral and AK100, Hospal-Gambro, Lyon, France; 2008E and 4008E, Fresenius, Bad Homburg, Germany). Real Qb was measured with the ultrasound dilution method and compared with the set Qb (indicated by the dialysis machine); R, also evaluated by ultrasound dilution, was evaluated at various Qb with nonreversed lines; therefore, a total of 121 measures were performed. Arterial and venous pressures (PA and PV) were recorded simultaneously. The 33 measures at a set Qb of 200 mL/min showed a mean effective Qb of 210 +/- 18 mL/min and a mean R of 5.3 +/- 5.3%. At a Qb of 300 mL/min, 33 repeated measures resulted in mean effective Qb of 303 +/- 21 mL/min and R of 8.5 +/- 7.0%; 28 measures performed at a set Qb of 350 mL/min showed that the effective Qb was 336 +/- 24 mL/min and that R was 7.8% +/- 6.7%. Finally, an effective Qb of 372 +/- 26 mL/min and an R of 10.9 +/- 8.6% were found for the 27 measures performed at an indicated Qb of 400 mL/min. The difference between indicated and effective Qb was particularly significant for set Qb equal to or above 350 mL/min (P < 0.001). Variable correlations were observed between obtained parameters: Qb eff and R (r = 0.34), PV and R (r = 0.36), Qb eff and PV (r = 0.78), Qb eff and PA (r = 0.71), and PV and PA (r = 0.53). In conclusion, TwinCath delivers an effective Qb of nearly 375 mL/min when Qb is set at 400 mL/min on most dialysis machines. Mean R in TwinCath varies between 5% and 11% for Qb within the range of 200 to 400 mL/min. In well-functioning TwinCath, the ratio between PV and Qb remains usually below 0.5.