Stable Continuous Ambulatory Peritoneal Dialysis Research Articles

Factors Affecting Bicarbonate Transfer with Bicarbonate-Containing CAPD Solution

To evaluate bicarbonate fluxes across the peritoneal membrane and bicarbonate gain in patients treated with continuous ambulatory peritoneal dialysis (CAPD) using dialysis solutions with different bicarbonate concentrations. Ninety-seven exchanges, using different dwell times and glucose and bicarbonate concentrations were performed in 43 stable CAPD patients. Dialysate effluent bicarbonate concentration and volumes were measured at different dwell times. Net dialytic bicarbonate gain was calculated. Patients' acid-base status was determined at the middle of the dwell. In prolonged dwells (6-12 hours) the dialysate effluent bicarbonate concentration correlated with arterial plasma bicarbonate concentration (F = 129, p < 0.0001), but not with ultrafiltration rate or dialysis solution bicarbonate concentration. In 4-hour dwells, effluent bicarbonate concentration correlated with both plasma bicarbonate concentration and ultrafiltration rate (F = 32.52, p < 0.0001 and F = 4.4, p < 0.05, respectively). The effluent bicarbonate concentration may be predicted from the patient's plasma bicarbonate concentration and net ultrafiltration rate for either a 4-hour or prolonged (6-12 hours) dwell time. Net bicarbonate gain by the patient correlated with ultrafiltration rate, plasma bicarbonate, and dialysis solution bicarbonate concentration (F = 100.56, p < 0.0001 at 4 hours and F = 108.08, p < 0.0001 at 6-12 hours), with the ultrafiltration rate being the predominant parameter. The effluent bicarbonate concentration is related to plasma bicarbonate concentration, with ultrafiltration playing a marginal role only during short dwells. However, the ultrafiltration rate has a profound effect on net patient bicarbonate gain. Multiple linear regression analysis allows the prediction of the effect of acid-base status, ultrafiltration, dwell time, and dialysis solution bicarbonate content on net patient bicarbonate gain. It seems that bicarbonate content in the CAPD dialysis solution should be progressively increased with increasing solution osmolality.

Low dialysate calcium in continuous ambulatory peritoneal dialysis: A randomized controlled multicenter trial

Hypercalcemia is a common complication in continuous ambulatory peritoneal dialysis (CAPD) patients treated with calcium-containing phosphate binders and using the standard dialysate calcium concentration of 3.5 mEg/L (SCa). Lowering the dialysate calcium was proposed to overcome this problem. The current randomized controlled multicenter study was designed to investigate efficiency and safety of a low calcium dialysate (2.00 mEq/L; LCa) compared with SCa (3.5 mEq/L) in CAPD patients. After an 8-week run-in period, 103 stable CAPD patients, 68 men, 35 women, aged 54.5 years (range, 20 to 77)) were randomly allotted to treatment with either LCa or SCa. All patients received calcium carbonate as oral phosphate binder to achieve serum phosphate levels < 6.2 mg/dL. If persistent hypercalcemia arose, CaCO 3 was replaced by AI(OH) 3 until normocalcemia was achieved. All patients received 0.25 μg calcitriol/d. Parameters monitored included total and ionized serum calcium, serum phosphate, phosphate binder intake, incidence of hypercalcemia, serum aluminium, intact parathyroid hormone (1,84PTH), osteocalcin, alkaline phosphatase, bone mineral density and hand skeletal x-ray. Primary end points were (a) number of hypercalcemic episodes, (b) tolerated doses of calcium-containing phosphate binders, and (c) 1,84PTH. After 6 months of therapy, total and ionized calcium were lower in LCa patients (total Ca:9.6 v 10.08 mEq/L, P = 0.005; iCa: 4.76 v 5.15 mg/dL; P = 0.013). In the LCa group, siginificantly fewer episodes of hypercalcemia were recorded (total S-calcium > 10.8 mg/dL: LCa 24 v SCa 86 episodes; P < 0.005). Use of LCa permitted the administration of more CaCO 3 (mean daily tablet number: LCa, 5.9 v SCa, 4.2; P < 0.05). More AI(OH) 3 was required in the SCa group (2.0 v 0.7 tablets/d per patient; P < 0.01). Control of serum phosphate was comparable, and initial and final serum levels did not differ between the groups. 1,84 PTH levels were within the desired range in the LCa group (medians: start of run-in, 15 pmol/L; start of therapy, 15.5 pmol/L; wk 24, 14 pmol/L), whereas in the SCa group, 1,84 PTH declined to the normal range (start of run-in, 15 pmol/L; start of therapy, 9.2; wk 24, 7.05 pmol/L; normal, 1 to 6 pmol/L). No radiologic signs of renal osteodystrophy or demineralization of the bones were observed with LCa. Adverse events were rare, with the exception of peritonitis. The frequency of peritonitis episodes and exit-site infections was similar, however, in LCa and SCa patients. In conclusion, this randomized controlled multicenter study in a large number of CAPD patients documents significantly better tolerance of calcium-containing phosphate binders with no adverse effects on PTH levels or other end points after 6 months of treatment when dialysate calcium concentration is lowered to 2.0 mEq/L.

Lyphatic absorption in CAPD patients with loss of ultrafiltration capacity.

During continuous ambulatory peritoneal dialysis (CAPD) treatment, loss of ultrafiltration capacity (UFC) is a common complication that can be associated with increased peritoneal fluid absorption rate. The aim of the present study was to investigate the relative importance of lymphatic absorption for total peritoneal fluid absorption in patients with permanent loss of UFC associated with a high peritoneal absorption rate (KE, ml/min; high-KE group, n = 4). Clinically stable CAPD patients (n = 23) as well as patients with loss of UFC associated with increased diffusive mass transport coefficients (KBD, ml/min; high-KBD group, n = 8) served as control groups. The patients were investigated with a 6-hour dwell study with 3.86% glucose solution. The total fluid absorption rate was estimated by the disappearance rate (KE) of 131I-radioiodinated human serum albumin (RISA) from the peritoneal cavity, and the lymphatic absorption rate was estimated by the rate of RISA appearance in plasma (KPP, ml/min). The values of KE and KPP in the high-KE group (4.65 +/- 0.93 and 0.42 +/- 0.31 ml/min, respectively) were markedly higher than in the clinically stable CAPD patients (1.77 +/- 0.60 and 0.15 +/- 0.06 ml/min, respectively; both p < 0.001 vs. the high-KE group). In the high-KBD group, KE was lower (2.19 +/- 0.38 ml/min, p < 0.001) compared to the high-KE group, whereas KPP was similar (0.26 +/- 0.09 ml/min, NS). The fraction of KE which could be accounted for by KPP was on average only 9 +/- 5% in the high-KE group and did not differ from the fractions in the clinically stable patients or in the high-KBD group (9 +/- 5 and 12 +/- 4%, respectively). In 5 patients in whom plasma RISA activity was measured for 24 h from the beginning of the 6-hour dwell study, a continuous increase of the RISA level in plasma was observed during this time period. We conclude that although KPP was increased in patients with UFC loss associated with high KE, it accounted for only a minor part of KE. Furthermore, the relatively slow but prolonged appearance of RISA in plasma indicates that the interstitial compartment may serve as a reservoir of macromolecules which are slowly absorbed by local lymphatics. The present study supports previous findings that direct lymphatic absorption is only of relatively minor importance for the fluid absorption in peritoneal dialysis.

Does Impaired Transcellular Water Transport Contribute to Net Ultrafiltration Failure during CAPD?

To assess the contribution of transcellular water transport in net ultrafiltration failure during continuous ambulatory peritoneal dialysis (CAPD). Retrospective. Renal Unit, Academic Medical Center, Amsterdam. One group of 6 patients with clinical severe ultrafiltration loss and a group of 10 stable CAPD patients without ultrafiltration problems. In all patients, two peritoneal permeability tests were done within one week, using glucose 1.36% dialysate on one day and glucose 3.86% on the other day. Dextran 70 was used as a volume marker. The difference in net ultrafiltration between 3.86% glucose and 1.36% glucose dialysate was 569 +/- 51 mL (control) and 153 +/- 103 mL (poor ultrafiltration group; p < 0.005). The dialysate/plasma (D/P) concentration ratios increased in both groups with glucose 1.36%. When using 3.86% glucose, the D/P ratio decreased in the control group with a median minimum value one hour after completion of inflow. It is possible that sieving of sodium was due to transcellular water transport by crystalloid osmosis during the hypertonic dwell, as a dissociation between the transport of water and sodium is unlikely to occur in transport through the much larger intercellular pores. The D/P sodium ratio after one hour was related to the mass transfer area coefficient (MTC) of creatinine and the percentage of glucose absorption in the control group. No decrease in D/P ratio was found in the poor ultrafiltration group. This suggests impairment of transcellular water transport. No significant differences were present between both groups with regard to MTC creatinine (10.2 and 14.0 mL/min), glucose absorption (71% and 71%), effective lymphatic absorption rate (1.34 and 1.01 mL/min), and residual volume (248 and 178 mL). Only 1 patient in the ultrafiltration loss group continued with CAPD. The others had to be transferred to hemodialysis; 1 of them developed sclerosing peritonitis. The sieving of sodium during CAPD may be caused by transcellular water transport. Deficient sieving as assessed by the absence of a decreased D/P ratio after one hour of a hypertonic dwell suggests impairment of transcellular water transport. This is associated with severe ultrafiltration failure. It indicates that failure of transcellular water transport, possibly by glycosylation of specific proteins on the cell membrane, may be considered one of the causes of ultrafiltration failure during CAPD.

Short-term effects of recombinant human growth hormone in CAPD patients

Protein and calorie malnutrition is common in chronic dialysis patients. Several interventions have been proposed to prevent and/or to treat malnutrition. Recombinant human growth hormone (rhGH) is a drug with anabolic properties and has been used in several catabolic conditions, such as patients with severe burns as well as in pediatric patients with chronic renal failure. In this study, we evaluated the short-term effects and safety of rhGH on urea kinetics and commonly measured biochemical parameters in 10 stable adult continuous ambulatory peritoneal dialysis (CAPD) patients. The design of the study was prospective, cross-over with the patients serving as their own controls. There were three study periods: baseline (PreGH), treatment (Tx), and follow-up (PostGH). During the seven day Tx period, patients self-administered 5 mg/day s.c. of rhGH. During this time, there was a significant decrease in blood urea nitrogen (BUN) (54 +/- 15 to 40 +/- 12 mg/dl), as well as in the combined dialysate and urine urea nitrogen excretion rate (5.69 +/- 1.86 to 4.04 +/- 1.13 g/day), and protein catabolic rate (0.82 +/- 0.13 to 0.67 +/- 0.09 g/kg/day), (all P < 0.001). Serum phosphorus (4.8 +/- 1.6 to 4.4 +/- 1.8 mg/dl) and potassium (4.0 +/- 0.4 to 3.6 +/- 0.2 mEq/liter) levels also showed a small but statistically significant decrease, in conjunction with a statistically significant increase in serum creatinine levels (12.2 +/- 5.7 to 12.9 +/- 5.7 mg/dl). Dietary protein intake, determined by dietary recall, did not change during the study (66.1 +/- 20.5 vs. 75.8 +/- 22.1 grams/day).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of Short-Chain Polypeptides as An Osmotic Agent in Continuous Ambulatory Peritoneal Dialysis Patients

To assess whether dialysate containing short-chain polypeptides is well tolerated in continuous ambulatory peritoneal dialysis (CAPD) patients and to determine its effect on fluid and solute transport, plasma amino acid levels, and biochemical parameters. Two-treatment, two-period cross-over design. Renal Unit, Academic Medical Center, Amsterdam and Renal Unit, University Hospital, Gent. Two groups of 10 stable CAPD patients. All patients received a trial solution (1.36% glucose and 1% peptides, 381 mOsm/kg) and a control solution (2.27% glucose, 404 mOsm/kg) in randomized order. The patients were examined on four consecutive days in which two dwell periods on days 1 and 3 of either 4 (Group I) or 8 hours (Group II) were performed. The peptide solution was well tolerated in all patients. In addition, no differences were found in the parameters for the effective peritoneal surface area and the intrinsic permeability, implying that no irritating effect of the peptide solution was present. Net ultrafiltration was not different in Group I: -43 +/- 125 versus 86 +/- 125 mL (mean +/- SEM) and marginally lower in Group II: -94 +/- 64 versus 51 +/- 64 mL, despite the lower osmolality of the trial solution compared to the control solution. Glucose absorption was higher than the peptide absorption in all patients: Group I: 66 +/- 10% versus 57 +/- 13% (p = 0.0003); Group II: 80 +/- 5% versus 72 +/- 11% (p = 0.006). No differences in plasma amino acid profiles could be detected. Short-chain polypeptides are absorbed less than glucose and can be used as an osmotic agent in CAPD patients. However, longer-term studies are needed to evaluate possible additional effects of peptides on the nutritional status of CAPD patients.

Protein Clearance and Icodextrin

Objective To analyze the peritoneal transport of serum proteins during continuous ambulatory peritoneal dialysis (CAPD) with icodextrin. Design A comparison was made between CAPD with glucose-based dialysate and, in the same patients, 4 weeks after the instillation of icodextrin for the long night dwell, with icodextrin-based dialysate. Patients Ten stable CAPD patients, who participated in a large randomized multicenter study comparing icodextrin with glucose-based dialysate. Five patients used glucose 1.5% dialysate for the night dwell before its replacement by icodextrin (good ultrafiltration group), and 5 used glucose 4.25% (poor ultrafiltration group). Results The clearance of β2-microglobulin increased by 28% on icodextrin, due to increased convective transport. The clearances of the larger proteins -albumin, IgG, fibronectin, and α2-macroglobulin -remained unaltered, indicating transport of these proteins across the large pore system. The patients with poor ultrafiltration had a higher β2-microglobulin clearance on glucosebased dialysate than the high ultrafiltration group. This indicates that the ultrafiltration failure was caused by a large effective peritoneal surface area, leading to a rapid absorption of glucose. Icodextrin produced significantly more ultrafiltration in the poor ultrafiltration patients than in the high ultrafiltration group. A correlation was found for the β2-microglobulin clearance on glucose-based dialysate and the ultrafiltration produced by icodextrin. Conclusions Icodextrin causes ultrafiltration through the small pore system, whereas glucose-based dialysate has its effect on transcellular water transport. Therefore, the use of icodextrin causes an increased clearance of β2 microglobulin, but not of larger proteins. Icodextrin was especially useful in patients with a large effective surface area leading to ultrafiltration failure during treatment with glucose-based dialysate.

Magnesium and Parathyroid Hormone Changes to Magnesium-Free Dialysate in Continuous Ambulatory Peritoneal Dialysis Patients

For the normalization of serum magnesium (Mg) concentration, dialysate Mg concentration tends to be reduced in continuous ambulatory peritoneal dialysis (CAPD) patients. The aim of this study was to evaluate the influence of Mg on parathyroid hormone (PTH). Prospective study of the utilization of Mg-free dialysate for 8 weeks. Dialysis service, Itabashi Hospital, Nihon University School of Medicine. Five stable CAPD patients (1 male; 4 female; age 49.7 +/- 1.3 years; duration of CAPD 27 +/- 9 months). Serum Mg, serum high sensitive PTH, and Mg content in mononuclear cells were measured at 4-week intervals. In comparison to baseline, serum Mg concentration was significantly reduced at week 4 (p < 0.01) and week 8 (p < 0.01), and serum PTH was significantly increased at week 4 (p < 0.05) and at week 8 (p < 0.05). However, the PTH level at week 8 was lower than that at week 4. Furthermore, the Mg content in mononuclear cells was significantly decreased at week 4 (p < 0.01) and at week 8 (p < 0.01). Serum-ionized calcium and phosphate concentrations did not change. The removal of Mg by Mg-free dialysate leads to Mg depletion in CAPD patients. In addition, Mg depletion stimulates PTH synthesis or secretion at 4 weeks, but at 8 weeks PTH synthesis or secretion is also influenced by other factors.

Protein and energy intake, nitrogen balance and nitrogen losses in patients treated with continuous ambulatory peritoneal dialysis

The aim of this investigation was to analyze factors which influence the dietary protein intake (DPI), the energy intake and the utilization of ingested protein, and to determine the relationship between various types of nitrogen losses in stable continuous ambulatory peritoneal dialysis (CAPD) patients. We performed 23 nitrogen balance (NB) studies of 6 to 11 days duration in 12 CAPD patients. One study was performed in all patients 3.4 +/- 1.2 months after starting CAPD (early studies). The study was then repeated in nine patients after 12.1 +/- 2.6 months, and two of these patients were studied again after 16 and 24 months, respectively (late studies). Before each NB study, the dietary intakes prior to the study were assessed in diaries and interviews. During a few days preceding the NB periods and during the NB periods each patient received an individualized diet composed so as to resemble the patients' spontaneously chosen diet regarding DPI and dietary energy intake (DEI). Total nitrogen, protein, urea and creatinine were analyzed in the dialysate and urine collected daily. Total nitrogen was also analyzed in the feces, collected over the whole NB period. Total nitrogen appearance (TNA), non-protein nitrogen appearance (NPNA) and urea nitrogen appearance (UNA) were calculated by correcting total nitrogen output, non-protein nitrogen output, that is, TNA minus the total protein losses (PL) and urea nitrogen output for changes in total body urea nitrogen. Glucose was determined in the collected dialysate and the daily glucose absorption was calculated. DPI varied between 0.62 and 2.09 g/kg/day, DEI between 21 and 42 kcal/kg/day and the peritoneal energy (glucose) intake (PEI) between 4 and 13 kcal/kg/day. DPI (but not DEI) correlated with Kt/V(urea) and Kt/VCr and with total and renal clearances for urea and creatinine. NB (not corrected for "unmeasured" nitrogen losses) was positive in most studies, and it correlated with DPI and the total energy intake (TEI) in the early studies, but only with TEI in the late studies. DPI correlated with TNA, NPNA, UNA, non-protein-non-urea nitrogen loss and fecal nitrogen loss. UNA was highly correlated with TNA and NPNA (r = 0.95). We used data from 33 NB studies in CAPD patients (our present data combined with data from the literature) to calculate regression equations describing the relationship between TNA and NPNA, respectively, and UNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Peritoneal Transport during Dialysis with Amino Acid-Based Solutions

To evaluate the potential clinical role of amino acids as an osmotic agent. The peritoneal transport of fluid, amino acids, and other solutes was investigated during a 6-hour single-cycle peritoneal dialysis with PDA 1% versus 1.36% glucose (n = 6) or PDA 2.7% versus 3.86% glucose solution (n = 9). Fifteen stable nondiabetic continuous ambulatory peritoneal dialysis (CAPD) patients. The fractional absorption of the osmotic agents at 6 hours was higher with PDA 2.7% versus glucose 3.86% (p < 0.005). The diffusive mass transport coefficient, KBD, calculated for a period of dialysate isovolemia was higher with PDA 2.7% versus PDA 1% for essential, nonessential (p < 0.005), and total (p < 0.05) amino acids. The intraperitoneal volume-over-time curves and KBD values for urea, creatinine, glucose, albumin, beta 2-microglobulin, and total protein did not differ between the amino acid solutions and the corresponding glucose solutions. KBD for urea was significantly higher during the dwell with PDA 2.7% versus PDA 1% (p < 0.05). Plasma amino acid concentrations increased substantially during the first 1-2 hours and then decreased gradually. Valine and methionine rose to 792% and 1119% of baseline values, respectively. We conclude that the peritoneal transport of fluid and investigated solutes, except amino acids, was not different with the amino acid solutions compared with the corresponding equimolar glucose solutions. However, ultrafiltration tended to be lower with amino acid solutions. Furthermore, the fractional absorption of amino acids and KBD values for amino acids was higher with PDA 2.7% versus PDA 1%, suggesting an effect of the hypertonic amino acid solution on the peritoneal membrane transport properties. Also, the hypertonic PDA 2.7% solution yielded nonphysiologically high plasma levels of several amino acids. We therefore consider this solution not to be safe enough for long-term clinical use.

Short Term Clinical Study with Bicarbonate-Containing Peritoneal Dialysis Solution

The evaluation of the efficacy, adequacy, clinical tolerance, and safety of a new bicarbonate continuous ambulatory peritoneal dialysis (CAPD) solution. A 6-week cross-over clinical study in 6 stable CAPD patients was performed. After a control period (2 weeks) with a standard CAPD solution (lactate, 35 mmol/L), a two-chamber bag containing 34 mmol/L of bicarbonate was used for 4 weeks. A breakable valve divided the two chambers, one containing bicarbonate and the other calcium. The two solutions were mixed just before use, thus avoiding the calcium and magnesium carbonate precipitation. No differences between control and study periods were found for blood urea nitrogen, creatinine, total proteins, albumin, total and ionized calcium, phosphate, sodium, potassium, chlorine, and hemoglobin. Blood bicarbonate significantly increased from 21.25 +/- 2.02 to 23.36 +/- 1.15 (p < 0.05) during the study. The peritoneal equilibration tests for urea nitrogen, creatinine, proteins, sodium, potassium, and glucose were slightly reduced during bicarbonate dialysate, but this effect was compensated for by a slight increase of ultrafiltration, thus keeping peritoneal clearances constant. Residual renal function did not change during the study. No side effects occurred during the bicarbonate period. A CAPD bicarbonate solution is effective in uremic acidosis correction, does not affect dialysis adequacy, is safe, and well tolerated.

Effects of Subcutaneous Recombinant Human Erythropoietin in Patients on Continuous Ambulatory Peritoneal Dialysis

The use of recombinant human erythropoietin (rHuEPO) has revolutionized the treatment of renal anemia, but the dose regimens, the optimal frequency, and the effects on other target organs like the central nervous systems (CNS) are still under discussion. We designed a prospective, ongoing study with 10 stable continuous ambulatory peritoneal dialysis (CAPD) patients (6 males, 4 females; mean age 64.4 +/- 7.8 years), with a pretreatment hemoglobin (Hb) < 7.0 g% and requiring regular blood transfusions. Seven patients were treated with 4000 U rHuEPO once weekly (Eritrogen, Boehringer Mannheim), 2 patients received 4000 U every 5 and 8 days, and the last one 4000 U every 10 days. The target hematocrit was 33% and Hb 10.0 g%. The CNS activity was recorded as visual (VEP), brainstem (BAER), and somatosensory (SEP)-evoked potentials. The mean Hb concentration increased from 6.9 +/- 1.2 g% to 10.3 +/- 1.6 g% (p < 0.001) over 8 weeks. There were no significant changes in urea, creatinine, and potassium levels, and urine output. rHuEPO induced a decrease in latency of P100 VEP, in the four main components of BAER, and in the P27-N35 intertime of SEP. Parallel to the improvement of red cell indices, patients experienced a dramatic improvement in well-being. The subcutaneous administration of a single vial of rHuEPO is safe, convenient, and inexpensive in CAPD. The role of rHuEPO treatment in improving the electrophysiological brain function in uremic and anemic patients remains to be studied and may not necessarily be based on improved cerebral oxygenation.

The Effect of Dialysate Osmolality on Ultrafiltration and Vascular Refilling Rate

The osmotic gradient is the main driving force for ultrafiltration (UF) in continuous ambulatory peritoneal dialysis (CAPD). Depending on glucose absorption, its changes over a period of time could influence the plasma refilling rate. The aim of this study was to evaluate the influence of changes in the plasma refilling rate obtained by dialysates of different osmolalities upon the rate of UF. Stable CAPD patients were studied twice during a 4-hour exchange 2 weeks apart with dialysate containing 1.5% and 4.25% glucose, respectively. UF was estimated by the autologous hemoglobin dilution method every 30 minutes. Hematocrit and colloidosmotic pressure (COP) decrease when using 1.5% glucose dialysate, reflecting a rise in plasma water mediated by the plasma refilling rate. This water shift is greater than the osmotic gradient generated between peritoneal and intravascular compartments as reflected by a low UF rate. However, when the osmotic gradient increases by means of 4.25% glucose dialysate, the plasma refilling rate is efficiently counter-balanced by UF.

Limitations of kinetic models as predictors of nutritional and dialysis adequacy in continuous ambulatory peritoneal dialysis patients.

Nutrition has been shown to predict clinical outcome in continuous ambulatory peritoneal dialysis (CAPD) patients. However, despite the positive relationship between KT/V (urea) and the normalised protein catabolic rate, the ability of urea kinetic modelling to predict clinical outcome or nutrition remains inconclusive. We have evaluated the relationship between nutrition and achieved dialysis in a cross-sectional study of 147 stable CAPD patients on dialysis for a mean period of 22 months. Protein-energy malnutrition was present in 22-32% of the study population. 39 and 41% of the population failed to achieve suggested adequacy targets of 50 liters/week for total creatinine clearance and a weekly KT/V (urea) of 1.7, respectively. Severely malnourished patients had significantly greater normalised clearance and adequacy values than well-nourished patients. Intrinsic actual peritoneal clearance bore no relation to patient size. The subsequent normalisation of this value by a component of patient mass results in a mathematical bias against well-nourished or obese patients. This may explain the failure of such adequacy values to reflect outcome and argues against accepting such values as measures of dialysis well-being.

Mass Transfer Coefficient: Comparison between Methods

The mass transfer area coefficient (MTC) is the best parameter for solute transport evaluation in continuous ambulatory peritoneal dialysis (CAPD) patients. We compared three simplified MTC methods (calculated according Garred, Krediet, or Lindholm) and the peritoneal equilibration test (PET) (Twardowski) to complex MTC (MTCX) (Randerson and Farrell) for urea and creatinine, by means of 29 tests performed in 24 stable CAPD patients. There were no significant differences (paired t-test) between MTCX and each of the simplified MTC, except for creatinine MTC calculated by Krediet's method, which was significantly different (MTCX: 9.36 +/- 4.32, K-MTC: 10.48 +/- 4.55, p < 0.05). Likewise, there was an acceptable correlation between complex MTC and each of the simplified methods including the PET. However, a more detailed study of the MTC's categorizations shows poor agreement with complex MTC categorization. Better results are obtained by PET categorization, which reaches good likelihood ratios either for positive or negative events. We conclude that simplified MTC or the dialysate/plasma ratio at 240 minutes for urea and creatinine has an acceptable correlation with complex MTC and can be useful in clinical practice. There is poor agreement between solute transport categorizations of simplified MTC and complex MTC. There is a better coincidence between the PET (D/P at 240 minutes) and complex MTC categorizations.

How long can continuous ambulatory peritoneal dialysis be continued?

We investigated how long continuous ambulatory peritoneal dialysis (CAPD) could be continued in the face of peritoneal sclerosis. 15 CAPD patients with no experience of peritonitis were selected and the time limitation for CAPD was examined retrospectively, based on the dialysate osmolality, serum creatinine concentration, etc.. The values for the dialysate osmolality and serum creatinine concentration increased gradually with the duration of CAPD and were significantly increased from 6 months. 5 patients whose serum creatinine concentration during the first 6 months after initiation of CAPD increased more than 5 mg/dl, could not continue CAPD for more than 24 months because of the appearance of peritoneal membrane failure. When the time limitation for CAPD was assessed in 10 stable patients, close relationships between the mean dialysate osmolality and duration of CAPD (Y = 0.52X + 351.25, r = 0.83, P < 0.01), and between the mean serum creatinine concentration and duration of CAPD (Y = 0.18X + 6.84, r = 0.95, P < 0.001) were recognized. If the practical limitation for CAPD was set at 400 mOsm/l in terms of the dialysate osmolality or 20 mg/dl in terms of serum creatinine concentration, its value became 94.1 months or 73.1 months, respectively. It is concluded that the time limitation for CAPD can be expected to be approximately 6 to 8 years in stable CAPD patients, and we need to resolve CAPD-induced problems involving the peritoneal membrane in order to continue CAPD for more than 10 years.

The Effect of the Dialysate on Food Consumption by Continuous Ambulatory Peritoneal Dialysis Patients

The effect of intra-abdominal dialysate on food consumption was studied in 10 stable adult continuous ambulatory peritoneal dialysis (CAPD) subjects with persistent hypoalbuminaemia. Each subject recorded food intake for 2 consecutive weeks. During one of the weeks, subjects ate their food after draining out the fluid and in the other week, meals were consumed with the dialysate in the peritoneal cavity. There were no significant differences in protein, carbohydrate, fat, or calorie intakes, irrespective of whether the fluid was in or out. There was a marked variation in maximum and minimum daily food intakes during either week: mean difference for protein was 48 g/d. Thus the presence of intra-abdominal dialysate does not directly affect food consumption in CAPD patients. Reduction of the variability of nutrient intake might improve nutrition. The effect of intra-abdominal dialysate on food consumption was studied in 10 stable adult continuous ambulatory peritoneal dialysis (CAPD) subjects with persistent hypoalbuminaemia. Each subject recorded food intake for 2 consecutive weeks. During one of the weeks, subjects ate their food after draining out the fluid and in the other week, meals were consumed with the dialysate in the peritoneal cavity. There were no significant differences in protein, carbohydrate, fat, or calorie intakes, irrespective of whether the fluid was in or out. There was a marked variation in maximum and minimum daily food intakes during either week: mean difference for protein was 48 g/d. Thus the presence of intra-abdominal dialysate does not directly affect food consumption in CAPD patients. Reduction of the variability of nutrient intake might improve nutrition.

A Comparison of Employment Rates of Patients Treated With Continuous Ambulatory Peritoneal Dialysis vs In-Center Hemodialysis (Michigan End-Stage Renal Disease Study)

This study examines factors associated with employment status in a stratified subsample of the Michigan End-Stage Renal Disease Study population. To reduce the variation in employment potential, the subsample consisted of nondiabetic patients aged 20 to 64 years. The patients were stratified on the basis of their treatment histories as follows: (1) treated by in-center hemodialysis only; (2) primarily treated by continuous ambulatory peritoneal dialysis; and (3) failed continuous ambulatory peritoneal dialysis, substituted by another form of dialysis. A significantly higher percentage of the patients undergoing stable continuous ambulatory peritoneal dialysis were in the labor force than were those undergoing in-center hemodialysis (27.4% vs 9.6%). Using logistic regression, even when adjusted for sex, race, age, education, marital status, primary diagnosis, and duration of end-stage renal disease, the stable continuous ambulatory peritoneal dialysis group was significantly more likely to be employed than the group undergoing either in-center hemodialysis only or the group that failed continuous ambulatory peritoneal dialysis.

Peritoneal Ultrafiltration and Fluid Reabsorption During Peritoneal Dialysis

Peritoneal ultrafiltration and fluid reabsorption characteristics for 18 patients undergoing continuous ambulatory peritoneal dialysis (CAPD) were investigated in single dwell studies of 6 h duration with 21 of 3.86% glucose dialysis fluid. Dialysate volumes were determined in situ using radioiodinated serum albumin (RISA) as volume marker with a correction applied for the total elimination of RISA from the peritoneal cavity. The RISA elimination rate was calculated as 2.1 +/- 0.5 ml/min. The true dialysate volume after 360 min was on average 28% less than the apparent volume calculated without correction for the elimination of RISA. The mean maximum true volume plus sampling losses was 3255 ml at 240 min, corresponding to a mean net ultrafiltration volume of 762 ml between 3 min and 240 min. The mean net fluid reabsorption rate between 240 min and 360 min was 1.2 +/- 0.7 ml/min. This study of standard dialysate volume/time curves in clinically stable CAPD patients using hypertonic dialysis fluid shows that about 90% of the total net ultrafiltration is achieved during the first 90 min of the dwell. After an extended period of dialysate isovolaemia, usually lasting as long as between 120 min and 240 min, fluid reabsorption is observed in all patients.

Effects of Dietary Fish Oil on Serum Lipids and Blood Coagulation in Peritoneal Dialysis Patients

The effects of a daily fish oil supplement rich in eicosapentaenoic acid were studied in 11 stable continuous ambulatory peritoneal dialysis (CAPD) patients. Serum lipids, platelet aggregation studies, and template bleeding times were determined before and after 4 weeks of fish oil treatment. The lipid studies were repeated approximately 20 weeks after stopping fish oil supplement. At the end of the treatment period, serum triglycerides (mean +/- SEM) decreased from 297 +/- 42 to 211 +/- 29 mg/dL (P less than .01), high density lipoprotein (HDL) cholesterol fell from 45 +/- 3 to 41 +/- 3 mg/dL (P less than .05), and low density lipoprotein (LDL) cholesterol increased from 172 +/- 16 to 208 +/- 19 mg/dL (P less than .05). After discontinuing the fish oil supplement, the triglycerides increased to 278 +/- 39 mg/dL, which was no different than the value before fish oil treatment. No significant changes occurred in template bleeding time (TBT), platelet count, hematocrit, or platelet aggregation response. Clinically important uremic bleeding was not apparent. We conclude that in CAPD patients a fish oil supplement favorably effects hypertriglyceridemia and can be ingested without promoting uremic bleeding. The likely beneficial impact on atherogenesis resulting from the lowering of the triglycerides may, however, be counteracted by concomitant changes in HDL- and LDL-cholesterol.