A crystalloid`s in vivo effects on plasma pH are described by 3 general rules: SID > [inline image] increases plasma pH (alkalosis); SID < [inline image] decreases plasma pH (alkalosis); and SID = [inline image] yields no change in plasma pH.
The in vitro pH of commercially prepared crystalloid solutions has little to no effect on plasma pH because of their low titratable acidity.
Appreciation of IV fluid composition and an understanding of basic physicochemical principles provide therapeutically valuable insights about how and why fluid therapy can produce and correct alterations of plasma acid-base equilibrium.
The ideal balanced crystalloid should (1) contain species-specific concentrations of key electrolytes (Na+, Clâ, K+, Ca++, Mg++), particularly Na+ and Clâ; (2) maintain or normalize acid-base balance (provide an appropriate SID); and (3) be isosmotic and isotonic (not induce inappropriate fluid shifts) with normal plasma.
Source: Muir, W. (2017), Effect of Intravenously Administered Crystalloid Solutions on Acid-Base Balance in Domestic Animals. Journal of Veterinary Internal Medicine, 31: 1371â1381. doi: 10.1111/jvim.14803
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