Characteristics of the peritoneal mass transfer of parathormone in patients under continuous ambulatory peritoneal dialysis therapy

Peritoneal Functional Parameters after Five Years on Continuous Ambulatory Peritoneal Dialysis (CAPD): The Effect of Late Peritonitis

Functional stability of the peritoneum is essential for patients on long-term continuous ambulatory peritoneal dialysis (CAPD) treatment. Sixteen patients on CAPD treatment for at least 4 years were studied. Their mean age was 47 ± 15 years, 5 were males, and none were diabetic. Residual creatinine clearance at the beginning was 2.1 ± 2.6 mL/min.

Once yearly since starting CAPD, we have evaluated their peritoneal ultrafiltration (UF) and diffusion capacities by calculating the peritoneal mass transfer coefficient (MTC, mL/min) for urea and creatinine. Patients were categorized so that we could distinguish the effect of peritonitis, betablockers, and hypertension. For all patients the average initial and final MTCs and UF values were not different.

Early episodes of peritonitis (those occurring <36 months after starting CAPD) did not influence long-term function. However, late peritonitis (occuring >36 months since initiation) induced a decrease in urea-MTC (22.3 ± 6 to 15.8 ± 3.9, p < 0.05), creatinine-MTC (9.4 ± 3.1 to 7.4 ± 2.5, p < 0.05), and a corresponding increase in UF (1.25 ± 0.4 to 1.4 ± 0.3, mL/min, p < 0.05).

Age, sex, betablockers and hypertension did not influence the peritoneal parameters followed.

After 5 years on CAPD, functional stability of the peritoneum is evident, except for patients who suffer late episodes of peritonitis. We speculate that the peritoneum in patients who have been on long-term CAPD are more susceptible to injuries, such as peritonitis, and that this results in functional deterioration.

Management of Renal Osteodystrophy in Peritoneal Dialysis Patients

The term “renal osteodystrophy” encompasses all forms of metabolic bone disease found in dialysis patients. The primary approach to the treatment of renal osteodystrophy in peritoneal dialysis (PD) patients is similar to that in hemodialysis patients. However, the increased prevalence of adynamic bone histology, together with the difficulty in judging calcium balance, the inability to practicably give intravenous vitamin D, and the clearance of vitamin D and parathyroid hormone via dialysate require a different therapeutic approach in PD compared to hemodialysis patients. Clearly, more comparative studies of new agents are needed to find the optimal approach to achieving the K/DOQI guidelines in PD patients. The unique aspects of the approach to renal osteodystrophy in PD patients are the focus of this review.

Endogenous Sympathetic Activity in CAPD Patients: Its Relationship to Peritoneal Diffusion Capacity

Endogenous agents, as catecholamines, may influence peritoneal mass transport by modifying peritoneal blood flow. Such endogenous mechanisms could explain certain functional peculiarities of the peritoneum in CAPD patients. In 27 randomly selected patients on CAPD we calculated peritoneal mass-transfer coefficient (MTC) for urea, creatinine, uric acid and parathormone (PTH) using mathematical modelling techniques. Also we measured simultaneously the renin-angiotensin and catecholamine levels in blood and dialysate.

The dialysate level of catecholamines and especially noradrenaline was significantly higher than the blood levels. Most of these patients had higher renin and aldosterone blood levels than the controls; we found no renin activity in the dialysate of any of these patients; (Plasma) aldosterone values correlated directly with renin activity. Multivariant analysis provided no evidence that the MTCs values were affected by two or more variables. Linear regression analysis of all variables studied showed direct correlation between dialysate noradrenaline and MTCs, and negative relationship between noradrenaline and ultrafiltration capacity. The catecholamine plasma levels, which were within the normal range, did not correlate with MTCs or with ultrafiltration.

Our findings suggest that, in some cases, noradrenaline produced in the peritoneum may influence peritoneal mass transport through a vasoactive effect. Dialysate catecholamine levels correlate with that of plasma, but the latter does not influence peritoneal transport.

Stability of the peritoneal membrane in long-term peritoneal dialysis patients

One of main challenges of peritoneal dialysis (PD) is the functional and vital long-term stability of the peritoneal membrane. Few longitudinal and controlled studies on peritoneal function have been published, and the results are somewhat contradictory. We have performed a longitudinal study with 90 patients. The overall analysis has shown that creatinine mass transfer coefficient (MTC) significantly increases and ultrafiltration (UF) capacity decreases over time. Nevertheless, urea MTC remained unaltered and MTC ratios significantly decreased after the third year. Subsequently, we examined the clinical outcomes and identified 19 patients who required peritoneal resting periods for Type I UF failure and 71 patients who did not require such a procedure. The latter patients did not show any significant functional change over time, whereas the former 19 patients showed an increase of peritoneal creatinine transport and a loss of UF capacity. These data corroborate changes in long-term peritoneal function in approximately 20% of PD patients. These changes consist of an increase in effective exchange area, peritoneal permeability, or both, accompanied by signs suggestive of mesothelial regenerative capacity loss. Infectious peritoneal injuries, especially appearing during late PD periods, are deleterious to the peritoneum. The remainder of the functional-structural changes are related to the effects of currently used dialysate. Early diagnosis, preemptive, and therapeutic measures should permit better management of long-term PD patients. The particular response to these injuries has individual characteristics that when addressed permit PD to be used long-term.

Functional longevity of the human peritoneum: how long is continuous peritoneal dialysis possible? Results of a prospective medium long-term study

Long-term peritoneal dialysis requires the maintenance of the transport function of the peritoneal membrane, and appropriate studies of possible changes are necessary. The quantification of peritoneal mass transfer coefficients (MTCs) has been judged to be the ideal method for the evaluation of peritoneal diffusion. The aim of the present study was to show the results of the prospective evaluations in long-term continuous ambulatory peritoneal dialysis patients. We have studied the clinical incidents and peritoneal function of 56 patients who started continuous ambulatory peritoneal dialysis between 1980 and 1988, and have completed at least 3 years of follow-up. Ultrafiltration capacity was calculated with a standardized formula. All patients were studied for peritoneal diffusion of urea and creatinine at least once a year. The evaluation consisted of a kinetic study done by means of a peritoneal equilibration curve for urea and creatinine, applying a bicompartmental mathematical model to calculate the MTCs. The sequential mean values for urea-MTC did not show significant changes over the observation period (20.7 +/- 5.9 mL/min for the first year v 19.8 +/- 6 mL/min for the fifth year). Creatinine-MTC values showed a significant increase over this period in the paired data analysis. The decrease of the urea-MTC to creatinine-MTC ratio may be an early and appropriate index for measuring these changes when the individual values are in the normal range. On the other hand, peritoneal ultrafiltration capacity significantly decreased over this period (1,800 +/- 530 mL/d v 1,400 +/- 600 mL/d, P < 0.01). The high rate of accumulated days of peritoneal inflammation was related to these significant changes, and thus may be proposed to be a good prognostic index of long-term peritoneal survival. These long-term functional changes might be related to the effect of injuries on the preservation of the normal peritoneal structure. We conclude that after 5 to 11 years, the human peritoneum shows functional stability (diffusion and water transport) in patients with low rates of peritoneal inflammation. With a few exceptions, represented by patients with a high rate of peritoneal inflammation, long-term peritoneal dialysis accomplished its newly entrusted task.

Comparative Study between Intact PTH and Fragments of PTH in Patients on Hemodialysis and CAPD

Twenty-nine patients on hemodialysis (HO) and 29 patients on continuous ambulatory peritoneal dialysis (CAPO) were studied. Serum calcium and phosphorous levels were similar in the 2 groups. Serum parathyroid hormone (PTH) levels were determined by 4 different methods. Mid-molecule PTH levels were higher in HO (1099.5±876.8 pmol/L) than in CAPO patients (541.0±138.8 pmol/L), p<0.001, while intact PTH levels were similar. The ratio MM-PTHllntact PTH was higher in HO (55.2±29.0) than in CAPO patients (39.0±20.0), where p<0.01. In patients with similar C-PTH, those on CAPO had higher levels of intact PTH (46.0±27.0 pmollL) than those in HO (29.3±29.0 pmoIIL), p<0.01. The ratio C-PTHlintact PTH was higher in HO (104.9±39.6) than in CAPO patients (59.3±32.3), p<0.001. The Peritoneal Saturation Index (PSI) of MMPTH was 23.4±12%, and it showed a hyperbolic correlation in respect to MM-PTH serum levels. We concluded that CAPO can modify the plasma C-PTH and MM-PTH serum levels by peritoneallosses of these fragments.