**5. Conclusions**

224 Technical Problems in Patients on Hemodialysis

There was no statistically difference in the recirculation between diabetic versus non diabetic

The distances between arterial and venous needles were 5.53±2.69 cm and 13.17 ± 3.38 cm respectively. It represents that there is a significant association between distances of needles

The average time between creation and use of A-V fistula were 71±31 days and 46 ± 13 days.

The measurement of A-V Fistula Recirculation in HD patients is an important issue, since it appears to be an important cause of inadequate HD. In addition, some clinical guidelines are suggested regular monitoring of HD vascular access by methods such as vascular access

An accurate assessment of access fistula recirculation can be made by urea-based method as the same as the present study and nonurea-based techniques by ultrasound dilution

In urea-based method, it's usually measured by comparing the systemic and dialyzer inlet blood urea concentration. Urea concentration in blood entering the dialyzer (A in the above formula) is assumed to be equal to the systemic urea concentration (P in the above formula)

There are different protocols for systemic blood urea sampling in the urea-based method measurement of access recirculation. In the three-needle or traditional method, the systemic urea concentration has been obtained from a peripheral vein in the contralateral arm. However, it is now recognized that this approach is inaccurate and tends to overestimate access recirculation because the BUN obtained from a peripheral vein is often higher than the BUN in the blood entering the dialyzer inlet, even in the absence of recirculation.(14) Two factors contribute to this problem: Cardiopulmonary recirculation and veno/venous disequilibrium.(15, 16, 17) Thusthree-needle method dose not routinely use due to its requirement for additional venipuncture, unpredictable manner, and overestimation of

Sampling peripheral arterial blood eliminates the effects of both cardiopulmonary recirculation and venovenous disequilibrium. However arterial puncture during HD is not

Preferred alternatives to the peripheral vein or three-needle method and arterial puncture is two needle technique as same as use in the present study. In the study, systemic urea concentration is obtained from the dialyzer blood inlet line after slowing the blood pump to 50mL/min for about 30 seconds (P in the above formula).(18) This "two-needle" technique as opposed to the use of three needles are presumably more accurate for the determination of

In our study, the average degree of A-V fistula recirculation was 9.56±2.32 percent and it was almost similar to findings of salimi et al in 2008, Bay et al in 1998, Besarab et al in1997. These groups used two needle technique urea-based method as same as present study for measurement of recirculation. The average degree of recirculation in these groups were 8.7%,

(P =0.28) and hypertensive versus normotensive (P =0.21%) hemodialysis patients.

(P=0.002) and improper needle placement (P=0.000) with degree of recirculation.

The length of time of A-V fistula use was 26.59± 9.37 months and 33.20± 7.35 months. The mean A-V fistula flow rate in both groups was more than 400 ml/min. The mean A-V

There were also a significant difference between them (P=0.043).

recirculation for early detection and correction of access dysfunction.(10)

technique, conductivity, or potassium-based dilutional method.(11, 12, 13)

fistula flow rate was significantly (p = 0.001).

**4. Discussions** 

if there is no recirculation.

access recirculation.

access recirculation.(19)

also practical and does not recommended.

11.8 ± 9.9% and 5.5 ± 0.8% respectively.(20, 21, 22)

The measurement of A-V Fistula Recirculation has important diagnostic implications in Hemodialysis patients because it is an important cause of inadequate dialysis. According to the study it was a common occurrence. Although, the role of improper arterial and venous needles placement in recirculation usually ignore, it was the most common cause in our HD patients. Therefore we should have more emphasis on education and training of Hemodialysis staffs.
