title: Impaired renal function is associated with greater urinary strong ion differences in critically ill patients with metabolic acidosis.
abstract: OBJECTIVE
  Urinary excretion of chloride corrects metabolic acidosis, but this may be hampered in patients with impaired renal function. We explored the effects of renal function on acid-base characteristics and urinary strong ion excretion using the Stewart approach in critically ill patients with metabolic acidosis.
  
  
  METHODS
  We examined the plasma and urine chemistry in 65 critically ill (mixed medical and surgical) patients with metabolic acidosis. The apparent strong ion difference, effective strong ion difference, strong ion gap, and urinary simplified strong ion difference (urinary SID) were calculated. Linear regression analyses were used (1) to assess whether plasma creatinine concentrations were related to urinary SIDs values, adjusted for blood pH levels, and (2) to determine whether urinary SID values were associated with blood pH levels.
  
  
  RESULTS
  Creatinine concentrations were positively and significantly (P < .001) associated with urinary SIDs values, adjusted for pH levels. Urinary simplified strong ion difference values were inversely and significantly (P < .001) related to pH levels.
  
  
  CONCLUSIONS
  In critically ill patients with metabolic acidosis, impaired renal function was associated with greater urinary SIDs. Subsequently, the higher urinary SIDs values were related to lower pH levels, illustrating the importance of renal chloride excretion to correct for acidosis.
authors.affiliation: Department of Intensive Care Medicine, Jeroen Bosch Hospital, 's-Hertogenbosch, 5223HH, The Netherlands.
authors.forename: Miriam
authors.initials: M
authors.lastname: Moviat
authors.forename: Anniek M
authors.initials: AM
authors.lastname: Terpstra
authors.forename: Johannes G
authors.initials: JG
authors.lastname: van der Hoeven
authors.forename: Peter
authors.initials: P
authors.lastname: Pickkers
mesh_terms: D000138:Acidosis / Q000097:blood / Q000150:complications / Q000652:urine*; D058186:Acute Kidney Injury / Q000097:blood / Q000150:complications / Q000652:urine*; D000368:Aged; D002712:Chlorides / Q000097:blood / Q000652:urine*; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies
chemical_list: D002712:Chlorides; D003404:Creatinine