Effect of Intravenously Administered Crystalloid Solutions on Acid‐Base Balance in Domestic Animals

• Published in: Journal of veterinary internal medicine Vol. 31; no. 5; pp. 1371 - 1381
• Main Author: Muir, W.
• Format: Journal Article
• Language: English
• Published: United States John Wiley and Sons Inc 01.09.2017
• Subjects: Acid-Base Equilibrium - drug effects; Acidosis - veterinary; Acid‐base balance; Animals; Base replacement; Crystalloid Solutions; Fluid therapy; Fluid Therapy - veterinary; Hydrogen-Ion Concentration; Infusions, Intravenous - veterinary; Isotonic Solutions - administration & dosage; Isotonic Solutions - pharmacology; Metabolic acidosis; Physiology; Review; Small Animal; Fluid therapy; Physiology; Acid-base balance; Base replacement; Metabolic acidosis
• ISSN: 0891-6640; 1939-1676
• DOI: 10.1111/jvim.14803

Intravenous fluid therapy can alter plasma acid‐base balance. The Stewart approach to acid‐base balance is uniquely suited to identify and quantify the effects of the cationic and anionic constituents of crystalloid solutions on plasma pH. The plasma strong ion difference (SID) and weak acid concentrations are similar to those of the administered fluid, more so at higher administration rates and with larger volumes. A crystalloid's in vivo effects on plasma pH are described by 3 general rules: SID > [HCO3−] increases plasma pH (alkalosis); SID < [HCO3−] decreases plasma pH (alkalosis); and SID = [HCO3−] 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+, Cl−, K+, Ca++, Mg++), particularly Na+ and Cl−; (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.