title: Solute loss plays a major role in polydipsia-related hyponatraemia of both water drinkers and beer drinkers.
abstract: BACKGROUND
  Polydipsia-related hyponatraemia is generally considered an acute dilutional state.
  
  
  OBJECTIVE
  To determine whether solute loss plays a role in the pathogenesis of polydipsia-related hyponatraemia.
  
  
  METHODS
  Prospective uncontrolled study.
  
  
  METHODS
  We studied routine biochemical volume-related parameters before and after 2 l isotonic saline infusion over 24 h, in 10 consecutive hyponatraemic polydipsia patients (mean age 55 +/- 11 years; 6 beer drinkers and 4 compulsive water drinkers) with initial urinary osmolality <220 mosm/kg H(2)O. In five of these patients, we measured balance data over 24 h.
  
  
  RESULTS
  Mean initial plasma protein concentration in the 10 studied polydipsia patients was 7 +/- 0.7 g/dl, unexpectedly high for an acute dilutional state. Mean plasma sodium concentration increased from 126 +/- 5 mmol/l before saline, to 135 +/- 5 mmol/l after infusion of 2 l isotonic saline (p < 0.01). Balance data in five polydipsia patients showed a mean decrease of 1.6 kg of their initial body weight and a mean salt retention of 406 mosm.
  
  
  CONCLUSIONS
  Polydipsia-related hyponatraemia is a mixed disorder, in which about half of sodium decrease is due to solute loss. This explains the apparent paradox of a normal plasma protein concentration, despite the increase in body weight due to water intoxication.
authors.affiliation: Department of Internal Medicine, Bracops Hospital, Research Unit for the Study of Hydromineral Metabolism, Erasme University Hospital, Free University of Brussels, Brussels, Belgium.
authors.forename: W
authors.initials: W
authors.lastname: Musch
authors.forename: O
authors.initials: O
authors.lastname: Xhaet
authors.forename: G
authors.initials: G
authors.lastname: Decaux
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000009:adverse effects; D001515:Beer; D001798:Blood Proteins / Q000378:metabolism; D001835:Body Weight / Q000502:physiology; D004326:Drinking / Q000502:physiology; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
chemical_list: D001798:Blood Proteins