Correction of discrepancy between prescribed and actual blood flow rates in chronic hemodialysis patients with use of larger gauge needles.

The blood flow rate delivered by the dialysis machine (d-BFR) may not be accurately reflected by the blood flow rate set on the machine (sm-BFR). High negative arterial pressure may lead to deformity of the blood pump-segment tubing, resulting in a lower stroke volume and d-BFR. The Hagen-Poiseuille law predicts that the use of larger gauge needles should make arterial pressure less negative. Twenty-two patients on chronic hemodialysis therapy with a percentage of reduction in urea (PRU) levels less than 65% and/or a greater than 10% difference between sm-BFR and d-BFR underwent dialysis using one-gauge larger arterial and venous needles. d-BFR increased by 23 +/- 5 mL/min. Arterial pressure became less negative by 58 +/- 5 mmHg, and venous pressure decreased by 31 +/- 7 mm Hg. Changes in arterial and venous pressures allowed sm-BFR to be increased to 500 mL/min in all 22 patients, resulting in an increase in d-BFR of 83 +/- 7 mL/min. This translated into an increase in PRU of 5% +/- 0.01%. All results were significant at P < 0.001. A survey showed that less than 5% of needles used in our region were 14 G. This study shows that the use of larger gauge needles can significantly increase d-BFR and PRU as a result of changes in arterial and venous pressures, resulting in a significantly increased dialysis dose at no additional cost. Copyright 2002 by the National Kidney Foundation, Inc.