Impact of nitric oxide on blood pressure in hemodialysis patients.

Nitric oxide (NO) is a powerful vasoactive agent that contributes to the regulation of blood pressure (BP). However, the role of NO in uremic patients and during the course of hemodialysis is still debated. Blood L-arginine concentrations and exhaled NO concentrations were measured in 22 healthy controls and in 22 hemodialysis patients before and after dialysis. On the basis of their BP response during hemodialysis, the patients were divided into three groups: 6 of the 22 patients presented with a decrease in BP during dialysis (group 1), eight presented with a stable BP (group 2), and eight with an increase in BP (group 3). The exhaled NO concentration was higher in dialysis patients than in healthy controls (22.7 +/- 2.6 ppb in dialysis patients v 16.7 +/- 0.9 ppb in controls, mean +/- SEM, P = 0.044). The predialysis and postdialysis exhaled NO concentrations were inversely correlated with the change in BP during hemodialysis (r = -0.47, P = 0.013). Patients with a decrease in BP (group 1) had the highest NO concentrations; patients with an increase in BP (group 3) had the lowest values; and patients with a stable BP during the course of dialysis (group 2) had intermediary values (trend test, P = 0.0291). In addition, both the exhaled NO concentration and the blood L-arginine concentration decreased during dialysis in all patients (P = 0.005 and P = 0.001, respectively). These results provide several novel insights into NO metabolism and BP regulation during hemodialysis: (1) maintenance hemodialysis is associated with a chronic increase in NO concentrations; (2) changes in BP during hemodialysis are inversely correlated with exhaled NO concentrations, higher NO levels being associated with a decrease in BP and lower NO levels with an increase in BP during dialysis; (3) blood L-arginine levels decrease during hemodialysis, and this reduction may in turn influence NO production.