Can regional anticoagulation with calcium-free dialysate be extended to maintenance hemodialysis?

BACKGROUND: Regional anticoagulation in hemodialysis avoids the use of heparin, which is responsible for both hemorrhagic and non-hemorrhagic complications. Typically, blood is decalcified by injecting citrate into the arterial line of the extracorporeal circuit. Calcium-free dialysate improves anticoagulation efficacy but requires injection of a calcium-containing solution into the venous line and strict monitoring of blood calcium levels. Recent improvements have made regional anticoagulation with calcium-free dialysate safer and easier. OBSERVATIONS: (1) Adjusting the calcium injection rate to ionic dialysance avoids the risk of dyscalcemia, thus making unnecessary the monitoring of blood calcium levels. This adjustment could be carried out automatically by the hemodialysis monitor. (2) As calcium-free dialysate reduces the amount of citrate required, this can be supplied by dialysate obtained from currently available concentrates containing citric acid. This avoids the need for citrate injection and the risk of citrate overload. (3) Calcium-free dialysate no longer needs the dialysate acidification required for avoiding calcium carbonate precipitation in bicarbonate-containing dialysate. CONCLUSIONS: Regional anticoagulation with calcium-free dialysate enables an acid- and heparin-free procedure that is more biocompatible and environmentally friendly than conventional bicarbonate hemodialysis. The availability of specific acid-free concentrates and adapted hemodialysis monitors is required to extend this procedure to maintenance hemodialysis.

Clinical evaluation of an expert system for arteriovenous fistula assessment.

The monitoring of ionic dialysance in hemodialysis allows early detection of arterio-venous fistula stenosis. One limitation to the practical use of ionic dialysance is that the analysis is very time consuming on a majority of normal cases.The purpose of the study is to evaluate the utility of an expert system reproducing a human analysis and allowing continuous monitoring of the ionic dialysance by helping the physician to focus his or her expertise on the abnormal cases.The method is based on a Bayesian model that analyzes the blood flow rate, the ionic dialysance, and the venous and arterial pressures measured on the extra corporeal circuit.The clinical evaluation was performed on 90 dialysis patients at the hospital dialysis center of Saint Brieux in France with a history of at least four consecutive months of validated recording. The retrospective automated analysis was evaluated in comparison to vascular access problems identified from invasive investigation or treatment. The sensitivity of the automated analysis is 92% with a specificity of 75%.As a conclusion we suggest that this expert system could be used in a continuous vascular access monitoring procedure consisting in a weekly review of the patient population at the dialysis center. The patients with the highest risk score need a further investigation of their historical data and their medical history in order to decide whether or not to perform an invasive intervention.

Regional citrate anticoagulation during hemodialysis: a simplified procedure using Duocart biofiltration.

BACKGROUND: Regional citrate anticoagulation during hemodialysis is promising, but its clinical implementation is routinely cumbersome because a continuous adjustment of calcium infusion at the dialyzer outlet is needed. Duocart biofiltration (DCB) is a new hemodialysis method using a calcium and magnesium-free dialysate containing only sodium chloride and bicarbonate combined with the infusion into the venous line of a solution containing the ionic complement (K, Ca, Mg) and glucose. Since the dialysate is calcium- and magnesium-free and infusion rate of the solution containing calcium is automatically determined by the dialysis delivery system according to the on-line measured value of ionic dialysance, DCB seems a technique especially suitable for citrate anticoagulation procedure. METHODS: Thirty DCB sessions were performed in 10 patients with increased risk of bleeding. A commercially available mixture of trisodium citrate, citric acid and glucose was infused into the arterial line at a rate equal to 3% of dialyzer blood flow. The ionic complement (K: 48 mM, Ca: 42 mM, Mg: 14 mM, glucose: 110 mM) was infused at a rate equal to 1/24 ionic dialysance value automatically determined each 15 min by the dialysis monitor. DCB sessions were compared to 21 conventional bicarbonate hemodialysis (BHD) sessions with low-molecular-weight heparin anticoagulation. RESULTS: Whole blood activated clotting time (WBACT) measured in the venous line (before infusion of ionic complement) was 200% of the WBACT value in the arterial line. Clotting and citrate-related adverse events were not observed. Postdialysis compression time of the arteriovenous access is significantly (p<0.001) shorter after DCB sessions (3.9+/-1.1 min) compared with BHD sessions (8.7+/-4.6 min). CONCLUSION: Citrate anticoagulation during Duocart biofiltration is effective, safe and suitable for routine use because calcium infusion rate is automatically adjusted without the need of monitoring degree of anticoagulation and level of ionized calcium.

Improved removal of small proteins using continuous venovenous hemofiltration to treat acute renal failure.

Continuous venovenous hemodialysis (CVVHD) or hemofiltration conducted with pre- (CVVHpre) or post- (CVVHpost) dilution modes are recommended to treat patients with acute renal failure (ARF) and cardiovascular instability. The efficiency of the three techniques was compared in a study including 18 critically ill patients with ARF. Their mean age was 62.1 +/- 16.7 years, and their mean SAPS II score was 59.5 +/- 14.3. They were treated sequentially with the three techniques for periods of 24 hours each (randomized assignment to one technique the first 24 hours followed by the two others). The PRISMA device and M 100 (AN69S) membrane were used in all instances. Blood and replacement (or dialysis) flow rates were kept at 150 and 25 ml/min, respectively. Urea, creatinine, uric acid, inorganic phosphorus, beta2 microglobulin (beta2m), and retinol binding protein (RBP) were measured every 12 hours in plasma and in 12 hours filtrate collection for 3 days. The results are expressed as filtrate/mean plasma (F/P) ratio for the 12 hour period. Removal of small molecules was 16% higher using CVVHD and CVVHpost than CVVHpre. For beta2m and RBP, CVVHpre was, respectively, 43% and 26% more efficient than CVVHD. CVVHpost gave higher but statistically different removal than CVVHpre only for beta2m. CVVHpost was the most efficient technique for removal of small proteins, but this advantage could be easily counterbalanced using higher volume substitution.

Ionic dialysance vs urea clearance in the absence of cardiopulmonary recirculation.

BACKGROUND: Several studies have shown a slight discrepancy between ionic dialysance (D) and dialyser urea clearance (UK), even in the absence of access recirculation. As it has been suggested that this discrepancy could be due to the cardiopulmonary recirculation, we studied the relationship between these two parameters in a particular dialysis setting without cardiopulmonary recirculation. METHODS: Paired measurement of urea clearance and ionic dialysance were performed in five patients without arterio-venous access who were dialysed via an internal jugular vein twin catheter. Fifty paired measurements were used for statistical analysis. Vascular access recirculation was assessed by an ultrasound dilution technique. The measured value of ionic dialysance was corrected (D(0)) for the effect of vascular access recirculation and was compared with instant urea clearance calculated from the dialysate side. RESULTS: The difference between the paired measurements of D(0) and UK (n=50) was equal to 0.6+/-16.9 ml/min (NS). With a statistical power of 90% and taking into account this standard deviation, this study might have shown a difference of at least 10.9 ml/min. The correlation was highly significant (P<0.0001). The discrepancy of the two parameters varied with dialysis efficiency, with a decreasing D(0):UK ratio for the higher dialysis efficiency. CONCLUSIONS: Compared with our previous results obtained in patients dialysed on arterio-venous access and performed with similar methods, the relationship between D(0) and UK is modified. This difference between D(0) and UK gets lower in patients dialysed on central catheters and this variance is in accordance with that expected when the influence of the cardiopulmonary recirculation on the measurement of ionic dialysance is taken into account. The limits of agreement (+/-2 SD) between D(0) and UK (+/-34 ml/min, Bland-Altman analysis) were higher than expected and raised questions about the accuracy of the measurement of each parameter via a central venous catheter.