EFFECTS OF HYPERCHLOREMIA ON BLOOD-OXYGEN BINDING IN HEALTHY CALVES

Three different levels of hyperchloremia were induced in healthy Fries ian calves to study the effects of chloride on blood oxygen transport. By infusion, the calves received either 5 ml/kg of 0.9% NaCl (low-lev el hyperchloremia; group A), 5 ml/kg of 7.5% NaCl (moderate hyperchlor emia; group B), or 7.5 ml/kg of 7.5% NaCl (high-level hyperchloremia; group C). Blood was sampled from the jugular vein and the brachial art ery. Chloride concentration, hemoglobin content, arterial and venous p H, Pco(2), and Po-2 were determined. At each time point (0, 15, 30, 60 , and 120 min), the whole blood oxygen equilibrium curve (OEC) was mea sured under standard conditions. In groups B and C, hyperchloremia was accompanied by a sustained rightward shift of the OEC, as indicated b y the significant increase in the standard Po-2 at 50% hemoglobin satu ration. Infusion of hypertonic saline also induced relative acidosis. The arterial and venous OEC were calculated, with body temperature, pH , and Pco(2) values in arterial and venous blood taken into account. T he degree of blood desaturation between the arterial and the venous co mpartments [O-2 exchange fraction (OEF%)] and the amount of oxygen rel eased at tissue level by 100 ml of bovine blood (OEF vol%) were calcul ated from the arterial and venous OEC combined with the Po-2 and hemog lobin concentration. The chloride-induced rightward shift of the OEC w as reinforced by the relative acidosis, but the altered Po-2 values co mbined with the lower hemoglobin concentration explained the absence o f any significant difference in OEF (% and vol%). We conclude that inf usion of hypertonic saline induces hyperchloremia and acidemia, which can explain the OEC rightward shift observed in arterial and periphera l venous blood.