title: Altering plasma sodium concentration rapidly changes blood pressure during haemodialysis.
abstract: BACKGROUND
  Plasma sodium is increased following each meal containing salt. There is an increasing interest in the effects of plasma sodium concentration, and it has been suggested that it may have direct effects on blood pressure (BP) and possibly influences endothelial function. Experimental increases of plasma sodium concentration rapidly raise BP even when extracellular volume falls.
  
  
  METHODS
  Ten patients with end-stage renal failure established on haemodialysis were studied during the first 2 h of dialysis without fluid removal during this period. They were randomized to receive haemodialysis with (i) dialysate sodium concentration prescribed to 135 mmol/L and (ii) 145 mmol/L in random order in a prospective, single-blinded crossover study. BP measurements and blood samples were taken every 30 min.
  
  
  RESULTS
  Pre-dialysis sitting BP was 137/76 ± 7/3 mmHg. Lower dialysate sodium concentration (135 mmol/L) reduced plasma sodium concentration [139.49 ± 0.67 to 135.94 ± 0.52 mmol/L (P < 0.001)], whereas plasma sodium concentration was not altered by higher dialysate sodium (145 mmol/L) (140.17 ± 0.66 mmol/L at baseline to 140.72 ± 0.43 mmol/L at 120 min). Systolic BP was lower with dialysate sodium concentration 135 mmol/L [area under the curve (AUC) 15823.50 ± 777.15 (mmHg)min] compared with 145 mmol/L [AUC 17018.20 ± 1102.17 (mmHg)min], mean difference 1194.70 ± 488.41 (mmHg)min, P < 0.05. There was a significant positive relationship between change in plasma sodium concentration and change in systolic BP. This direct relationship suggests that a fall of 1 mmol/L in plasma sodium concentration would be associated with a 1.7 mmHg reduction in systolic BP (P < 0.05).
  
  
  CONCLUSIONS
  The potential mechanism for the increase in BP seen with salt intake may be through small but significant changes in plasma sodium concentration.
authors.affiliation: Epsom and St Helier University Hospitals NHS Trust.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Suckling
authors.forename: Pauline A
authors.initials: PA
authors.lastname: Swift
authors.forename: Feng J
authors.initials: FJ
authors.lastname: He
authors.forename: Nirmala D
authors.initials: ND
authors.lastname: Markandu
authors.forename: Graham A
authors.initials: GA
authors.lastname: MacGregor
mesh_terms: D001794:Blood Pressure / Q000187:drug effects*; D018592:Cross-Over Studies; D015314:Dialysis Solutions / Q000737:chemistry*; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000628:therapy*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D006435:Renal Dialysis; D012307:Risk Factors; D016037:Single-Blind Method; D012964:Sodium / Q000097:blood* / Q000494:pharmacology*; D015996:Survival Rate
chemical_list: D015314:Dialysis Solutions; D012964:Sodium
keywords: blood pressure; dietary salt; plasma sodium