title: Renal physiology in elderly persons with severe immobility syndrome.
abstract: OBJECTIVE
  The immobility syndrome (IS) is a common condition in the elderly and consists of a reduction in the capacity to perform daily activities because of motor function deterioration. This syndrome leads to characteristic structural and physiological changes in the body, but renal physiology studies have not been conducted on this population. For this reason, we decided to study prospectively changes in renal function in these individuals.
  
  
  METHODS
  We enrolled into this study 17 volunteers over 64 years of age, all of whom lived in the same nursing home. The patients were divided into two groups: nine healthy mobile persons and eight others who suffered from severe IS. Exclusion criteria were the presence of any disease or use of any drug that could induce water and electrolytes alteration. Blood and urine samples were drawn to measure sodium, potassium, creatinine, urea, calcium, phosphorus, magnesium, and uric acid in order to obtain their fractional excretion. Plasma osmolality and vasopressin were also measured. Total body water and lean body mass were obtained by bioelectrical impedance analysis. Statistical analysis was performed applying Student's t-test (P = 0.01) and Pearson's correlation test.
  
  
  RESULTS
  A significant difference in body water composition was found between the groups. Thus in the IS group plasma sodium level was slightly lower and total water content was significantly higher than in the mobile subjects: 140 +/- 5 vs. 143 +/- 1 mmol/l (P = 0.01); 61 +/- 8% vs. 50 +/- 10% (P < 0.001), respectively. Despite these differences, plasma osmolality and vasopressin values were within the normal range in both groups. However, there was a good positive correlation between these two variables in the mobile group only: R 0.9 (mobile) vs. R -0.2 (immobile). We found no significant difference in plasma creatinine or fractional excretion of sodium, potassium, calcium, phosphorus, magnesium, urea, and uric acid between the groups.
  
  
  CONCLUSIONS
  Total body water content was significantly higher in the elderly who suffered from severe immobility syndrome than in healthy mobile elderly. In contrast with the mobile group, for which there was a good positive correlation between plasma osmolality and plasma vasopressin, for individuals with IS there was no correlation between plasma osmolality and plasma vasopressin.
authors.affiliation: Nephrology Department, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina. carlos.musso@hospitalitaliano.org.ar
authors.forename: Carlos
authors.initials: C
authors.lastname: Musso
authors.forename: Vassilios
authors.initials: V
authors.lastname: Liakopoulos
authors.forename: Norma
authors.initials: N
authors.lastname: Pangre
authors.forename: Julio
authors.initials: J
authors.lastname: DiTrolio
authors.forename: Ricardo
authors.initials: R
authors.lastname: Jauregui
authors.forename: Raul
authors.initials: R
authors.lastname: De Miguel
authors.forename: Ioanis
authors.initials: I
authors.lastname: Stefanidis
authors.forename: Nora
authors.initials: N
authors.lastname: Imperiali
authors.forename: Luis
authors.initials: L
authors.lastname: Algranati
mesh_terms: D000203:Activities of Daily Living; D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D012307:Risk Factors; D013577:Syndrome