Access Recirculation Research Articles

Numerical/Experimental Synergy: More Than Just a Reality Check

In “Comparison of Symmetrical Hemodialysis Catheters Using Computational Fluid Dynamics” ( 1 Clark T.W.I. Isu G. Gallo D. Verdonck P. Morbiducci U. Comparison of Symmetric Hemodialysis Catheters using Computational Fluid Dynamics. J Vasc Interv Radiol. 2015; (In press) PubMed Google Scholar ), Clark and coworkers use computational fluid dynamics (CFD) to analyze the hemodynamics of three symmetric permanent hemodialysis catheters. Based on previous publications, the hemodynamic characteristics that may influence catheter function are identified and described, and then CFD is used to quantify and compare these characteristics between catheters. The catheters are evaluated based on how effectively they display positive characteristics including: less thrombogenic flow patterns, less shear-induced platelet activation, less recirculation, and greater flow deflection angle. Comparison of Symmetric Hemodialysis Catheters Using Computational Fluid DynamicsJournal of Vascular and Interventional RadiologyVol. 26Issue 2PreviewSymmetric-tip dialysis catheters have become alternative devices because of low access recirculation and ease of tip positioning. Flow characteristics of three symmetric catheters were compared based on computational fluid dynamics (CFD) as they relate to catheter function. Full-Text PDF Open Access

Comparison of Symmetric Hemodialysis Catheters Using Computational Fluid Dynamics

PurposeSymmetric-tip dialysis catheters have become alternative devices because of low access recirculation and ease of tip positioning. Flow characteristics of three symmetric catheters were compared based on computational fluid dynamics (CFD) as they relate to catheter function. Materials And MethodsIn Palindrome, GlidePath, and VectorFlow catheters, a computational fluid dynamics–based approach was used to assess (i) regions of flow separation, which are prone to thrombus development; (ii) shear-induced platelet activation potency; (iii) recirculation; and (iv) venous outflow deflection. A steady-state, laminar flow model simulated catheter tip position within the superior vena cava. Catheter performance was investigated at high hemodialysis flow rate (400 mL/min). Blood was assumed as a Newtonian fluid. ResultsWide regions of flow separation downstream of the Palindrome side slot and close to the distal tip were observed in forward and reversed line configurations. Geometric asymmetry of the distal guide wire aperture of the GlidePath catheter produced the highest levels of inverted velocity flow when run in reversed configuration. The lowest mean shear-induced platelet activation was exhibited by GlidePath and VectorFlow catheters; the Palindrome catheter exhibited 152% higher overall platelet activation potency. All catheters were associated with a recirculation close to zero; the helically contoured lumens of the VectorFlow catheter produced the greatest amount of deflection of venous flow away from the arterial lumen. ConclusionsThe VectorFlow catheter produced less shear-induced platelet activation than the Palindrome catheter and less flow separation than the Palindrome and GlidePath catheters irrespective of line configuration. These findings have potential implications for differences in thrombogenic risk during clinical performance of these catheters.

Vascular access for hemodialysis: postoperative evaluation and function monitoring

Vascular access (VA) survival is a crucial issue associated with morbidity and mortality of patients undergoing maintenance hemodialysis. The development of stenosis is the major factor that leads to VA failure. Strategies for early detection of lesions within a VA system before serious complications arise are therefore crucial. The implementation of a VA surveillance program could lead to timely detection of VA dysfunction and referral for correction, reduction in central venous catheter use and decrease in hospitalization and VA-related cost. Suggested methods for arteriovenous fistulae and grafts surveillance include blood flow measurement, static pressure evaluation and duplex ultrasonography. Physical examination is an accepted method in contrast to nonstandardized dynamic pressure measurement for grafts. Access recirculation (not urea based) and dynamic pressure measurements are accepted methods for fistulae. Decreasing URR or Kt/V (otherwise unexplained) and increased (negative) arterial pressure in the dialysis machine are methods of limited sensitivity and specificity for both fistulae and grafts. Measurement of access blood flow has been proposed as the gold standard for the screening of all types of VA. Access flow can be measured by various techniques which are direct or indirect. Several studies about VA surveillance programs have demonstrated conflicting results. Larger, randomized controlled trials need to be carried out in order to clarify whether surveillance programs are necessary and which is the best surveillance strategy for each type of VA.

A Review Article: Access Recirculation Among End Stage Renal Disease Patients Undergoing Maintenance Hemodialysis

BackgroundThe presence of arterio-venous (A-V) fistula recirculation among hemodialysis (HD) patients markedly decrease adequacy of dialysis.ObjectivesThe present article summarize some of observations about clinical significance, causes, the most common techniques for measurement, and main source of pitfall in calculation of access recirculation.Materials and MethodsA variety of literature sources such as PubMed, Current Content, Scopus, Embase, and Iranmedex; with key words such as inadequate dialysis and arterio-venous fistula access recirculation were used to collect current data. Manuscripts published in English language as full-text articles or as abstract form were included in our review study.ResultsAny access recirculation among HD patients should be considered abnormal and if it presents prompt investigation should be performed for its causes. There are two most common techniques for accurate assessment of access recirculation: Urea (or chemical) and nonurea-based method by ultrasound dilution technique. The most common causes of access recirculation are the presence of high-grade venous stenosis, inadequate arterial blood flow rate, close proximity, or misdirection of arterial and venous needles placement by HD staff especially in new vascular accesses due to a lack of familiarity with the access anatomy.ConclusionsThe presence of access recirculation among HD patients can lead to significant inadequate dialysis thereby resulting in reducing the survival of these patients. Therefore, periodic assessment of access recirculation should be performed in HD wards.

Identifying Hemodialysis Catheter Recirculation Using Effective Ionic Dialysance

Vascular catheter use for dialysis remains highly prevalent, however, it is frequently adversely affected by access recirculation (AR). We previously reported the utility of effective ionic dialysance (EID)/blood flow rate (Qb) ratio in identifying significant (>5%) AR in arteriovenous (AV) fistulas (Mohan et al ASAIO J 56:427-433, 2010). We present data from 58 patients, receiving hemodialysis via venous catheters (85% tunneled cuffed catheters) who underwent intermittent monitoring for AR with the saline dilution technique (Transonic HD02 monitor) and had EID and Qb measurements from Diascan biosensor in the Gambro Phoenix dialysis machine available. Among the 193 hemodialysis sessions studied, 74 instances of significant access recirculation (sAR) were identified. A higher incidence of sAR occurred with temporary catheters and catheters in the femoral vein. We report a significant correlation between the EID/Qb ratio and AR in addition to demonstrating the predictive utility of the ratio for identifying dysfunction catheters with sAR (area under the receiver operator characteristic curve of 0.86 with a sensitivity of 79% and a specificity of 76% at an EID/Qb ratio of ≤ 0.60). Our data demonstrate the utility of the EID/Qb ratio as an indicator of sAR in dialysis catheters albeit at a different threshold than that seen with AV fistulae.

DOUBLE LUMEN CATHETERS

Objective: To measure recirculation by Urea based Method in double lumen catheters in patients undergoing hemodialysis. Design: Cross sectional study. Place and duration of study: Hemodialysis unit of Nephrology department of Shaikh Zayed Hospital, Lahore, and Quaid- i-Azam Medical College Bahawalpur for period of eight months from October 2007 to May 2008. Patients and methods: Total 125 adult patients selected with Non probability purposive sampling technique in which hemodialysis were done through double lumen catheter, were studied for recirculation. Access recirculation by urea based method with three sample technique was calculated from following formula; Percentage Recirculation= Systemic (S) – Arterial (A)/ systemic – Venous (V) x 100. Results: Out of 125 patients 53 (42%) were males, whereas 72 (58%) were females. Their mean age was 43.4 ± 15.7 years. Percentage recirculation by urea based method was 10.3± 6.64 with range from 3.6 to 24.8. Conclusions: Our results have shown the upper limit of acceptable recirculation (10.3± 6.6) through double lumen catheter. Central venous catheter remains an important temporary access and in some cases the only achievable access for the patients. This recirculation should be considered when measuring adequacy level in these patients.

The influence of between‐needle cannulation distance on the efficacy of hemodialysis treatments

There is a belief that there should be a minimum of 5 cm between two cannulating needles of an arteriovenous fistula. This study examined the effect of reduction of space between needles from 5 cm to 2.5 cm on access recirculation, the measurement of access blood flow rate (by indicator dilution technology), and dialysis efficiency (by effective ionic dialysance). Twelve patients were studied, with half having their dialysis needles placed 2.5 cm apart for five consecutive dialysis treatments followed by placing needles 5 cm apart for a further five consecutive treatments. The other half initiated with 5 cm followed by 2.5 cm distance for a similar number of treatments. All 120 dialyses had successful cannulations with access recirculation excluded. Access blood flow (Qa mL/min) measurement was attempted for each patient twice, with each of the two needle positions. The Qa with needles 2.5 cm apart was 1310.95 ± 525.7 mL/min (M ± SD, n = 21) and was 1001.0 ± 240.4 mL/min when 5 cm apart (n = 22) (p = 0.014). There was a correlation between these two sets of Qa values (r = 0.554; p = 0.011). The effective ionic dialysance values obtained with needles 2.5 cm or 5 cm apart were similar and correlated strongly (r = 0.71; p = 0.000). Hemodialysis treatments using arteriovenous fistulae and two needles as close as 2.5 cm apart are possible without access recirculation and impairment of clearance. Indicator dilution access blood flow measurements are not recommended under these circumstances.

Evaluation of a New Method for Measuring Vascular Access Recirculation

Together with Nikkiso in Shizuoka, Japan, we developed a new method for measuring the rate of vascular access recirculation by the blood volume monitor. This measurement is performed via a method of dilution that employs a marker produced by rapid ultrafiltration using a dialysis machine. In this paper, we evaluate the reliability and safety of this machine, in vitro and in vivo. The safety of this method was evaluated by investigating hemolysis after rapid ultrafiltration. The measurement of free hemoglobin, potassium and haptoglobin in the circulating blood were performed before and after rapid ultrafiltration. No data was found to indicate hemolysis in vivo, detected by an increase in potassium or a decrease in haptoglobin. Evaluation of reliability in an experimental system was also performed on an in vitro recirculation system at a rate of 0, 10, 25, 50, and 70%. Almost all of the measured rates were within ± 10% of the theoretical rate. We performed 20 hemodialysis experiments with vascular access recirculation applying this monitor and simultaneous urea and creatinine dilution methods, which were the recommended standard measurements for vascular recirculation. In 53 measurements of standard vascular shunts with no postural change, differences of the results between the monitor and both dilution methods were only 4.0% and 3.2%, respectively. Regression analysis showed a significant and positive correlation between them (P < 0.0001). We conclude that this new method for measuring vascular access recirculation is applicable in terms of both accuracy and ease of operation.

Influence of switching connection ports of double-lumen permanent tunnelled catheters on total solute removal during dialysis

Catheter dysfunction is a concern when using double-lumen catheters in hemodialysis (HD). Reversing the connection mode results in higher blood flows, but also enhanced recirculation. We evaluated total solute removal (TSR) of different uremic retention solutes during a complete HD session, once with reversed (RL) and once with correctly connected lines (CL). Genius dialysis was performed in 22 HD patients at maximum blood flow (QB), once with CL and once with RL. TSR was determined for urea, creatinine, phosphate and ß2-microglobulin (ß2M). Using a kinetic model, we simulated TSR and reduction ratio (RR) for urea for different percentages of access recirculation and different QB during CL vs. RL. RR and TSR of the tested solutes were not different in clinical practice between CL and RL. Mathematically, urea RR did not differ with CL or RL, but TSR decreased by 4.5%-23.3% when changing from CL to RL for a recirculation of 5%-25%, respectively. For a recirculation of 5%-25%, QB in RL should be increased by 6.7% and 52.0%, 8.5% and 72.0%, and 10.0% and 115.2%, respectively, for a blood flow in CL mode of 150, 200 or 250 ml/min. Connecting patients to double-lumen dialysis catheters in RL does not impair TSR in clinical practice. Mathematically, TSR during RL was dependent upon the obtained QB and degree of recirculation. A nomogram indicating the increase in QB needed in RL to obtain equal TSR as in the CL mode, at different degrees of recirculation, is provided.

Automated monitoring of hemodialysis adequacy by dialysis machines: potential benefits to patients and cost savings

Hemodialysis adequacy can be quantified using ultraviolet absorbance of the spent dialysate, or by analysis of dialysate conductivity at the dialyzer inlet and outlet in response to changes in dialysate electrolyte concentration. These measurements can be made at every dialysis, including initial and acute treatments and can help detect access recirculation. No disposables or reagents are required. Cost may be reduced by reducing the need for blood sampling and laboratory analysis.

Effective Ionic Dialysance/Blood Flow Rate Ratio: An Indicator of Access Recirculation in Arteriovenous Fistulae

Effective ionic dialysance (EID) is an online measure of hemodialysis (HD) effective urea clearance that is calculated using changes in dialysate sodium conductivity. Effective ionic dialysance is blood flow (Q(b)) dependent. The presence of significant (> or =5%) access recirculation (sAR) during dialysis lowers EID at a given Q(b), thereby lowering EID/Q(b). We propose using EID/Q(b) as a useful chairside tool for detection of sAR in arteriovenous fistulae (AVF). Data were collected from 47 patients with AVF (72% men, mean age 49 +/- 11.8 years, duration on dialysis 3.78 +/- 3.4 years, duration of fistula use 3.35 +/- 3.42 years) dialyzed with an high-efficiency dialyzer with a mass transfer area coefficient (KoA) of 1714 ml/min. Effective ionic dialysance were measured at regular intervals by the Gambro Phoenix dialysis system during treatments. The access recirculation (AR) and access blood flow (Q(a)) were measured using the reference standard saline dilution technique (Transonic HD-02 monitor). Among the 323 HD sessions where Q(b), EID, AR, and Q(a) were available, we identified 17 instances of sAR. The performance of EID/Q(b) as indicator of sAR was assessed by a receiver operator characteristic (ROC) curve (Stata version 10.1). The area under the ROC curve was 0.935 (95% confidence interval 0.869-1.000), which demonstrated a sensitivity of 76.5% and specificity of 96.4% at an EID/Q(b) < or =50% with a positive likelihood ratio of 21, negative likelihood ratio of 0.24, positive predictive value of 54.2%, and negative predictive value of 98.7%. We found similar test performance in patients who received HD with dialyzers with smaller surface areas and lower KoAs. The high specificity of EID/Q(b) makes it an excellent yet simple and early chairside indicator of AVF recirculation.

Intra-abdominal hypertension can be monitored with femoral vein catheters during CRRT and may cause access recirculation

Intra-abdominal hypertension (IAH) is an increasingly recognized disorder, and its diagnosis depends on accurate pressure monitoring. Bladder-based protocols are favored, but are not always clinically feasible. Abdominal venous (i.e. vena cava) pressure measurements are an alternative but are logistically challenging. We hypothesized that for patients suffering acute kidney injury, transducers built into renal replacement therapy (RRT) machines offer a simple opportunity to monitor pressures using catheters inserted via femoral veins. We performed in vitro testing of the accuracy of pressure transducers incorporated into continuous RRT devices, using highly calibrated instrumentation in the IAH-relevant range of 0 to +50 mmHg. We developed a protocol for using this modality in vivo, by stopping all pumps so as to allow equilibration of pressures: clinical application in a patient with femoral vein catheters and IAH was then described. In vitro analyses showed accuracy of the extracorporeal pressure transducers with an r² of 0.998, p < 0.001. In the patient case, the pressure transduced at the RRT device was identical to those obtained from bladder catheters. IAH also led to access recirculation and ineffective therapy. Pressure sensors incorporated into continuous RRT machines can be accurate in the IAH physiologic range, and thus may be used to easily measure intra-abdominal pressure via appropriate-length femoral vein-inserted access catheters. If not relieved, IAH can be an under-appreciated cause of access recirculation and ineffective clearance for any RRT modality (continuous or intermittent) using femoral catheters.

A Mathematical Model of Regional Citrate Anticoagulation in Hemodialysis

Background/Aims: Regional citrate anticoagulation (RCA) during hemodialysis (HD) has several advantages over heparin anticoagulation, but calcium (Ca) derangements are a major concern necessitating repeated monitoring of systemic ionized Ca (Ca²⁺). We developed a mathematical model of Ca and citrate (Ci) kinetics during RCA. Methods: Using patient- and treatment-related parameters, including pre-HD serum Ca and protein concentrations, hematocrit, blood and dialysate flow rates, dialysate composition and access recirculation, the model computes all relevant aspects of RCA based on physicochemical, biochemical and physiological principles such as chemical Ca and Ci equilibria, transmembrane solute fluxes and Ci metabolic rate. The model was validated in 17 treatments using arterial Ci infusion, Citrasate® dialysate, and no postdialyzer Ca substitution. Results: Measured and predicted systemic Ca²⁺ before HD was 1.08 ± 0.06 and 1.05 ± 0.05 mmol/l, respectively (difference –0.03 ± 0.046, 95% confidence interval, CI, –0.055 to –0.007), and at 15 min into the treatment 1.01 ± 0.05 and 1.02 ± 0.05 mmol/l, respectively (difference 0.012 ± 0.054, 95% CI –0.015 to 0.04). At 15 min, the measured and predicted predialyzer Ca²⁺ was 0.33 ± 0.06 and 0.39 ± 0.05 mmol/l, respectively (difference 0.06 ± 0.03; 95% CI 0.044–0.077), and the measured and predicted postdialyzer Ca²⁺ was 0.7 ± 0.05 and 0.61 ± 0.05 mmol/l, respectively (difference –0.09 ± 0.04; 95% CI –0.11 to –0.07). Bland-Altman analysis showed no systematic bias in these predictions. Conclusion: This novel model of RCA shows excellent accuracy in predicting systemic, pre- and postdialyzer Ca²⁺ concentrations and may prove valuable in both research and clinical applications of RCA.

Two-Operator Glucose Infusion Test (GIT2) for Vascular Access Recirculation Measurement during Hemodialysis

Vascular access recirculation rate (AR) monitoring is fundamental to guarantee treatment adequacy and to detect access failure early. We have evaluated the GIT2 test to measure AR unaffected by cardio-pulmonary recirculation (CPR), based on a short glucose infusion in place of the bolus and on a two-operator sampling, differently from the classical glucose infusion test (GIT). The GIT2 test is based on four steps: 1) basal (B) glucose arterial sample; 2) 10% glucose infusion for 1 min, by infusion pump at 600 ml/hr; (or 20% at 300 ml/hr); 3) simultaneous sampling at arterial (A) and venous (V) ports, after 35-40 sec from starting the infusion, taking care to avoid blood pump stop during the test; 4) AR=100*((A-B)/(V-B)). In vitro tests by dialysis on a 40 L tank containing a urea solution, with AR volumetrically simulated at 0, 5, 10, 20%, and in vivo comparison of GIT, GIT2 with stop-flow (SF) urea method. Our results have shown in vitro an almost perfect correspondence of SF urea method and a better reliability of GIT2 than GIT. The methylene-blue test has shown that a single color bolus in V reaches the A port after variable time, depending on blood flow and AR, while the continuous infusion determines a steady gradient after about 30". In vivo tests (n=24) show good correspondence between GIT2 (4.37 +/- 3.36) and SF (4.51 +/- 3.62), while GIT data (1.01 +/- 0.51) are significantly underestimated. In conclusion, our preliminary results have evidenced a good reliability of the new test, the continuous infusion causing a steady gradient in V and A that more precisely reflects the AR rate.

Automated Regional Citrate Anticoagulation: Technological Barriers and Possible Solutions

Background: Large-scale adoption of regional citrate anticoagulation (RCA) is prevented by risks of the technique as practiced traditionally. Safe RCA protocols with automated delivery on customized dialysis systems are needed. Methods: We applied kinetic analysis of solute fluxes during RCA to design a protocol for sustained low-efficiency dialysis (SLED) for critically ill patients. We used a high-flux hemodialyzer, a zero-calcium (Ca) dialysate, a dialysis machine with online clearance and access recirculation monitoring, and a separate optical hematocrit (Hct) sensor. Flow rates were Q_B = 200 ml/min for blood; Q_D = 400 ml/min for dialysate, with Na = 140 mmol/l and HCO₃ = 32 mmol/l; Q_citrate = 400 ml/h of acid citrate dextrose A; ultrafiltration as indicated. The Q_Ca was infused into the return blood line, adjusted hourly based on online Hct and a <24-hour-old albumin level. Results: Using the SLED-RCA protocol in an anhepatic, ex vivo dialysis system, ionized Ca (iCa) was >1 mmol/l in the blood reservoir and <0.3 mmol/l in the blood circuit after citrate but before Ca infusion (Q_Ca) with normal electrolyte composition of the blood returning to the reservoir. Clinically, SLED-RCA completely abrogated clotting, without adverse electrolyte effects. The Q_Ca prediction algorithm maintained normal systemic iCa (0.95–1.4 mmol/l) in all patients. The high citrate extraction on the dialyzer prevented systemic citrate accumulation even in shock liver patients. Safety analysis shows that building a dialysis system for automated SLED-RCA is feasible. Conclusion: Using predictive Q_Ca dosing and integrating control of the infusion pumps with the dialysis machine, SLED-RCA can be near-automated today to provide a user-friendly and safe system.

Vascular Access Recirculation in Hemodialysis Patients With Two Noncuffed, Single‐lumen, Jugular Catheters in the Same Jugular Vein

Having achieved excellent results with single-lumen temporary hemodialysis catheters as a long-term vascular access in our center, in this study we examined the amount of vascular access recirculation in the case of using two single-lumen catheters in a single jugular vein. In 11 adult end-stage renal disease patients on chronic hemodialysis (HD), vascular access recirculation was studied using a thermodilution technique during dialysis at our center. The vascular access in all patients consisted of two pre-curved, 15 cm-long, 8-Fr catheters inserted in the right jugular vein. Recirculation measurements were performed with the blood flow set to 250 mL/min in all patients. In five patients, additional measurements were performed with the blood flow set to 200 mL/min. During 16 HD procedures, 55 recirculation measurements were taken. The rate of recirculation was <15% in 50 measurements, between 15% and 20% in four measurements, and >20% in one measurement. The average recirculation rate during a single procedure was <15% in 10 patients, and 16.2% in one patient. We did not find any significant differences in the recirculation rates measured either at higher or lower blood flow rates. The clinical importance of vascular access recirculation was noted in a single patient. Vascular access recirculation in hemodialysis patients with two single-lumen catheters in the same jugular vein is mostly acceptable. Some measures for preventing clinically important recirculation are also suggested.

Subcutaneous Transposition of the Superficial Femoral Artery for Arterioarterial Hemodialysis: Technique and Results

We report the use of subcutaneous transposition of the femoral artery (STFA) for placement of both inflow and outflow needles in 14 hemodialysis (HD) adult patients with difficult access. Follow-up time was 318 months during which a total of 3215 arterioarterial HD sessions were done. Kt/V values ranged between 0.71 and 1.59. Elevated access recirculation and dialysis outflow pressures were common findings to all patients. Complications were: (i) two episodes of bleeding secondary to puncture-related arterial wall laceration, repaired by stitching; (ii) three episodes of thrombosis in two patients, all successfully declotted; (iii) three puncture-related complications needing placement of a vein interposition graft, namely, aneurysm, pseudoaneurysm, and arterial stenosis; and (iv) one case of arterial ligation because of suppurative puncture site infection, without subsequent distal ischemia signs or claudication. The use of STFA should only be reserved for patients in urgent need for vascular access with no remaining options.

Arterial line pressure control enhanced extracorporeal blood flow prescription in hemodialysis patients

BackgroundIn hemodialysis, extracorporeal blood flow (Qb) recommendation is 300–500 mL/min. To achieve the best Qb, we based our prescription on dynamic arterial line pressure (DALP).MethodsThis prospective study included 72 patients with catheter Group 1 (G1), 1877 treatments and 35 arterio-venous (AV) fistulae Group 2 (G2), 1868 treatments. The dialysis staff was trained to prescribe Qb sufficient to obtain DALP between -200 to -250 mmHg. We measured ionic clearance (IK: mL/min), access recirculation, DALP (mmHg) and Qb (mL/min). Six prescription zones were identified: from an optimal A zone (Qb > 400, DALP -200 to -250) to zones with lower Qb E (Qb < 300, DALP -200 to -250) and F (Qb < 300, DALP > -199).ResultsTreatments distribution in A was 695 (37%) in G1 vs. 704 (37.7%) in G2 (P = 0.7). In B 150 (8%) in G1 vs. 458 (24.5%) in G2 (P < 0.0001). Recirculation in A was 10.0% (Inter quartile rank, IQR 6.5, 14.2) in G1 vs. 9.8% (IQR 7.5, 14.1) in G2 (P = 0.62). IK in A was 214 ± 34 (G1) vs. 213 ± 35 (G2) (P = 0.65). IK Anova between G2 zones was: A vs. C and D (P < 0.000001). Staff prescription adherence was 81.3% (G1) vs. 84.1% (G2) (P = 0.02).ConclusionIn conclusion, an optimal Qb can de prescribed with DALP of -200 mmHg. Staff adherence to DLAP treatment prescription could be reached up to 81.3% in catheters and 84.1% in AV fistulae.

Retrospective Analysis of Catheter Recirculation in Prevalent Dialysis Patients

Catheter recirculation (CR) occurs when blood returning from the venous limb of the catheter re-enters the arterial limb of the catheter without passage through the circulation. Adequacy of dialysis is influenced by the degree of access recirculation. In this study we evaluate factors influencing the degree of dialysis central venous catheter (CVC) recirculation in prevalent hemodialysis patients. This is a retrospective study of all patients undergoing hemodialysis via a catheter at the Wake Forest University Outpatient Dialysis Facilities from September 1, 2006 to May 15, 2007. CR was correlated to catheter type, catheter brand, site of placement, catheter length, time on dialysis, time on the current catheter, and was measured via ultrasound dilution technique. A total of 165 catheters were identified. Seventy-one catheters were in the right internal jugular position, 43 in the left internal jugular position, 13 in the right subclavian, one in the left subclavian, eight in the right femoral, two in the left femoral, and four in the trans-lumber position. CR was 6.3 +/- 7.5% in symmetric tip catheters (n = 14), 6.0 +/- 8.3% in split-tip catheters (n = 102), 8.4 +/- 11.7% in step-tip catheters (n = 10), and 23.0 +/- 8.2% in temporary catheters (n = 3), respectively. These results are borderline significant if temporary catheters are included (p = 0.052); however, the overall p-value is only 0.80 for tunneled dialysis catheters. There was no correlation between CR and time on dialysis (p = 0.66) or time on the current catheter (p = 0.48). The current study suggests that the CVC recirculation is independent of catheter brand, type, time on dialysis, or time on current catheter.

Arteriovenous Fistula Puncture: An Essential Factor for Hemodialysis Efficiency

Objective. To determine the blood recirculation ratio in the vascular access of patients on hemodialysis, and to calculate the Kt/Vs obtained with the different techniques of arteriovenous fistula punctures. Materials and Methods. A total of 174 patients were divided according to the technique used for arteriovenous fistula puncture: group 1, needles in opposite directions and with a distance of 5 cm or more between them; group 2, needles in opposite directions but with a distance of less than 5 cm; group 3, unidirectional needles with both directed to the heart and with a distance of 5 cm or more; group 4, unidirectional needles but separated by a distance of less than 5 cm between needles; and group 5, patients carrying a temporary venous catheter. Blood samples were collected for urea analysis, pre and post-dialysis for Kt/V rate, and other samples for calculation of the access recirculation. Results. Group 1 presented the lowest rate of access recirculation (8.51 ± 4.90%) and the best Kt/V (1.71 ± 0.36), while group 4 presented the worst access recirculation (20.68 ± 4.92%) and Kt/V (1.16 ± 0.26). All groups differed significantly from group 4 (p < 0.05), except group 5 with regard for Kt/V parameter. Discussion. The technique of arteriovenous fistula puncture is an essential factor to decrease the access recirculation and assure better results of measurement of hemodialysis adequacy. On the basis of the results obtained, insertion of the needles in the same direction and with a distance of less than 5 cm between them should be avoided.