Reduced production of nitric oxide during haemodialysis

Objective: To examine the influence of systemic nitric oxide (NO) synthesis on blood pressure in patients with chronic renal failure undergoing haemod ialysis, since nitric oxides are susceptible to renal excretion or are dial ysed, a different indicator that is unaffected by renal function, such as t he level of exhaled NO was evaluated. We examined the levels of the endogen ous NO before and after a haemodialysis session. Design and methods: We evaluated the serum concentrations of nitrite/nitrat e and the rate of nitric oxide release into exhaled air in 10 patients with hypertension who were receiving maintenance haemodialysis. Results: The serum concentrations of nitrite/nitrate before haemodialysis w ere significantly higher than those in 10 normal controls (183 +/- 151 mu M vs 42 +/- 17 mu M, P < 0.05). These levels decreased significantly by the end of haemodialysis (42 +/- 26 mu M). Because the amount of nitric oxide i n the deepest expirate correlated well with the duration of exhalation, we were able to derive the rate of release of NO. The rate of NO release was 0 .034 +/- 0.012 nmol/sec before haemodialysis, similar to that in normal con trols (0.031 +/- 0.013 nmol/sec). The rate was significantly reduced after dialysis (0.023 +/- 0.010 nmol/sec) (P < 0.05). The mean pre-dialysis mean blood pressure (109 +/- 11 mm Hg) and the post-dialysis blood pressure (106 +/- 9 mm Hg) were the same. Conclusions: These data indicate that NO production does not appear to have a critical role in control of arterial blood pressure across haemodialysis in patients with chronic renal failure.