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PubMed1996

Transcapillary ultrafiltration and peritoneal equilibration test in pediatric patients.

The usefulness of the peritoneal equilibration test (PET) in children is unknown. The relationship between transcapillary ultrafiltration and PET was investigated in order to evaluate the usefulness of PET in children. PET was performed on 14 patients undergoing peritoneal dialysis. Their age and bodyweight ranged from 3.8 to 23.6 years and 10.2 to 55.8 kg, respectively. The patients were divided into two groups according to bodyweight; group A patients weighed < or = 40 kg (n = 7) and group B patients weighed > 40 kg (n = 7). There was no significant difference in the mean infusion volume per bodyweight between the two groups, but the mean infusion volume per body surface area was smaller in group A than in group B. Group A showed a more rapid equilibration of dialysate glucose and creatinine than group B. Higher normalized mass transfer area coefficients were evident in group A. In spite of the lower effective glucose gradient in group A, the transcapillary ultrafiltration capacity (TUFC) showed no difference between the two groups. When the slope indices of the regression equations between the two groups were compared, the slopes of the regression in the relationship between TUFC and dialysate (D) ratios D/Do glucose or D/P creatinine in group A were steeper than those in group B. Results of the present study indicate that the larger peritoneal area to infusion volume in patients with smaller body size results in both a rapid equilibration of solutes and sufficient transcapillary ultrafiltration.

Adolescent↗
PubMed2004

Regulation of PTH1 receptor expression by uremic ultrafiltrate in UMR 106-01 osteoblast-like cells.

BACKGROUND: Homologous down-regulation/desensitization of the parathyroid hormone receptor (PTH1R)/adenylate cyclase system has been demonstrated in uremia, and may contribute to parathyroid hormone (PTH) resistance; however, additional studies have shown that parathyroidectomy fails to normalize the down-regulation of the PTH1R. The present studies were designed to test directly, in vitro, the hypothesis that factors circulating in the uremic environment, other than PTH, decrease the response of osteoblastic cells to PTH. METHODS: Studies were conducted in confluent cultures of UMR 106-01 osteoblast-like cells. Uremic ultrafiltrate (UUF) was obtained from patients on hemodialysis. Cells were exposed to media containing 50% uremic ultrafiltrate for periods of up to 72 hours. Control cultures were exposed to a buffered salt solution containing a comparable ionic composition to that of the UUF. PTH-stimulated cyclic adenosine monophosphate (cAMP) generation was determined by radioimmunoassay (RIA), PTH binding and PTH1R mRNA levels were determined by radioligand binding and Northern analysis, respectively. RESULTS: PTH-stimulated cAMP generation from cultures treated with uremic ultrafiltrate for 48 hours was 1385.8 +/- 183.2 pmol/culture/5 minutes, whereas control cultures generated 2389.5 +/- 271 pmol cAMP/culture/5 minutes (P < 0.05). PTH binding was decreased by 30% in cultures incubated with UUF as compared to controls. The decrease in binding induced by UUF was accompanied by a decrease in PTH1R mRNA levels. CONCLUSION: These findings demonstrate that factors present in UUF decrease PTH-stimulated cAMP generation by a mechanism that involves a decrease in the levels of PTH1R mRNA levels. Thus, the skeletal resistance to PTH in the setting of chronic kidney disease, may be explained, at least in part, by circulating factors other than PTH.

Binding, Competitive↗
PubMed1991

Development of a new antithrombogenic continuous ultrafiltration system.

By interfacing a polyacrylonitrile (PAN)-polyethyleneoxide (PEO) membrane with an ionically heparin-bound catheter, tubing, and module header, a totally antithrombogenic continuous ultrafiltration system (ACUS) was developed and its performance, persistent antithrombogenicity, and well-maintained ultrafiltration level were confirmed through animal experiments. Although the amount of heparin released and accumulated in vitro from those heparinized parts was very low and stable (on the order of 1 x 10(-2) U/cm2/min), partial thromboplastin time evaluated in vivo was not elongated during passage through the ACUS. Extracorporeal circulation time with the ACUS in unheparinized dog model was 458 +/- 302 min (n = 24), whereas those of partially modified (antithrombogenic) system did not exceed 100 min. As compared with that in a conventional continuous arteriovenous hemofiltration system, an extracorporeal circulation with the ACUS in an unheparinized dog model revealed significantly less fluctuation of platelet count, and no adherent platelets were observed on the surface of the PAN-PEO membrane. An ACUS consisting of a PAN-PEO membrane and heparinized parts was thus demonstrated to have good platelet compatibility. An ACUS with a surface area of 0.25 m2 was applied to two patients with acute renal failure. Hemofiltration without systemic heparinization lasted for 44 h per hemofilter, and a stable level of ultrafiltration was maintained. This system seems to be applicable for the clinical management of volume overload, especially in patients with bleeding tendencies or postoperative bleeding.

Acrylic Resins↗
PubMed1962

Nutrition of Leptospira pomona. 1. A chemically defined substitute for rabbit serum ultrafiltrate.

Johnson, R. C. (Fort Detrick, Frederick, Md.) and N. D. Gary. Nutrition of Leptospira pomona. I. A chemically defined substitute for rabbit serum ultrafiltrate. J. Bacteriol. 83:668-672. 1962.-Poor growth of Leptospira pomona, strain Wickard, in a medium containing exhaustively dialyzed rabbit serum was corrected by addition of rabbit serum ultrafiltrate. A dialyzed serum medium was used to investigate the nutritional qualities of various compounds when tested as substitutes for the ultrafiltrate fraction. l-Asparagine was the only amino acid that markedly stimulated growth. l-Glutamine was active only when autoclaved (converted to the ammonium salt of pyrrolidone carboxylic acid), and NH(4)Cl and urea satisfactorily replaced l-asparagine. Results indicated that amino acids functioned primarily as a nitrogen source in this medium. Thiamine was the only vitamin required for growth. The lag phase was usually decreased by 1 day with NaHCO(3).A medium composed of 0.02 m phospate buffer (pH 7.4), 15% dialyzed rabbit serum, thiamine (5 mug/ml), and NH(4)Cl (10(-3)m) supported growth equivalent to that obtained with undialyzed rabbit serum medium. L. pomona was transferred six times, in this medium and seven other serotypes were transferred three times, without any decrease in amount of growth. Growth of L. pomona was initiated with 20 organisms per ml.

Animals↗
PubMed1977

Dynamics of glomerular ultrafiltration. IX. Effects of plasma protein concentration.

Experiments were carried out on 42 Munich-Wistar rats with surface glomeruli accessible to micropuncture to investigate the effects of reduction in systemic plasma protein concentration. CA, and thus afferent oncotic pressure, IIA, on the determinants of glomerular ultrafiltration. In animals in which CA was reduced by a variety of maneuvers, observed values for single-nephron GFR were lower than values predicted by the Starling relation, when the latter were calculated assuming that the observed increase in the net driving pressure for ultrafiltration (due to the reduction in IIA) was the only factor perturbed. In all experimental conditions where CA was reduced, rats were invariably observed to be at filtration pressure disequilibrium, permitting calculation of unique values of the ultrafiltration coefficient, Kt. In all low-CA groups, mean values of Kf were uniformly lower than values obtainedin normoproteinemic control animals. The failure of SNGFR to rise to predicted values when CA is reduced is therefore due to the concomitant reduction in Kf. No morphological basis for this reduction in Kf was discerned.

Animals↗
PubMed1985

Glomerular ultrafiltration dynamics: historical perspective.

Our knowledge of the structure and function of the renal glomerulus is reviewed in a historical context. The glomerular corpuscles were first described by Malpighi in 1666. Subsequent injection studies led to conflicting claims concerning a glomerular-tubular connection. This connection was accepted only after the convincing demonstration of the anatomical relationship essentially as we now know it by Bowman in 1842. Ludwig was the first to propose that the mechanism of separation of fluid in the glomeruli was by ultrafiltration. Estimates of the ultrafiltration forces in mammals led to conflicting speculation as to whether or not filtration-pressure equilibrium was reached in glomerular capillaries. Results of direct determinations in some Munich-Wistar rats indicate filtration pressure equilibrium, an ultrafiltration coefficient (Kf) of 0.08 nl X s-1 X mmHg-1, and a strong influence of plasma flow on filtration rate (GFR). In contrast, evidence has been presented that filtration dynamics in other Munich-Wistar rats and several other strains of rats are characterized by filtration disequilibrium, a Kf of 0.04 nl X s-1 X mmHg-1, and a weak dependence of GFR on plasma flow. In conscious and anesthetized rats, kidney GFR is usually relatively stable in the presence of renal vasodilation. Filtration disequilibrium is reported in the dog and equilibrium in the squirrel monkey. Although predictions for humans suggest filtration disequilibrium, final conclusions await an in-depth analysis of direct measurements.

Animals↗
PubMed1986

Effect of albumin on glomerular ultrafiltration coefficient in isolated perfused dog glomerulus.

To evaluate the direct effect of albumin concentration on the glomerular capillary ultrafiltration coefficient (Kf), we compared the effect of "normal" (3.4 g/100 ml), "low" (0.1 g/100 ml), and "no albumin" (less than 0.005 g/100 ml) concentration on the determinants of single-nephron glomerular filtration rate (SNGFR) as measured with the isolated perfused glomerulus technique. When the albumin concentration was decreased from normal to low concentrations, the afferent flow rate increased from 318 +/- 147 (mean +/- SE) to 450 +/- 174 nl/min, the filtration fraction increased from 0.19 +/- 0.04 to 0.35 +/- 0.08, and the SNGFR increased from 49 +/- 21 to 126 +/- 34 nl/min. These changes were associated with a small though significant increase in Kf from 2.79 +/- 1.01 to 3.74 +/- 0.98 nl/(min X mmHg) (P less than 0.05). When the albumin concentration was decreased from low to no albumin the filtration fraction and SNGFR increased even further and were associated with a marked increase in Kf to a value of 27.04 +/- 11.43 nl/min X mmHg). We conclude that there is very little effect of decreases in albumin concentration on Kf until extremely low levels are reached, and at that point there is a marked increase in the ultrafiltration coefficient. Furthermore, when these extremely low concentrations of albumin are reached an important role for albumin in the basic function of the ultrafiltration barrier is demonstrable.

Animals↗
PubMed2001

Extracorporeal ultrafiltration for the treatment of overhydration and congestive heart failure.

Fluid overload may occur in patients with congestive heart failure. Under normal conditions, this is treated with inotropic support and diuretics. However, when diuretics fail, fluid removal becomes uncontrolled and other therapeutic options must be undertaken. Extracorporeal ultrafiltration is a possible solution to restore a status of fluid balance close to normal. Several new technologies have made ultrafiltration available today in all centers and easy to be instituted. Acute isolated schedules of ultrafiltration may, however, be too aggressive and result in severe hemodynamic instability. For this reason, continuous extracorporeal techniques have been applied in such patients and the therapy is generally carried out with success. Excellent hemodynamic stability, a good cardiovascular response and often diuresis restoration are the most common effects encountered using continuous forms of extracorporeal fluid removal. The potential for a home-based application of these techniques represents a further stimulating concept to be investigated.

Diuresis↗
PubMed1991

Effect of phosphatidylcholine on ultrafiltration in patients on continuous ambulatory peritoneal dialysis.

Oral phosphatidylcholine at 900 mg/day was given to 4 patients with high lymph absorption for 8 weeks. Fluid and solute transfer before and after treatment were compared to 4 similar controls given placebo. None of the patients had overt ultrafiltration problems. After treatment, overnight peritoneal effluent phospholipid content did not change significantly. Ultrafiltration as well as solute and glucose transfer remained unchanged at the end of 8 weeks. A controlled trial on patients with overt ultrafiltration problems for a longer duration is required to further elucidate the role of phosphatidylcholine supplementation in patients on continuous ambulatory peritoneal dialysis.

Absorption↗
PubMed1994

Evidence against transmission of hepatitis C virus through hemodialysis ultrafiltrate and peritoneal fluid.

Hepatitis C virus (HCV) infection is highly prevalent in the chronic renal failure population treated in dialysis units. Transmission of HCV via blood transfusions is becoming an increasing problem, but, nevertheless, the routes by which this transmission occurs are incompletely known. We have searched for the presence of HCV RNA by the polymerase chain reaction (PCR) in serum and dialysis ultrafiltrate in 12 hemodialysis and 5 continuous ambulatory peritoneal dialysis (CAPD) patients, all of whom were HCV-antibody-positive. Serum PCR were positive for HCV RNA in all the cases, whereas PCR performed on samples of hemodialysis ultrafiltrate or peritoneal effluent were always negative for HCV RNA. In addition, 13 patients tested positive for HCV antibodies and 19 out of 32 patients sharing the dialysis monitors with 17 PCR-positive individuals remained negative. From these findings, we conclude that the dialysis ultrafiltrate or peritoneal fluid seems to be an improbable source of HCV dissemination in the dialysis setting. Moreover, a significant group of patients remained HCV-antibody-negative although they shared the same dialysis machine with positive patients. Therefore, the importance of other sources of HCV transmission, namely blood-contaminated material, should be emphasized.

Ascitic Fluid↗
PubMed1978

Modulation by prostaglandin synthesis inhibitors of the action of exogenous angiotensin II on glomerular ultrafiltration in the rat.

We studied the effects of angiotensin II (A II) infusion, with and without inhibition of prostaglandin (PG) synthesis, on the determinants of glomerular ultrafiltration in 27 plasma volume-expanded Munich-Wistar rats. The effects of PG inhibition alone and infusion of vehicle alone also were investigated. With a pressor dose of A II single nephron (SN) GFR and total GFR did not change significantly, despite declines in both glomerular plasma flow rate (QA) and the ultrafiltration coefficient (Kf), due to an offsetting rise in the transcapillary hydraulic pressure difference (deltaP). Afferent and efferent arteriolar resistances (RA and RE) increased by approximately 100% above control during A II infusion. Inhibition of PG synthesis alone and infusion of vehicle alone similarly failed to affect SNGFR and total GFR, and only slight changes occurred in the determinants of glomerular ultrafiltration in these rats. When A II infusion was accompanied by inhibition of PG synthesis, however, profound declines in SNGFR and total GFR were seen, due to further reductions in QA and 2-fold greater increases in RA and RE than occurred with the same dose of A II alone. The A II-induced fall in Kf was not affected by simultaneous PG inhibition. Thus, endogenous PGs attenuate the vasoconstrictor actions of A II on the superficial renal microvasculature and minimize changes in QA, SNGFR, and total GFR. It is likely that an interaction between A II and PG may be important in pathophysiological conditions in which endogenous A II levels are elevated.

Angiotensin II↗
PubMed2000

Simple modified ultrafiltration.

After reviewing all available methods of modified ultrafiltration (MUF), an attempt was made to develop a more simplified approach to this beneficial method of post-bypass fluid removal by withdrawing blood from the right atrium and reinfusing into the aortic cannula (venoarterial). The simplicity of operation, ease of setup and analysis of hemoglobin, hematocrit, total proteins and colloid osmotic pressure, and fluid removed were examined in 12 consecutive neonatal and pediatric patients undergoing cardiac surgery. Results indicate that this simplified modified ultrafiltration (SMUF) is comparable to all other methods of MUF by achieving dramatic improvements in all parameters measured. In addition, SMUF provides the perfusionist with the ability to run conventional ultrafiltration throughout the bypass procedure, using this one circuit design. As well as finding the learning curve for SMUF to be very short, this method was found to be superior in its simplicity of operation, ease of setup, reduced risk of complications and acceptance by the surgeon and anesthetist.

Aorta↗
PubMed1982

Ultrafiltrable serum citrate and the relationship between serum and urinary citrate results in controls and renal calcium stone formers.

The total and ultrafiltrable citrate of serum were measured in healthy controls, and in patients with calcium-containing kidney stones classified into the various calciuria types (normocalciuria, renal, absorptive, resorptive hypercalciuria). The total citrate in two subgroups (normocalciuria, renal hypercalciuria) was significantly higher than in controls. Two independent analyses showed a mean ultrafiltrable fraction of 0.86 (controls and stone formers, with the exception of resorptive hypercalciuria) and 0.95 (resorptive hypercalciuria), i.e., the calculated extent of binding of citrate to serum macromolecules (greater than 10 000 Daltons). The differences in the fraction of free citrate between controls and renal stone formers are not significant. The apparent mean association constants are (1/mol) 0.24 x 10(2) (controls) and 0.29 x 10(2) (normocalciuria). There is a high correlation between the ultrafiltrable fraction and total citrate in the serum, and also between the ratios urinary/serum creatinine and urinary/serum total citrate, during a 2 h endogenous creatinine clearance in the morning (fasting). These findings suggest that 1) there is citrate binding in the serum, 2) the normal portion of free citrate in total serum citrate of normocalciuric stone formers cannot explain the decreased citrate excretion in 24 h urine of these subjects, 3) under defined conditions of examination (morning; fasting) urinary citrate is determined largely by the filtered load of citrate in the proximal renal tubule.

Adult↗
PubMed1993

Parathyroid hormone and osteocalcin levels in plasma and ultrafiltrate during hemofiltration.

The effects of hemofiltration (HF) on serum levels of intact parathyroid hormone (PTH), as well as its mid-C regional and C-terminal fragments and bone Gla-protein (bone gamma-carboxyglutamic acid, osteocalcin), were investigated in 17 patients during one session of HF. During HF there was a significant decrease in the serum concentrations of both intact PTH (p < 0.01), mid-C regional PTH (p < 0.01) and C-terminal PTH (p < 0.01) as well as in the osteocalcin concentrations (p < 0.01). There was a significant increase in serum calcium (p < 0.05) during the procedure and this increase correlated with the reduction in PTH (r = 0.56, p < 0.05). Mid-C regional PTH and osteocalcin were found in the ultrafiltrate of all patients, while intact PTH was found in the ultrafiltrate of 8 of 17 patients and C-terminal PTH was detected only in the ultrafiltrate of one patient. The data demonstrate that the permeability of HF membranes is high enough to cause filtration of both intact PTH, PTH fragments and osteocalcin. An inhibited secretion of PTH probably played a major part in reducing intact PTH in serum during HF.

Adult↗
PubMed1999

Veno-arterial modified ultrafiltration in children after cardiopulmonary bypass.

A method of performing veno-arterial modified ultrafiltration is described that utilizes conventional blood flow through the aortic and venous cannulae. A dual-pump blood cardioplegia console is adapted to aspirate blood from the cardiopulmonary bypass venous line. The blood is ultrafiltered, sent through the cardioplegia heat exchanger, and returned to the aorta via the cardioplegia needle. Veno-arterial modified ultrafiltration has produced no visual evidence of air entrainment in the cardiopulmonary arterial line. This method allows the immediate resumption of cardiopulmonary bypass without the need for the surgeon to recannulate or alter tubing. Thirty-five children underwent veno-arterial modified ultrafiltration; the results show significant increases in postoperative hematocrit, early extubation, and improved rheology.

Cardiopulmonary Bypass↗
PubMed2001

Conventional and conventional plus modified ultrafiltration during cardiac surgery in high-risk congenital heart disease.

BACKGROUND: This prospective nonrandomized study is the critical assessment of conventional ultrafiltration (CUF) and modified ultrafiltration (MUF) techniques and their efficiency in congenital heart disease surgeries. Use of cardiopulmonary bypass (CPB) in children is associated with body water retention as a consequence of prime volume and systemic inflammatory reaction. The CUF during CPB has reduced body water excess and the MUF after CPB, removes inflammatory mediators, improves hemodynamic performance, and decreases transfusion requirements. METHODS: Forty-one patients, aged 9 to 36 months, submitted to surgical correction for cardiac defects, using CPB, were divided into 2 similar groups: CUF (21 patients) operated between 1996-1997 were ultrafiltered during CPB, and CUF+MUF, (20 patients) operated between 1997-1998 and ultrafiltered during and after CPB. Postoperative duration of ventilator support, pediatric intensive care unit stay (PICU), hospital stay of the groups with and without preoperative pulmonary hypertension (PH), as well as transfusion requirement, hematocrit and platelet counts were compared. RESULTS: There were no technical complications and a significant ultrafiltrate in the CUF+MUF group was observed as compared to the CUF group. No significant differences were observed between the CUF and CUF+MUF groups regarding ventilatory support, PICU stay and hospital stay. Requirements for red cell transfusion, Ht and platelet counts were not statistically different. CONCLUSIONS: CUF and CUF+MUF were safe and efficient methods for patient stabilization independent of diagnosis and complexity of surgery. Future clinical evaluation should address a larger population of patients to research the different variables.

Algorithms↗
PubMed2002

[Sonographic study of the diameter of the inferior vena cava for optimal ultrafiltration in hemodialysis].

The objective of the work was to evaluate the results of sonographic examination of the diameter of the vena cava inferior (VCI) as a parameter of hydratation of haemodialyzed patients. In a group of 84 haemodialyzed patients, mean age 66.32 years, the collapsibility index of the IVC was measure. The collapsibility index (CI) was calculated according to the formula: [formula: see text] where IVCexp = the maximum diameter of the IVC in maximum inspiration. Values of the index within the range from 40-75% corresponded to normal hydratation. The results were compared with ultrafiltration (total and expressed as % of body weight after haemodialyzation), "dry" body weight and with changes of BP during haemodialysis. The mean value of CI was 63.24 +/- 18.54. In 54 instances it was within the normal range (62.26 +/- 11.4), in 10 it was lower (27.7 +/- 6.02; possible sign of inadequate ultrafiltration during dialysis) and in 20 instances it was higher (84.9 +/- 7.53; risk of excessive ultrafiltration). Clinically assessed "dry" weight was adequate in 64% cases. In 24% UF was excessive. With this corresponded also the incidence of hypotension (40%) and in these patients the "dry" weight was subsequently elevated. The predictive importance of low values of CI for inadequate UF is however not unequivocal. Some of these patients were hypotensive even in case of low UF and did not tolerate its increase.

Adult↗
PubMed1977

Chalone-like inhibition of Ehrlich ascites cell proliferation in vitro by an ultrafiltrate obtained from the ascitic fluid.

An aqueous ultrafiltrate (10 000-50 000 dalton) prepared from the cell-free ascitic fluid of mice bearing Ehrlich ascites tumour (EAT) in the plateau phase of growth (12-16 days after transplantation) was investigated with regard to its inhibitory effects on the proliferation of EAT cells in a 24-hr suspension culture. The following results were obtained: (1) The in vitro proliferation of cells obtained from the plateau phase of in vivo growth was reversibly inhibited. (2) The dose-response curves show a plateau with a maximum inhibition of about 50%, which suggests that not all cells can be affected. (3) Young cells (4-6 days after transplantation) were not inhibited. (4) Preincubation of plateau phase cells in the culture medium before treatment abolishes the inhibitory effect of the ultrafiltrate. This effect of preincubation is dependent on time and serum concentration. It provides the possibility to differentiate between true "chalone-like" and cytotoxic effects. (5) the inhibitory properties of the ultrafiltrate are destroyed by heating or trypsin treatment. (6) Extracts prepared in the same way from ascitic fluid of mice bearing lymphocytic leukemia L1210 do not inhibit the proliferation of EAT cells. Corresponding extracts from ascitic fluid of mice bearing myelocytic leukemia YM were found to be inhibitory; however, the inhibitory effect was also found on preincubated cells and is therefore considered to be due to an unspecific cytotoxicity. In conclusion, evidence was obtained for a factor from the ascitic fluid of mice bearing EAT, which prevents EAT cells from entering the proliferating state.

Animals↗