Hypoproteinemia, strong-ion difference, and acid-base status in critically ill patients

J Appl Physiol (1985). 1998 May;84(5):1740-8. doi: 10.1152/jappl.1998.84.5.1740.


The present study was a prospective, nonrandomized, observational examination of the relationship among hypoproteinemia and electrolyte and acid-base status in a critical care population of patients. A total of 219 arterial blood samples reviewed from 91 patients was analyzed for arterial blood gas, electrolytes, lactate, and total protein. Plasma strong-ion difference ([SID]) was calculated from [Na+] + [K+] - [Cl-] - [La-]. Total protein concentration was used to derive the total concentration of weak acid ([A]tot). [A]tot encompassed a range of 18.7 to 9.0 meq/l, whereas [SID] varied from 48.1 to 26.6 meq/l and was directly correlated with [A]tot. The decline in [SID] was primarily attributable to an increase in [Cl-]. A direct correlation was also noted between PCO2 and [SID], but not between PCO2 and [A]tot. The decrease in [SID] and PCO2 was such that neither [H+] nor [HCO-3] changed significantly with [A]tot.

MeSH terms

  • Acid-Base Equilibrium / physiology*
  • Adult
  • Aged
  • Carbon Dioxide / blood
  • Chlorides / blood
  • Critical Illness / epidemiology
  • Electrolytes / blood*
  • Humans
  • Hypoproteinemia / physiopathology*
  • Middle Aged
  • Regression Analysis
  • Sodium / blood


  • Chlorides
  • Electrolytes
  • Carbon Dioxide
  • Sodium