A comparison of solute clearance and ultrafiltration volume in peritoneal dialysis with total or fractional (50%) intraperitoneal volume exchange with the same dialysate flow rate

Background: The most efficient way to perform automated peritoneal dialysis (APD) has not yet been defined. Tidal peritoneal dialysis (TPD) has been claimed to be more efficient than traditional intermittent peritoneal dialysis (IPD), but few comparative studies have been done keeping dialysate flow the same in the two treatment techniques. Method: Six patients were treated with 10, 14 and 24 litres total dialysis fluid volume during 9 h (flow rate 18,5, 25.9 and 44.4 ml/min), receiving the treatments both as IPD and TPD. Glucose concentration in the fluid was held constant during all treatments. Transperitoneal clearances (ml/min) for urea, creatinine and uric acid and ultrafiltration volume was calculated, and comparisons made between TPD and IPD. The total intraperitoneal dwell time was calculated for each treatment session. A peritoneal equilibration test was also done for each patient. Results: The ratio of the creatinine concentration in dialysate to the concentration in plasma at 4 h obtained with the peritoneal equilibration test (PET) averaged 0.77 (range 0.69-0.82). Urea clearance was higher for IPD than for TPD with 10 litres: 14.3±2.4 and 13.3±2.7 (P=0.0092). For 14 and 24 litres urea clearance for IPD and TPD was 17.9±2.3 and 15.9±3.5 (n.s.) and 20.9±3.6 and 19.9±5.6 (n.s) respectively. Creatinine clearance was higher for IPD than for TPD with 10 litres: 9.6±1.3 and 8.9±1.3 (P=0.0002). For 14 and 24 litres creatinine clearance for IPD and TPD was 11.0±0.7 and 9.9±2.0 (n.s.) and 12.3±1.2 and 12.4±2.2 (n.s.) respectively. Uric acid clearance was higher for IPD than for TPD with 10 litres: 8.4±1.3 and 7.7±1.0 (p=0.0054). For 14 and 24 litres uric acid clearance for IPD and TPD was 9.4±1.7 and 8.9±2.2 (n.s.) and 11.3±2.9 and 10.6±2.6 (n.s.) respectively. IPD gave significantly higher ultrafiltration volume (ml) than IPD for both 10 and 14 litres: 944±278 and 783±200 (P=0.0313) and 1147±202 and 937±211 (P=0.0478). For 24 litres there was no significant difference between IPD and TPD: 1220±224 and 1253±256. Conclusion: With the lowest dialysate flow rate (18.5 ml/min), solute clearance and ultrafiltration volume was higher on IPD than on TPD. With the intermediate flow rate (25.9 ml/min) the ultrafiltration volume was higher on IPD, but no difference was found for solute clearance. With the highest flow rate (44.4 ml/min) there as no difference neither for ultrafiltration nor for solute clearance.     

Peritoneal sodium mass removal in continuous ambulatory peritoneal dialysis and automated peritoneal dialysis: influence on blood pressure control.

BACKGROUND/AIM: Sodium and water retention is common in peritoneal dialysis patients and contributes to cardiovascular disease. As peritoneal sodium removal depends partly on dwell time, and automated peritoneal dialysis (APD) often uses short dwell time exchanges, the aim of this study was to compare the 24-hour peritoneal sodium removal in APD and standard continuous ambulatory peritoneal dialysis (CAPD) patients and to analyze its possible influence on blood pressure control. METHODS: A total of 53 sodium balance studies (30 in APD and 23 in CAPD) were performed in 36 stable peritoneal dialysis patients. The 24-hour net removal of sodium was calculated as follows: M = ViCi - VdCd, where Vd is the 24-hour drained volume, Cd is the solute sodium concentration in Vd, Vi is the amount of solution used during a 24-hour period, and Ci is the sodium concentration in Vi. Peritoneal sodium removal was compared between APD and CAPD patients. Residual renal function, serum sodium concentration, daily urinary sodium losses, weekly peritoneal Kt/V and creatinine clearance, 4-hour dialysate/plasma creatinine ratio, proportion of hypertonic solutions, net ultrafiltration, systolic and diastolic blood pressures, and need for antihypertensive therapy were also compared between the groups. RESULTS: Peritoneal sodium removal was higher (p < 0.001) in CAPD than in APD patients. There were no significant differences in residual renal function, serum sodium concentration, urinary sodium losses, peritoneal urea or creatinine clearances, 4-hour dialysate/plasma creatinine ratio, or proportion of hypertonic solutions between groups. The net ultrafiltration was higher in CAPD patients and correlated strongly (r = 0.82; p < 0.001) with peritoneal sodium removal. In APD patients, peritoneal sodium removal increased significantly only in those patients with a second daytime exchange. The systolic blood pressure was higher (p < 0.05) in APD patients, and the proportion of patients with antihypertensive therapy was also higher in APD patients, although no significant relationship between blood pressure values and amount of peritoneal sodium removal was found. CONCLUSIONS: The 24-hour sodium removal is higher in CAPD than in APD patients, and there is a trend towards better hypertension control in CAPD patients. As hypertension control and volume status are important indices of peritoneal dialysis adequacy, our results have to be considered in the choice of the peritoneal dialysis modality.     

Simultaneous peritoneal dialysis catheter insertion and removal in catheter-related infections without interruption of peritoneal dialysis

Catheter-related infections result in high patient morbidity, the need for temporary haemodialysis, and high costs. These infections are the main cause of limited technique survival in peritoneal dialysis. We introduced a protocol for the simultaneous peritoneoscopic insertion and removal of peritoneal catheters in patients with catheter-related infections. Peritoneal dialysis was continued the day after surgery using low-volume dwells and a dry abdomen during the daytime. The dialysate leukocyte count had to be below 100/mm³ before exchanging catheters, which was performed under antibiotic therapy based on culture sensitivity. The old catheter was removed after the new catheter had been inserted in the opposite abdominal region. CAPD patients were switched to APD for 1 week, which made prolonged hospitalization necessary. Simultaneous catheter insertion and removal was performed 25 times in 22 patients on CCPD and 15 times in 14 patients on CAPD. In CCPD patients, peritoneal dialysis was restarted after 1.0+0.1 days in 24 cases. One patient had sufficient residual renal function and discontinued CCPD until day 10. In 10 CAPD patients (11 procedures) APD was started 1.3±0.2 days after the procedure with CPD beginning 7.1±0.6 days thereafter. Three CAPD patients preferred haemodialysis and restarted CAPD 10.0±2.1 days after surgery. One patient continued CAPD the day after surgery. In addition to minor complications (e.g. position-dependent outflow problems), dialysate leakage occurred in two patients. Two patients developed peritonitis within the first 30 days after surgery, one of which was procedure related. One patient had severe lower gastrointestinal bleeding 2 weeks after the procedure, which was not related to the catheter replacement. Ultimately, in 38 of 40 procedures the patients could successfully continue peritoneal dialysis. We conclude that simultaneous insertion and removal of a peritoneal dialysis catheter without interruption of peritoneal dialysis is a safe procedure in patients with catheter-related infections.     

The role of tidal peritoneal dialysis in modern practice: A European perspective

Tidal peritoneal dialysis (TPD) has been introduced to optimize adequacy of peritoneal dialysis (PD). Early studies reported similar or even better small solute clearances with TPD than those achieved with continuous ambulatory peritoneal dialysis or continuous cyclic peritoneal dialysis. However, in many studies treatment volumes were much higher during TPD compared with other PD modalities. Based on current evidence, TPD provides no advantage of increased small solute clearances, middle molecule clearances, or peritoneal ultrafiltration as compared to non-tidal automated peritoneal dialysis (APD) when dialysate flow is kept constant. However, TPD reduces drainage pain and nightly alarms during cycler treatment. Tidal volume should be kept as high as possible in these patients, especially in those with low average peritoneal transport rates. Based on theoretical considerations and little evidence, TPD could provide better clearances than conventional APD when a very high dialysate flow (>or=5 l/h) is used. Such dialysate flow rates are not routinely prescribed in home APD patients. However, they may be interesting for in-center PD patients. One randomized crossover trial reported higher small solute clearances with TPD compared to non-tidal APD in patients with acute renal failure. TPD is also the preferred treatment modality in patients with ascites as it allows a controlled outflow of fluid from the peritoneal cavity. Newer treatment modalities, for example, continuous flow PD, may be interesting alternatives in an effort to increase efficacy of PD in the future. However, because such treatment regimens are expensive and elaborate they have not been established for routine use until now.     

Use of a modified peritoneal equilibration test to optimize solute and water clearance

The standard peritoneal equilibration test (PET) characterizes the peritoneal transport of fluid, creatinine and urea. However, the applicability of the standard PET may be limited in patients on cycling peritoneal dialysis due to the choice of 2- and 4-h sampling times which exceed the usual dwell time of most patients on cycling peritoneal dialysis. We have performed a modified PET on seven pediatric dialysis patients in an effort to optimize dwell time to achieve maximal clearance of solutes and fluid. When compared with the standard PET, values obtained for dialysate/plasma urea and dialysate/plasma creatinine with the modified PET are significantly different. This resulted in an increased estimated creatinine clearance in five of seven and increased estimated urea clearance in six of seven patients. The modified PET is a more appropriate method for evaluation of peritoneal clearances in children as well as older patients who may require cycling peritoneal dialysis.     

Measurement of peritoneal dialysis delivery in children

We measured urea [weekly urea clearance/total body water (KT/V_urea)] and creatinine (C _Cr) clearances on 35 occasions in 15 stable chronic peritoneal dialysis patients to determine the feasibility and reproducibility of such measurements in children. In addition, we performed peritoneal equilibration tests (PETs) to characterize our patients' peritoneal membranes and to estimate weekly clearances. We demonstrated that dialysis delivery can be quantified by these standard measurements in children of widely varying size. Further, we found that clearances predicted from PET data were similar to measured values in all patients. However, predicted and measured values were most significantly correlated in patients with high and high-average peritoneal membrane permeability. KT/V_urea andC _Cr were correlated overall, but differences in scaling affected the validity of the relationship. When both clearances were scaled to weight, the correlation was closer, but still differed between PET-determined peritoneal membrane types.     

"Dry Days" in Automated Peritoneal Dialysis: Impact on Dialysis Delivery

In our peritoneal dialysis program, it is common practice in continuous cyclic peritoneal dialysis (CCPD) patients to omit the daytime dwell without a medical reason for doing so (e.g., ultrafiltration problems). This practice eliminates more than half of the patient's daily dialysate-membrane contact. Since the value of continuous ambulatory peritoneal dialysis (CAPD)/ICCPD is based to a significant extent on the enhanced middle molecule clearance that depends on continuous dialysate-membrane contact, I am concerned about the risks that “dry days” entail. Mightn't outcomes be different (worse) in these patients even if Kt/IV urea (or even creatinine clearance) is maintained?     

Continuous Cyclic Peritoneal Dialysis: A Preliminary Report

Continuous cyclic peritoneal dialysis (CCPD) was designed to reduce the high incidence of peritonitis and eliminate the multiple interruptions created by dialysate exchanges during the day needed for CAPD, while maintaining the quality of dialysis. Three nocturnal cycles with 2 liters of dialysate lasting 3 hours each are provided by an automated cycler while the patient sleeps. Two liters are left in the abdomen in the morning. Only one daily connection and one disconnection are required between the peritoneal catheter and the cycler line. Our 84 patient months experience with 14 patients reveals a low incidence of peritonitis (1 per 42 patient months), satisfactory ultrafiltration rates and clearances that compare favorably with those of CAPD (C_urea 67, C_creatinine 58, and C_B12 45 L/wk). Blood pressure control has been excellent while most patients enjoy liberal diets.
This preliminary study suggests that CCPD may indeed reduce the rate of peritonitis, provide excellent clearance and ultrafiltration, allow more free time to the patient and maintain a steady physiological state.     

Tailoring the Peritoneal Dialysis Prescription

M. D., a 62-year-old female with renal disease secondary to bilateral polycystic kidneys and hypertension, opted for continuous ambulatory peritoneal diaiysis (CAPD) when her renal function deteriorated (24-hr urinary creatinine clearance of 6.8 ml/ min in a total urinary volume of 1200 ml) and uremic symptoms developed. The patient lived about a 3-hr drive from the nearest dialysis center. This factor weighed heavily in the patient's decision to choose home dialysis .
A Swan Neck Missouri peritoneal dialysis catheter was inserted by a surgeon under local anesthesia with no complications. Since the patient was symptomatic from the uremia, peritoneal dialysis using a cycler in the supine position was initiated about 18 hr after the catheter insertion. To avoid dialysis solution leak from the incision site, 1 1 volumes per exchange and a 0.5-hr cycle time were chosen. The cycler dialysis continued for 36 hr. The amount of ultrafiltration achieved was 2200 ml. The patient received two additional treatments using cycler dialysis during the next seven days before CAPD training was begun. CAPD training was accomplished in five working days. A baseline peritoneal equilibration test (PET) was carried out and thr residual renal function was determined. Based on the D/P creatinine ratio and the glucose results of the PET, the patient was classified as having a high peritoneal membrane transport rate. The renal creatinine and urea clearances were 5.7 and 4.2 ml/min, respectively (24-hr urine volume was 926 ml ).     

CAPD与CCPD对钙、磷和PTH转运的对比研究

目的:探讨持续非卧床腹膜透析(continuous ambulatory peritoneal dialysis,CAPD)与持续循环腹膜透析(con-tinuous cyclic peritoneal dialysis,CCPD)对钙、磷、甲状旁腺激素(parathyroid hormone,PTH)及血肌酐、尿素氮转运的影响。方法:选择2010年1月～2012年12月在北京大学深圳医院腹透中心常规CAPD治疗透析不充分并伴继发性甲状旁腺功能亢进的腹透患者20例,行腹膜平衡试验(peritoneal equilibration test,PET)了解腹膜转运特性,并计算基础Kt/V,然后给予CCPD治疗10d,检测CCPD治疗前后血及腹透液肌酐、尿素氮、Ca2+、P3-、Ca×P、iPTH,记录患者每日超滤量和尿量;比较CAPD与CCPD两种透析模式对上述指标影响。结果:CCPD治疗10d后总Kt/V由基线的1.73±0.33升高至2.30±0.37(P<0.05),Ccr/w由(47.43±7.61)L·wk-1·1.73m-2升高(61.69±10.52)L·wk-1·1.73m-2(P<0.05);血磷由(2.39±0.52)mmol/L降至(2.03±0.43)mmol/L(P<0.01);钙磷乘积由(66.73±15.84)mg2/dl2降至(58.81±13.64)mg2/dl2(P<0.05);iPTH由(84.85±15.84)pmol/L降至(58.81±13.64)pmol/L,差异均有统计学意义(P<0.05)。结论:短期CCPD能增加腹膜对小分子毒素(Cr、BUN)的清除,提高Kt/V和CCr值,并能降低血磷、iPTH水平。     

Dioctyl sodium sulphosuccinate increases net ultrafiltration in peritoneal dialysis

Background. The surface-active substance dioctyl sodium sulphosuccinate (DSS) has been reported to increase the peritoneal clearances of urea and creatinine. This study investigated the effects of DSS on the fluid and solute transport characteristics of the peritoneum. Design. A 4-h single-dwell experiment session of peritoneal dialysis using 25 ml of 3.86% glucose dialysis solution with an intraperitoneal volume maker was performed in 16 male Sprague-Dawley rats. In eight rats, 0.005% (50 p.p.m.) DSS was added to the dialysis fluid. No DSS was given to the other eight rats (control group). The transport of fluid, glucose, potassium, sodium, urea, phosphate and urate were analysed. Results. There was a significant increase in the intraperitoneal volume in the DSS group (33.0±2.9 ml) was significantly higher compared to the control group (28.8±2.1 ml. P<0.01). This increase in the drain volume was mainly due to a decrease in peritoneal fluid absorption rate in the DSS group (0.040±0.013 ml/min) as compared to the control group (0.054±0.010 ml/min, P0.05). There was no significant difference in the diffusive permeability and sieving coefficient for the small solutes between these two group. However, the clearances for urea and sodium were higher in the DSS group, mainly due to the increase in the dialysate volume. Conclusion. Our results suggest that DSS significantly increases the net ultrafiltration of peritoneal dialysis. This effect, which was mainly due to a decrease in the fluid absorption rate, contributed to the increased clearances for urea and sodium. DSS did not alter the diffusive permeability and sieving coefficient for the small solutes.