Objective —To compare the effects of IV administration of isotonic (1.3%) and hypertonic (8.4%) sodium bicarbonate (NaHCO ₃ ) solutions on acid-base status in dehydrated calves with strong ion (metabolic) acidosis.

Design —Randomized controlled clinical trial.

Animals —50 calves with diarrhea and severe dehydration.

Procedures —Calves were randomly assigned to receive isotonic NaHCO ₃ solution (65 mL/kg [29.5 mL/lb], IV) over 3 hours (n = 30) or hypertonic NaHCO ₃ solution (10 mL/kg [4.5 mL/lb], IV) over 20 minutes (20). Blood samples were collected at 0 hours (immediately prior to solution administration) and at 0.5, 1, 2, and 4 hours after administration began. Samples were submitted for blood gas analysis, serum biochemical analysis, and determination of blood Na ⁺ , K ⁺ , and Cl ⁻ concentrations and percentage change in plasma volume.

Results —Calves that received isotonic NaHCO ₃ solution had an increase in venous blood pH, HCO ₃ concentration, and base excess; a small, transient increase in P o ₂ ; and no change in P co ₂ within 4 hours after administration began. Calves that received hypertonic NaHCO ₃ solution had an immediate increase in venous blood pH, HCO ₃ concentration, and base excess; a small, transient increase P co ₂ ; and no change in P o ₂ within 0.5 hours after treatment began. Plasma volume increased to a greater extent following administration of isotonic solution than after administration of hypertonic solution.

Conclusions and Clinical Relevance —IV administration of 8.4% NaHCO ₃ solution in small volumes provided fast and effective improvement of severe acid-base abnormalities in calves with severe strong ion acidosis but did not improve hydration status as well as administration of a larger volume of isotonic NaHCO ₃ solution.