Compared time profiles of ultrafiltration, sodium removal, and renal function in incident CAPD and automated peritoneal dialysis patients

BACKGROUND

Fluid and sodium removal rates may not be equivalent in patients undergoing automated peritoneal dialysis (APD) and continuous ambulatory peritoneal dialysis (CAPD). This may influence compared cardiovascular outcomes in both groups.

METHODS

The authors compared prospectively the time courses of ultrafiltration, sodium removal, and residual renal function (RRF) in a group of incident patients treated with CAPD (n = 53) or APD (n = 51) for at least 1 year (mean follow-up, 28.9 months; range, 13 to 62). The authors analyzed potential effects of these factors on blood pressure (BP) control and cardiovascular morbidity and mortality.

RESULTS

Ultrafiltration and sodium removal rates were consistently lower in APD patients (mean differences, 236 mL/d; P = 0.012, and 36 mmol/d; P = 0.018, respectively, end of first year). Moreover, univariate and multivariate analysis indicated that APD therapy results in a moderate, but significantly faster decline of RRF than CAPD therapy. Analysis of clinical outcomes showed that CAPD (versus APD) therapy or higher ultrafiltration or sodium removal rates were associated with a better time course of systolic, but not diastolic, BP. We were unable to identify PD modality, ultrafiltration, or sodium removal rates as independent predictors of cardiovascular morbidity and mortality.

CONCLUSION

Ultrafiltration and sodium removal rates are consistently lower in incident APD patients than in their counterparts undergoing CAPD. Moreover, RRF declines faster during APD than during CAPD therapy, although this difference may be partially counteracted by a detrimental effect of ultrafiltration on RRF. Aside from a better control of systolic BP in CAPD patients, these differences do not portend significant cardiovascular consequences during the first years of PD therapy.

Blood pressure measurement in research and in clinical practice: recent evidence

PURPOSE OF REVIEW

For over a century the technique of blood pressure measurement developed by Riva-Rocci and Korotkoff has provided most of the data on hypertension diagnosis and treatment. Its limitations, however, are becoming increasingly evident and therefore alternative solutions are under investigation. This paper is intended to provide an overview of important recent progress in this field, and to highlight future perspectives.

RECENT FINDINGS

A major development in blood pressure measurement is the technical improvement of electronic manometers for use either in the clinic (with the auscultatory approach, as an alternative to use of mercury columns), or in automated oscillometric devices yielding blood pressure measurements devoid of observer-dependency, and allowing long-term blood pressure monitoring. In the latter case, blood pressure measurement is made possible in settings other than the physician's office, either through ambulatory blood pressure monitoring or through self blood pressure measurement at home. These methods are growing in clinical importance, but further studies are needed to define their indications more precisely in the clinical evaluation of hypertensive patients. Recently, important steps towards better standards of blood pressure measurement have been taken, as summarized in the guidelines jointly issued by the European Society of Hypertension (ESH) and the European Society of Cardiology (ESC), in the 7th Joint National Committee Report and (in even more detail) in the Blood Pressure Measurement Guidelines published by the ESH Working Group on Blood Pressure Monitoring.

SUMMARY

Blood pressure measurement is a rapidly developing field, the importance of which is increasingly acknowledged in the light of the growing awareness of the impact of hypertension on public health. Despite remarkable progress, many methodological issues still remain to be properly addressed.

The implications of the ADEMEX study for the peritoneal dialysis prescription: the role of small solute clearance versus salt and water removal

PURPOSE OF REVIEW

This review examines the results of the ADEMEX (Adequacy of Peritoneal Dialysis in Mexico) study in the context of other recent advances in peritoneal dialysis, and assesses the implication of this new knowledge for the optimal peritoneal dialysis prescription.

RECENT FINDINGS

The prospective randomized controlled ADEMEX study demonstrated no survival advantage of an increased dose of peritoneal small molecule clearance delivered by chronic ambulatory peritoneal dialysis. Coincident with this finding, there has been increasing awareness that many peritoneal dialysis patients are volume expanded, and that there are adverse cardiovascular consequences to this chronic overhydration. As a result there has been a shift away from interest in peritoneal small solute clearance with renewed interest in peritoneal removal of salt and water. There is also increasing evidence of the importance of residual renal function in maintaining euvolemia and as a prognostic indicator for survival.

SUMMARY

The ADEMEX study and subsequent investigations have changed the way we perceive the optimal peritoneal dialysis prescription. This has resulted in de-emphasis of peritoneal small molecule clearance and increased emphasis on clinical assessment of dialysis adequacy, preservation of residual renal function, and optimization of salt and water removal.

Icodextrin improves the fluid status of peritoneal dialysis patients: results of a double-blind randomized controlled trial

Worsening fluid balance results in reduced technique and patient survival in peritoneal dialysis. Under these conditions, the glucose polymer icodextrin is known to enhance ultrafiltration in the long dwell. A multicenter, randomized, double-blind, controlled trial was undertaken to compare icodextrin versus 2.27% glucose to establish whether icodextrin improves fluid status. Fifty patients with urine output <750 ml/d, high solute transport, and either treated hypertension or untreated BP >140/90 mmHg, or a requirement for the equivalent of all 2.27% glucose exchanges, were randomized 1:1 and evaluated at 1, 3, and 6 mo. Members of the icodextrin group lost weight, whereas the control group gained weight. Similar differences in total body water were observed, largely explained by reduced extracellular fluid volume in those receiving icodextrin, who also achieved better ultrafiltration and total sodium losses at 3 mo (P < 0.05) and had better maintenance of urine volume at 6 mo (P = 0.039). In patients fulfilling the study's inclusion criteria, the use of icodextrin, when compared with 2.27% glucose, in the long exchange improves fluid removal and status in peritoneal dialysis. This effect is apparent within 1 mo of commencement and was sustained for 6 mo without harmful effects on residual renal function.

Effect of icodextrin on volume status, blood pressure and echocardiographic parameters: a randomized study

Overhydration is a risk factor for hypertension and left ventricular hypertrophy in peritoneal dialysis patients. Recently, a high prevalence of subclinical overhydration was observed in peritoneal dialysis patients. Aim of the present open-label randomized study was to assess the effect of a icodextrin 7.5% solution on fluid status [extracellular water (ECW) bromide dilution], blood pressure regulation (24-hour ambulatory measurements) and echocardiographic parameters during a study period of 4 months, and to relate the effect to peritoneal membrane characteristics (dialysate/plasma creatinine ratio). Forty peritoneal dialysis patients (22 treated with icodextrin, 18 controls) were randomized to either treatment with icodextrin during the long dwell or standard glucose solutions. Thirty-two patients (19 treated with icodextrin, 13 controls] completed the study. The use of icodextrin resulted in a significant increase in daily ultrafiltration volume (744 +/- 767 mL vs. 1670 +/- 1038 mL; P = 0.012) and a decrease in ECW (17.5 +/- 5.2 L vs. 15.8 +/- 3.8 L; P = 0.035). Also the change in ECW between controls and patients treated with icodextrin was significant (-1.7 +/- 3.3 L vs. +0.9 +/- 2.2 L; P = 0.013). The effect of icodextrin on ECW was not related to peritoneal membrane characteristics, but significantly related to the fluid state of the patients (ECW:height) (r = -0.72; P < 0.0001). Left ventricular mass (LVM) decreased significantly in the icodextrin-treated group (241 +/- 53 grams vs. 228 +/- 42 grams; P = 0.03), but not in the control group. In this randomized open-label study, the use of icodextrin resulted in a significant reduction in ECW and LVM. The effect of icodextrin on ECW was not related to peritoneal membrane characteristics, but was related to the initial fluid state of the patient.

Fluid status in CAPD patients is related to peritoneal transport and residual renal function: evidence from a longitudinal study

BACKGROUND

Both peritoneal transport characteristics as well as residual renal function are related to outcome in patients treated with continuous ambulatory peritoneal dialysis (CAPD). It has been suggested that part of this relationship might be explained by an effect of both parameters on the fluid state in CAPD patients or by the relationship between inflammation and peritoneal transport.

METHODS

In the present study, the relationship between fluid state [extracellular water (ECW) (sodium bromide); total body water (TBW) (deuterium oxide)] with peritoneal transport characteristics (2.27% glucose dialysate/plasma creatinine [D/P (creat)] ratio), residual renal function (residual glomerular filtration rate [rGFR] by urine collection) and C-reactive protein (CRP) was assessed in 37 CAPD patients in a cross-sectional and longitudinal design, with 25 patients completing the study.

RESULTS

In the cross-sectional part ECW, corrected for height (ECW:height), was inversely related to rGFR (r=-0.40, P=0.016), whereas during the longitudinal part, D/P[creat] was related to the change in ECW (r=0.40, P=0.05). Neither D/P[creat] nor rGFR were related to CRP, whereas a significant relationship was observed between ECW:height and CRP (r=0.58, P=0.0001). Patients were dichotomized according to rGFR (<2 or >2 ml/min). Despite a higher daily peritoneal glucose prescription (216.3+/-60.0 vs 156.5+/-53.0 g/24 h; P=0.004) and peritoneal ultrafiltration volume (1856+/-644 vs 658+/-781 ml/24 h, respectively; P=0.0001), the patients with a rGFR <2 ml/min showed a higher ECW:height compared with the group with rGFR >2 ml/min (12.5+/-3.8 vs 9.2+/-2.2 l/m, respectively; P=0.003). Results for TBW were comparable.

CONCLUSION

Fluid state was significantly related to peritoneal transport characteristics and rGFR. The larger ECW:height in CAPD patients with a negligible rGFR existed despite a higher peritoneal ultrafiltration volume and higher peritoneal glucose prescription. These findings raise doubts as to whether fluid state in CAPD patients with a diminished rGFR can be adequately controlled on standard glucose solutions without an additional sodium and fluid restriction. The preliminary finding of a relationship between CRP and fluid state might suggest a relationship between overhydration and inflammation.