Hemoglobin and plasma vitamin C levels in patients on peritoneal dialysis.

OBJECTIVE: To determine the contribution of vitamin C (Vit C) status in relation to hemoglobin (Hb) levels in patients on long-term peritoneal dialysis (PD). METHODS: 56 stable PD patients were evaluated in a cross-sectional survey. Plasma samples were collected for Vit C (analyzed by HPLC with electrochemical detection) and high-sensitivity C-reactive protein (hs-CRP) determinations. Clinical records were reviewed for Hb, transferrin saturation (TSAT), ferritin, erythropoietin (EPO) dose, and other clinical parameters. Dietary Vit C intake was evaluated by patient survey and from patient records. Total Vit C removed during PD treatment was measured in 24-hour dialysate collections. RESULTS: Patients showed a highly skewed distribution of plasma Vit C levels, with 40% of patients below normal plasma Vit C levels (<30 µmol/L) and 9% at higher than normal levels (>80 µmol/L). Higher plasma Vit C levels were associated with higher Hb levels (Pearson r = 0.33, p < 0.004). No direct connection between Vit C levels and reported dietary intake could be established. In stepwise multiple regression, plasma Vit C remained significantly associated with Hb (p = 0.017) but there was no significant association with other variables (dialysis vintage, age, ferritin, TSAT, hs-CRP, residual renal function, and EPO dose). In 9 patients that were evaluated for Vit C in dialysate, plasma Vit C was positively associated (Spearman r = 0.85, p = 0.01) with the amount of Vit C removed during dialysis treatment. CONCLUSIONS: These data indicate that plasma Vit C is positively associated with higher Hb level. Vit C status could play a major role in helping PD patients to utilize iron for erythropoiesis and achieve a better Hb response during anemia management.

The utility of two daytime icodextrin exchanges to reduce dextrose exposure in automated peritoneal dialysis patients: a pilot study of nine patients.

BACKGROUND: The use of dextrose-containing solutions in peritoneal dialysis (PD) is thought to be associated with glucose-related toxicity both to the peritoneal membrane and systemically. There has, therefore, been considerable interest in minimizing the use of dextrose exposure during PD. The present study was designed to explore the use of icodextrin in patients with high/high-average transporter characteristics for two exchanges per day to minimize glucose exposure. METHODS: We performed a 6-month prospective cohort study using two icodextrin exchanges per day in a group of high/high-average transporters maintained on automated PD. Icodextrin levels, serum sodium levels, and glucose exposure were measured at baseline, 3 and 6 months. RESULTS: Nine patients completed the study protocol. While the total volume of PD solution remained the same, there was a reduction in mean glucose exposure from a baseline mean value of 410 +/- 75 to 275 +/- 57 g/day at 3 months and 300 +/- 75 g/day at 6 months. Serum icodextrin levels rose from a baseline mean of 345 +/- 145 to 615 +/- 120 mg/dl at 3 months and 620 +/- 108 mg/dl at 6 months. Serum sodium levels remained stable. CONCLUSION: The use of two (double) icodextrin exchanges in high/high-average transporters on PD can contribute to reduction in glucose exposure for patients maintained on automated PD and appears to be safe.

Measurement of intraperitoneal volume by segmental bioimpedance analysis during peritoneal dialysis.

BACKGROUND: Currently, ultrafiltration during peritoneal dialysis is determined from direct measurement of weight differences between the initial filling and final draining volumes. A new technique based on segmental bioimpedance analysis (SBIA) has been developed to accurately measure intraperitoneal volume continuously during peritoneal dialysis. METHODS: Twenty-two peritoneal dialysis patients were studied in a supine position during peritoneal dialysis consisting of 4 tidal exchanges (TPD). For bioimpedance measurements, 4 electrodes were placed, 1 on each hand and foot, to inject an alternating current. Sensing electrodes were placed on the lower ribs and the buttocks on both sides of the body. Calibration of the SBIA method was performed by first filling a known volume of dialysate to establish the relationship between change in resistance and a known fluid volume in the peritoneal cavity. The increase of fluid volume in the peritoneal cavity during dwell time was considered to be equal to net ultrafiltration volume occurring during this period. These measurements were compared with those obtained by the difference in weight between the total filling and draining volumes. RESULTS: The change in intraperitoneal volumes measured by differences in weight (0.39 +/- 0.29 L) did not differ significantly from those established from SBIA (0.41 +/- 0.31 L). Bland-Altman analysis yielded limits of agreement of 0.12 L. CONCLUSION: The SBIA technique provides a continuous noninvasive approach to the measurement of changes in intraperitoneal fluid volume.