Comparison of arteriovenous fistula recirculation by thermodilution and urea - based method

To compare arteriovenous fistula recirculation by thermodilution technique and urea based two needle slow flow method.

Comparative cross-sectional study.

Hemodialysis Unit of Nephrology Department of Shaikh Zayed Hospital, Lahore, from October 2005 to December 2005.

Thirty one patients with end stage renal disease on maintenance hemodialysis through arteriovenous fistula were selected on purposive design. Hemodialysis was done on Fresenius 4008 S machines with in-built blood temperature monitoring module to measure recirculation by thermodilution method. Recirculation by the thermodilution method was calculated with the blood flow rate of 300 milliliter /minute and dialysate flow of 500ml /minute. Access recirculation by urea based method was calculated by taking three blood samples for blood urea nitrogen. Two samples were taken simultaneously from the arterial and venous ports respectively. Third sample was taken from the arterial port after slowing the blood flow pump to 50 milliliter/minute and waiting for 30 seconds. Relationship of thermodilution and urea based method was assessed by calculating Pearson correlation coefficient (r).

Out of 31 patients, 18 (58.1%) were males, whereas 13 (41.9%) were females. Their mean age was 47.29 +/- 13.42 years. Mean access recirculation by thermodilution method was 7.31 +/- 3.03 and by urea based method was 9.55 +/- 6.64. Correlation coefficient (r) was 0.706 with p-value of < 0.001, which was highly significant.

Arteriovenous fistula recirculation calculated by thermo-dilution technique has a strong correlation with the recirculation calculated by the two-needle urea based method.