In several circumstances in hemodialysis, the regular direction of blood fl
ow has to be reversed or changed, such as in access dysfunction or insuffic
ient blood flow being obtained through the arterial port, as well as to mea
sure actual access blood flow in fistulas or grafts by using the formula Qa
= Qb*((1-R)/R), where R represents recirculation in the reversed line conf
iguration. We invented a disposable switch device made from standard blood
line tubing that can be introduced into the dialysis circuit and allows for
on-line reversal of lines, without needing to manually disconnect and reco
nnect tubing or interrupt the hemodialysis procedure. Over a period of eigh
t months, 16 patients (8 arteriovenous fistula, 8 PTFE) underwent 193 hemod
ialysis sessions with the switch in place. Circuit pressures, pump, and act
ual blood flows measured with ultrasound dilution were monitored before and
after reversing the lines. Switching was accomplished within 1-2 seconds.
Arterial circuit (r = 0.99*), venous circuit pressures (r = 0.6*), and actu
al pump flow (364 +/- 56 vs. 350 +/- 57 ml/min; r = 0.73*) correlated very
well preswitching and postswitching (* p < 0.0001). Dialysis circuit flow m
easured with an ultrasound dilution technique decreased from 364 +/- 56 (23
0-480) ml/min preswitching to 350 +/- 57 (220-490) ml/min postswitching (p
< 0.001). No difficulties or complications were observed. This switch devic
e is a useful addition to the technology of hemodialysis in that it greatly
facilitates the procedure of reversing the lines in an extracorporeal circ
uit while not significantly interfering with circuit pressures and connecti
ons.