Nitric Oxide Synthetic Capacity in Relation to Dialysate Temperature

Abstract

Background: During hemodialysis, vascular reactivity is impaired, which can be corrected by lowering dialysate temperature. It has also been shown that nitric oxide (NO) is related to intradialytic hypotension. As NO synthesis may be temperature-dependent, this study addressed the influence of dialysate temperature on the NO synthetic capacity of plasma. Methods: NO synthetic capacity was studied during hemodialysis with a dialysate temperature of 37.5°C (dialysis-37.5°C) and programmed extracorporeal blood cooling (cool dialysis; Blood Temperature Monitor; Fresenius C) in 12 stable patients. NO synthetic capacity was assessed ex vivo by [³H]L-citrulline formation from [³H]L-arginine in cultured endothelial cells after incubation with plasma samples obtained during the respective sessions. Results: Core temperature decreased (–0.32 ± 0.10°C) and energy transfer rate was significantly lower (–27.5 ± 2.8 W; p < 0.05) during cool dialysis compared to dialysis-37.5°C (0.19 ± 0.06°C and –0.8 ± 1.2 W respectively; p < 0.05). Systolic blood pressure decreased during dialysis-37.5°C (–19 ± 4 mm Hg; p < 0.05), but not during cool dialysis (–6 ± 5 mm Hg). NO synthetic capacity increased during dialysis-37.5°C (55.5 ± 9.3 to 73.5 ± 10.2 pmol/10⁵ cells; p < 0.05), in contrast to cool dialysis (67.3 ± 11.1 to 66.2 ± 10.8 pmol/10⁵ cells). Conclusion: The stimulatory effect of uremic plasma on endothelial NO synthesis was augmented during dialysis-37.5°C but not during cool dialysis.

Cardiac response to hemodialysis with different cardiovascular tolerance: Heart rate variability and QT interval analysis

“…4,6 Indeed in vitro data 27 indicated that even the small amount of acetate in BD is able to induce NO production in the endothelial cells, whereas in AFB this effect is absent 28 synthesis was augmented during conventional dialysis but not during AFB with cold infusion. 29 The depression of LF power component of HRV that we found in BD supports the hypothesis of an enhanced NO synthesis. In fact, a modulation of the HRV spectral components by NO has recently been shown by several studies.…”

“…As already discussed in Cavalcanti et al a possible explanation for the reduced responsiveness to adrenergic stimulus is an enhanced production of endogenous NO in BD with respect to AFB, as NO overload inhibits the myocardial and vascular contractile responses to adrenergic stimulation by limiting the transmembrane calcium L‐type current 4,6 . Indeed in vitro data 27 indicated that even the small amount of acetate in BD is able to induce NO production in the endothelial cells, whereas in AFB this effect is absent 28 while recently Beerenhout et al have analyzed the influence of dialysate temperature on the NO synthetic capacity of plasma, showing that the stimulatory effect of uremic plasma on endothelial NO synthesis was augmented during conventional dialysis but not during AFB with cold infusion 29 . The depression of LF power component of HRV that we found in BD supports the hypothesis of an enhanced NO synthesis.…”

Reduction in Platelet Activation by Citrate Anticoagulation Does Not Prevent Intradialytic Hemodynamic Instability

“…Noteworthy in this respect are the high plasma nitric oxide (NO) levels in HD patients, particularly in those prone to hypotension [8]. Moreover, it has been shown that the NO synthetic capacity is related to the dialysate temperature [9]. …”

Randomized Clinical Trial of Dialysate Cooling and Effects on Brain White Matter

“…15,16 These beneficial effects of using a lower dialysate temperature are thought to be mainly driven by improved systemic vascular resistance; one study suggested higher production of nitric oxide when using a dialysate temperature of 37.5°C compared with a cooled dialysate. 17 However, the long-term effects of cooling the dialysate on vulnerable vascular beds are still unknown. Optimal temperature for the dialysate is also not known.…”