Hypotensive Episodes in Children on Hemodialysis: Role of Nitric Oxide

Background: In children with end stage renal disease, under regular haemodialysis therapy, hypotensive episodes during haemodialysis are the most frequent cardiovasc . lar complications during the dialysis procedure. It has been suggested that nitric oxide (NO), a gaseous free tdical derived from L-arginine that mediates important physiological processes including the regulation of cardiovascular dynamics, could be a factor in the development of these haemodialysis-related hypotensive episodes through its relaxing effect on the microvasculature. A possible cause for excessive NO production in uremia can be guanidosuccinate, a uraemic toxin, that accumulates in uraemic patients and upregulates NO synthesis from endothelial cells. Objectives: Our aim was to investigate the possible involvement of endogenous NO in acute hypotensive episodes during maintenance haemodialaysis. Methods: This study was conducted on 25 children (16 males and 9 females) with end stage renal disease (ESRD). Their ages ranged from 6 to 18 years with mean of (14.88 ± 3.9) on regular haemodialaysis therapy, following up at the Pediatric Dialysis Unit, Children's Hospital, Ain Shams University. The studied group included 13 normotensive patients (5 of them had hypotensive episodes) and 12 hypertensive patients (7 of them had hypotensive episodes). A group of 10 healthy children were selected to serve as a control group. Patients have undergone careful clinical examination with special emphasis on measurement of blood pressure: before, during and after dialysis. Plasma concentration of nitrate and nitrite (NO2+NO 3), NO stable end products, were measured in the control subjects and in the patients before, during and after dialysis sessions. Results: It was found that in all end stage renal disease children, under regular haemodialysis, there were significant increases in plasma NO2+NO3 levels compared to controls either before, during or after dialysis. Furthermore, there was a strong negative correlation between the mean % change of plasma NO2+NO 3 levels and mean % change of arterial blood pressure. Before dialysis, plasma NO2+NO3 levels were significantly lower in patients who experienced hypotensive episodes, while during dialysis, patients with hypotensive episodes showed significant increase in their plasma NO2+NO3 levels in comparison to their level in those with no hypotensive episodes. There was no statistically significant difference between normotensive and hypertensive patients as regards their plasma NO either before, during or after dialysis. Conclusion: These findings suggest that hypotension during dialysis in ESRD may be related, at least in part, to the increase in NO in some patients. The basis for the rising level of NO is not well understood. From our study, it could be suggested that the low predialysis plasma level of NO in patients with hypotensive episodes may stimulate NO production and this sudden increase of plasma NO level may be the cause of hypotensive episodes during haemodialysis in those patients. INTRODUCTION Nitric oxide (NO), a gaseous free radical derived from L-arginine, is a potent modulator of vascular tone and platelet function" ) . It exerts a variety of renal and extra-renal physiological and pathophysiological effects (2) . Nitric oxide is produced within the kidney and plays an important role in the control of many intrarenal processes, which