BACKGROUND/AIMS: The dialysis outcome is strongly affected by the function of the vascular access. It has been suggested that access clotting may be related to increased hematocrit (Hct) or excessive ultrafiltration during dialysis. The present study was designed to evaluate the changes of vascular access flow during hemodialysis in 18 end-stage renal disease patients with native arteriovenous fistulas and the possible correlations with Hct and mean arterial pressure (MAP). METHODS: We utilized a noninvasive vascular access flow measurement technique, based on a transcutaneous optical sensor, to evaluate the flow in the access before and after a single hemodialysis session. At the beginning and at the end of the session, the blood flow was measured noninvasively, placing the sensor approximately 2 in from the point of insertion of the arterial needle. At the same time, Hct and MAP were measured directly. All patients were on hemodialysis for more than 3 months. RESULTS: There was a significant increase in Hct, likely due to ultrafiltration and consequent hemoconcentration, from the beginning to the end of the dialysis session. In detail, the Hct increased from 32.6 +/- 1.9 to 35.4 +/- 1.8% (p < 0.001), while the MAP did not present significant variations. The blood flow did not show significant variations, increasing from 780 +/- 312 to 919 +/- 411 ml/min after the session. Because of the stability of the MAP, we could dissociate the effects of the Hct from those of the MAP on blood flow variations. CONCLUSION: Our study suggests that the blood flow in native fistulas is not affected by the acute rise in Hct due to ultrafiltration during hemodialysis. The transcutaneous access flow measurement technique appears to be reliable and accurate, and it could represent an important diagnostic tool.

Arteriovenous Fistula↗

PubMed2002

In vitro removal of therapeutic drugs with a novel adsorbent system.

BACKGROUND/AIMS: Substances in the middle molecular weight range have been shown to play a significant pathogenetic role in as diverse disorders as end-stage renal disease and multiple organ failure. To overcome the limitations in the amount removed by hemofilters, new sorbents with a high biocompatibility are actively being developed. Furthermore, biocompatible sorbents by their nonspecific adsorptive behavior could have great impact on detoxification treatment in exogenous intoxications. We performed an in vitro evaluation of a newly developed highly biocompatible sorbent cartridge (Betasorb((R))), examining its adsorptive capacity concerning therapeutic drugs. METHODS: Uremic blood spiked with a range of therapeutic drugs was recirculated for 2 h in an in vitro hemoperfusion circuit containing a Betasorb device for hemoperfusion. The drug concentrations before and after the passage of the cartridge were measured, and the total amount removed was calculated. RESULTS: The sorbent showed effective removal of glycopeptide antibiotics, digoxin, theophylline, phenobarbital, phenytoin, carbamazepine, and valproic acid. Moderate removal could be demonstrated for tacrolimus and cyclosporine A; aminoglycosides were removed to a small extent only. CONCLUSION: Betasorb hemoperfusion shows a potent adsorptive capacity concerning therapeutic drugs (except aminoglycosides) and could be of major value in the treatment of intoxications. On the other hand, drug monitoring and possible adjustments are necessary during Betasorb hemoperfusion to maintain the therapeutic ranges of the drugs in blood.

Adsorption↗

PubMed2002

High-volume hemofiltration in sepsis. Theoretical basis and practical application.

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Hemofiltration↗

PubMed2002

Blood and dialysate flow distributions in hollow-fiber hemodialyzers analyzed by computerized helical scanning technique.

The efficiency of a hemodialyzer is largely dependent on its ability to facilitate diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. This article describes the distribution of the blood and dialysate flows in hollow-fiber hemodialyzers analyzed with a computerized scanning technique. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation using human blood with hematocrit (Hct) adjusted at 25 and 40%. Sequential images were obtained with a helical scanner in a 1-cm-thick fixed longitudinal section of the dialyzer. Average and regional blood flow velocity and wall shear rates were measured by using the reconstructed imaging sequence. The method allowed the calculation of single-fiber blood flow and single-fiber wall shear rate (SF wSh) in different regions of the hemodialyzer. In 38 patients on chronic hemodialysis, creatinine and phosphate clearance displayed a significantly negative correlation with Hct (P < 0.05), but this correlation was not found for urea, although a trend toward reduction could be observed. The suggested explanation of this phenomenon is the significant reduction in effective plasma water flow across the hemodialyzer in presence of a progressive rise in Hct. The second explanation for this phenomenon may be found in the nonhomogeneous distribution of blood flow within the fibers observed at the sequential imaging. This, in fact, could also explain the negative trend observed for urea. At higher Hct levels, single-fiber blood flow velocity and SF wSh were significantly lower in the fibers situated at the periphery of the bundle. At the same time, SF wSh tended to decrease in peripheral fibers, showing a value near half of that observed in the central fibers of the bundle (165 versus 301 s(-1)). A similar technique was used to study the flow distribution in the dialysate compartment in three different types of hemodialyzers with characteristic dialysate compartment design: (A) standard configuration; (B) space yarns (spacing filaments preventing contact between fibers); and (C) Moiré structure (wave-shaped fibers to prevent contact between adjacent fibers). Clinical sessions of hemodialysis were also carried out to measure blood- and dialysate-side urea clearances in the different hemodialyzers. Macroscopic and densitometric analysis revealed that flow distribution was most homogeneous in the dialyzer with Moiré structure (type C) and least homogeneous in the standard dialyzer (type A). Space yarns (type B) gave an intermediate dialysate flow distribution. Urea clearance (P < 0.001) increased significantly with types B and C, compared with the standard dialyzer. Type C had the highest clearances, although they were not significantly greater than type B. In conclusion, a significant blood-to-dialysate flow mismatch may occur in hollow-fiber hemodialyzers due to either uneven blood flow distribution or a dialysate channeling phenomenon external to the fiber bundle. Improvement in dialyzer design may overcome these problems, at least in part.

Aged↗

PubMed2002

Membranes for dialysis. Composition, structure and function.

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Humans↗

PubMed2000

How to feed patients with renal dysfunction.

Renal dysfunction is common in critically ill patients and its presence has, in the past, posed serious challenges to nutritional support. Such challenges were due to the increased azotemia induced by protein or amino acid administration, the fluid overload caused by the administration of nutrients, and the difficulties associated with the control of these complications by means of conventional dialytic techniques.The development and increasing application of continuous renal replacement therapy has removed such concerns, because control of azotemia and fluid balance can be predictably and reliably achieved in all patients. Accordingly, the presence of renal failure should in no way influence the amount or type of nutritional support administered to a critically ill patient. We recommend that approximately 30-35 kCal/kg/d be administered enterally and begun within the first few hours of admission to the intensive care unit, and that protein intake be kept in the 1.5-2 g/kg/d range.Accumulating evidence also suggest that immune-enhancing enteral preparations decrease the duration of hospital stay, the number of infections, and perhaps mortality. Such preparations should be used in these patients. Finally, adequate vitamin and trace element supplementation is recommended to counterbalance the decrease in antioxidants and the loss of some vitamins during continuous renal replacement therapy. Available evidence suggests that if these steps are applied as part of a protocol-based approach to the nutritional support of patients with renal failure, morbidity and perhaps mortality can be significantly decreased.

Journal Article↗

PubMedDate not supplied

APD prescription: achieving the adequacy goals.

In the last few years, automated peritoneal dialysis (APD) has undergone considerable improvements due to technological developments. The definition of a minimal dose of peritoneal dialysis (PD) has not yet been completely assessed. Appropriate use of APD requires an evaluation of dialytic efficiency in terms of dialytic indexes and their targets. Many dialytic treatment modalities have been performed in order to achieve adequacy targets. Some aspects have to be taken into consideration to reach the optimal dialytic dose: optimizing mass transfer in correlation with intraperitoneal volumes, prescribing tailored treatment modalities according to different characteristics of peritoneal membranes and individual patient needs, and performing more biocompatible treatments using different glucose profiling and alternative physiologic PD fluids. New high-flow techniques such as continuous flow PD can ensure better urea and creatinine clearances and ultrafiltration rates, leading to a higher utilization of the APD modality.

Automation↗

PubMedDate not supplied

Continuous flow peritoneal dialysis: principles and applications.

Continuous flow peritoneal dialysis (CFPD) is a technique of renal replacement therapy (RRT) dating back to the 1960s. Its essential features are a fixed intraperitoneal volume and rapid, continuous movement of dialysis solution into and out of the peritoneal cavity. Inlet and outlet catheters and a means of generating a large volume of sterile dialysate are required. External regeneration of dialysate via conventional hemodialysis (HD) equipment or sorbent technology mitigates the need for large volumes of sterile fluid and makes the technique feasible. Clearance depends on the peritoneal mass transfer coefficient, rate of dialysate flow, and efficiency of external regeneration. Studies to date all demonstrate small solute clearances three to eight times greater than conventional automated peritoneal dialysis (PD). Catheter design is crucial to the clinical success of the technique and will be discussed. Potential applications include daily home dialysis, treatment of acute renal failure in the intensive care unit (ICU), and ultrafiltration of ascites. Clinical experience with the latter will be presented in detail.

Acute Kidney Injury↗

PubMedDate not supplied

Longitudinal study of apoptosis in chronic uremic patients.

Uremia is associated with a state of immune dysfunction, increasing infection and malignancy rates. Dysregulation of homeostasis may be directly related to abnormal apoptosis regulation, a process which is crucial for the maintenance of the biologic system. Abnormal apoptosis rates (ARs) have been reported in the literature. We performed a longitudinal study over a 10-week period in three groups of uremic subjects-hemodialysis (HD), peritoneal dialysis (PD), and predialysis chronic renal failure (CRF). Our results showed that ARs were consistent over the observed period. Monocytes extracted from HD and CRF subjects had higher ARs compared to PD and controls (HD: 26.06 +/- 8.82; CRF: 26.96 +/- 12.81; PD: 14.77 +/- 5.87; C: 11.42 +/- 4.60) when placed in culture medium. The plasma of HD and CRF subjects when incubated with U937 cells had a stronger apoptogenic potential compared with PD and controls (HD: 26.08 +/- 11.39; CRF: 24.87 +/- 9.07; PD: 12.13 +/- 4.51; C: 11.69 +/- 4.02). Inflammatory markers (C-reactive protein [CRP], procalcitonin) and cytokines (interleukin [IL]-1beta, IL-2, IL-10) had a generally poor correlation except for tumor necrosis factor (TNF)-alpha (p < 0.001). The phagocytic ability of U937 cells when incubated with the various plasma demonstrated impaired response in the HD and CRF subjects (HD: 27.56 +/- 6.67; CRF: 30.24 +/- 9.08; PD: 36.55 +/- 9.80; C: 40.04 +/- 6.98). These results suggest continuous renal purification, such as in continuous ambulatory peritoneal dialysis (CAPD), may have advantages over intermittent therapies in regulating apoptosis and maintaining biologic function and homeostasis.

Adult↗

PubMedDate not supplied

Temperature control by the blood temperature monitor.

The rationale of temperature control during hemodialysis (HD) is to prevent heat accumulation, which increases body temperature and enhances hypotensive susceptibility. Treatments where thermal energy is neither delivered nor removed from the patient through the extracorporeal circulation (so-called extracorporeal thermoneutral treatments) lead to a marked increase in body temperature and to considerable heat accumulation during HD. Since this accumulation of heat cannot be explained by increased heat production, it must be related to reduced heat dissipation through the body surface. Peripheral vasoconstriction, and cutaneous vasoconstriction in particular, compensating for the ultrafiltration-induced decrease in blood volume is considered an important component in this setting. Therefore, to maintain temperature homeostasis, thermal energy has to be cleared from the patient by the extracorporeal system because cutaneous clearance of thermal energy is compromised intradialytically. The focus on dialysate temperature alone does not properly address the problem of controlled extracorporeal heat removal because dialysate temperature is only one of the variables involved in that process. These difficulties can be addressed by changing from the control of dialysate temperature to control of body temperature. Control of body temperature and temperature homeostasis is achievable by the physiologic feedback control system realized in the temperature control mode (T-mode) of the blood temperature monitor (BTM). The delivery of isothermic dialysis, that is, dialysis where body temperature is controlled to remain constant during the treatment, has impressively improved hemodynamic stability in hypotension prone patients.

Body Temperature Regulation↗

PubMedDate not supplied

Surveillance of fistula function by frequent recirculation measurements during high efficiency dialysis.

Native fistulae are assumed to remain patent even with low access flows and are likely to cause access recirculation in high efficiency treatments done with high extracorporeal blood flows. We tested whether frequent recirculation measurements could be used to identify fistulae at risk to fail because of low access flow. High efficiency hemodialysis was delivered by 2008H machines equipped with blood temperature monitors (BTM) to measure recirculation within the first hour of every hemodialysis treatment. Access flow was measured when two consecutive BTM recirculation measurements exceeded a threshold of 15%. If access flow was < 500 ml/min, patients were referred for fistula revision. Eighty patients with native AV fistulae were studied for a period of 6 months. Nine of 11 interventions performed during the whole observation period were triggered by a BTM recirculation above the threshold. Two fistulae thrombosed in spite of a BTM recirculation below the threshold. One fistula with a BTM recirculation above the threshold had an access flow of 1,550 ml/min and was not referred for revision. BTM recirculation to detect fistulae for revision is sensitive (81.8%) and specific (98.6%) in the presence of cardiopulmonary recirculation and can be done with minimum intervention and without loss of efficient treatment time.

Adult↗

PubMedDate not supplied

On-line clearance: a useful tool for monitoring the effectiveness of the reuse procedure.

Reprocessing of a dialyzer for repeated use in the same patient is widely practiced. The dialyzer fiber bundle volume (FBV) is monitored as an indicator of the dialyzer's suitability for continued use, with standards for reprocessed dialyzers requiring a FBV of greater than 80% of a new dialyzer to be maintained. We have used on-line measurement of clearance of sodium (OLC module, Fresenius Medical Care, Walnut Creek, CA) to assess small molecule clearance changes during and between treatments for a group of 29 chronic hemodialysis patients who reused high flux polysulfone dialyzers (F80, Fresenius Medical Care, Lexington, MA) reprocessed using citric acid and heat (95 degrees C). Data pertaining to the initial, 5th, 10th, and 15th uses were analyzed and showed that, within a single dialysis session, there was a trend for the clearance to reduce throughout the treatment (p < 0.001). Overall, there was also a trend for clearances to decline with increasing number of reuses (p < 0.008). Changes in FBV occurred, but such changes remained within the guidelines suggested by standards. It is concluded that on-line clearance measurements provide a simple noninvasive method to monitor dialyzer performance over each use and between uses.

Aged↗