Diversity of environmental Mycobacterium isolates from hemodialysis water as shown by a multigene sequencing approach.
(65/189)
Here we used a multigene sequencing approach for the identification and molecular typing of environmental mycobacteria of the fast-growing subgroup. Strains were isolated from hemodialysis water and clinical samples. Eleven type strains of related species of the genus were also included in this study. To gain further insight into the diversity of the environmental mycobacteria, we analyzed several housekeeping genes (16S rRNA, ITS1, gyrB, hsp65, recA, rpoB, and sodA). No individual phylogenetic tree allowed good discrimination of all of the species studied. However, a concatenated and a consensus analysis, combining the genes, allowed better discrimination of each strain to the species level, and the increase in sequence size also led to greater tree robustness. This approach is useful not only for the discrimination and identification of environmental mycobacteria but also for their molecular typing and studies of population genetics. Our results demonstrate high genetic diversity among the isolates obtained, which are probably new species of the genus. (+info)
Trace element removal during in vitro and in vivo continuous haemodialysis.
(66/189)
BACKGROUND: Continuous renal replacement therapy (CRRT) increasingly is being used to treat critically ill patients with renal disease. CRRT removes waste products but also nutrients. Our understanding of trace element CRRT clearance has been limited by poor assay sensitivity. The development of inductively coupled plasma mass spectrometry (ICP-MS) allows for the measurement of CRRT trace element removal. METHODS: Continuous venovenous haemodialysis (CVVHD) transmembrane clearances of trace elements and urea were assessed using a bovine blood-based in vitro model using two different haemodialyser types. These findings were validated in 10 critically ill adult patients receiving continuous venovenous haemodiafiltration (CVVHDF). Calculated daily trace element loss was compared with a typical dose of daily trace element supplementation. RESULTS: The mean +/- SD in vitro CVVHD transmembrane clearances (ml/min) for the polysulfone haemodialyser were chromium 0.97 +/- 0.23, copper 0.47 +/- 0.18, manganese 4.6 +/- 3.6, selenium 1.2 +/- 0.63 and zinc 2.3 +/- 0.32 and for the cellulose diacetate haemodialyser chromium 1.54 +/- 0.91, copper 0.21 +/- 0.07, manganese 7.8 +/- 4.1, selenium 0.76 +/- 0.39 and zinc 2.7 +/- 0.37. The in vivo CVVHDF transmembrane clearances (ml/min) were chromium 5.4 +/- 2.4, copper 0.45 +/- 0.33, manganese 1.9 +/- 4.6, selenium 1.6 +/- 1.2, and zinc 4.0 +/- 1.3. CONCLUSION: ICP-MS assays detected the five trace elements in the effluent of CVVHDF patients. Trace element CVVHD transmembrane clearance estimates for our in vitro model were supported by the in vivo CVVHDF findings. Calculated daily trace element loss attributed to CVVHD and CVVHDF with dialysate flow rates of 33.3 ml/min is less than what is provided in a daily dose of a trace element supplementation product. (+info)
Temperature and concentration distribution within the Genius dialysate container.
(67/189)
BACKGROUND: The Genius single-pass batch system, using a closed dialysate container, is increasingly applied for dialysis treatment. Although fluid separation between fresh and spent dialysate is maintained in the container during standard dialysis, dialysate mixing may occur under certain clinical conditions. An in vitro study showed that differences in dialysate temperature and solute content between fresh and spent dialysate determine the occurrence and moment of dialysate mixing. METHODS: To better understand the maintenance of separation of fresh and spent dialysate in the prevention of mixing, a mathematical model of the 75 l Genius container was developed and the general fluid, mass and heat transfer equations were solved, simulating a dialysis session of 300 min with 1 g/l urea as starting 'blood' urea concentration and 36.2 degrees C starting dialysate temperature. Boundary and initial conditions were chosen according to two different strategies applied in previous in vitro tests, with spontaneous cooling of the reservoir on the one hand and heating of the spent dialysate to maintain an equal temperature as the fresh dialysate on the other. RESULTS: Our simulation data show that dialysate inside the container is cooling down near the container wall in both scenarios and near the central glass tube in the setup with spontaneous cooling. In the setup with heating of spent dialysate, the upper layers are heated near the central tube. Since density stratification is maintained at each time point, solutes will rise towards warmer zones. This is halfway between the container axis and wall for spontaneous cooling and, even to a larger extent, near the central tube for simulations with heated spent dialysate. Hence, the contaminated volume in the case of heating is much larger than theoretically supposed. CONCLUSIONS: These computer simulations unravel temperature and concentration distribution inside the container, offering insight into the complicated mixing phenomenon and indicate that temperature is a major impacting factor. (+info)
The AN69 ST haemodialysis membrane under conditions of two different extracorporeal circuit rinse protocols a comparison of thrombogenicity parameters.
(68/189)
BACKGROUND: Thrombogenicity is an important parameter of haemodialysis (HD) membrane biocompatibility. The surface of the polyacrylonitrile AN69 ST membrane is coated with a polyethylenimine. This modification allows heparin adsorption. The binding of heparin to the membrane surface occurs during priming of the extracorporeal circuit (ECC) by rinsing it with saline and heparin. Our aims were to assess and compare the thrombogenicity of the AN69 ST membrane under conditions of two extracorporeal circuit (ECC) rinse protocols-with and without unfractionated heparin (UFH). METHODS: In a prospective, crossover and randomized study, we examined 10 patients during HD after ECC preparation with either rinse protocols. Prior to HD and at 15, 60 and 240 min, we determined plasma levels of the thrombin-antithrombin complexes (TAT), platelet factor 4 (PF4), heparin concentration (antiXa) and thrombocyte count. Systemic anticoagulation was performed using UFH. RESULTS: During HD after ECC rinse without UFH, there was a significantly earlier and more marked increase in TAT compared with UFH-containing rinse (P <0.05). Using Spearman coefficient, we demonstrated a significant correlation between TAT and antiXa at 60 min (r = -0.534) and 240 min (r = -0.538). A comparison of the TAT/antiXa ratios between rinses at 60 min revealed a significantly higher increase in TAT following UFH-free rinse (P <0.05). There was no difference in PF4 between the rinses. Platelet count did not change significantly during HD using either rinse protocol. CONCLUSION: Based on plasma TAT levels, ECC priming with an UFH-containing solution reduces the thrombogenicity of the AN69 ST membrane. There is no significant difference between both types of priming concerning PF4 and thrombocyte count. (+info)
Icodextrin metabolism and alpha-amylase activity in nonuremic rats undergoing chronic peritoneal dialysis.
(69/189)
OBJECTIVE: To study the metabolism of icodextrin and alpha-amylase activity following daily exposure to dialysis solutions containing either glucose or icodextrin as osmotic agent in rats. METHODS: Male Wistar rats with implanted peritoneal catheters were infused twice daily for 3 weeks with 20 mL 7.5% icodextrin-based peritoneal dialysis fluid (IPDF; ICO group, n = 12) or 3.86% glucose-based peritoneal dialysis fluid (GLU group, n = 11). A 4-hour dwell study using 30 mL IPDF was performed on day 10 (D1) and day 21 (D2) in both the ICO and the GLU groups. Radiolabeled serum albumin (RISA) was used as a macromolecular volume marker. Dialysate samples were collected at 3, 15, 30, 60, 90, 120, and 240 minutes. Blood samples were drawn before the start and at the end of the dwell. RESULTS: During all dwell studies, the dialysate concentrations of total icodextrin decreased due to decrease in high molecular weight (MW) fractions, whereas there was a marked increase in icodextrin low MW metabolites. alpha-Amylase activity increased in dialysate and decreased in plasma. About 60% of the total icodextrin was absorbed from the peritoneal cavity during the 4-hour dwells. Low MW icodextrin metabolites were present in the dialysate already at 3 minutes, and maltose (G2), maltotriose (G3), maltotetraose (G4), and maltopentaose (G5) increased progressively, reaching maximum concentrations at 60 minutes. Maltohexaose (G6) and maltoheptaose (G7) were also detected already at 3 minutes but did not change significantly during the dwells. During the two 4-hour dwell studies (D1 and D2), the concentrations of total icodextrin and icodextrin metabolites and alpha-amylase activity in dialysate did not differ between the ICO and GLU groups, during either D1 or D2. No icodextrin metabolites were detected in plasma at the end of the dwells. alpha-Amylase activity in the dialysate increased six- to eightfold whereas plasma alpha-amylase activity decreased by 21% - 26% during the two 4-hour dwells in both the ICO and the GLU groups; there were no significant differences between the ICO and the GLU groups during either D1 or D2. alpha-Amylase activity in the dialysate correlated strongly with the disappearance rate of icodextrin from the peritoneal cavity during the 4-hour dwells, and with the concentrations of G2, G3, G6, and G7 in dialysate. CONCLUSIONS: The decline in the dialysate concentrations of high MW fractions and the increase in low MW metabolites of icodextrin suggest intraperitoneal alpha-amylase mediated the metabolism of icodextrin and the transport of predominantly the smaller icodextrin metabolites from dialysate. However, no icodextrin could be detected in plasma, suggesting that it was metabolized and excreted by the kidney in these nonuremic rats. In contrast to uremic peritoneal dialysis patients, chronic exposure to IPDF did not seem to further affect alpha-amylase activity or icodextrin metabolism. The much higher alpha-amylase activity in plasma and dialysate in rats than in humans explains the much more rapid metabolism of icodextrin in rats compared with peritoneal dialysis patients. (+info)
Hemodialysis blood access flow rates can be estimated accurately from on-line dialysate urea measurements and the knowledge of effective dialyzer urea clearance.
(70/189)
Measurement of blood flow rate (Qa) is used to monitor arteriovenous fistulas and grafts that are used for hemodialysis blood access. Most Qa measurements use indicator dilution techniques to measure the recirculation that is induced by the reversal of hemodialysis blood lines. R plus the dialysis circuit flow (Qb) allows the calculation of Qa. The principle of needle reversal also can be used with a dialysate urea monitor (e.g., DQM 200 [Gambro]) without injection of diluent; the effect of the reversal on urea concentration is observed. Access blood water flow rate (Qaw) in relation to the effective clearance (K) is found from the urea concentrations in the dialysate with needles in the normal (Cn) and reverse (Cr) positions: K/Qaw = (Cn - Cr)/Cr. Qa is calculated by adjusting Qaw for hematocrit and protein. For testing of this theoretical relationship, 20 patients who were dialyzed on Integra (Hospal) and Centrysystem 3 (Cobe) machines that were fitted with DQM 200 were studied. During each treatment, lines were reversed and Qa was measured by ultrasound velocity dilution (Transonic HD01 monitor); at the same time, Cn and Cr were measured by DQM 200 and K was calculated. K1 was determined from a predialysis blood urea concentration (Cb), initial dialysate urea concentration (Cd), dialysate flow rate (Qd), and the relationship K x Cb = Qd x Cd (K1). K was determined separately from a conductivity step method using Diascan (Hospal) attached to Integra machines only (K2). With the use of K1, 127 comparisons were made; a correlation existed (r = 0.916), although Bland-Altman analysis showed that the dialysate urea method gave a mean value 5.3% +/- 15.3 (+/-SD) higher than that of Transonic (P < 0.001). With the use of K2, there also was a correlation of (r = 0.944; n = 63), and Bland-Altman testing showed an NS difference of +3.5% between the dialysate urea and Transonic methods. Qa can be estimated from on-line dialysate urea measurements that are taken before and after line reversal together with knowledge of K. (+info)
Hysteresis of the parathyroid hormone response to hypocalcemia in hemodialysis patients with low turnover aluminum bone disease.
(71/189)
During the study of parathyroid function in 19 hemodialysis patients with low turnover aluminum bone disease, it was observed that serum parathyroid hormone (PTH) levels were higher during the induction of hypocalcemia than during the recovery from hypocalcemia. This type of PTH response has been termed hysteresis. Hypocalcemia was induced during hemodialysis with a calcium-free dialysate. When the total serum calcium level decreased to 7 mg/dL, the dialysate calcium concentration was changed to 3.5 mEq/L and the dialysis session was completed. One week later, hypercalcemia was induced during hemodialysis with a high-calcium dialysate. The mean basal PTH level was 132 +/- 37 pg/mL (normal, 10 to 65 pg/mL; immunoradiometric (IRMA), Nichols Institute, San Juan Capistrano, CA) and increased to a maximal PTH level of 387 +/- 91 pg/mL during hypocalcemia. For the same ionized calcium concentration, the PTH level was higher during the induction of hypocalcemia than during the recovery from hypocalcemia. Conversely, for the same ionized calcium concentration, the PTH level was greater when hypercalcemia was induced from the nadir of hypocalcemia than when hypercalcemia was induced from basal serum calcium. The set point of calcium (defined as the serum calcium concentration required to reduce maximal PTH by 50%) was greater during the induction of hypocalcemia than during the recovery from hypocalcemia (4.44 +/- 0.10 versus 4.25 +/- 0.09 mg/dL; P = 0.03). The mean basal ionized calcium concentration and the mean ionized calcium concentration at the intersection of the two PTH-calcium curves were the same (4.61 +/- 0.13 versus 4.61 +/- 0.12 mg/dL).(ABSTRACT TRUNCATED AT 250 WORDS) (+info)
Exit of catheter lock solutions from double lumen acute haemodialysis catheters--an in vitro study.
(72/189)
BACKGROUND: Double lumen dialysis catheters are routinely heparin or citrate 'locked' to maintain patency. Heparin lock-related bleeding episodes and antibiotic lock-related toxicity have been reported. The aim of this study is to quantify the amount of leak during 'lock' procedures and to compare leakage for different double lumen dialysis catheters. METHODS: In an experimental, in vitro study at a University research laboratory, five different double lumen dialysis catheters were tested using three different lock volumes. RESULTS: Using the catheter flush volume, leak ratios for Flexxicon II 15 cm and 20 cm catheters were greater than that seen in the Arrow 16 cm catheter (P < 0.05). Using 20% less than the catheter flush volume, the Flexxicon II 20 cm catheter had greater leak than the Duo-flow 15 and 20 cm catheters and Arrow 16 cm catheter (P < 0.05). The Flexxicon II 15 cm catheter had greater leak than the Duo-flow 15 cm and Duo-flow 20 cm catheters with 20% less locking volume (P < 0.05). Using 20% greater than the catheter flush volume, the Duo-flow 20 cm catheter had significantly less leak ratio than the Flexxicon II 20 cm catheter (P < 0.05). There were no other significant differences in leak ratios between the catheters. CONCLUSION: All double lumen dialysis catheters we tested have a substantial amount of leak even when the catheter 'lock' volumes were used, and leak ratio increases significantly with 20% overfill. There is a leak even when using 20% less 'lock' volume. The amount of leak can be clinically important and may explain the reports of bleeding episodes after heparin lock and antibiotic toxicity after antibiotic and anticoagulant combination lock. Some devices have lower leak ratios than others, likely related to catheter design. (+info)