Intraperitoneal Dialysate Volume Research Articles

Long Peritoneal Dialysis Dwells With Icodextrin: Kinetics of Transperitoneal Fluid and Polyglucose Transport.

Background and objective: During peritoneal dialysis (PD), the period of effective net peritoneal ultrafiltration during long dwells can be extended by using the colloidal osmotic agent icodextrin but there are few detailed studies on ultrafiltration with icodextrin solution exceeding 12 h. We analyzed kinetics of peritoneal ultrafiltration in relation to icodextrin and its metabolites for 16-h dwells with icodextrin.Design, setting, participants, and measurements: In 20 clinically stable patients (mean age 54 years; 8 women; mean preceding time on PD 26 months), intraperitoneal dialysate volume (VD) was estimated from dilution of 125I-human serum albumin during 16-h dwell studies with icodextrin 7.5% solution. Sodium was measured in dialysate and plasma. In 11 patients, fractional absorption of icodextrin from dialysate, dialysate, and plasma amylase and high and low (Mw <2 kDa) Mw icodextrin fractions were analyzed.Results: Average VD increased linearly with no difference between transport types. At 16 h, the cumulative net ultrafiltration was 729 ± 337 ml (range −18 to 1,360 ml) and negative in only one patient. Average transcapillary ultrafiltration rate was 1.40 ± 0.36 ml/min, and peritoneal fluid absorption rate was 0.68 ± 0.38 ml/min. During 16 h, 41% of the initial mass of icodextrin was absorbed. Plasma sodium decreased from 138.7 ± 2.4 to 136.5 ± 3.0 mmol/L (p < 0.05). Dialysate glucose G2–G7 oligomers increased due to increase of G2–G4 metabolites while G6–G7 metabolites and higher Mw icodextrin fractions decreased. In plasma maltose and maltotriose (G2–G3 metabolites) increased while higher Mw icodextrin oligomers were almost undetectable. Dialysate amylase increased while plasma amylase decreased.Conclusions: Icodextrin resulted in linear increase of VD with sustained net UF lasting 16 h and with no significant difference between peritoneal transport types. In plasma, sodium and amylase declined, G2–G3 increased whereas larger icodextrin fractions were not detectable. In dialysate, icodextrin mass declined due to decrease of high Mw icodextrin fractions while low Mw metabolites, especially G2–G3, increased. The ability of icodextrin to provide sustained UF during very long dwells – which is usually not possible with glucose-based solutions – is especially important in anuric patients and in patients with fast peritoneal transport.

Drain pain, overfill, and how they are connected.

Drain pain and overfill are two complications of peritoneal dialysis (PD) that get very little attention in the published literature. A “PubMed” search reveals no articles about PD with ‘drain pain’ in the title and only one addressing ‘overfill’ in the sense of an excessive intraperitoneal dialysate volume (1). Are these complications both rare? Or are they trivial curiosities not worthy of more clinical attention? This commentary will argue that one of the two is very common, that both need to be understood better, and that they have recently become related in an unforeseen way.

Computer simulations of osmotic ultrafiltration and small-solute transport in peritoneal dialysis: a spatially distributed approach

The aim of this study was to simulate clinically observed intraperitoneal kinetics of dialysis fluid volume and solute concentrations during peritoneal dialysis. We were also interested in analyzing relationships between processes in the peritoneal cavity and processes occurring in the peritoneal tissue and microcirculation. A spatially distributed model was formulated for the combined description of volume and solute mass balances in the peritoneal cavity and flows across the interstitium and the capillary wall. Tissue local parameters were assumed dependent on the interstitial hydration and vasodilatation induced by glucose. The model was fitted to the average volume and solute concentration profiles from dwell studies in 40 clinically stable patients on chronic ambulatory peritoneal dialysis using a 3.86% glucose dialysis solution. The model was able to describe the clinical data with high accuracy. An increase in the local interstitial pressure and tissue hydration within the distance of 2.5 mm from the peritoneal surface of the tissue was observed. The penetration of glucose into the tissue and removal of urea, creatinine, and sodium from the tissue were restricted to a layer located within 2 mm from the peritoneal surface. The initial decline of sodium concentration (sodium dip) was observed not only in intraperitoneal fluid but also in the tissue. The distributed model can provide a precise description of the relationship between changes in the peritoneal tissue and intraperitoneal dialysate volume and solute concentration kinetics. Computer simulations suggest that only a thin layer of the tissue within 2-3 mm from the peritoneal surface participates in the exchange of fluid and small solutes between the intraperitoneal dialysate and blood.

Peritoneal Transport in Peritoneal Dialysis Patients Using Glucose-Based and Amino Acid-Based Solutions

To evaluate peritoneal transport of fluid and solutes in continuous ambulatory peritoneal dialysis (CAPD) patients using amino acid (AA)-based versus glucose-based dialysis solutions. Using iodine-labeled human serum albumin ((125)I-HSA) as intraperitoneal volume marker, peritoneal transport was investigated in a group of 20 clinically stable patients (11 females and 9 men, age 53 +/- 15 years) on CAPD for 15 - 101 months. Two paired 4-hour dwells, one with 1.36% glucose and one with 1.1% AA dialysis solution, were performed in each patient. Intraperitoneal dialysate volume, fluid absorption rate, and diffusive mass transport coefficients (K(BD)) and sieving coefficients (S) for glucose, creatinine, urea, potassium, and total protein were estimated for each dwell study. Dwell studies with AA solution were used to estimate K(BD) values for individual AAs. Intraperitoneal dialysate volume was higher for AA solution in comparison with glucose solution due to the higher osmolality of the AA solution. No statistically significant difference was found for K(BD) or S for creatinine, urea, potassium, or total protein in the dwell studies with either solution, whereas K(BD) for glucose was higher with AA than with glucose solution. Mean values of K(BD) of AA were similar but with high standard deviation, reflecting inter-individual variations in peritoneal transport rate. Our results indicate that the AA peritoneal transport rate is strongly dependent on transport characteristics of the individual peritoneal membrane.

Fluid and Solute Transport in CAPD Patients before and after Permanent Loss of Ultrafiltration Capacity

Two major types of permanent loss of ultrafiltration capacity (UFC) were previously distinguished among patients treated with CAPD: 1) type HDR with high diffusive peritoneal transport rate of small solutes and low osmotic conductance,but with normal fluid absorption rate, and 2) type HAR with high fluid absorption rate, but with normal diffusive peritoneal transport rate of small solutes and normal osmotic conductance. However, the detailed pattern of changes in peritoneal transport parameters in patients developing loss of ultrafiltration capacity is not known. Analysis of solute and fluid transport parameters in the same patient before and after UFC loss. Seven CAPD patients who had undergone repeated dwell studies,which were carried out before and/or after the onset of UFC loss. Dialysis fluids (2 L) with glucose or a mixture of amino acids as osmotic agent at three basic tonicities were applied during 6 hour dwell studies. Fluid and solute transport parameters were previously shown not to be affected by these dialysis solutions (except by hypertonic amino acid-based solution). Intraperitoneal dialysate volume and fluid absorption rate were assessed using radiolabeled human serum albumin (RISA). Osmotic conductance (a(OS))was estimated by a mathematical model as ultrafiltration rate induced by unit osmolality gradient. Diffusive mass transport coefficients, K(BD), for glucose,urea,and creatinine were estimated using the modified Babb-Randerson-Farrell model. Five patients had increased K(BD) for small solutes after the onset of UFC loss,and three of them had decreased a(OS),whereas two patients had normal a(OS). In one of them, a(OS) decreased with time after the onset of UFC loss with concomitant normalization of glucose absorption. In all studies of these five patients the fluid absorption rate was within the normal range. Two other patients had increased fluid absorption rate (about 5 ml/min),and one of them also had increased K(BD) for small solutes,in two consecutive dwell studies in each patient with the second study being carried out at 1 and 7 months respectively after the first one. In all four studies in these two patients, the a(OS) was within the normal range. The sodium dip during dialysis with 3.86% glucose-based solution was lost, not only among most patients with UFC loss related to reduced osmotic conductance, but also in patients with increased K(BD). The occurrence of two major types of UFC loss was confirmed. However, a case of a mixed type of UFC loss with high fluid absorption rate and high K(BD) for small solutes, but normal osmotic conductance, and with normalization of initially high K(BD) for small solutes, linked with decreasing initially normal osmotic conductance,was also found. As a reduced sodium dip with hypertonic glucose solution is not only seen in patients with reduced osmotic conductance, it cannot reliably be used as a single measure of decreased aquaporin function. Permanent ultrafiltration capacity loss may be a dynamic phenomenon with a variety of alterations in peritoneal transport characteristics.

Kinetic modeling of fluid and solute transport in peritoneal dialysis.

Mathematical models for fluid and solute transport during peritoneal dialysis are described. A model for the transport of the so-called volume marker enables the correct estimation of the kinetics of the intraperitoneal dialysate volume as well as the rate of peritoneal fluid absorption. On the basis of these estimations, the solute transport components (diffusion, convective solute transport with ultrafiltrate and peritoneal solute absorption) may be separated within the net solute transport using a modified version of the Babb-Randerson-Farrell (BRF) model. The diffusive mass transport coefficient and sieving coefficient are given by the model. A simplified method for the estimation of the diffusive mass transport coefficient during the so-called isovolemia period is also described and compared to the BRF modeling. The three-pore model and the distributed model, which describe the structure-function relationship for the peritoneum, are also addressed.

Peritoneal Fluid and Solute Transport with Different Polyglucose Formulations

To study peritoneal fluid and solute transport characteristics using different polyglucose solutions with and without the addition of glucose. Thirty-one rats were divided into three groups. A 4-hour dwell study with frequent dialysate and blood samples was performed in each rat using 25 mL of 7.5% polyglucose solution (PG, n = 11), 7.5% polyglucose + 0.35% glucose solution (PG1, n = 12), or 3.75% polyglucose + 1.93% glucose solution (PG2, n = 8). Radiolabeled human albumin (RISA) was added to the solutions as an intraperitoneal volume (i.p.V) marker. In addition, polyglucose degradation was evaluated ex vivo over 24 hours. Thirty-one male Sprague-Dawley rats (300 g) were used. Fluid and solute (glucose, urea, sodium, potassium, and total protein) transport characteristics as well as changes in dialysate osmolality were evaluated. The i.p.V was higher in the PG1 and PG2 groups than in the PG group during the first 2 hours of the dwell. The i.p.V, in fact, decreased during the first hour of the dwell in the PG group. However, the net ultrafiltration at 4 hours tended to be lower in the PG2 (3.2 +/- 1.5 mL) group compared to the PG (5.1 +/- 2.3 mL) and the PG1 groups (5.2 +/- 2.1 mL) (p = 0.07), and no significant difference was found between the PG and PG1 groups. Adding glucose to the PG solution increased the RISA elimination rate (KE, representing the fluid absorption rate from the peritoneal cavity): 25.5 +/- 8.2, 37.5 +/- 12.2, and 42.5 +/- 8.9 microL/min for the PG, PG1, and the PG2 group, respectively, p < 0.01. Dialysate osmolality (D[OS]) increased with the dwell time in the PG and PG1 groups but decreased in the PG2 group.The increase in D(OS) was partially due to the degradation of glucose polymer, which was supported by the marked increase in osmolality over 24 hours of incubation of PG solution with peritoneal fluid, ex vivo. The diffusive mass transport coefficient for the investigated solutes did not differ among the three groups (except for glucose, which was significantly lower in the PG group). The sieving coefficient for sodium was significantly higher in the PG group compared to the PG1 group (p < 0.05). Our results suggest that, although there was an initial decrease in the intraperitoneal dialysate volume, significant amounts of fluid can be removed by polyglucose solution during a single 4-hour dwell in rats, despite the low osmolality of the solution. The positive fluid removal induced by the PG solution is partially due to the lower fluid absorption rate associated with this solution and may, to some extent, also be due to the degradation of glucose polymer within the peritoneal cavity, resulting in increased dialysate osmolality. The addition of glucose to the polyglucose solution does not seem to improve ultrafiltration in a 4-hour dwell in the rat model. However, the peritoneal fluid absorption rate may be increased, and peritoneal transport of glucose and sodium may be altered, by adding glucose to the polyglucose solution.

Sieving coefficients for small solutes during experimental peritoneal dialysis in rats.

A single 4-hour experimental peritoneal dialysis was performed in 6 normal Sprague-Dawley rats to investigate sieving coefficients (S) for small solutes during peritoneal dialysis. A modified 3.86% Dianeal solution with approximately the same concentrations of urea, sodium, and potassium as in the rat plasma (isochratic solution) was used to avoid diffusion of investigated solutes and to achieve sufficient ultrafiltration. As a control, a 4-hour peritoneal dialysis in 7 normal Sprague-Dawley rats was performed using the conventional 3.86% Dianeal solution. The infusion volume was 30 ml. A dilution of radioiodinated serum albumin was used to determine the intraperitoneal dialysate volume. S was calculated (1) from the mass and volume balances for the initial 30 min of the exchange with the isochratic solution (SI, isochratic method) and (2) by using a membrane model based on the thermodynamic theory of mass transport (SM). The diffusive mass transport coefficient KBD for the solutes investigated was estimated using the membrane model. The SI values for urea, sodium, and potassium were similar with the isochratic solution. For urea and sodium, the S values were within the physiological range 0-1, whereas the S values for glucose were close to 0 and for potassium were negative. SM for glucose, urea, and sodium using the conventional solution did not differ from the values obtained with the isochratic solution; however, SM for potassium was significantly lower than with the isochratic solution. SI and SM for potassium and sodium were correlated. The KBD values for glucose, urea, and sodium using the isochratic solution did not differ from the values obtained with the conventional solution, whereas the KBD values for potassium were significantly higher with the isochratic solution as compared with the conventional solution. We conclude that the net sieving coefficients SI and SM for urea and sodium were lower than unity in the rats dialyzed with the two solutions and did not differ from the previously reported S values measured in continuous ambulatory peritoneal dialysis patients with the isochratic solution. However, the transport of potassium was abnormal with the isochratic solution, suggesting mechanisms other than passive diffusive and convective potassium transport.

REFRACTORY CHF AND MODEST RENAL FAILURE: III

This 72‐year‐old white woman with diabetes mellitus (Type II) and ischemic cardiomyopathy was referred for evaluation on the day she was discharged from hospital, November 10, 1992. She was referred by her cardiologist for help managing recurrent episodes of congestive heart failure (CHF) complicated by moderate renal failure, both due to diabetes. In the preceding five months, control of heart failure required multiple visits to the cardiologist and five hospital admissions, for a total of 32 hospital days. The inttrval between admissions was becoming progressively shorter—the last two just 10 days apart. In spite of bumetanide 4 mg qid, metolazone 10 mg qod, Lanoxicaps 0.05 mg qd, hydralazine 25 mg qid, clonidine 0.2 mg tid, and Procardia 60 mg XL qd, the patient would leave the hospital only to experience rapid return of edema, progressive dyspnea on exertion and a nonproductive cough. She always slept on three pillows and was never able to life flat. Review of systems disclosed no symptoms of uremia except perhaps a poor appetite. Past medical history included Type II diabetes mellitus, since 1967; coronary artery bypass grafts in 1983 and 1988; left hemicolectomy for adenocarcinoma, Duke's grade C, 1990 with normal colonoscopy July 1992. Because of a neurogenic bladder, the patient performed self catheterization intermittently. In the more distant past she also had a cholecystectomy, appendectomy, and total abdominal hysterectomy. Physical examination revealed an elderly individual whose neck veins were visible to the angle of the jaw when sitting. Her weight was 66.8 kg, height 165 cm, and blood pressure 150/72 supine and afier 2 min of standing. The lungs were clear to auscultation. No pericardial rub was present. The liver span was 15 cm. No bruit was present and the spleen was not palpable or percussable. Well‐healed right subcostal, right paramedian and infraumbilical (umbilicus to pubis) scars marked her previous surgical procedures. Marked edema was present to above both knees. No asterixis, myoclonus, or fetor uremicus were detected. Laboratory results: April 9, 1992—‐BUN 95 mg/dl, creatinine 4.3 mg/dl, sodium 138 mEq/l, potassium 4.1 mEq/l. chloride 102 mEq/l, total CO2 28 mEq/l; April 4, 1992—‐albumin 3.2 g/d, total protein 6.4 g/d, cholesterol 173 mg/d, WBC 5,400, lymphocytes 17%, total lymphocyte count 900 cells/mcl. The advantages and disadvantages of hemodialysis and peritoneal dialysis were discussed with the patient and her family. Continuous Ambulatory Peritoneal Dialysis (CAPD) was encouraged because of the continuous ultrafiltration. The potential difficulty in placing the catheter because of multiple prior surgical procedures was explained. The patient elected to try CAPD. A single cuff, curled Tenckhoff peritoneal dialysis catheter was placed laparoscopically by a surgeon in the operating room on November 18, 1992. The catheter placement went without incident and the patient was discharged the same day. Intermittent peritoneal dialysis was started the next day and continued for about 8 hr/day thrice weekly with 1 then 1.5 l exchanges to allow time for wound healing while providing help with volume control. CAPD training was carried out from December 7 to 10. By December 16, her weight was down to 57.3 kg, a loss of 10 kg. As of her clinic visit of April 23, 1993, she had no hospital admissions since November 10, 1992, except for the dialysis catheter insertion. Although she still sleeps on three pillows, the neck veins are flat at a head elevation of 30 degrees and there is no orthopnea or change in respiratory rate lying flat. Ankle edema is again 4 + at 68 kg. Appetite has improved and she attributes part of her increased weight to increased (oral) calorie intake resulting from improved breathing. The dialysis catheter has continued to function well, and no catheter related complications have developed. The 2 l intraperitoneal dialysate volume has not caused any symptoms. The only cardiac or antihypertensive medications are Procardia 60 mg XL and Lanoxicaps 0.05 mg qd.

Evaluation of an experimental rat model for peritoneal dialysis: fluid and solute transport characteristics

The aim of this study was to develop a reference model of fluid and solute transport during experimental peritoneal dialysis in rats, which would simulate the conditions of clinical dialysis in CAPD patients as much as possible. For this purpose a 4-h dialysis study was performed in 13 normal Sprague-Dawley rats with conventional glucose solutions (Dianeal 1.36% solution, n = 6 and Dianeal 3.86% solution, n = 7) and a protocol and methods like those used in clinical dwell studies. The dilution of a marker, radioactive human serum albumin (RISA), was used to determine the intraperitoneal dialysate volume with corrections for the elimination of RISA from the peritoneal cavity and sample volumes. The isovolumetric method was employed to calculate the diffusive mass transport coefficients. To compare our data with reference values in CAPD patients, the data were scaled by a factor calculated as a ratio of the dialysate volume in CAPD to the dialysate volume in the rats. In a separate series of experiments the intraperitoneal hydrostatic pressure was monitored with increasing infusion volumes. The fluid transport characteristics, described as the percentage changes of the initial intraperitoneal volume, were essentially comparable to those in CAPD patients. However, the intraperitoneal volume curves were shifted more to the left than were the reported values in CAPD patients. The scaled diffusive mass transport coefficient for urea was similar to that in CAPD patients. However, the transport of other solutes, in particular glucose, was faster in the rats than in CAPD patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer simulations of peritoneal fluid transport in CAPD

To model the changes in intraperitoneal dialysate volume (IPV) occurring over dwell time under various conditions in continuous ambulatory peritoneal dialysis (CAPD), we have, using a personal computer (PC), numerically integrated the phenomenological equations that describe the net ultrafiltration (UF) flow existing across the peritoneal membrane in every moment of a dwell. Computer modelling was performed according to a three-pore model of membrane selectivity as based on current concepts in capillary physiology. This model comprises small "paracellular" pores (radius approximately 47 A) and "large" pores (radius approximately 250 A), together accounting for approximately 98% of the total UF-coefficient (LpS), and also "transcellular" pores (pore radius approximately 4 to 5 A) accounting for 1.5% of LpS. Simulated curves made a good fit to IPV versus time data obtained experimentally in adult patients, using either 1.36 or 3.86% glucose dialysis solutions, under control conditions; when the peritoneal UF-coefficient was set to 0.082 ml/min/mm Hg, the glucose reflection coefficient was 0.043 and the peritoneal lymph flow was set to 0.3 ml/min. Also, theoretical predictions regarding the IPV versus time curves agreed well with the computer simulated results for perturbed values of effective peritoneal surface area, LpS, glucose permeability-surface area product (PS or "MTAC"), intraperitoneal dialysate volume and dialysate glucose concentration. Thus, increasing the peritoneal surface area caused the IPV versus time curves to peak earlier than during control, while the maximal volume ultrafiltered was not markedly affected. However, increasing the glucose PS caused both a reduction in the IPV versus time curve "peak time" and in the "peak height" of the curves. The latter pattern was also seen when the dialysate volume was reduced. It is suggested that computer modelling based on a three-pore model of membrane selectivity may be a useful tool for describing the IPV versus time relationships under various conditions in CAPD.

Endoscopic Management of Shoulder Pain in Long-Term Haemodialysis Patients

In this study a simple rat model for evaluating the ultrafiltration by peritoneal dialysis solutions is described. Anaesthetised male Sprague-Dawley rats were injected intraperitoneally with dialysis solutions. Zero, 1, 3, or 6 h later, the dialysate volume was determined directly: the abdomen was carefully opened, the intraperitoneal liquid was withdrawn with a syringe and its volume was measured. Good recovery of dialysate, highly reproducible results, and the similarity between the ultrafiltration profiles in rats and published profiles in CAPD patients for control solutions, indicate that the model is valid. The model was then used to evaluate peritoneal dialysis solutions containing a mixture of glycerol and amino acids. Both osmotic agents are chemically compatible and these mixtures provide amino acids and carbohydrates in a single solution. For three mixtures, intraperitoneal dialysate volume were determined as a function of dwell time and the formulation with the desired ultrafiltration could be selected.