**3. Results**

Overall**,** thirty seven patients 15 male (40.54%) and 22 female (59.45%) were on HD therapy in our centers. From them, thirty seven patients have an A-V fistula and they were on HD more than three months that they enrolled for the study.

#### **3.1 Experimental system**

220 Technical Problems in Patients on Hemodialysis

Fig. 3. Experimental systems with both the optical absorbance probe in patients in

**2.3 Measure process of urea concentration in blood in laboratory technical** 

group 1 patients without recirculation and group 2 patients with recirculation.

group's quantitative data, the means were compared by using student's t test.

more than three months that they enrolled for the study.

We used the two needles technique for the recirculation measure in the vascular access. In hemodialysis session, the flow in the vascular access is measured by employs the optical sensor for practice the on-line measure of Urea in blood and blood samples for evaluation

To treatment started the flow is the 400 ml/min after 30 min. We proceed to taking of samples in blood in the arterial (A) and venues (V) line in a simultaneous way, next time diminishes the flow to 50 ml/min during 30 seconds, which this proceeds to a second blood sample in the arterial line (S), concluded this activity with continues the hemodialysis

The all measurements samples were evaluated in laboratory and on line measurement prototype for urea in hemodialysis treatment. The patients were divided into two groups,

For each patient distances between arterial and venous needles and distances of needles from A-V fistula and its directions was recorded. The findings were analyzed by SPSS statistical program. Chi square test or Fisher Exact test were used for qualitative data. For two

Association between risk factors and recirculation rate was evaluated by COX regression

Overall**,** thirty seven patients 15 male (40.54%) and 22 female (59.45%) were on HD therapy in our centers. From them, thirty seven patients have an A-V fistula and they were on HD

model. Statistical significance was assessed at the 0.05 probability level in all analyses.

hemodialysis treatment.

session to the arterial flow prescribed.

in laboratory.

**3. Results** 

The direct results obtained with the prototype display the optical transmittance in the range of 600-620 nm, corresponding to a Red LED show the evolution in the urea concentration estimated during the experimental Hemodialysis procedure in a patient. In the Figure 4 show the recirculation evolution of the urea concentration during Hemodialysis treatment in a patient shows values in the A-V fistula.

#### **3.2 Clinical measurements**

To verify the functioning system, we comparing the urea concentration values obtained with the online prototype values versus Laboratory. Successive measurements under same conditions (connectors, power, temperature, etc.) observing a small dispersion.

The results obtained with optical system and Laboratory (Dade Behring equipment) was coherent. In the Figure 5 we can observe that statistic factor between laboratory and prototype for recirculation percentage in Permanent Vascular Access (PVA). The average estimation for recirculation percentage impermanent accesses via laboratory is 3.57 ± 2.28 %, with optical system is 4.55±2.35%The Figure 6 we can observe that statistic estimation for recirculation percentage in Permanent Hemodialisys Catheter (PHC)

The average accesses via laboratory is 6.25 ± 4.16 %, with optical system is 8.77±5.13%. The show results indicate good correlation in average and standard deviation, the equal forms both measurement systems show wide dispersion The correlation coefficient between optical system and laboratory in the recirculation measurement in permanent accesses is R² = 0.69 was temporary accesses R² = 0.66

Fig. 4. Recirculation measurement by optical system, the calculation is based in the voltages estimation during Hemodialysis Treatment, Peripheral (S), Arterial (A) and Venous (v) blood samples when two needles technique.

Measuring System of Urea in Blood by Application in Recirculation for Hemodialysis Treatment 223

Fig. 7. Correlation between the laboratory analysis and optical system results for recirculation measurement in Permanent Vascular Access (PVA) is R² = 0.66.

Fig. 8. Correlation between the laboratory analysis and optical system results for recirculation measurement in Permanent Hemodialisys Catheter (PHC) is R² = 0.69

Fig. 6. Results obtained by Laboratory vs. Optical system for recirculation percentage Permanent Hemodialisys Catheter (PHC).

Fig. 5. Results obtained by Laboratory vs. Optical system for recirculation percentage in

Fig. 6. Results obtained by Laboratory vs. Optical system for recirculation percentage

Permanent Vascular Access (PVA).

Permanent Hemodialisys Catheter (PHC).

Fig. 7. Correlation between the laboratory analysis and optical system results for recirculation measurement in Permanent Vascular Access (PVA) is R² = 0.66.

Fig. 8. Correlation between the laboratory analysis and optical system results for recirculation measurement in Permanent Hemodialisys Catheter (PHC) is R² = 0.69

Measuring System of Urea in Blood by Application in Recirculation for Hemodialysis Treatment 225

Depner et al have measured recirculation by ultrasound dilution technique and they reported

The most common causes of A-V fistula recirculation in HD` patients are the presence of high-grade venous stenoses, improper needle placement, inadequate arterial inflow and

Moderate to sever venous stenoses can obstruct or restrict venous outflow from A-V fistula and as a result some dialyzed blood reenters to the dialytic circuit through the arterial needle for some times, thereby blood entering the dia-lyzer can become diluted with blood that has just left the dialyzer.Thus it can re-duce the effective clearance obtained in the course of a

Backflow or recirculation may increase with improper needle placement.(25) Close proximity and or misdirection of needles will increase the reentry of dia-lyzed blood into the arterial needle. Unfortunately, the role of misplacement of needles in recirculation, usually ignore but

Some other centers have also reported that improper needle placement is a common source. Schneditz, for example, reported that improper needle place-ment is a common cause of A-V

Therefore we should have more emphasis on specific training and education of HD nursing staffs. HD staffs should also know anatomy and physiology of A-V fistula and A-V fistula

On the other hand, access recirculation can also be facilitated by inadequate arterial inflow.(24) In this setting, backflow from the venous side of the access is necessary to support the dialytic blood flow rate set by the blood pump. It appears that inadequate arterial inflow was not a cause in our study because although A-V fistula flow rate was between 400- 500ml/min in four patients, dialytic blood flow rate was lower and it was maintained at 300 mill/min.

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

[1] USRDS: The United States Renal Data System: Overall hospitalization and mortality.

[2] Beladi Musavi, SS, Hayati, F, Alemzadeh Ansari, MJ, et al. Survival at 1, 3, and 5Years in Diabetic and Nondiabetic Hemodialysis Patients. IJKD 2010; 4; 74-7. [3] USRDS: The United States Renal Data System. Excerpts from the USRDS 2008 annual

[4] Mailloux, LU, Bellucci, AG, Napolitano, B. Survival estimates for 683 patients starting

data report: Atlas of end-stage renal disease in the United States. Am J Kidney Dis

dialysis from 1970 through 1989: Identification of risk factors for survival. Clin

Am J Kidney Dis 2003; 42 (6 suppl 5): S136-40.

according to the present study it was the most common source of recirculation.

fistula recirculation, even after such placement had been previously recognized.(25)

recirculation rate of 8.82% during 34 HD session in 28 patients.(23).

congestive heart failure.(24, 25)

dialysis session.

recirculation.

**5. Conclusions** 

Hemodialysis staffs.

2009; 1 (Suppl 1): S1.

Nephrol1994; 42: 127.

**6. References** 

There was no statistically difference in the recirculation between diabetic versus non diabetic (P =0.28) and hypertensive versus normotensive (P =0.21%) hemodialysis patients.

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

The average time between creation and use of A-V fistula were 71±31 days and 46 ± 13 days. There were also a significant difference between them (P=0.043).

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 fistula flow rate was significantly (p = 0.001).

## **4. Discussions**

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

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

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) if there is no recirculation.

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 access recirculation.

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

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 access recirculation.(19)

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

Depner et al have measured recirculation by ultrasound dilution technique and they reported recirculation rate of 8.82% during 34 HD session in 28 patients.(23).

The most common causes of A-V fistula recirculation in HD` patients are the presence of high-grade venous stenoses, improper needle placement, inadequate arterial inflow and congestive heart failure.(24, 25)

Moderate to sever venous stenoses can obstruct or restrict venous outflow from A-V fistula and as a result some dialyzed blood reenters to the dialytic circuit through the arterial needle for some times, thereby blood entering the dia-lyzer can become diluted with blood that has just left the dialyzer.Thus it can re-duce the effective clearance obtained in the course of a dialysis session.

Backflow or recirculation may increase with improper needle placement.(25) Close proximity and or misdirection of needles will increase the reentry of dia-lyzed blood into the arterial needle. Unfortunately, the role of misplacement of needles in recirculation, usually ignore but according to the present study it was the most common source of recirculation.

Some other centers have also reported that improper needle placement is a common source. Schneditz, for example, reported that improper needle place-ment is a common cause of A-V fistula recirculation, even after such placement had been previously recognized.(25)

Therefore we should have more emphasis on specific training and education of HD nursing staffs. HD staffs should also know anatomy and physiology of A-V fistula and A-V fistula recirculation.

On the other hand, access recirculation can also be facilitated by inadequate arterial inflow.(24) In this setting, backflow from the venous side of the access is necessary to support the dialytic blood flow rate set by the blood pump. It appears that inadequate arterial inflow was not a cause in our study because although A-V fistula flow rate was between 400- 500ml/min in four patients, dialytic blood flow rate was lower and it was maintained at 300 mill/min.
