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Comparison of three methods of glomerular filtration rate measurement with and without captopril pretreatment in groups of patients with left ventricular dysfunction.

Methods of glomerular filtration rate measurement by 51Cr EDTA elimination, inulin clearance and creatinine clearance were compared with and without captopril pretreatment in 10 chronic heart failure patients and in 20 patients after transmural myocardial infarction. Strong intermethod correlations were found in chronic heart failure patients (EDTA: inulin r = 0.87; EDTA: creatinine r = 0.84; inulin: creatinine r = 0.9; all P less than 0.00001). Despite this, substantial absolute differences were observed in results obtained by different techniques. In particular, creatinine clearance significantly overestimated both 51Cr EDTA (18.0 +/- 18.4 ml.min-1, mean difference +/- SD, P less than 0.001) and inulin clearance (26.8 +/- 17.0 ml.min-1, P less than 0.001). The slight reduction in 51Cr EDTA elimination on captopril versus placebo (-8.3 +/- 9.2 ml.min-1, P less than 0.05) was related to a similar treatment difference in inulin clearance (r = 0.67, p = 0.03), but changes observed by either method were unrelated to captopril-induced changes in creatinine clearance. Thus, creatinine clearance is an unsatisfactory means of assessing the effect of angiotensin converting enzyme inhibition on glomerular filtration rate in chronic heart failure. In the post-myocardial infarction group, correlations between methods were poorer (EDTA: inulin r = 0.79; EDTA: creatinine r = 0.76; inulin: creatinine r = 0.67). In this group no significant effect of captopril on glomerular filtration rate was detected by any technique. As compared to the chronic heart failure patients, the weaker relationship between techniques post-myocardial infarction may be related to interference by thrombolytic or aspirin treatment.

Captopril↗

Expressing glomerular filtration rate in terms of extracellular fluid volume.

Glomerular filtration rate (GFR) is routinely calculated from the second exponential of the bi-exponential plasma clearance of filtration markers such as Cr-51 EDTA and Tc-99m DTPA. By ignoring the first exponential, true GFR is overestimated, an error which increases with increasing GFR. The rate constant, lambda 2, of the second exponential represents the rate at which glomerular filtration 'turns over' the extracellular fluid (ECF) and so closely approximates GFR/ECF volume. Again, the error in the estimation of this ratio increases with increasing GFR, although in this case it underestimates the true ratio. Expressing GFR in terms of ECF volume, rather than in terms of body surface area, offers considerable technical and physiological advantages. The relationship between GFR/ECF volume and lambda 2, over a wide range of renal function, expressed as a second order polynomial, was GFR/ECF volume = -0.093 + 1.06 lambda 2 + 0.009 lambda 2(2) ml.min-1.l-1. The corresponding relationship between 'true' GFR (C1) and approximate GFR (i.e. based only on the second exponential--C2) was C1 = -0.58 + 1.012C2 -0.0011 C2(2) ml.min-1 For any level of renal function, the error in GFR/ECF volume, expressed as lambda 2, is less than the error in GFR expressed as C2. Since GFR may change as a direct result of a change in ECF volume, it is physiologically more relevant, and technically very much easier, to express GFR in terms of ECF volume rather than body surface area.

Adult↗

Effects of hypertonic saline, mannitol, and urea with regard to absorption and rebound filtration in cat skeletal muscle.

OBJECTIVE: To study the effects of the hypertonic solutions 15% mannitol, 3% and 7.5% saline, and 30% urea at clinically relevant plasma concentrations with regard to absorption and rebound effects on tissue volume in skeletal muscle. DESIGN: A prospective, experimental study. SETTING: University laboratory. SUBJECTS: Twenty-eight anesthetized cats. INTERVENTIONS: The study was performed on an autoperfused and denervated cat calf muscle placed in a fluid-filled plethysmograph. Muscle volume changes and capillary filtration coefficient (reflecting capillary fluid conductivity) were measured before, during, and after intra-arterial infusion (4 mL/hr) of the hypertonic solutions. Mannitol and 3% saline have the same osmolality and were compared specifically in an attempt to distinguish osmotic effects from those specific to the compound. MEASUREMENTS AND MAIN RESULTS: All solutions reduced muscle volume during the infusion (p < .05). The maximum volume reduction persisted after 2 hrs of infusion for 3% and 7.5% saline, whereas there was a tendency for volume recovery during the urea infusion and a complete recovery back to control for mannitol. After discontinuation of the infusions, the muscle volume increased for all four solutions, stabilizing at the initial control for 3% and 7.5% saline, whereas it increased to levels above control for mannitol and urea (p < .05). Capillary filtration coefficient was increased by hypertonic saline (p < .05) but was unaffected by mannitol and urea. CONCLUSIONS: The effectiveness of a hypertonic solution in reducing tissue volume and its tendency to cause a rebound volume increase depends not only on the osmolality of the solution. Hypertonic saline may in the long run be superior to mannitol and urea to increase plasma volume or decrease tissue volume of an organ, because it lacks rebound effects. Alterations in capillary filtration coefficient (fluid conductivity) may reflect volume changes of the capillary endothelial cell and thereby differences in cell membrane permeability for the hypertonic solutions, also consistent with the obtained differences in tissue volume effects.

Animals↗

Estimation of glomerular filtration rate from low-dose injection of iohexol and a single blood sample.

Clearance of a small dose of iohexol (7 g I) was compared with the glomerular filtration rate (GFR) marker 51Cr EDTA in 11 healthy volunteers. The two tracers were injected simultaneously. The plasma concentration of iohexol was measured with x-ray fluorescence technique. Glomerular filtration rate was determined using blood samples drawn three and four hours after injection. An excellent correlation (0.92 less than r less than 0.97) between iohexol clearance and 51Cr EDTA clearance was found. Glomerular filtration rate can be reliably determined with a low dose of iohexol and a single blood sample obtained three hours after the injection in persons with normal serum creatinine. This new method is a good alternative to the methods using radiopharmaceuticals; it causes no radioactive burden to the patients, increases patient comfort, reduces costs, and requires no special license.

Adult↗

Verapamil alters the relationship between renal perfusion pressure and glomerular filtration rate and renin release: the mechanism of the antihypertensive effect.

The renal hemodynamic and renin release responses to verapamil were analyzed in order to determine if the antihypertensive action of the calcium entry blocker could be due to its renal effects. Hemodynamic and renin release measurements were compared in a control group of anesthetized rabbits (N = 9) and in a group of rabbits given verapamil (N = 10) (200 micrograms/kg i.v. initially, 4 micrograms/kg/min thereafter) starting 30 min before data collection. Measurements were made over a range of controlled renal perfusion pressure from 100 to 40 mm Hg. The renal blood flow (RBF) at 100 mm Hg of the verapamil-treated group was 18% greater than (p less than 0.02) that of the control group, while the glomerular filtration rate (GFR) was 51% greater than (p less than 0.001) that of the control group. RBF and GFR autoregulation was highly effective in the control group down to 80 mm Hg, but both variables were poorly regulated in the verapamil group. The filtration fraction of the treated group was 36.9 +/- 1.5% versus 28.5 +/- 1.6% in the control group (p less than 0.003) at 100 mm Hg, and the filtration fraction of the treated group remained significantly greater down to 40 mm Hg. Renin release rates of the two groups were similar at the 100 mm Hg pressure level, but the increase in release due to the progressive reduction in perfusion pressure was significantly greater in the treated group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Colloid infusions reduce glomerular filtration in resuscitated burn victims.

OBJECTIVE: Colloids are used clinically to minimize edema yet may have detrimental consequences on glomerular filtration. The purpose of this study is to assess the renal and hormonal effects of colloid supplementation in the fluid resuscitation of burn victims. DESIGN: Analytic cohort study. MATERIAL AND METHODS: Immediately following their 24 hour post-burn fluid resuscitation with Ringer's lactate, six burn patients (% total body surface area burn 30-57%) were given primed, continuous infusions of inulin and p-aminohippuric acid for 6 hours. Albumin (25% solution, 3 mL/kg/h) was given for the final 4 hours of study. MEASUREMENTS AND MAIN RESULTS: Albumin infusion increased plasma volume by 37%; however, glomerular filtration rate decreased by 32% (p < 0.05). There was no significant change in urine output, sodium excretion, or effective renal plasma flow. Plasma volume expansion with albumin normalized elevated basal levels of aldosterone and plasma renin activity. CONCLUSIONS: These findings illustrate that despite substantially increasing plasma volume, colloid infusions reduce glomerular filtration and may limit any associated diuresis. Furthermore, this study demonstrates that hormonal regulation of blood volume remains intact after moderate burn injury.

Adult↗

Filtration of particulates in the human nose.

This report reviews the current theories on the deposition of inhaled particulates in the human nose. The inhalation of particulates represents a challenge to the upper respiratory tract. The concentration of airborne particulates and pollutants varies between occupational and nonoccupational exposure. Regional deposition of potentially hazardous inhaled material determines the local and systemic toxicity. In vitro experiments using casting and molding techniques with water dye models or laser Doppler anemometry indicate that nasal airflow is determined by the size of the nasal valve and the turbinates. The main airstream during inspiration passes through the lower nasal passage. Filtration capacity of the human nose can be expressed mathematically or experimentally. In vivo experiments applying monodisperse or polydisperse aerosols during single or multiple respiratory cycles have shown by using microscopic or laser-optic identification that particles larger than 3 microm have a maximum deposition in the anterior part of the nose (nasal valve). Particles smaller than 3 microm and larger than 0.5 microm are filtered by the nasal mucosa and transported by cilia propulsion to the nasopharynx. The filtration for particles smaller than 0.5 microm is low. They seem to pass easily into the lower respiratory tract. This knowledge has an impact on nasal septal surgery and rhinoplasty. By influencing the structure of the nasal valve and the lower turbinates, the filtration capacity of the nose can be significantly decreased.

Aerosols↗

The microbiologic effect of gas filtration.

BACKGROUND: Air and expansile gases commonly are injected into the eye in both vitreoretinal surgery and anterior segment surgery. Although the halogenated gases are filtered routinely before injection, air often is not prepared in this manner. This study was designed to investigate the effect of filtration on the microbiology of gas mixtures. METHODS: Two separate studies were conducted, one examining medical grade perfluoropropane gas (C3F8), and the other evaluating air collected from an ophthalmic operating room or emergency room. Aliquots of air or gas were collected through a 0.22-micron filter before and after filtration. The filter discs were cultured for bacterial and fungal organisms. RESULTS: Of 514 samples collected, none grew either bacterial or fungal organisms. There was no difference with regard to recovered microbes between filtered and unfiltered air or C3F8, nor was there a difference between operating room air and emergency room air. Positive controls using aerosolized microorganisms yielded heavy growth. CONCLUSION: Based on results obtained in this study and available information on the concentration of airborne microbes, the microbiologic effect of gas filtration is of little significance for volumes routinely injected in ophthalmic surgery.

Air↗

Application of newer clearance techniques for the determination of glomerular filtration rate.

Glomerular filtration rate (GFR) is the standard measure of renal function and is critical for the management of renal diseases. Rigorous assessment of GFR requires the measurement of renal clearance of a filtration marker, such as inulin. This method, however, is not suitable for routine clinical practice. Labelled compounds as alternative filtration markers provide accurate and precise GFR measurement, but their use may be limited for safety reasons. Thus investigators have proposed clearance procedures using minute doses of non-radioactive contrast agents, including iothalamate and iohexol. Their renal clearance provides similar accuracy as inulin clearance in GFR estimation, but the need of urine collection again poses certain limitations to the procedure. Thus, plasma clearance of suitable exogenous markers, such X-ray contrast media, has been suggested for measuring renal function, in which the elimination rate of the tracer after a single intravenous injection is evaluated. Plasma clearance of these markers estimated by multiple blood samples provides precise information, but repeated sampling makes this method cumbersome. Abbreviated kinetic profiles have been proposed to predict GFR from the plasma disappearance curve. The simplified method that uses a one-compartment model corrected by the Bröchner-Mortensen formula gives an excellent correlation with inulin clearance and is currently employed for measuring GFR in multi-centre clinical trials.

Contrast Media↗

Apical leakage of resin based root canal sealers with a new computerized fluid filtration meter.

In this in vitro study, the apical leakage of three root-canal sealers: AH Plus, Diaket, and EndoREZ was evaluated using a new computerized fluid filtration meter. Forty-five extracted human premolar teeth with single root and canal were used. The coronal part of each tooth was removed and the root canals were prepared using GT Rotary files and crown-down technique. The roots were randomly divided into three groups of 15 samples, filled with one of the test materials and gutta-percha cones by the cold lateral condensation technique and were stored at 37 degrees C and 100% humidity for 7 days. One-week later, apical parts of roots of 10 +/- 0.05 mm were attached to computerized fluid filtration meter. Apical leakage quantity was determined as microl/cmH(2)O/min(-1). Statistical analysis indicated that root fillings with Diaket in combination with cold lateral condensation technique showed lower apical leakage than the others (p < 0.05). In addition, this new computerized fluid filtration meter allowed quantitative measurement of leakage easily. As it is a newly developed device to measure apical leakage of endodontic sealers, the reliability of it needed to be tested.

Bismuth↗

Renal reserve filtration capacity before and after kidney donation.

Renal reserve filtration capacity (RRFC) was investigated in 20 kidney donors before and within 3 months after uninephrectomy. Glomerular filtration rate (GFR) was measured by the clearance of 125I-iothalamate, and effective renal plasma flow (ERPF) was determined by the clearance of 131I-hippurate. RRFC was tested by infusion of a low dose of dopamine, by intravenous administration of an amino acid solution and, finally, by combined infusion of amino acids and low-dose dopamine. After kidney donation, the median value of the GFR was 65% of its initial value. The median value of the ERPF was 69% of its value before uninephrectomy. The filtration fraction declined significantly from 0.251 to 0.238 (medians; P less than 0.02). Median values for dopamine-induced increases in GFR were 13.8% before and 5.3% after kidney donation (P less than 0.005). Infusion of amino acids led to an increase in GFR of 11.2% before and 9.6% after donation (NS). During combined infusion, the median values for the increases in GFR were 20.0% before and 12.6% after uninephrectomy (P less than 0.02). Median changes in ERPF before and after kidney donation were 33.4 vs. 23.0% during dopamine infusion (P less than 0.005), 10.0 vs. 8.3% during amino acid infusion (NS), and 36.2 vs. 24.3% during the combined infusion of dopamine and amino acids (P less than 0.02). Infusion of dopamine induces a decrease in renal vascular resistance, resulting in a rise in glomerular blood flow. Since RRFC tested by means of dopamine infusion was significantly decreased after kidney donation, it is concluded that glomerular hyperfiltration after kidney donation is at least partially due to a rise in glomerular blood flow.

Amino Acids↗

Adsorption of anaphylatoxins and platelet-specific proteins by filtration of platelet concentrates with a polyester leukocyte reduction filter.

Anaphylatoxins generated during storage of platelet concentrates (PCs) may potentially have side effects on platelet transfusion. We evaluated the anaphylatoxin-scavenging abilities of white blood cell reduction filters. Among the commercially available filters for PCs, one made with polyester fiber (PL50) dramatically adsorbed C3a and C4a anaphylatoxins to the respective mean level of 1,721-208 ng/ml and 1,240-141 ng/ml in 3-day-old PCs. C3a and C4a were measured as the native and des Arg form of each complement by radioimmunoassay. C3a and C4a anaphylatoxins in the supernatant plasma fraction from 3-day-old PC again decreased from 1,136 to 114 ng/ml and from 1,086 to 65 ng/ml, respectively. The filter also adsorbed 85% of platelet factor 4 (PF4) and 31% of beta-thromboglobulin (beta-TG), which had been released from platelets into the plasma during storage. The plasma levels of adhesive proteins such as fibronectin, fibrinogen, and von Willebrand factor, and plasma lactate dehydrogenase activity did not decrease after filtration. Another polyester filter (PL5A), on the other hand, significantly increased C3a and C4a levels with filtration. In addition, there was no PF4 adsorption ability during the filtration. The filters for red cells (RC50, BPF4, and R500A) had no anaphylatoxin adsorption capabilities. The observed specific adsorption of anaphylatoxins might be attributed to the electrostatic force between the positively charged anaphylatoxins with high pI and the possibly negatively charged filter membranes. Since PF4 and beta-TG have positively charged moieties in the C-terminal position, the same adsorption mechanism might operate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗

Influence of blood prestorage conditions and white blood cell filtration on the bacterial load of blood deliberately inoculated with Gram-positive and Gram-negative pathogens.

BACKGROUND AND OBJECTIVES: Currently, the bacterial contamination of blood constitutes one of the major infectious risks of transfusion. The aim of this study was to evaluate the bactericidal effect of blood on various bacterial species and to determine the influence of prestorage conditions and white blood cell (WBC) filtration on the reduction of the bacterial load in isolated red blood cells (RBCs). MATERIALS AND METHODS: The growth kinetics of eight different species of bacteria were studied at 20 degrees C in deliberately contaminated RBC units. Further experiments evaluated the effect of prestorage conditions and WBC filtration on the viability of two model bacteria (Klebsiella oxytoca and Staphylococcus epidermidis) in comparison to previous results obtained with Yersinia enterocolitica. RESULTS: For bacteria susceptible to the bactericidal effect of blood (mainly Gram-negative rods), a reduction of the bacterial load was obtained within 2 h of prestorage at 20 degrees C. When the prestorage period was prolonged beyond 3 h at 20 degrees C, rapid growth was observed with some Enterobacteriaceae. Whereas WBC filtration reduced dramatically the viability of Y. enterocolitica, it had only a minimal effect on the viability of S. epidermidis and K. oxytoca. However, the two latter species of bacteria did not survive prolonged storage at 4 degrees C. CONCLUSIONS: Experiments conducted under realistic conditions are needed to determine whether it would be worthwhile recommending the rapid storage of RBCs at 4 degrees C after WBC reduction of the blood product.

Bacteriological Techniques↗

Comparisons of sperm quality, morphometry and function among human sperm populations recovered via SpermPrep II filtration, swim-up and Percoll density gradient methods.

The purpose of this study was to compare the morphology/morphometry and fertilizing capacity of human spermatozoa recovered via swim-up method, Percoll density gradient method, and SpermPrep II filtration method. Thirty-three ejaculates were equally divided into 2 aliquots. Aliquot 1 was processed via the direct swim-up method, whereas aliquot 2 was filtered via a SpermPrep II column. The Percoll density gradient method was compared with the SpermPrep II method in a similar protocol using 43 ejaculates. Sperm populations recovered via the SpermPrep II filtration method showed significantly higher hypoosmotic swelling test results, acrosin profiles, and percentage of hyperactivated spermatozoa than sperm fractions recovered by the swim-up method. Furthermore, significant differences were found in most of sperm morphometric parameters between the above sperm populations. However, sperm fractions recovered via the SpermPrep II method did not show significantly different values for these same tests and for most of sperm morphometric parameters compared to the Percoll density gradient method. These results suggest that the SpermPrep II filtration and Percoll density gradient method are equally efficient in isolating sperm subpopulations with better functional parameters than the swimup method.

Cell Separation↗

Filtration of human seminal specimens using LeukoSorb leukocyte-retention medium.

OBJECTIVE: To compare LeukoSorb filtration with Percoll centrifugation in preparing sperm. METHODS: Each of 26 human seminal specimens were analyzed before and after two preparation methods. RESULTS: In normospermic specimens (n = 11), LeukoSorb produced higher results than Percoll did with regard to mean percentage of motility (72.7% vs 59.2%), total swollen sperm in a hypo-osmotic swelling test (84.8% vs 59.0%), (g)-type swollen sperm (37.8% vs 23.4%) and tail abnormality (20.4% vs 10.1%). In asthenospermic specimens (n = 15), LeukoSorb produced higher results than Percoll did with regard to mean percentage of motile sperm recovery (22.2% vs 10.1%), motility (46.9% vs 23.2%), viability (75.6% vs 54.7%), total swollen sperm (84.8% vs 59.0%) and tail abnormality (42.2% vs 24.3%), although the mean percentage of head abnormality was lower with LeukoSorb than with Percoll (30.6% vs 40.2%) vs 40.2%). In pyospermic specimens (n = 10), the mean concentration of round cells after LeukoSorb decreased significantly more than with Percoll (p = 0.029). The filtration time correlated with the total sperm concentration. CONCLUSION: LeukoSorb filtration is useful for preparing asthenospermic and pyospermic seminal specimens.

Centrifugation↗

Short-term inhibition of prostaglandin synthesis has no effect on the elevated glomerular filtration rate of early insulin-dependent diabetes.

Glomerular filtration rate and renal plasma flow (constant infusion technique using 125I-iothalamate and 131I-hippuran) were measured twice within a 1-week interval in nine young males with insulin-dependent diabetes of short duration (2-5 years). The study was performed in a randomized double-blind design, with the patients receiving either indomethacin (150 mg/day) or placebo for 3 days before the study. Measures of metabolic control did not change. No differences were found in glomerular filtration rate (144 +/- 9 versus 144 +/- 9 ml/min X 1.73 m2, mean +/- S.E.M.) or renal plasma flow (579 +/- 43 versus 560 +/- 52 ml/min X 1.73 m2), when measured during placebo or indomethacin treatment, respectively. It is concluded that the steady-state enhancement of glomerular filtration rate and renal plasma flow found in early insulin-dependent diabetes is not due to an excessive activity of the prostaglandin system.

Adult↗

Evaluation of Cryptosporidium parvum oocyst recovery efficiencies from various filtration cartridges by electrochemiluminescence assays.

AIMS: To evaluate four types of filtration cartridges for their capacities, efficiency for capture and release of Cryptosporidium parvum oocysts for detection. METHODS AND RESULTS: Filtration cartridges included in this evaluation were IDEXX Filta-Max, Gelman Envirochek HV, Corning CrypTest, and Filterite Sigma+. Various dosages of C. parvum oocysts were spiked into water samples with a wide range of turbidity (10-50 NTU). Electrochemiluminescence assays were employed to enumerate viable or total number of C. parvum oocysts in these eluates. Among the cartridges tested, Filta-Max consistently showed higher oocyst recovery efficiency, especially with large volume, highly turbid water samples. CONCLUSIONS: Filta-Max filter is the best performer because of its higher oocyst recovery efficiency. SIGNIFICANCE AND IMPACT OF THE STUDY: The overall sensitivities of various C. parvum oocyst detection assays in water samples can be improved if highly efficient oocyst recovery filtration cartridges such as Filta-Max are incorporated in sample preparation.

Animals↗

Glomerular filtration and saturable absorption of iohexol in the rat isolated perfused kidney.

1. The renal handling of iohexol was examined in the rat isolated perfused kidney (IPK) over a perfusate concentration range of 5-20 micrograms ml-1. 2. At a concentration of 5 micrograms ml-1, a ratio of renal clearance over clearance by glomerular filtration (ClR/GF) of 0.63 +/- 0.06 could be determined. This ratio increased until 1.02 +/- 0.06 at 20 micrograms ml-1, indicating that a saturable mechanism is involved in the luminal disappearance of the drug. 3. Pretreatment of the kidneys with polylysine, probenecid or diatrizoate resulted in a significantly enhanced clearance of iohexol, probably due to inhibition of membrane binding. Renal clearance data were fitted to a kinetic model including filtration into the primary urine followed by saturable absorption at the luminal membrane. An absorption constant, KA, of 7.3 +/- 1.3 micrograms ml-1, and a maximum rate of absorption, VA,Max, of 1.4 +/- 0.1 micrograms min-1 were determined. 4. Iohexol accumulated in kidney tissue, reaching a concentration of 2 to 7.5 times the perfusate concentration. In freshly isolated proximal tubular cells and kidney cortex mitochondria, iohexol reduced the uncoupled respiratory rate at a concentration comparable to the highest tissue concentration found in the IPK. 5. In conclusion, iohexol is not only filtered by the kidney but also reabsorbed via a saturable mechanism, which results in tubular accumulation. Intracellularly sequestered iohexol may affect mitochondrial oxidative metabolism. Our results indicate that iohexol is not a true filtration marker.

Animals↗