Iatrogenic hypocalcaemia during parenteral fluid therapy of diarrhoeic calves

Acid-base balance and electrolyte concentrations, including ionised calcium , were monitored during intravenous fluid therapy of 11 collapsed diarrhoei c suckler calves aged five to 10 days. Six healthy calves of similar age an d type were used to provide control data. All the diarrhoeic calves were se verely acidotic (TCO2<12 mmol/litre). Isotonic sodium bicarbonate (1.3 per cent) was administered until the metabolic acidosis was half corrected, as indicated by the TCO2 increasing to 17 to 24 mmol/litre when the infusion w as changed to an extracellular volume replacement fluid containing 144 mmol /litre Na+, 35 mmol/litre HCO3-, 4 mmol/litre K+ and 113 mmol/litre Cl- whi ch was administered until the calf was discharged. Milk feeding was started as soon as the calf had a suck reflex. The treatment was successful in 10 calves. At admission the diarrhoeic calves were hypocalcaemic compared with the control calves, but their ionised calcium was significantly higher; wi th significantly less calcium being protein bound. Treatment with isotonic sodium bicarbonate resulted in a significant improvement in acid-base balan ce, but both total and ionised calcium decreased significantly, the decreas e in ionised calcium being proportionately greater owing partly to a signif icant increase in the protein binding of calcium. The mean total, bound and ionised calcium concentrations were all significantly lower in the treated calves after they had received isotonic sodium bicarbonate than in the con trol calves. Further treatment with replacement fluid had no significant ef fect on any of the parameters apart from pCO(2) which increased significant ly. Milk feeding had no significant effect on plasma calcium concentrations . The calves' mean ionised calcium concentration was significantly lower at the end of the treatment than before it, but there was no difference in th e mean total and bound calcium concentrations. The calves' mean plasma pota ssium and magnesium concentrations decreased significantly during the cours e of the treatment.