Background/Aims:Nitric oxide (NO) plays a key role in the regulation of vascular tone and controls both local and systemic hemodynamics. Here, we estimated systemic NO production rates of hemodialysis (HD) patients, based on the time course of plasma concentration of nitrate (an oxidative end product of NO) and investigated possible roles of NO-related factors. Methods: We measured plasma concentrations of nitrate, L-arginine (a substrate of NO synthase: NOS), asymmetric dimethylarginine (ADMA, an endogenous NOS inhibitor), tetrahydrobiopterin (BH₄, a NOS cofactor), dihydrobiopterin (BH₂, an oxidized form of BH₄) and oxidized low-density lipoprotein (oxyLDL; an index of oxidative stress) before and after 30-min and 4-hour HD (n = 10). Results:The time-averaged NO production rate during HD was estimated by fitting the time course of plasma nitrate concentration with a single-compartment model (4.00 ± 0.82 µmol/min, 4.99 ± 1.08 µmol/kg/h). The L-arginine/ADMA ratio (L-arginine availability) after 30-min HD showed a positive correlation with the NO production rate (p < 0.05). Conclusion: The systemic NO production rate during HD could be estimated by the single-compartment analysis. The L-arginine/ADMA ratio seems to play an important role in the regulation of the NO production during HD.

To investigate the characteristics of the ratio of extracellular water (ECW) to total body water (TBW) volume (ECW/TBW) in a large group of healthy adults, measured by multi-frequency bioelectrical impedance (bioimpedance) analysis (MF-BIA). Subjects and methods: The correlation between ECW and TBW was studied in 957 healthy adults who underwent general medical examinations. Differences between measured and predicted ECW from ECW-TBW correlation equations (ΔECW) were calculated, and possible factors for non-zero ΔECW were explored. To investigate the influence of percent fat mass (%FM) on ECW/TBW, the ECW/TBW values of "lean" and "obese" groups, classified by %FM, were compared. ECW/TBW was also compared between "non-obese" and "obese class I-II" groups, classified by the body mass index for both genders. Results: ECW and TBW showed strong positive correlations in both genders. ΔECW was within ±0.2 L and increased with advancing age; ECW/ TBW also increased. There were no significant differences in ECW/TBW between the "lean" and "obese" groups in either gender, or between the "non-obese" and "obese class I-II" groups in the female group. Conclusions: ECW/TBW measured by MF-BIA was considered to be an index of body water distribution in healthy adults ranging from "lean" to "obese class I-II," which is not significantly affected by body fat.

The ratio of the volumes of extracellular water to total body water (ECW/TBW) obtained by multi-frequency bioelectrical impedance analysis (MF-BIA) indicates body water balance. However, the characteristics of ECW/TBW in hemodialysis (HD) patients have not been fully investigated yet. We evaluated correlations of ECW/TBW with body composition, circulatory and body fluid status, and nutritional status in 60 stable maintenance HD patients using MF-BIA. ECW/TBW increased with increasing age and showed significant positive correlations with volume index (VI), cardiothoracic ratio, and brain natriuretic peptide, all of which are indices of circulatory and body fluid status. Furthermore, there were significant negative correlations between ECW/TBW and serum albumin (Alb), the geriatric nutritional risk index, and the normalized protein catabolic rate, all of which indicate nutritional status. Following multiple regression analysis, the independently related factors for total subjects were age, VI, and Alb. In obese HD patients, ECW/TBW tended to decrease, indicating intravascular dehydration. In conclusion, ECW/TBW in HD patients was shown to increase with age and can reflect circulatory, body fluid, and nutritional status, as well as the difference between predetermined dry weight and "optimal body weight" which may change along with a patient's nutritional status. Keywords aging, circulatory and body fluid status, hemodialysis (HD), multi-frequency bioelectrical impedance analysis (MF-BIA), nutritional status, ratio of extracellular water to total body water volume (ECW/TBW)

Background: In recent years, many reports have investigated the usefulness of brachial artery blood flow (BAF) measured by ultrasonography as an evaluation index for the vascular access (VA) stenosis of hemodialysis patients. However, the mechanism of VA dysfunction, despite BAF being higher than the preset blood flow, has not been clarified to date. Methods: The relationship between actual blood-removal flow and recirculation rate with decreasing VA flow was examined using a VA flow path model and pure water as a model fluid. The blood-flow rate was set at 180 mL/min, and the set VA flow rate was lowered stepwise from 350 to 50 mL/min. VA flow rate, blood-removal flow rate, and flow waveform measured between two needle-puncture sites were recorded, and then the actual blood-removal flow rate and recirculation rate were calculated. Results: Recirculation was observed at a VA flow rate < 300 mL/min. The recirculation was due to the VA flow rate, which was transiently reduced to the level below the blood-removal flow rate, resulting in backflow. In contrast, no decrease in the actual blood-removal flow rate was observed. Conclusion: It is suggested that the mechanism of the VA dysfunction, despite the BAF being higher than the preset blood-flow rate, was due to the diastolic BAF being lower than the blood-removal flow rate.