Methylene blue, a nitric oxide inhibitor, prevents haemodialysis hypotension

Background. Plasma nitric oxide (NO) levels have been found to be high in h aemodialysis (HD) patients, especially in those prone to hypotension in dia lysis. The aim of the study was to prevent dialysis hypotension episodes by i.v. administration of methylene blue (MB). an inhibitor of NO activity an d or production. Methods. MB was given i.v. in 18 stable HD patients with hypotensive episod es during almost every dialysis, in 18 HD patients without hypotension duri ng dialyses, and in five healthy controls. MB was given as a bolus of 1 mg/ kg bodyweight followed by a constant infusion of 0.1 mg/kg bodyweight lasti ng 210 min until the end of the dialysis session and only as a bolus on a n on-dialysis day. Systolic and diastolic blood pressures (BP) were measured at 10-min intervals during HD sessions with or without MB and on a non-dial ysis day with MB. Results, In hypotension-prone patients, MB completely prevented the hypoten sion during dialysis and increased both systolic and diastolic BP on nondia lysis days. In normotensive patients, MB increased BP during the first hour of dialysis and for 90 min on the non-dialysis day. The BP in the healthy controls remained unchanged. Plasma and platelet NO2 + NO3 (stable metaboli tes of NO) levels were determined, The NO2+NO3 generation rate in the first postdialysis day was calculated. The plasma and platelet NO2 + NO3 were hi gher in the hypotensive group than in the normotensive dialysis group. The generation rate of nitrates was higher (P < 0.01) in the hypotensive group (1.21<plus/minus>0.13 mu mol/min and 0.74 +/-0.16 after MB) than in the nor motensive patients (0.61 +/-0.11 mu mol min and 0.27 +/-0.14 after MB). No side-effects were recorded. Conclusions, MB is an efficient therapy in the prevention of dialysis hypot ension.