Effects of intravenous rehydration protocols based on an acetate-containing electrolyte solution, isotonic saline, and an isotonic mixture of saline/sodium bicarbonate on acid-base status and plasma electrolyte concentrations in calves with diarrhoea.

Strong ion (metabolic) acidosis, dehydration, and electrolyte imbalances are common in neonatal calves with diarrhoea. Balanced crystalloids may provide advantages for rehydration purposes in those animals due to their polyionic composition and higher buffer capacity compared to conventional buffer-free fluids such as 0.9 % NaCl. This randomized clinical trial aimed to compare the effects of three infusion solutions - an acetate-containing balanced electrolyte solution (Sterofundin® ISO; Stero), 0.9 % saline (NaCl), and an isotonic saline-sodium bicarbonate mixture (NaClBic) - on acid-base status and plasma electrolyte concentrations in neonatal calves with diarrhoea. Thirty-three calves with diarrhoea, metabolic acidosis (plasma HCO3- < 25 mmol/L), and signs of clinical dehydration were enrolled. After initial correction of metabolic acidosis using 5.6 % sodium bicarbonate over 55 min, each of 11 calves randomly received one of the three infusion solutions at 8 mL/kg/h for 22 h. All three crystalloids had an acidifying effect, which was most pronounced in the NaCl group and least in the NaClBic group. At 18 and 24 h after initiation of treatment, plasma bicarbonate concentrations were significantly lower (P < 0.05) in the Stero and NaCl groups compared to the NaClBic group. Hyperchloraemia was observed in calves treated with 0.9 % NaCl. No statistically significant differences in clinical variables or plasma potassium, magnesium, and calcium concentrations were observed between groups after 24 h. In conclusion, the acetate-containing balanced solution did not provide a clinically relevant advantage over NaCl and NaClBic. However, findings support the use of chloride-restricted solutions for rehydration purposes in dehydrated neonatal calves with diarrhoea.