Dry weight and sodium balance.

To achieve good blood pressure control and minimal intradialytic patient discomfort, it is very important to define the correct dry weight and individualize the "adequate" dialysate sodium concentration. Given the highly variable amounts of sodium introduced during interdialytic periods, the use of the sodium and conductivity kinetic models guarantees adequate sodium removal in each patient with each treatment. According to our data, the imprecision of the sodium kinetic model was less than 0.84 mEq/L; that of the conductivity kinetic model, which has the advantage not requiring blood or dialysate samples, was less than 0.14 mS/cm. In paired filtration dialysis (PFD), the corresponding figures were less than 1.1 mEq/L and less than 0.1 mS/cm. A multicenter prospective, controlled and randomized trial has demonstrated that the application of the conductivity kinetic model in PFD makes it possible to improve cardiovascular stability in patients prone to dialysis hypotension. The sodium kinetic model is difficult to apply in routine clinical practice because of the need for blood and dialysate samples, but this may be overcome by the conductivity kinetic model, which is a very promising tool for achieving a zero intradialytic sodium balance and improving cardiovascular stability.

The renoprotective effect of antihypertensive drugs.

Some antihypertensive drugs may have a renoprotective effect, that is partially independent of their ability to reduce blood pressure. ACE-inhibitors are safe and effective agents that are capable of reducing proteinuria and preventing CRF progression. The results of the AIPRI extension study suggest that they may also have a long-term renoprotective effect. ACE gene polymorphism may partially influence the response to these agents. Angiotensin II receptor 1 antagonists (AT1RA) are effective in reducing proteinuria, but their clinical impact is still a matter of study. It has been shown that non-dihydropyridine and some dihydropyridine calcium channel blockers (CCBs) reduce proteinuria and are also renoprotective, but there is a lack of large-scale prospective randomised trials. Given that the use of various drugs is usually needed to achieve good blood pressure control in patients with CRF, the possibility that a combination of ACE-inhibitors with CCBs or ATIRAs may have an additive renoprotective effect is intriguing.

GBV-C/HGV infection in end-stage renal disease: a serological and virological survey.

Patients with end-stage renal disease (ESRD) appear to be at high risk for GBV-C/HGV infection. This information has been obtained with virological techniques (RT-PCR) but few serological data exist. A prototype enzyme immunoassay has now been developed to detect antibodies against the putative envelope protein (E2) located on the surface of the GBV-C/HGV virion particle. We studied the prevalence of GBV-C/HGV infection, as detected by RT-PCR and anti-E2 GBV-C/HGV antibody, in a cohort of chronic dialysis patients (n=157) and renal transplant (RT) recipients (n=77); as a control group, 136 healthy blood donors were tested. The total prevalence of GBV-C/HGV in ESRD was 23% (54/234). The frequency of GBV-C/HGV viremia was 7.7% (18/234) in ESRD and 4.4% (3/68) among healthy blood donors; the prevalence of anti-E2 GBV-C/HGV was 15% (36/234) and 8.8% (12/136) in ESRD and controls, respectively. No relationship was seen between anti-E2 GBV-C/HGV antibody (or GBV-C/HGV viremia) and age, sex, time on renal replacement therapy, anti-HCV, HBsAg and transfusion requirement. No statistical association was observed between GBV-C/HGV and AST/ALT activity. Two of 54 GBV-C/HGV positive patients (3.7%) had raised ALT but were negative for HBV/HCV. In the majority of patients (35/36, 97%) the presence of anti-E2 GBV-C/HGV antibody was linked with the loss of GBV-C/HGV viremia from serum. In conclusion, GBV-C/HGV infection, as detected by RT-PCR and anti-E2 antibody, was common in ESRD, and the rate of infection was higher than in controls. No association was seen between GBV-C/HGV and various demographic or clinical factors. A small group of GBV-G/HGV positive patients tested negative for HBV/HCV and had raised ALT. In many patients exposed to GBV-C/HGV infection the virus was cleared. The clinical significance of GBV-C/HGV in ESRD remains controversial. Prospective studies with additional serological assays are in progress.

Sodium balance during extra corporeal dialysis.

In order to reduce intradialytic and interdialytic morbidity, it is important to obtain a zero sodium balance at the end of each dialysis session. This can be achieved by matching exactly the interdialytic sodium and water intake with the intradialytic sodium and water removal. A positive sodium balance can be obtained by using hypernatric dialysis or "sodium ramping" or convective techniques. While reducing the intradialytic side effects (hypotension, cramps, nausea, vomiting), these methods may increase the interdialytic side effects (thirst, weight gain, hypertension and pulmonary edema). Given the highly variable amounts of sodium introduced during the interdialytic periods, the use of sodium-conductivity kinetic models allows removing exactly the amount of sodium accumulated in the interdialytic period. This strategy may be advantageous towards cardiovascular stability in patients prone to dialysis hypotension.