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PubMed1987

Plasma ultrafiltrable magnesium in insulin dependent diabetics.

Plasma ultrafiltrable (MgUF) and total magnesium concentrations were measured in 60 insulin dependent diabetics and compared with values in an age matched control group. Although the diabetic patients had lower plasma albumin concentrations (p less than 0.05), both ultrafiltrable and total magnesium concentrations were significantly decreased by 6.8% and 7.6%, respectively, compared with those of the controls (p less than 0.001). In the diabetic group MgUF varied inversely with fasting plasma glucose (r = -0.269, p less than 0.05). In 14 patients with significant hypomagnesaemia, fasting plasma glucose concentration was higher (p less than 0.01) and the diabetes was of shorter duration (p less than 0.05) than in 46 patients with an MgUF in the control range. The fasting urinary magnesium creatinine ratio was greater in the diabetic patients (p less than 0.05). Patients with retinopathy did not have lower plasma magnesium values than those without retinopathy.

Diabetes Mellitus, Type 1↗
PubMed1982

Glomerular ultrafiltration in the pseudopregnant rat.

Whole kidney and single nephron indices of glomerular ultrafiltration were measured by clearance and micropuncture techniques in anesthetized virgin, 9-day pregnant, and 9-day pseudopregnant Munich-Wistar rats. Whole kidney glomerular filtration rate (GFR) and single nephron glomerular filtration rate (SNGFR) were elevated in pregnant and pseudopregnant rats compared with virgins (0.78 +/- 0.05, 0.75 +/- 0.06 vs. 0.57 +/- 0.03 ml/min, P less than 0.005 and P less than 0.001; 32.1 +/- 2.5, 30.0 +/- 2.8 vs. 22.1 +/- 2.0 nl/min, P less than 0.01 and P less than 0.05, respectively). Total renal plasma flow rate (RPF) and single glomerular plasma flow rate (QA) were also increased in pregnant and pseudopregnant rats compared to virgins (3.05 +/- 0.19, 2.90 +2- 0.24 vs. 2.28 +/- 0.21 ml/min, P less than 0.01 and P less than 0.05; 109.0 +/- 15.8, 100.4 +/- 12.8 vs. 68.0 +/- 6.9 nl/min, both P less thn 0.05). There was little difference in the other determinants of ultrafiltration among the three groups. Plasma volume was measured in separate experiments and was higher in pregnant and pseudopregnant rats compared with virgins (9.4 +/- 0.2, 9.8 +/- 0.4 vs. 8.4 +/- 0.3 ml, P less than 0.01 and P less than 0.05, respectively). The gestational increase in GFR in the rat occurs as the result of increased RPF, which is due to both plasma volume expansion and renal vasodilation. Since the changes in renal hemodynamics seen in pseudopregnancy were almost identical to those occurring in pregnant rats, the early stimulus to increased GFR must be maternal and not fetoplacental in origin.

Animals↗
PubMed1983

Glomerular ultrafiltration dynamics during increased renal venous pressure.

The effects of unilateral partial renal venous ligation on whole kidney and single nephron function were determined in anesthetized euvolemic Munich-Wistar rats using clearance, blood flow, and micropuncture techniques. Increased venous pressure (4-22 mmHg) reduced glomerular filtration rate (GFR) and renal plasma flow (RPF) to 60% of control values; filtration fraction (FF) was constant. Similar responses occurred in the superficial cortex, as evidenced by a 40% fall in SNGFR determined while intratubular pressure was maintained at the elevated precollection level. Fractional reabsorption by the proximal convoluted tubule remained constant, indicating maintenance of glomerulotubular balance. The contralateral kidney exhibit a diuresis and natriuresis while GFR and RPF were stable. In the experimental kidney single nephron glomerular plasma flow decreased by 35% due to increments in preglomerular and efferent arteriolar resistance. The transcapillary hydrostatic pressure gradient was unchanged since there were similar 7- to 8-mmHg increases in glomerular capillary and Bowman's space pressures. Filtration pressure disequilibrium was observed in control and experimental periods. Mean effective ultrafiltration pressure was similar in both periods. Specific values for the ultrafiltration coefficient (Kf) fell from 0.023 to 0.015 nl . s-1. mmHg-1. Accordingly, partial renal venous ligation produces ipsilateral vasoconstriction and a fall in GFR that is primarily due to a proportional decline in Kf.

Animals↗
PubMed1984

Ultrafiltration by hyperosmotic peritoneal dialysis fluid excludes intracellular solutes.

During peritoneal dialysis, progressive increments in the osmotic gradient increase ultrafiltration rate. Solute transport by convective flux is thereby raised but there is no preferential increase in potassium clearance. The data imply that ultrafiltrate derives from extracellular fluid alone. Mesothelial cells appear to resist solute and water flux in response to an immediately adjacent osmotic gradient.

Animals↗
PubMed1976

Ultrafiltrable uric acid in serum of healthy humans and patients with renal calcium lithiasis.

Ultrafiltrable serum uric acid (u.a.) was determined by ultrafiltration under in vivo conditions in humans using a reliable technique described in detail. It could be demonstrated that u.a. binding to macromolecules occurs in healthy humans (controls) and in patients with renal calcium stones. The percentage of free u.a. in controls (n=60) averages 86.2 +/- 0.9 SEM. With increasing age, bound u.a. rises slightly. On the other hand, younger (less than 40 years) stone patients have significantly more bound u.a. than matched controls (80.7 +/- 1.0 SEM; p less than 0.001), whereas this is not found in elderly patients. The degree of binding is not related to concentration of plasma proteins but inversely related to free fatty acid concentration in healthy controls (r= -0.52; p less than 0.01). It is suggested that no augmentation of tubular u.a. filtered by the glomeruli could have occurred. The origin of fasting hyperuricosuria shown earlier to be a prominent feature of young renal calcium stone formers is yet unknown.

Adolescent↗
PubMed1978

High Rates of controlled ultrafiltration combined with optimal diffusion: recent advances in hemodialysis technique.

A system which permits high rates of middle molecule removal while preserving the removal of low molecular weight substances is described. It consists of a high fluid flux hollow fiber artificial kidney and an ultrafiltration controller. When used in combination, high rates of convective transport can be achieved through rapid ultrafiltration and reconstitution of blood with physiologic salt solutions. The theoretical impact of changing from conventional dialysis to this form of therapy on the body burden of middle molecules is estimated.

Diffusion↗
PubMed1978

Modular single-needle haemodialysis; ultrafiltration characteristics.

In vitro and in vivo work has been carried out examining a modular single-needle system for fistula haemodialysis. Ultrafiltration characteristics of the single-needle system are defined and conclusions upon flow patterns are reached. Applying the mean blood pressure formula to the extracorporeal system pressures, the transmembrane pressure can be calculated and the ultrafiltration rate forecast. High transmembrane pressures can be modified, with sacrifice of blood flow, by amendment of the blood flow phase durations.

Humans↗
PubMed1981

The importance of osmolality fall and ultrafiltration rate on hemodialysis side effects. Influence of intravenous mannitol.

The decreases in serum osmolality as well as the rate of ultrafiltration during hemodialysis and the influence of each upon the side effects of this treatment were studied in 13 chronic stable dialysis patients. Mannitol (9 mosm/kg water) was infused in two out of four dialyses, in a double blind fashion. A solution of 5% glucose in water was used as control. 1 week after the treatment, there was no residual mannitol in the patients' serum (p less than 0.0005). The decrease in osmolality during dialysis was lower when the patients received treatment with mannitol than with placebo: 14.7 versus 25.0 mosm/kg water (p less than 0.001). The symptoms during dialysis were much less severe when the patients received mannitol (p less than 0.05). Analyzed separately, ultrafiltration rate had no effect on severity of symptoms during dialysis (p greater than 0.1). Decrease in serum osmolality during dialysis seems to be the most important factor in the genesis of dialysis symptoms in chronic stable dialysis patients and are counteracted by the infusion of an osmotically active substance such as mannitol, 1 g/kg/dialysis; this results in a slight increase in body weight between dialyses, and cannot be used routinely because of slow accumulation.

Adult↗
PubMed1982

Echocardiographic hemodynamic study during ultrafiltration sequential dialysis.

4 patients on regular dialysis were studied by the echocardiographic method during ultrafiltration and dialysis performed sequentially according to two different protocols. Blood pressure, heart rate, cardiac output, stroke volume, systolic and diastolic dimension of the left ventricle, systolic and diastolic volumes of the left ventricle, ejection fraction, shortening fraction and total peripheral vascular resistance index were measured. During ultrafiltration there is an increase of the total peripheral vascular resistance index. Myocardial contractility improves only during dialysis. Physiopathologic implications are discussed.

Adult↗
PubMed1983

Rapid correction of severe lactic acidosis with massive isotonic bicarbonate infusion and simultaneous ultrafiltration.

Patients with severe lactic acidosis and oliguria who receive large amounts of sodium bicarbonate may develop fluid overload and hyperosmolarity. We infused massive amounts of isotonic sodium bicarbonate and simultaneously removed the excess sodium and water with ultrafiltration if 2 patients with lactic acidosis. The first patient received 1,125 mmol of bicarbonate over 4.5 h with a rise in pH from 7.00 to 7.36 and in HCO3 from 3.5 to 15.7 mmol/l. The second received 968 mmol of bicarbonate over 5.25 h with a rise in pH from 7.00 to 7.27 and in HCO3 from 5.3 to 14 mmol/l. Blood pressure remained stable or rose, electrolytes normalized, excess fluid was removed, and a higher pH was maintained. Isotonic bicarbonate infusion with simultaneous ultrafiltration is a safe and rapid method of correcting the metabolic status of patients with severe lactic acidosis who have not responded to standard therapy.

Acidosis↗
PubMed1983

Permanent loss of ultrafiltration capacity of the peritoneum in long-term peritoneal dialysis: an epidemiological study.

Permanent loss of the ultrafiltration (UF) capacity of the peritoneum has been observed with an increasing frequency among our patients treated by long-term intermittent (IPD) and/or continuous ambulatory peritoneal dialysis (CAPD). The analysis of various characteristics of our PD population (patients age, dialysis techniques, peritoneal infection rate and treatment duration) indicates that the incidence of this complication increases exponentially with the duration of PD, the loss of UF capacity being observed after a shorter period in CAPD than in IPD. These observations suggest that long-term irrigation of the peritoneal cavity leads to a progressive deterioration of the peritoneum resulting in its altered permeability with loss of the ability to ultrafiltrate; the cause of this abnormality is as yet unknown.

Adult↗
PubMed1993

Heterogeneity in peritoneal transport during continuous ambulatory peritoneal dialysis and its impact on ultrafiltration, loss of macromolecules and plasma level of proteins, lipids and lipoproteins.

We investigated the effect of heterogeneity in the peritoneal transport of plasma proteins on dialysis efficiency and plasma levels of proteins, lipids and lipoproteins in 32 patients undergoing long-term continuous ambulatory peritoneal dialysis (CAPD; 9 females and 23 males, 18-76 years old). Eleven patients were studied on several occasions (at 0-42 months) and the remainder at 6-60 months on CAPD (n = 49). We have divided our patients arbitrarily into two equal groups according to their protein concentration in the peritoneal effluent at the end of an 8-hour cycle. Patients with a high peritoneal protein concentration (> or = 2 g/l/1.73 m2) have lower ultrafiltration capacity, higher glucose absorption rate and increased loss of most plasma proteins [including albumin, immunoglobulins (Ig), complement components and high-density lipoproteins (HDL)] compared to patients with a low peritoneal protein concentration (< 2 g/l/1.73 m2). Consequently, plasma levels of albumin, IgM and HDL were lower in patients with a high peritoneal protein concentration. The latter had also increased levels of plasma triglycerides and very-low-density lipoproteins. The difference observed in peritoneal transport between the groups could be ascribed only in part to the duration of CAPD treatment, and hence to the number of peritonitis episodes but not to medications. Therefore, we suggest that inherent constitutional factors may be responsible for some of the observed heterogeneity in the peritoneal transport of these patients which is already evident at the start of CAPD treatment. Patients with high peritoneal transport are exposed to an augmented atherogenic plasma lipid profile in addition to a reduction in dialysis efficiency (ultrafiltration failure). These patients may become prone also to nutritional and immunological disturbances. Therefore, we suggest taking these effects into consideration before choosing the appropriate dialysis modality in patients with increased peritoneal transport for plasma proteins.

Adolescent↗
PubMed1972

Ultrafiltration of lipoproteins through a synthetic membrane. Implications for the filtration theory of atherogenesis.

To investigate the interaction of lipoproteins with semipermeable membranes, solutions of low density lipoproteins (LDL), very low density lipoproteins (VLDL), mixtures of the two, and diluted, normal, and hyperlipidemic serum were ultrafiltered through a synthetic membrane (500 A nominal pore diameter) using a stirred laboratory ultrafiltration cell. The pressure dependence of ultrafiltrate flux showed that a concentrated layer of lipoproteins was built up at the membrane surface (concentration polarization) and that VLDL was more subject to polarization than LDL. This phenomenon controlled the observed lipoprotein transport behavior. Whereas true membrane rejection (the fraction of the solute on the membrane surface which does not pass through the membrane) was greater than 0.95 for both LDL and VLDL, observed solute rejection varied from nearly 0 to 1.0, depending upon experimental conditions. If concentration polarization occurs in the arterial system, these results suggest that lipoprotein transport into arterial wall may be influenced not only by arterial blood pressure and the properties of the arterial wall, but also by local hemodynamic conditions and by the relative as well as absolute magnitudes of LDL and VLDL concentration.

Arteriosclerosis↗
PubMed1983

Total, ultrafiltrable, dialysable and ionised calcium measurements in randomly selected samples compared with clinical diagnoses.

Total, ultrafiltrable (Worthington 'Ultrafree'), dialysable and ionised (Orion SS-20) calcium levels were measured in 110 serum samples selected randomly from patients for whom total calcium was ordered as a routine test. The available medical records were used to categorize most of the 86 patients as a guide to determining if the calcium results were appropriate to the diagnosis. Total calcium measurement was precise and reliable but was affected by the albumin level. Dialysable calcium measurement was good for diagnostic purposes and was not affected by albumin. Of 25 patients with apparently normal calcium metabolism, six had elevated ultrafiltrable calcium results. Ionised calcium measurement required the most time and sample and offered few, if any, clear advantages in diagnosis over the other free calcium tests. Further improvements in ionised calcium measurements appear to be needed.

Calcium↗
PubMed1986

Micro-scale ultracentrifugation as an alternative to ultrafiltration for the determination of the unbound fraction of phenytoin in human serum.

Free phenytoin has been determined using micro-scale ultracentrifugation followed by analysis by EMIT. The effect of temperature on the determined free fraction was investigated and the ultracentrifugation procedure validated against ultrafiltration. Ultracentrifugation gave free fractions which were on average 16% lower than those obtained using ultrafiltration, but correlation was good, as was the correlation with measurements of total phenytoin (r = 0.90). Micro-scale ultracentrifugation is a simple procedure which can be of great utility in the measurement and investigation of free drug levels.

Blood Proteins↗
PubMed2001

Modified ultrafiltration removes serum interleukin-8 in adult cardiac surgery.

Cardiopulmonary bypass (CPB) causes an increase in serum cytokine levels and systemic inflamatory responses, which may trigger the onset of various types of postoperative organ failure. In the present study, modified ultrafiltration (MUF) was applied in cases of adult cardiac surgery and an attempt was made to determine whether MUF reduces serum interleukin-8 (IL-8) levels. Nine patients who underwent cardiovascular surgery with CPB and MUF between June 1996 and June 1997 were compared with nine control patients who underwent cardiovascular surgery without MUF in the same period. Modified ultrafiltration was performed, based on a method proposed elsewhere. Serum IL-8 was measured by enzyme immunoassay at the start of CPB, immediately after CPB, immediately after MUF and 3 h after MUF. The mean filtrated volume was 1550.0 +/- 173.2 ml. In the MUF group, haematocrit increased significantly from 21.2 +/- 2.0 to 24.9 +/- 3.3% (p = 0.0008), while systolic blood pressure increased from 97.5 +/- 16.7 to 116.5 +/- 23.9 mmHg (p = 0.0024) after MUF. In contrast, there were no changes in either haematocrit or blood pressure in the control group. In the MUF group, serum IL-8 was reduced from 69.5 +/- 33.5 to 58.9 +/- 32.4 pg/ml after MUF (p = 0.0029), whereas it was not reduced in the control group. The results of the present study suggest that MUF has beneficial effects on postoperative haemodynamics, and can reduce serum IL-8 levels in adult cardiac surgery.

Adult↗
PubMed1993

Blood conservation during pediatric cardiac surgery: ultrafiltration of the extracorporeal circuit volume after cardiopulmonary bypass.

After separation of pediatric patients from cardiopulmonary bypass (CPB), the authors salvaged red blood cells (RBCs) from the extracorporeal circuit by ultrafiltration and reinfused them to the patients. The purposes of this study were to determine 1) the effects of infusion of hemoconcentrated RBCs on hemoglobin, plasma free hemoglobin, and activated clotting time, and 2) the incidence of perioperative homologous RBC transfusion. Data were collected prospectively from 200 consecutive infants and children undergoing CPB during correction of congenital heart defects. The patients' hemoglobin, plasma free hemoglobin, and activated clotting time were measured both before and after infusion of 10 mL/kg of hemoconcentrate. Guidelines for intraoperative and postoperative transfusion of homologous RBCs were followed, and such transfusions were recorded. Significant increases in hemoglobin concentrations occurred when the hemoconcentrate was infused, as did statistically significant, but clinically manageable, increases in plasma free hemoglobin and activated clotting time. Perioperative homologous RBC transfusion was performed in 67% of patients (56% received intraoperative transfusion). Intraoperative transfusion was more frequent in small infants who were more hemodiluted by the clear CPB priming solution. Postoperative transfusion was more frequent in patients who had operation for cyanotic heart disease. Hemoconcentration by ultrafiltration after CPB is an effective and safe means of salvaging RBCs and reducing homologous RBC transfusion.

Adolescent↗
PubMed2004

Evaluation of a candidate reference measurement procedure for serum free testosterone based on ultrafiltration and isotope dilution-gas chromatography-mass spectrometry.

BACKGROUND: To assess the analytical validity of free testosterone (FTe) measurements, a reference measurement procedure (RMP) is required. For steroids, isotope dilution-mass spectrometry is accepted as state-of-the-art technology. Because FTe is defined as the hormone fraction in serum water in equilibrium with the protein-bound fraction, the RMP should include a physical separation step. The use of equilibrium dialysis (ED) or ultrafiltration (UF) is advocated. Our objective was to develop such a candidate RMP. METHODS: We selected UF combined with isotope dilution-gas chromatography-mass spectrometry (ID-GC/MS) for direct measurement of Te in the ultrafiltrate. After optimization of the UF process, the complete procedure was validated by use of split-sample comparisons with indirect ED (iED) and symmetric dialysis (SyD). RESULTS: The candidate RMP gave maximum within-day, between-day, and total CVs of 3.0%, 3.1%, and 4.3%. The Deming regression equations for the respective method comparisons were: UF-ID-GC/MS = 0.98(iED) - 53 pmol/L (r = 0.94; S(y|x)= 42 pmol/L) and UF-ID-GC/MS = 0.92(SyD) + 21 pmol/L (r = 0.97; S(y|x)= 31 pmol/L). CONCLUSIONS: We achieved the objective of a state-of-the-art candidate RMP, which agreed well with iED and SyD. However, we also demonstrated that a degree of discordance remains, which may require a decision from an authoritative organization on the recommended procedure to measure free hormone concentrations.

Blood Proteins↗