title: Hyponatremia of cirrhosis: role of vasopressin and decreased 'effective' plasma volume.
abstract: BACKGROUND
  The mechanism(s) of hyponatremia of cirrhosis is not completely clarified. Although increased vasopressin activity has been proposed in some studies, there have been reports disputing its role in the pathogenesis of profound hyponatremia in patients with decompensated liver disease. Methodologic flaws and lack of correlation with indices of circulatory dysfunction may have contributed to these discrepancies. The aims of the present study were to measure levels of vasopressin both in plasma and in urine and to correlate them with the volume-dependent hormonal systems of plasma renin activity (PRA) and atrial natriuretic factor (ANF).
  
  
  METHODS
  Plasma vasopressin, ANF, and PRA were measured by radioimmunoassay in 19 patients with cirrhosis, ascites, and severe hyponatremia (mean serum sodium, 121.8 mmol/l) and 11 patients with cirrhosis and normal serum sodium (mean, 137.6 mmol/l). Vasopressin levels were also assessed by radioimmunoassay in urine.
  
  
  RESULTS
  Patients with hyponatremia had higher plasma and urine vasopressin levels than patients with normal serum sodium concentrations (plasma, 2.9 versus 1.0 pg/ml, P = 0.0009; urine, 38.3 versus 12.3 ng/g creatinine, P = 0.0008). PRA was higher (4.8 versus 1.0 ng/ml/h, P = 0.0004) and plasma ANF lower (111.1 versus 148.7 pg/ml, P = 0.01) in patients with hyponatremia.
  
  
  CONCLUSIONS
  These results indicate that plasma and urine vasopressin levels are inappropriately increased in patients with cirrhosis and severe hyponatremia. The concomitant increase of PRA and decrease of plasma ANF suggest that decreased 'effective' plasma volume generates nonosmotic stimuli for vasopressin hypersecretion in these patients.
authors.affiliation: University of Southern California Liver Unit, Rancho Los Amigos Medical Center, Downey 90242, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Akriviadis
authors.forename: M G
authors.initials: MG
authors.lastname: Ervin
authors.forename: F
authors.initials: F
authors.lastname: Cominelli
authors.forename: D A
authors.initials: DA
authors.lastname: Fisher
authors.forename: T B
authors.initials: TB
authors.lastname: Reynolds
mesh_terms: D000328:Adult; D000368:Aged; D009320:Atrial Natriuretic Factor / Q000097:blood* / Q000378:metabolism; D004232:Diuretics / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D007677:Kidney Function Tests; D008103:Liver Cirrhosis / Q000150:complications / Q000188:drug therapy / Q000401:mortality / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010953:Plasma Volume / Q000502:physiology; D011379:Prognosis; D011863:Radioimmunoassay; D012016:Reference Values; D012083:Renin / Q000097:blood* / Q000378:metabolism; D015996:Survival Rate; D016482:Urinalysis; D014667:Vasopressins / Q000097:blood* / Q000378:metabolism / Q000652:urine*
chemical_list: D004232:Diuretics; D014667:Vasopressins; D009320:Atrial Natriuretic Factor; D012083:Renin