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PubMed1981

Hypoxic vasoconstriction and fluid filtration in pig lungs.

We have studied the effect of hypoxia [inspired partial pressure of O2 (Po2) 50 mmHg] on the relationships among pulmonary blood flow, pulmonary arterial pressure, and fluid filtration rates in isolated blood-perfused pig lungs. Our results indicate that hypoxia constricted the vasculature in a manner that caused a parallel shift of the pressure-flow curve to higher pressures. During normoxia, filtration rate was zero at flows less than 1.5 1/min but increased with increases in blood flow above this level. In both cases the shape of this relationship was similar, but during hypoxia it was shifted to higher filtration rates. These findings can be interpreted using a parallel-channel Starling resistor model of the lung with a distribution of critical pressures. All the effects of hypoxia found in this study could be explained simply by an increase in critical pressure. According to the model, this increase in critical pressure during hypoxia caused a greater filtration rate because of an increase in the mean intravascular filtration pressure and an increase in the mean filtration coefficient.

Animals↗
PubMed2000

White blood cell subsets in buffy coat-derived platelet concentrates: the effect of pre- and poststorage filtration.

BACKGROUND AND OBJECTIVES: Our objective was to study the effect of storage time on the filtration of platelet concentrates (PCs). We compared the total number of white blood cells (WBC), as well as the distribution of WBC subsets, in units filtered before and after storage. MATERIALS AND METHODS: Buffy coat-derived PCs were filtered either fresh or after 5 days of storage, and total WBC were enumerated by flow cytometry. WBC subsets were analyzed by flow cytometry with three-color fluorescence. RESULTS: The total number of white cells before filtration was significantly higher in fresh units compared with stored units, whereas in postfiltration samples the number of white cells was significantly lower in the fresh compared with the stored units. Although absolute numbers were significantly reduced, filtration also induced significant changes in the proportions of subsets in both fresh and stored units; the percentage of T cells was decreased, whereas the percentage of B cells and monocytes was increased after filtration. CONCLUSION: Our results suggest that prestorage WBC filtration of platelet concentrates is superior in reducing the absolute numbers of WBC. However, both pre- and poststorage WBC filtration significantly affect the proportions of WBC in the final product, decreasing the number of T cells while apparently increasing the proportion of MHC class II-positive cell populations.

Blood Platelets↗
PubMed1994

Structural basis for reduced glomerular filtration capacity in nephrotic humans.

Previous studies have established that in a variety of human glomerulopathies the reduced glomerular filtration rate (GFR) is due to a marked lowering of the ultrafiltration coefficient (Kf). To identify the factors which lower Kf, we measured the filtering surface area per glomerulus, filtration slit frequency, basement membrane thickness, and GFR and its determinants in patients with minimal change and membraneous nephropathies and in age-matched healthy controls. Overall values of Kf for the two kidneys were calculated from GFR, renal plasma flow rate, systemic colloid osmotic pressure, and three assumed values for the transcapillary pressure difference. "Experimental" values of the glomerular hydraulic permeability (kexp) were then calculated from Kf, glomerular filtering surface area, and estimates of the total number of nephrons of the two kidneys. Independent estimates of the glomerular hydraulic permeability (kmodel) were obtained using a recent mathematical model that is based on analyses of viscous flow through the various structural components of the glomerular capillary wall. Individual values of basement membrane thickness and filtration slit frequency were used as inputs in this model. The results indicate that the reductions of Kf in both nephropathies can be attributed entirely to reduced glomerular hydraulic permeability. The mean values of kexp and kmodel were very similar in both disorders and much smaller in the nephrotic groups than in healthy controls. There was good agreement between kexp and kmodel for any given group of subjects. It was shown that, in both groups of nephrotics, filtration slit frequency was a more important determinant of the water flow resistance than was basement membrane thickness. The decrease in filtration slit frequency observed in both disorders caused the average path length for the filtrate to increase, thereby explaining the decreased hydraulic permeability.

Adolescent↗
PubMed2003

Feeding mechanisms in carp: crossflow filtration, palatal protrusions and flow reversals.

It has been hypothesized that, when engulfing food mixed with inorganic particles during benthic feeding, cyprinid fish use protrusions of tissue from the palatal organ to retain the food particles while the inorganic particles are expelled from the opercular slits. In crossflow filtration, the particle suspension is pumped parallel to the filter surface as filtrate exits through the filter pores, causing the suspension to become more concentrated as it travels downstream along the filter. We used high-speed video endoscopy to determine whether carp Cyprinus carpio use crossflow filtration and/or palatal protrusions during benthic feeding. We found that carp use crossflow filtration to concentrate small food particles in the pharyngeal cavity while expelling small dense inorganic particles through the opercular slits and via spits. Our results suggest that, during feeding on small food particles, palatal protrusions serve a localized chemosensory function rather than a mechanical particle-sorting function. However, palatal protrusions did retain large food particles while large inorganic particles were spit anteriorly from the mouth. We also investigated whether flow is continuous and unidirectional during suspension feeding in carp. As reported previously for ventilation in hedgehog skates and for certain industrial crossflow filtration applications, we observed that flow is pulsatile and bidirectional during feeding. These results have implications for hydrodynamic models of crossflow filtration in suspension-feeding fishes.

Animals↗
PubMed1993

Diagnostic image quality and dose reduction using niobium filtration for cephalometric radiography.

The usefulness of added filtration is contingent upon the maintenance of high image quality while effectively reducing the radiation dose. High-quality cephalometric radiographs, defined objectively by a panel of orthodontists, were obtained of a tissue-equivalent phantom both without and with 30 microns and 50 microns supplemental niobium filtration. Skin entrance doses in the temporomandibular joint region were compared at diagnostically acceptable exposures where there was no significant difference in radiographic image quality. Dose reductions ranged from 17% to 31% with 30 microns niobium filtration, and 17% to 39% with 50 microns. However, as kVp and HVL were increased to maintain the same level of perceived image quality, image contrast decreased. Contrast loss with 30 microns and 50 microns niobium filtration averaged 8% and 22% respectively compared with standard aluminium filtration. It would appear that additional niobium filtration can be used to reduce radiation dose without significant loss of image quality.

Analysis of Variance↗
PubMed1991

Indirect estimation of filtration variables in rat lungs calculated by protein concentration or osmotic pressure method.

We reported a new way for estimating filtration variables: K(filtration coefficient), Ppmv (perimicrovascular pressure) and sigma (protein reflection coefficient), from 3 different measurements of weight gain at two protein concentrations of perfusate (Cmv) and at two vascular pressures (Pvasc). We used the Starling equation for calculating those variables using two different formulas which expressed that all protein moves by convection. In this report, we compared those two formulas: 1) 1--sigma = pi pmv/pi mv, which is already reported (Tanita et al. 1990), and 2) 1--sigma = Cpmv/Cmv. We measured filtration rate (Q) by a gravimetric method in isolated rat lung lobes in zone 1 conditions (alveolar pressure = 20 cmH2O) at two vascular pressures, Pvasc = 15 or 8 cmH2O and perfused the lobes with plasma containing a low or a high concentration of protein. By extrapolating the log of the rate of weight gain to t = 0, we obtain the initial filtration rate. Cmv was measured and pi mv was estimated by Yamada's equation (Yamada et al. 1985). The reflection coefficient calculated in 1--sigma = pi pmv/pi mv method is computed 10% higher than that in 1--sigma = Cpmv/Cmv method. However, the filtration coefficient or the perimicrovascular pressure calculated in either method was identical. We conclude that filtration variables can be estimated easily by pi method and those variables are comparable to those estimated by C method which are theoretically more acculate but more complicated in calculation.

Animals↗
PubMed2003

Engraftment capacity of umbilical cord blood cells processed by either whole blood preparation or filtration.

Umbilical cord blood (UCB) preparation needs to be optimized in order to develop more simplified procedures for volume reduction, as well as to reduce the amount of contaminating cells within the final stem cell transplant. We evaluated a novel filter device (StemQuick((TM))E) and compared it with our routine buffy coat (BC) preparation procedure for the enrichment of hematopoietic progenitor cells (HPCs). Two groups of single or pooled UCB units were filtered (each n = 6), or equally divided in two halves and processed by filtration and BC preparation in parallel (n = 10). The engraftment capacity of UCB samples processed by whole blood (WB) preparation was compared with paired samples processed by filtration in the nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse animal model. Filtration of UCB units in the two groups with a mean volume of 87.8 and 120.7 ml, respectively, and nucleated cell (NC) content of 9.7 and 23.8 x 10(8) resulted in a sufficient mean cell recovery for mononucleated cells ([MNCs] 74.2%-77.5%), CD34(+) cells (76.3%-79.0%), and colony-forming cells (64.1%-86.3%). Moreover, we detected a relevant depletion of the transplants for RBCs (89.2%-90.0%) and platelets ([PLTs] 77.5%-86.1%). In contrast, the mean depletion rate using BC processing proved to be significantly different for PLTs (10%, p = 0.03) and RBCs (39.6%, p < 0.01). The NC composition showed a highly significant increase in MNCs and a decrease in granulocytes after filtration (p < 0.01), compared with a less significant MNC increase in the BC group (p < 0.05). For mice transplanted with WB-derived progenitors, we observed a mean of 15.3% +/- 15.5% of human CD45(+) cells within the BM compared with 19.9% +/- 16.8% for mice transplanted with filter samples (p = 0.03). The mean percentage of human CD34(+) cells was 4.2% +/- 3.1% for WB samples and 4.5% +/- 3.2% for filter samples (p = 0.68). As the data of NOD/SCID mice transplantation demonstrated a significant engraftment capacity of HPCs processed by filtration, no negative effect on the engraftment potential of filtered UCB cells versus non-volume-reduced cells from WB transplants was found. The StemQuick((TM))E filter devices proved to be a useful tool for Good Manufacturing Practices conform enrichment of HPCs and MNCs out of UCB. Filtration enables a quick and standardized preparation of a volume-reduced UCB transplant, including a partial depletion of granulocytes, RBCs, and PLTs without the need for centrifugation. Therefore, it seems very probable that filter-processed UCB transplants will also result in sufficient hematopoietic reconstitution in humans.

Animals↗
PubMed2006

Particle detachment during hydraulic shock loads in granular media filtration.

Particle breakthrough can occur by either the breakoff of previously captured particles (or flocs) or the direct passage of some influent particles through the filter. Filtration experiments were performed in a laboratory-scale filter using spherical glass beads with a diameter of 0.55 mm as collectors. A single type of particle suspension (Min-U-Sil 5) and three different destabilisation methods (pH control, alum and polymer destabilisation) were used to destabilise particles. The filtration velocity of 5 m/h was similar to that used in standard media filtration practice. To assess the possibility of particle detachment during normal filtration, a hydraulic shock load (20% increase of flow rate) was applied after 4 h of normal filtration. The magnitude of particle detachment was proportional to the particle size for non-Brownian particles. At the same time, less favourable particles, i.e. particles with larger surface charge, were easily detached during the hydraulic shock load. Therefore, proper particle destabilisation before filtration is crucial for maximum particle removal, as well as minimum particle breakthrough.

Alum Compounds↗
PubMedDate not supplied

Modeling depth filtration of activated sludge effluent using a compressible medium filter.

A new filter, using a compressible-filter medium, has been evaluated for the filtration of secondary effluent. The ability to adjust the properties of the filter medium by altering the degree of the medium compression is a significant departure from conventional depth-filtration technology. Unlike conventional filters, it is possible to optimize the performance of the compressible-medium filter (CMF) by adjusting the medium properties (i.e., collector size, porosity, and depth) to respond to the variations in influent quality. Because existing filter models cannot be used to predict the performance of the CMF, a new predictive model has been developed to describe the filtration performance of the CMF and the effect of medium-compression ratio. The model accounts for the fact that the properties of the filter medium change with time and depth. The model, developed for heterodisperse suspensions and variable influent total suspended solids concentrations, can be used to predict all possible phases of filtration (i.e., ripening, constant removal, and breakthrough). A hyperbolic-type, second-order, nonlinear, partial-differential equation was derived to model the CMF. The equation was solved using the finite-difference numerical method. The accuracy of the numerical method was tested by a sensitivity analysis and a convergence test. The model is first-order accurate with respect to medium depth and time. Field data were obtained for the filtration of settled secondary effluent using a CMF with a capacity of 1200 m3/d. Model predictions were compared with observed performance from filter runs conducted at medium-compression ratios between 15 and 40% and filtration rates from 410 to 820 L/m2 min. The difference between the observed and the predicted values was found to be within 0 to 15%.

Filtration↗
PubMed1993

Systolic blood pressure relates to the rate of decline of glomerular filtration rate in type II diabetes.

OBJECTIVE: To relate deterioration in kidney function to some potential cardiovascular risk factors in type II diabetic patients. RESEARCH DESIGN AND METHODS: Twenty-four normoalbuminuric and 13 microalbuminuric patients completed a 3.4-yr prospective observational study. Glomerular filtration rate, urinary albumin excretion rate, blood pressure, glycemic control, and lipids were measured on entry and at the end of the study. Of the patients, 19 normoalbuminuric and 8 microalbuminuric (73%) patients had no history of antihypertensive treatment. RESULTS: The glomerular filtration rate was significantly reduced during the follow-up period (-1.34 +/- 0.54 ml.min-1.1.73 m-2 [mean +/- SE], P < 0.02). The rate of decline varied considerably in normoalbuminuric and microalbuminuric patients (from -13.5 to 4.3 and from -7.0 to 4.2 ml.min-1.1.73 m-2 per year, respectively) but was on average not accelerated in normoalbuminuric or microalbuminuric patients (-1.3 +/- 0.7 and -1.5 +/- 0.8 ml.min-1.1.73 m-2 per year, respectively). Significant correlations were observed between the glomerular filtration rate fall rate and initial systolic blood pressure (r = -0.47, P < 0.01; patients without antihypertensive treatment: r = -0.42, P = 0.03) but not diastolic blood pressure. In a stepwise multiple linear regression analysis, baseline systolic blood pressure significantly determined the fall rate of the glomerular filtration rate (regression coefficient = -0.050, SE = 0.018, P = 0.011; patients without antihypertensive treatment: regression coefficient = -0.047, SE = 0.021, P = 0.030). CONCLUSIONS: In these type II diabetic patients neither normoalbuminuria nor microalbuminuria are at an average associated with an accelerated decline in kidney function. Still, systolic blood pressure is a determining factor for the rate of decline in the glomerular filtration rate. A longer follow-up time with consecutive glomerular filtration rate measurements are needed to determine the long-term implications of normoalbuminuria and microalbuminuria on kidney function in type II diabetic patients.

Aged↗
PubMed2003

Experimental study on sequencing batch biofilm reactor with biological filtration (SBBR-BF) for wastewater treatment.

A novel wastewater treatment technology combining a sequencing batch biofilm reactor and biological filtration in an SBBR-BF system was presented. Elastic plastic filaments were fixed as biofilms carrying media. Particle materials (sand or anthracite) and the settled sludge constituted the filtration layer. In the laboratory studies, operating results of SBR, SBBR and SBBR-BF were compared. Better quality and stable water quality of effluent could be achieved in SBBR-BF because the fixed film and filtration layer were added in the reactor. Other laboratory experiment results indicated that slow filtration, cycle water stirring and backwashing making use of the settled supernatant are successful methods for preventing clogging and saving energy. The velocity and headloss of filtration were significantly impacted by different MLSS concentration. The MLSS concentration in the reactor must be less than 1,400 mg/L for optimal results. The average velocity of filtration ranging from 0.6 to 1.0 m/h, the backwash velocity of 10-15 m/h and the backwash time of 20 seconds are recommended according to the laboratory experiment. On-site experiment and study showed that SBBR-BF is a stable and efficient system for domestic wastewater treatment, and is particularly suited for small wastewater treatment plants, because of the simple operation and compact installation.

Biofilms↗
PubMed2004

Physicochemical interaction and its influence on deep bed filtration process.

The capillary model was used to analyze the hydraulic conditions in the deep bed filtration process. The physicochemical interaction forces between the filter media and suspended particles and their influence on deep bed filtration process were also studied theoretically. Through the comparison of the hydraulic and physicochemical forces, the key influencing factors on the filtration process were proposed and investigated. Pilot study of the microflocculation deep bed filtration was carried out in the No. 9 Potable Water Treatment Plant of Beijing, and the experimental results of hydraulic head loss, particle distribution and entrapment were presented. The theoretical prediction was reasonably consistent with the experimental results under different conditions, which indicated that the regulation and control of micro-flocculation and deep bed filtration could be realized by the evaluation of the physicochemical interactions. Further theoretical and experimental research should be carried out to investigate the interaction mechanism and its application in the deep bed filtration and other cases.

Filtration↗
PubMed2004

Particle count and size alteration for membrane fouling reduction in non-conventional water filtration.

If coagulation is not completely successful and produces aggregates which are too small, fouling may increase. In some cases, a deep-bed filter could perhaps provide a solution. The paper examines these effects using experimental results for different waters. Activated sludge effluents, stormy seawater containing microalgae and spent filter backwash water (SFBW) were coagulated by alum or ferric chloride. Sand filtration tests were carried out. Tests were performed in a membrane filtration stirred cell, filtration pilot plant equipped with SDI analyzer (seawater) and pilot UF plant (SFBW). For activated sludge effluent, alum residual ratio curves of turbidity and total particle count (TPC) followed one another. With ferric chloride, low coagulant dosage showed negative turbidity removal. Contact granular filtration reduced membrane fouling intensity. Increasing the dose resulted in higher improvement in membrane flux. For seawater, a filter run period under storm conditions reached 35 hours with satisfactory filtrate quality. An iron chloride dose of 0.3 mg/l during normal conditions and 0.5 mg/l for stormy condition should be injected, mixed well before the filters, while maintaining 10 m/hr filtration rate and pH 6.8 value. For SFBW, alum flocculation pretreatment of SFBW was effective in reducing turbidity, TPC, viruses and protozoa. SFBW settling prior to flocculation did not enhance turbidity and TPC removal. The largest remaining particle fraction after alum flocculation was 3-10 microm in size, both Cryptosporidium and Giardia are found in this size range. Coagulation enhanced the removal of small size particles, a positive impact on reducing membrane fouling potential.

Alum Compounds↗
PubMed1988

Angiotensin converting enzyme inhibition and autoregulation of glomerular filtration.

The present study examines the influence of two angiotensin converting enzyme (ACE) inhibitors, perindopril and captopril, on renal plasma flow and on autoregulation of glomerular filtration in anaesthetized rats during reduction of renal perfusion pressure to 100, 90 and 80 mmHg. Groups 1 and 3 had a normal sodium intake (4 mmol/kg per day), while groups 2 and 4 were sodium depleted (0.5 mmol/kg per day) for 10 days. Renal perfusion pressure was measured before and after ACE inhibition in all groups. Groups 1 and 2 were given perindopril (0.3 mg/kg) and groups 3 and 4 were given captopril (3.0 mg/kg) intravenously. When renal perfusion pressure was reduced in group 1 following ACE inhibition with perindopril, the glomerular filtration rate remained unaltered. In group 3, captopril abolished autoregulation of the glomerular filtration rate, which decreased from 1.01 +/- 0.03 to 0.60 +/- 0.03 ml/min. Similarly, reduction in renal perfusion pressure was associated with an unaltered glomerular filtration rate in group 2, but in group 4 the glomerular filtration rate fell more significantly, from 0.89 +/- 0.06 to to 0.19 +/- 0.3 ml/min. Renal plasma flow decreased significantly in groups 1 and 3 during the renal perfusion pressure changes, both before and during ACE inhibition, but in groups 3 and 4 it remained relatively stable. These results indicate that ACE inhibition with captopril alters the normal autoregulation of the glomerular filtration rate, presumably by blocking the angiotensin II (Ang II) efferent arteriole vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

[Estimation of filtration variables in isolated rat lungs for evaluation of pulmonary microvascular permeability].

In order to evaluate the microvascular permeability of donor lungs, we calculated the filtration variables; K (reflection coefficient), simultaneously. For the calculation of filtration variables, the isolated rat lungs were kept in zone three conditions (pulmonary arterial pressure > pulmonary venous pressure > alveolar pressure). We used Krebs-Henseleit solution (K-H) with 6% bovine serum albumin for the perfusate, and maintained perfusion using a constant pressure circuit system. The pulmonary venous and alveolar pressures were maintained at 2.5 and 2.0 cmH2O, respectively, and pulmonary arterial pressure was set so that change in lung weight occurred. We increased both pulmonary arterial and venous pressures by 3 cmH2O simultaneously, and obtained the initial filtration rate. Then we diluted the perfusate with K-H to about half concentration, and obtained the initial filtration rate. We obtained values of filtration variables of K=4.55 mg.min-1.cm H2O-1.g-1], Ppmv=0.59 cmH2O, and sigma =0.617. These values agree with values from previous reports. Since these three filtration variables are interrelated, this method for simultaneous measurement is more accurate than independent measurements. The chief advantages of this method are that it does not require direct measurement of interstitial pressure or collection of lymph fluid, and all variables are obtained simultaneously. Using this method, the vascular permeability of isolated rat lungs, can be estimated.

Animals↗
PubMed1997

Kinetics of Permeate Flux Decline in Crossflow Membrane Filtration of Colloidal Suspensions.

A series of well-controlled membrane filtration experiments are performed to systematically investigate the dynamic behavior of permeate flux in crossflow membrane filtration of colloidal suspensions. Results are analyzed by a transient permeate flux model which includes an approximate closed-form analytical expression for the change of permeate flux with time. The model is based on a simplified particle mass balance for the early stages of crossflow filtration before a steady-state flux is attained, and Happel's cell model for the hydraulic resistance of the formed particle cake layer. The filtration experiments demonstrate that permeate flux declines faster with increasing feed particle concentration and transmembrane pressure and with a decrease in the particle size of the suspension. It is also shown that crossflow velocity (shear rate) has no effect on permeate flux at the transient stages of crossflow filtration. Pressure relaxation experiments indicate that the particle cake layer is reversible, implying no irreversible deposition (attachment) of particles onto the membrane surface or the accumulated (retained) particles. The experimental results are shown to be in very good agreement with the theoretical predictions, thus verifying the validity of the model for the transient permeate flux in crossflow filtration and the underlying assumptions in the derivation of the model. Copyright 1997 Academic Press.

Journal Article↗
PubMed2000

A Combined Pore Blockage and Cake Filtration Model for Protein Fouling during Microfiltration.

Previous studies of protein fouling during microfiltration have shown significant discrepancies between filtrate flux data and predictions of the classical pore blockage, pore constriction, and cake filtration models. A new mathematical model was developed for the filtrate flux which accounts for initial fouling due to pore blockage and subsequent fouling due to the growth of a protein cake or deposit over these initially blocked regions. The model explicitly accounts for the inhomogeneity in the cake layer thickness over different regions of the membrane arising from the time-dependent blockage of the pore surface. The model was shown to be in excellent agreement with experimental data obtained during the stirred cell filtration of bovine serum albumin solutions through polycarbonate track-etched microfiltration membranes over the entire course of the filtration. The model provides a smooth transition from the pore blockage to cake filtration regimes, eliminating the need to use different mathematical formulations to describe these two phenomena. In addition, the model provides the first quantitative explanation for some of the unusual observations reported previously in investigations of protein microfiltration. The results provide important insights into the underlying mechanisms of protein fouling during microfiltration. Copyright 2000 Academic Press.

Journal Article↗
PubMed1996

Pulmonary vascular filtration of starch-based macromolecules: effects on lung fluid balance.

BACKGROUND: Pulmonary edema is a complication of critical care fluid management that may be restricted by the use of oncotically effective resuscitation fluids. Potentially beneficial oncotic properties of starch-based plasma volume expanders such as hetastarch (Het), pentafraction (Pen), and Dextran-70 (Dex) may be compromised by their broad range of molecular masses, some of which are small enough to filter from the circulation. Leakage of these molecules into the pulmonary interstitium may limit their oncotic effectiveness and enhance fluid filtration. We measured the filtration of these three resuscitation solutions into lung lymph to evaluate their oncotic contribution to pulmonary edema formation. MATERIALS AND METHODS: Unanesthetized euvolemic adult sheep, prepared with chronic lung lymph fistulae, underwent plasma volume expansion with Het (n = 6), Pen (n = 6), or Dex (n = 6 ) (6%, 35 ml/kg/90 min). Oncotic effectiveness was determined by measuring plasma and lymph oncotic pressures and the oncotic pressures contributed by each starch. Pulmonary hydrostatic pressures and lung lymph flows (Q(L)) were also measured. Results are expressed as means +/- SEM. Comparisons were made by two-factor analysis of variance. RESULTS: Dex contributed 9.0 +/- 0.9 mmHg to the plasma oncotic pressure, significantly more than Het and Pen (5.3 +/- 0.6, 6.5 +/- 0.6 mmHg, respectively). However, Dex filtration also contributed 6.1 +/- 0.5 mmHg to the lymph oncotic pressure, compared to 3.1 +/- 0.3 and 4.7 +/- 0.5 mmHg for Het and Pen, respectively (P < or = 0.05). Dex, Het, and Pen raised Q(L) over baseline by 7.7 +/- 1.5, 4.3 +/- 1.0, and 3.2 +/- 0.7 ml/30 min, respectively (P < or = 0.05). Dex increased Q(L) significantly more than Het or Pen. CONCLUSIONS: Pen and Het demonstrated greater oncotic effectiveness because of restricted plasma-to-lymph macromolecular filtration and limited transvascular fluid flux. By comparison, Dex filtered rapidly and increased transvascular fluid filtration. Pen appears to possess filtration properties that optimize critical care fluid management compared to currently available colloid solutions such as Het and Dex.

Animals↗