Mass Transfer Area Coefficients in Children

1994 ◽  
Vol 14 (1) ◽  
pp. 30-33 ◽  
Author(s):  
Denis F. Geary ◽  
Elizabeth A. Harvey ◽  
J. Williamson Balfe
Keyword(s):  
Mass Transfer ◽  
Body Weight ◽  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Surface Area ◽  
Peritoneal Surface ◽  
Unit Body Weight ◽  
Rapid Transport ◽  
Sick Children

Objective Measurement of mass transfer area coefficients (MTAC) in children of different sizes to determine if solute transport varies with age and to compare with published adult values. Design Mass transfer area coefficients calculated from prospectively collected data in 28 selected patients. Participants All children starting maintenance peritoneal dialysis at the Hospital for Sick Children. Selected patients were also studied if hospitalized for unrelated reasons. Results Mean MTAC values for creatinine and glucose were 4.0 and 4.5 mL/min, respectively, both considerably lower than adult values. When scaled per 70 kg body weight, these results were greater, and when scaled per 1.73 m2 surface area, they were lower than reported adult values. The MTAC/kg body weight was inversely correlated to age. Conclusions Solute transport in children is directly related to age and does not approach adult values until later childhood. However, more rapid transport per unit body weight is observed in children and may reflect an increased effective peritoneal surface area.

scholarly journals Ultrafiltration Failure in Peritoneal Dialysis: A Pathophysiologic Approach

2015 ◽  
Vol 39 (1-3) ◽  
pp. 70-73 ◽  
Author(s):  
Isaac Teitelbaum
Keyword(s):  
Peritoneal Dialysis ◽  
Surface Area ◽  
Free Water ◽  
Fluid Loss ◽  
Free Water Clearance ◽  
Peritoneal Surface ◽  
Ultrafiltration Failure ◽  
Rapid Transport ◽  
Technique Failure ◽  
Sodium Sieving

Background: Ultrafiltration failure is a significant cause of technique failure for peritoneal dialysis and subsequent transfer to hemodialysis. Summary: Ultrafiltration failure is defined as failure to achieve at least 400 ml of net ultrafiltration during a 4 h dwell using 4.25% dextrose. Four major causes of ultrafiltration failure have been described. A highly effective peritoneal surface area is characterized by transition to a very rapid transport state with D/P creatinine >0.81. Low osmotic conductance to glucose is characterized by attenuation of sodium sieving and decreased peritoneal free water clearance to <26% of total ultrafiltration in the first hour of a dwell. Low effective peritoneal surface area manifests with decreases in the transport of both solute and water. A high total peritoneal fluid loss rate is the most difficult to diagnose clinically; failure to achieve ultrafiltration with an 8-10 h icodextrin dwell may provide a clue to diagnosis. Key Messages: Knowledge of the specific pathophysiology of the various causes of ultrafiltration failure will aid in the diagnosis thereof.

scholarly journals Role of the liver in small-solute transport during peritoneal dialysis.

1994 ◽  
Vol 5 (1) ◽  
pp. 116-120
Author(s):  
M F Flessner ◽  
R L Dedrick
Keyword(s):  
Mass Transfer ◽  
Peritoneal Dialysis ◽  
Surface Area ◽  
Peritoneal Cavity ◽  
Distributed Model ◽  
Blood Capillaries ◽  
Peritoneal Surface ◽  
Small Solute ◽  
Good Agreement

Peritoneal dialysis (PD) is dependent on the transport of water and solutes from the blood capillaries within the tissues that surround the peritoneal cavity. Because of their large blood supply and surface area, the viscera have been considered the most important tissues for PD transport. In animals, however, removal of the gastrointestinal tract decreases PD small-solute mass transfer by only 10 to 27%. To investigate the theoretical basis for these observations, a distributed model of peritoneal transport was extended to take into account the transport characteristics of four tissue groups that surround the cavity: the liver, the hollow viscera, the abdominal wall, and the diaphragm. The mass transfer-area coefficient (MTAC) of sucrose for each tissue was calculated from the following: MTAC = ([D(pa)]0.5)A, where D is the effective solute interstitial diffusivity, pa is the solute transcapillary permeability-area per unit tissue volume, and A is the apparent peritoneal surface area of the tissue. Our results for the adult human predict that the MTAC for the liver is comparable to that of all of the other viscera and makes up 43% of the total MTAC for the peritoneal cavity. The predicted MTAC is 4 cm3/min (plasma) or 6 cm3/min (blood), in good agreement with published values. It is concluded that the liver is responsible for a major portion of the small-solute MTAC. This also explains the earlier observations in eviscerated animals whose PD transport was likely preserved by intact livers.

Peritoneal Transport Characteristics of Water, Low-Molecular Weight Solutes and Proteins during Long Term Continuous Ambulatory Peritoneal Dialysis

1986 ◽  
Vol 6 (2) ◽  
pp. 61-65 ◽  
Author(s):  
Raymond T. Krediet ◽  
Elisabeth W. Boeschoten ◽  
Floris M.J. Zuyderhoudt ◽  
Lambertus Arisz
Keyword(s):  
Mass Transfer ◽  
Molecular Weight ◽  
Peritoneal Dialysis ◽  
Surface Area ◽  
Low Molecular Weight ◽  
Glucose Kinetics ◽  
Peritoneal Surface ◽  
Peritoneal Transport ◽  
Peritoneal Permeability

Peritoneal transport of water, low-molecular-weight solutes and proteins was studied on 75 occasions in 38 CAPD patients. Maximal ultrafiltration capacity decreased with time on CAPD, while there was an increase in the number of hypertonic bags used and the peritoneal absorption of glucose. A relationship was found between maximal ultrafiltration capacity and glucose kinetics. The duration of CAPD was longer in the patients with poor ultrafiltration, while they had a faster transport of glucose and creatinine, but not of proteins. In the group as a whole, no obvious changes were found in the mass transfer area coefficients of urea, creatinine and glucose, nor in the clearances of albumin and IgG. In the five patients with severe ultrafiltration loss, we found evidence of either decreased or increased peritoneal solute transport. Contrasting findings in transport of small solutes and proteins may reflect increased effective peritoneal surface area combined with decreased peritoneal permeability.

Relationship of Demographic, Dietary, and Clinical Factors to the Hydration Status of Patients on Peritoneal Dialysis

2004 ◽  
Vol 24 (3) ◽  
pp. 231-239 ◽  
Author(s):  
Ramzana B. Asghar ◽  
Sandra Green ◽  
Barbara Engel ◽  
Simon J. Davies
Keyword(s):  
Body Weight ◽  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Extracellular Fluid ◽  
Fat Free Mass ◽  
Single Frequency ◽  
Hydration Status ◽  
Clinical Factors ◽  
Membrane Function ◽  
Fluid Removal

Objectives To establish which clinical factors are associated with an increased proportion of extracellular fluid (ECF) in peritoneal dialysis (PD) patients. Design A single-center, cross-sectional analysis of 68 stable PD patients. Method Bioelectrical impedance measurements (RJL, single frequency; RJL Systems, Clinton, Michigan, USA) of resistance and reactance were used to determine the proportion of ECF comprising total body water (TBW) in 68 stable PD patients attending for routine clearance and membrane studies. All patients underwent detailed dietetic, adequacy, and membrane function tests. Blood pressure and antihypertensive requirements were also documented. Results Significant gender differences in body composition were observed, such that women had lower absolute TBW and fat-free mass per kilogram body weight, but proportionately more ECF for a given TBW, mean ECF:TBW 0.5 ± 0.03 versus 0.44 ± 0.05, p < 0.005. In view of this, patients were split into two groups, defined as “over-” or “normally” hydrated, either by using the single discriminator (median ECF:TBW = 0.47) for the whole population, which resulted in groups distorted by gender, or by using different discriminators according to gender (women: 0.49, men 0.45). In both analyses, overhydrated patients were older, had significantly lower plasma albumin, less total fluid removal per kilogram body weight, and higher peritoneal solute transport. When split by a single discriminator, the overhydrated patients had lower sodium removal and significantly less intracellular fluid volume due to an excess of women in this group who also had less residual function and had been on dialysis longer. Using gender-specific discrimination, overhydrated patients were heavier due to expansion of the ECF volume: 20 ± 4.1 L versus 16 ± 3.3 L, p < 0.001. Stepwise multivariate analysis found age ( p = 0.001), albumin ( p = 0.009), and fluid losses per kilogram body weight ( p = 0.025) to be independent predictors of gender-adjusted hydration status. Sodium intake did not vary according to hydration status. Conclusion Gender influences the assessment of hydration status of PD patients when employing bioimpedance, such that women tend to have more ECF. Taking this into account, age, albumin, and achieved fluid removal appear to be independently associated with hydration status, whereas peritoneal solute transport is not. Advice on dietary sodium should take account of hydration status and achievable losses.

The Influence of Peritoneal Surface Area on Dialysis Adequacy

2005 ◽  
Vol 25 (3_suppl) ◽  
pp. 137-140 ◽  
Author(s):  
Michel Fischbach ◽  
Céline Dheu ◽  
Pauline Helms ◽  
Joëlle Terzic ◽  
Anne Cécile Michallat ◽  
...  
Keyword(s):  
Peritoneal Dialysis ◽  
Surface Area ◽  
Contact Area ◽  
Peritoneal Membrane ◽  
Dialysis Adequacy ◽  
Peritoneal Surface ◽  
Vascular Area ◽  
Fill Volume ◽  
Peritoneal Dialysis Fluid ◽  
Dialysis Fluids

In children, the prescription of peritoneal dialysis is based mainly on the choice of the peritoneal dialysis fluid, the intraperitoneal fill volume (mL/m2 body surface area (BSA)], and the contact time. The working mode of the peritoneal membrane as a dialysis membrane is more related to a dynamic complex structure than to a static hemodialyzer. Thus, the peritoneal surface area impacts on dialysis adequacy. In fact, the peritoneal surface area may be viewed as composed of three exchange entities: the anatomic area, the contact area, and the vascular area. First, in infants, the anatomic area appears to be twofold larger than in adults when expressed per kilogram body weight. On the other hand, the anatomic area becomes independent of age when expressed per square meter BSA. Therefore, scaling of the intraperitoneal fill volume by BSA (m2) is necessary to prevent a too low ratio of fill volume to exchange area, which would result in a functional “hyperpermeable” peritoneal exchange. Second, the contact area, also called the wetted membrane, is only a portion of the anatomic area, representing 30% to 60% of this area in humans, as measured by computed tomography. Both posture and fill volume may affect the extent of recruitment of contact area. Finally, the vascular area is influenced by the availability of both the anatomic area and the recruited contact area. This surface is governed essentially by both peritoneal vascular perfusion, represented by the mesenteric vascular flow and, hence, by the number of perfused capillaries available for exchange. This vascular area is dynamically affected by different factors, such as composition of the peritoneal fluid, the fill volume, and the production of inflammatory agents. Peritoneal dialysis fluids that will be developed in the future for children should allow an optimization of the fill volume owing to a better tolerance in terms of lower achieved intraperitoneal pressure for a given fill volume. Moreover, future peritoneal dialysis fluids should protect the peritoneal membrane from hyperperfusion (lower glucose degradation products).

In Vivo Peritoneal Surface Area Measurement in Rats by Micro-Computed Tomography (μCT)

2008 ◽  
Vol 28 (2) ◽  
pp. 188-194 ◽  
Author(s):  
Elodie Breton ◽  
Philippe Choquet ◽  
Laure Bergua ◽  
Mariette Barthelmebs ◽  
Börje Haraldsson ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Body Weight ◽  
Contrast Agent ◽  
Surface Area ◽  
Area Measurement ◽  
Micro Computed Tomography ◽  
Peritoneal Surface ◽  
Iodinated Contrast ◽  
Fill Volume

Peritoneal dialysis (PD) uses the dynamic dialysis properties of the peritoneal membrane. The fraction of the anatomic peritoneal surface area (PSA) recruited is of importance for maximizing exchanges and is potentially impacted by parameters such as fill volume. We describe an in vivo assessment of the contact surface area by micro-computed tomography (μCT) using an iodinated contrast medium added to the PD fluid, a contrast agent presumed without surfactant property. In the isotropic volume (reconstructed voxel size 186 μm x 186 μm x 186 μm), the iodinated PD fluid is automatically selected, thanks to its contrast difference with soft tissues, and its surface area is computed. The method was first tested on phantoms showing the ability to select the PD fluid volume and to measure its surface area. In vivo experiments in rat consisted of μCT acquisition of rat abdomen directly after intraperitoneal administration (10 mL/100 g rat body weight) of a dialysis fluid containing 10% by volume iodinated contrast agent. Fluorescein isothiocyanate albumin was used as dilution marker. We found a strong linear relationship ( R2 = 0.98) between recruited PSA (cm2) and rat weight (g) in the range of 235 to 435 g: recruited PSA = (1.61 weight + 40.5) cm2. Applying μCT with a fill volume of 10 mL/100 g rat body weight, the in vivo measured PSA was in the order of magnitude of the ex vivo anatomic PSA as determined by Kuzlan's formula, considered in most instances as the maximal surface area that can be recruited by PD fluid. This new methodology was the first to give an in vivo high-resolution isotropic three-dimensional (3-D) determination of the PSA in contact with dialysate. Its sensitivity allows us to take into account the recruitment of fine 3-D structures of the PSA membrane that were not accessible to previous 2-D-based imaging methodologies. Its in vivo application also integrates the physiological natural tensile stress of tissues.

Peritoneal Solute Clearances in Diabetics

1990 ◽  
Vol 10 (1) ◽  
pp. 85-88 ◽  
Author(s):  
Hi Bahl Lee ◽  
Min Sun Park ◽  
Sung Hee Chung ◽  
Young Bae Lee ◽  
Kyung Soo Kim ◽  
...  
Keyword(s):  
Body Weight ◽  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Continuous Ambulatory Peritoneal Dialysis ◽  
Vascular Diseases ◽  
Glucose Absorption ◽  
Peritoneal Membrane ◽  
Before And After ◽  
Esrd Patients

In order to examine solute transport across the peritoneal membrane and responsiveness of the peritoneal microcirculation to a vasodilator in diabetics on continuous ambulatory peritoneal dialysis (CAPD), we obtained peritoneal clearances of urea (Curea) and creatinine (Ccr), protein concentrations in the drained dialysate (D PC), and percentage of peritoneal glucose absorption (% PGA) before and after nitroprusside (NP) addition to the dialysate in 13 diabetics (DM) and 13 nondiabetics (non-DM) matched for age, sex, body weight, and duration of CAPD. Control (before NP) Curea, Ccr, D PC, and %PGA were not different between DM and non-DM. NP significantly enhanced Curea, Ccr, and D PC in both DM and non-DM. Curea, Ccr, D PC, and %PGA after NP were again not different between DM and non-DM. The findings suggest that peritoneal solute clearances and responsiveness of the peritoneal microcirculation to NP in diabetics are not different from nondiabetics at the beginning of CAPD despite evidence for widespread vascular diseases in diabetic ESRD patients.

Dyslipidemia in Peritoneal Dialysis — Relation to Dialytic Variables

2000 ◽  
Vol 20 (3) ◽  
pp. 306-314 ◽  
Author(s):  
Ann-Cathrine Johansson ◽  
Ola Samuelsson ◽  
Per-Ola Attman ◽  
Börje Haraldsson ◽  
James Moberly ◽  
...  
Keyword(s):  
Peritoneal Dialysis ◽  
Creatinine Clearance ◽  
Glucose Uptake ◽  
Surface Area ◽  
Plasma Lipids ◽  
Plasma Concentrations ◽  
University Hospital ◽  
Protein Loss ◽  
Dialysis Unit ◽  
Peritoneal Surface

Objective To investigate whether the specific lipoprotein (LP) abnormalities of peritoneal dialysis (PD) are associated with functional variables of this mode of dialysis. Design A survey of the LP profile in relation to peritoneal dialysis capacity (PDC) variables. The LP profile was compared to that of a group of age- and sex-matched controls. Setting The Peritoneal Dialysis Unit at Sahlgrenska University Hospital in Gothenburg, Sweden. Patients Twenty-two nondiabetic PD patients (5 women, 17 men) who had been on PD for at least 6 months. Main Outcome Measures The LP profile included plasma lipids, apolipoproteins (Apo), and individual ApoA- and ApoB-containing LP. The PDC measurement determined peritoneal glucose uptake, protein losses, effective peritoneal surface area, and total weekly creatinine clearance. Results The patients had been on PD for 6 to 48 months (mean 15.3 months) and had a total weekly creatinine clearance of 69.7 ± 13.3 L/1.73m2 body surface area, an average peritoneal glucose uptake corresponding to 446 ± 162 kcal/24 hour, and a protein loss of 8.1 ± 2.5 g/24 hr. The patients had significantly higher total cholesterol (7.1 mmol/L), VLDL-cholesterol (1.0 mmol/L), LDL-cholesterol (4.7 mmol/L), and triglyceride levels (2.5 mmol/L); whereas the HDL-cholesterol level (1.2 mmol/L) was significantly lower than in controls. The PD patients had increased levels of ApoB-containing LPs, both of the cholesterol-rich LP-B and of the triglyceride-rich LP-B complex, reflected in higher plasma concentrations of ApoB, ApoC-III, and ApoE. Furthermore, they had significantly lower levels of LP-A-I:A-II, as well as of ApoA-I and ApoA-II. The LP-A-I:A-II and ApoA-II levels correlated inversely with the duration of PD treatment ( r = 0.54, p < 0.01 and r = 0.52, p < 0.05, respectively). The ApoA-II level was inversely correlated with the peritoneal surface area ( r = 0.53, p < 0.05). There were no other correlations between LP variables and PDC variables, nor did any of the LP variables correlate with peritoneal glucose uptake or protein losses. Conclusion The proatherogenic lipoprotein profile of patients on PD is characterized by increased concentrations of cholesterol-rich and triglyceride-rich ApoB-containing LPs. While the duration of treatment appears to have some influence on the development of this type of dyslipidemia, the pathophysiological links to the dialysis mode must be further explored.

Falcon Temperature Regulation

The Auk ◽  
1978 ◽  
Vol 95 (1) ◽  
pp. 80-84 ◽  
Author(s):  
James A. Mosher ◽  
Clayton M. White
Keyword(s):  
Body Weight ◽  
Ambient Temperature ◽  
Surface Area ◽  
Temperature Regulation ◽  
Body Temperatures ◽  
Unit Body Weight ◽  
Thermoregulatory Function

Abstract We measured tarsal and body temperatures of four species of large falcons in relation to rising ambient temperature and found that the tarsus has an apparent thermoregulatory function. Statistical efforts to separate the birds into ecological or plumage types yielded mixed results. An index of tarsal surface area per unit body weight was correlated with the temperature regimens of the birds, with species from the hottest climates having the greatest tarsal index values.

scholarly journals Peritoneal Fluid and Solute Transport: Influence of Treatment Time, Peritoneal Dialysis Modality, and Peritonitis Incidence

2002 ◽  
Vol 13 (4) ◽  
pp. 1055-1060
Author(s):  
Andreas Fußhöller ◽  
Sandra zur Nieden ◽  
Bernd Grabensee ◽  
Jörg Plum
Keyword(s):  
Mass Transfer ◽  
Peritoneal Dialysis ◽  
Solute Transport ◽  
Peritoneal Fluid ◽  
Fluid Transport ◽  
Treatment Time ◽  
Lymphatic Absorption ◽  
Ultrafiltration Failure ◽  
Small Solute

ABSTRACT. The integrity of the peritoneal membrane in peritoneal dialysis (PD) is of major importance for adequate dialysis and fluid balance. However, alterations in peritoneal fluid transport, such as ultrafiltration failure, often develop during long-term PD. To investigate peritoneal solute and fluid transport and to analyze the influence of treatment time, peritonitis incidence, and PD modality (continuous ambulatory PD [CAPD] or automated PD [APD]), a cross-sectional study with an extended peritoneal transport test that used dextran 70 in 2 L of glucose was performed in 23 nonselected chronic PD patients. Compared were long-term (>40 mo) with short-term PD patients (<40 mo), CAPD with APD patients, and those with a peritonitis incidence of >0.25/yr to those with an incidence of <0.25/yr. Dialysate/plasma (D/P) ratio and mass transfer area coefficient of creatinine, lymphatic absorption rate (LAR), transcapillary ultrafiltration, and effective ultrafiltration were measured. Long-term PD patients had higher D/P ratio of creatinine (73.5 ± 2.3% versus 65.9 ± 2.2%; P < 0.01) and higher LAR (243 ± 69 ml/4 h versus 96 ± 31 ml/4 h; P < 0.03), both resulting in lower effective ultrafiltration (242 ± 35 ml/4 h versus 324 ± 30 ml/4 h; P < 0.05). D/P ratio (r = 0.66) and LAR (r = 0.67) were positively correlated to PD duration. Patients on APD compared with those on CAPD and patients with a history of peritonitis compared with those without did not differ in terms of D/P ratio, mass transfer area coefficient, LAR, transcapillary ultrafiltration, and effective ultrafiltration. Lower ultrafiltration after long-term PD is both the result of increased small solute transport and increased lymphatic absorption. APD or CAPD modality and peritonitis incidence do not have a significant influence on small solute transport or fluid kinetics.

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