The Role of Peritoneal Dialysis as the First-Line Renal Replacement Modality

Twenty years after its introduction, peritoneal dialysis (PD) is a well-established alternative to hemodialysis (HD) as a modality of renal replacement therapy. Much debate and research is apparent in the literature, comparing hemodialysis and PD as “opposite” modalities and trying to ascertain which modality should be more optimal.

In our opinion, HD and PD are two distinct modalities, each with its own advantages and disadvantages. In addition, it is clear that for both HD and PD, rates of technique failure are high, causing patients to transfer between modalities. The question is thus not which modality is best, but rather, which flow-chart of modalities makes best use of the advantages of each modality, while avoiding its disadvantages. In this respect, HD and PD appear to be complementary modalities.

The better preservation of residual renal function, lower risk of infection with hepatitis B and C, better outcome after transplantation, preservation of vascular access, and lower costs are arguments to promote PD as a good initial treatment. When PD-related problems arise (adequacy, ultrafiltration, peritonitis, patient burnout), a timely transfer to HD has to be planned.

This editorial tries to review arguments supporting the complementary nature of both modalities, and especially the role of PD as the first-line renal replacement therapy.

Major and Minor Risk Factors for Cardiovascular Disease in Continuous Ambulatory Peritoneal Dialysis Patients

Uremia in general and peritoneal dialysis in particular bring with them risk factors for the development of cardiovascular disease. These factors include multiple lipid abnormalities, hyperhomocysteinemia, abdominal obesity, chronic inflammation, hypoalbuminemia, oxidative stress, and AGE formation. When these are combined with conventional risk factors, one can appreciate why the incidence of cardiovascular disease is so high in peritoneal dialysis patients. Treatment strategies should address each of these risks appropriately.

Low-Sodium Versus Standard-Sodium Peritoneal Dialysis Solution in Hypertensive Patients: A Randomized Controlled Trial

BACKGROUND

Peritoneal dialysis (PD) solutions with reduced sodium content may have advantages for hypertensive patients; however, they have lower osmolarity and solvent drag, so the achieved Kt/Vurea may be lower. Furthermore, the increased transperitoneal membrane sodium gradient can influence sodium balance with consequences for blood pressure (BP) control.

STUDY DESIGN

Prospective, randomized, double-blind clinical trial to prove the noninferiority of total weekly Kt/Vurea with low-sodium versus standard-sodium PD solution, with the lower confidence limit above the clinically accepted difference of -0.5.

SETTING & PARTICIPANTS

Hypertensive patients (≥ 1 antihypertensive drug, including diuretics, or office systolic BP ≥ 130 mmHg) on continuous ambulatory PD therapy from 17 sites.

INTERVENTION

108 patients were randomly assigned (1:1) to 6-month treatments with either low-sodium (125 mmol/L of sodium; 1.5%, 2.3%, or 4.25% glucose; osmolarity, 338-491 mOsm/L) or standard-sodium (134 mmol/L of sodium; 1.5%, 2.3%, or 4.25% glucose; osmolarity, 356-509 mOsm/L) PD solution.

OUTCOMES

Primary end point: weekly total Kt/Vurea; secondary outcomes: BP control, safety, and tolerability.

MEASUREMENTS

Total Kt/Vurea was determined from 24-hour dialysate and urine collection; BP, by office measurement.

RESULTS

Total Kt/Vurea after 12 weeks was 2.53 ± 0.89 in the low-sodium group (n = 40) and 2.97 ± 1.58 in the control group (n = 42). The noninferiority of total Kt/Vurea could not be confirmed. There was no difference for peritoneal Kt/Vurea (1.70 ± 0.38 with low sodium, 1.77 ± 0.44 with standard sodium), but there was a difference in renal Kt/Vurea (0.83 ± 0.80 with low sodium, 1.20 ± 1.54 with standard sodium). Mean daily sodium removal with dialysate at week 12 was 1.188 g higher in the low-sodium group (P < 0.001). BP changed marginally with standard-sodium solution, but decreased with low-sodium PD solution, resulting in less antihypertensive medication.

LIMITATIONS

Broader variability of study population than anticipated, particularly regarding residual kidney function.

CONCLUSIONS

The noninferiority of the low-sodium PD solution for total Kt/Vurea could not be proved; however, it showed beneficial clinical effects on sodium removal and BP.

Haemostasis in chronic kidney disease

The coagulation system has gained much interest again as new anticoagulatory substances have been introduced into clinical practice. Especially patients with renal failure are likely candidates for such a therapy as they often experience significant comorbidity including cardiovascular diseases that require anticoagulation. Patients with renal failure on new anticoagulants have experienced excessive bleeding which can be related to a changed pharmacokinetic profile of the compounds. However, the coagulation system itself, even without any interference with coagulation modifying drugs, is already profoundly changed during renal failure. Coagulation disorders with either episodes of severe bleeding or thrombosis represent an important cause for the morbidity and mortality of such patients. The underlying reasons for these coagulation disorders involve the changed interaction of different components of the coagulation system such as the coagulation cascade, the platelets and the vessel wall in the metabolic conditions of renal failure. Recent work provides evidence that new factors such as microparticles (MPs) can influence the coagulation system in patients with renal insufficiency through their potent procoagulatory effects. Interestingly, MPs may also contain microRNAs thus inhibiting the function of platelets, resulting in bleeding episodes. This review comprises the findings on the complex pathophysiology of coagulation disorders including new factors such as MPs and microRNAs in patients with renal insufficiency.

Prognostic value of arterial pulse wave velocity in peritoneal dialysis patients

BACKGROUND

Cardiovascular disease is the most common cause of mortality in chronic peritoneal dialysis (PD) patients. Increased arterial stiffness may be related to a high peritoneal permeability, resulting in fluid overload of PD patients. We examined the prognostic value and factors that govern the longitudinal change of arterial pulse wave velocity (PWV) in Chinese PD patients.

METHOD

We enrolled 155 new PD patients. PWV was measured at baseline and then repeated after 2 years of follow-up.

RESULTS

At 24 months, the survival of patients with baseline carotid-femoral (CF)-PWV above 10 m/s was significantly worse than that of those with CF-PWV below 10 m/s (76.1 vs. 88.6%, p = 0.006). However, after adjusting for confounding factors, CF-PWV was not an independent predictor of survival. Amongst the 100 patients who had repeated PWV measurement after 2 years, the average CF-PWV increased from 9.92 ± 2.04 to 11.00 ± 2.30 m/s (p < 0.0001). The change in CF-PWV over 2 years significantly correlated with systolic blood pressure (r = 0.241, p = 0.036), serum calcium level (r = 0.231, p = 0.044), and normalized protein nitrogen appearance (NPNA) (r = -0.337, p = 0.001).

CONCLUSIONS

A high baseline CF-PWV was associated with a lower overall survival of Chinese PD patients, but the prognostic value of CF-PWV disappeared after adjusting for confounding factors. After 2 years of PD, most patients had progressive increase in CF-PWV; the magnitude of increase is related to systolic blood pressure, serum calcium level, and baseline NPNA. Further study is needed to determine whether serial measurement of CF-PWV provides additional prognostic information.

Characterization of the pro-thrombotic state in CAPD patients

PURPOSE

To investigate whether a chronic pro-thrombotic tendency, which may contribute to a high rate of atherothrombotic disease, is present in patients treated for continuous peritoneal dialysis (CAPD), and, if so, what its pattern is. We investigated this issue by jointly exploring all the systems involved, the coagulation and fibrinolytic systems and platelets.

METHODS

Markers of coagulation activation, markers of fibrinolysis activation, and standard fibrinolytic parameters and platelet aggregation induced by different agents were measured in 15 patients treated by CAPD and in 15 matched, healthy controls. All CAPD patients received erythropoietin, were in the stable condition, and did not have acute disease or malignancy.

RESULTS

CAPD patients had substantially (p < 0.001) increased levels of prothrombin fragments F1+2, disclosing a low-grade activation of the coagulation system. D-dimer was also significantly (p < 0.05) increased, whereas the levels of t-PA antigen and activity, PAI antigen and activity, and plasminogen were comparable to controls, suggesting that slight secondary (and not primary) activation of fibrinolysis due to coagulation activation took place. Patients had significantly (p < 0.05) elevated levels of fibrinogen. A study of platelet aggregation (induced by adenosine diphosphate, collagen, and epinephrine) did not show platelet hyperactivity in patients.

CONCLUSIONS

We found that a pro-thrombotic tendency is present in the plasma of CAPD patients. The main reason for a pro-thrombotic state is chronic low-grade activation of the coagulation system and elevated levels of fibrinogen. The fibrinolytic system and platelets seemingly do not contribute to this pro-thrombotic tendency.

Relation of demographic, clinic and biochemical parameters to peritonitis in peritoneal dialysis

The relation of various demographic, clinical and biochemical parameters of peritoneal dialysis patients with peritonitis and other infections was evaluated. The age, gender, peritoneal dialysis (PD) period, educational status, peritonitis, exit site score, serum albumin, C-reactive protein (CRP), and triglyceride levels at the beginning and the last visit were recorded. Mean age of 32 patients was 45.1 years; PD period was 13.1 months. Albumin level was inversely proportional to the frequency of peritonitis. Patients with peritonitis had albumin levels that were lower at the last visit, and were independent of the CRP values at the start of PD and during follow-up. Significant correlation was detected between females and exit site scores. There was significant correlation between educational status and peritonitis. Albumin level at first visit was a factor that reduced the likelihood of peritonitis, and low levels obtained during follow-up constituted a risk for peritonitis. It was also shown that peritonitis risk tended to decrease inversely with education level.

Evaluation of aortic stiffness in children with chronic renal failure

The measurement of aortic stiffness (As) [aortic strain (S), pressure strain elastic modulus (Ep) and pressure strain normalized by diastolic pressure (Ep*)] is suggested as an excellent marker of subclinical arterial sclerosis. We aimed to investigate the presence of As and to determine the relationship between As and some risk factors in children with chronic renal failure (CRF). Twenty-six pre-dialysis (PreD) [female/male (F/M) 7/19] patients and 23 chronic peritoneal dialysis (CPD) (F/M 13/10) patients were assessed. Twenty-nine healthy children were selected as a control group (F/M 14/15). We determined anemia, abnormal calcium/phosphate metabolism, hypertension, diastolic dysfunction, increased left ventricular mass (LVM), hypertriglyceridemia, increased stiffness (Ep, Ep*), and decreased strain (S) in the CRF (PreD and CPD) group compared with the controls (P < 0.05). Presence of renal disease, LVM and usage of angiotensin-converting enzyme inhibitor (ACE-I) in all groups; female gender, duration of disease and the usage of anti-hypertensive drug therapy in CRF patients; and LVM and LVM index in healthy children were found to be independent predictors for aortic stiffness and/or strain. In conclusion, CRF is associated with significant arterial functional abnormalities in uremic children and not controlled by dialysis treatment. These results suggest that, even in young children, uremia has a profound impact on arterial function.

Volume control in diabetic and nondiabetic peritoneal dialysis patients

Diabetic patients especially the elderly have higher mortality on peritoneal dialysis treatment as compared to nondiabetic patients. As fluid overload is an important contributor for the high dropout rate in peritoneal dialysis therapy, the present study tried to compare the fluid status in diabetic and non-diabetic peritoneal dialysis patients and to investigate the effect of salt and water restriction on fluid status in diabetic peritoneal dialysis patients.

METHODS

A cross sectional study was performed in 58 peritoneal dialysis patients who had been treated for at least 3 months. Among them, 20 patients were diabetics and the others were nondiabetics. We reviewed their dialysis prescription, peritoneal ultrafiltration, urine volume and fluid status. Then the 20 diabetic patients were advised to restrict their salt and water intake and were followed for 3 months.

RESULTS

During the cross sectional study there were no significant differences in age, gender, height and urine volume between the diabetic and nondiabetic patients. However, body weight, normalized extracellular water (nECW), dialysis dose, dialysate glucose load, peritoneal ultrafiltration, total fluid removal and the prevalence and extent of edema were all significantly higher in diabetics as compared to nondiabetics. After restricting salt and water intake, body weight, nECW, edema, fasting blood glucose, dialysate dose, dialysate glucose load, peritoneal ultrafiltration and total fluid removal were all significantly decreased, whereas the urine volume did not change significantly.

CONCLUSIONS

The present study suggests that diabetic patients were more fluid overloaded as compared to nondiabetics despite use of more hypertonic glucose solutions and, as a consequence, higher peritoneal ultrafiltration and higher total fluid removal; this indicates that our diabetic patients must have had significantly higher salt and fluid intakes. It also suggests that restricting salt and water intake can effectively treat fluid overload in diabetic peritoneal dialysis patients. Dietary salt and fluid restriction may help reduce the use of hypertonic glucose solution and thus facilitate the blood glucose control in diabetic patients undergoing peritoneal dialysis.