Reversible sequestration of nitric oxide by hemoglobin during hemodialysisin end-stage renal disease

Background: During hemodialysis, patients whose plasma concentrations of ni tric oxide (NO) products increase reportedly experience hypotension. Theref ore, whether NO bound to hemoglobin (Hb) could contribute to various clinic al and laboratory changes during hemodialysis was explored in patients with endstage renal disease (ESRD). Methods: Ten patients were studied during 3 hemodialysis treatments with samples of blood analyzed for RBC nitrosyl Hb (HbNO), L-arginine, asymmetric dimethylarginine (ADMA), plasma nitrite+nit rate (NOx), and buffy coat NO synthase (NOS) activities. Results: HbNO befo re and during hemodialysis varied considerably. Those with higher predialys is levels had lower HbNO values during dialysis, whereas HbNO levels in tho se with lower levels before dialysis increased. Plasma NOx did not correlat e with HbNO, but change in HbNO in the first hour and change in NOx in the first 2 hours correlated with drop in diastolic and systolic blood pressure s (BP), respectively. HbNO concentrations increased in patients with >35% d rop in systolic BP, whereas in those with <35% drop, HbNO concentrations de creased. HbNO levels adjusted by the hematocrit showed a drop in HbNO for t he <35% group and a >3-fold increase in the >35% group. HbNO levels were hi gher in men than in women, and levels and changes correlated with the hemat ocrit, skin temperatures, plasma ADMA, arginine, and buffy coat NOS. Conclu sions: In patients with >35% drop in systolic BP, NO was scavenged by Hb in the circulating RBCs, undoubtedly attenuating the degree of hypotension. T hese data indicate that the amount of NO that is scavenged or released by H b in the circulating RBCS during dialysis is highly variable and reversible . Various predialysis factors relate to the concentration of HbNO before an d during dialysis, which in turn influence clinical findings that occur dur ing the interdialytic period.