[The effect of the albumin concentration on the relation between the concentration of ionized calcium and total calcium in the blood of dogs].

Based on the results of 367 healthy dogs of different age, it could be demonstrated that the concentration of ionized calcium corrected to the pH-value of 7.4 ([Cai (7.4)]) as well as the concentration of total calcium ([Catot]) clearly decreased with increasing age. The most obvious changes were found during the first four months. The [Cai (7.4)] was not influenced distinctly by sex or by breed. The reference range (2.5-97.5% quantil) for [Cai (7.4)] in heparinized plasma was 1.32-1.51 mmol/l in 4-months- to 1-year-old dogs and 1.22-1.46 mmol/l in dogs older than one year, corresponding to a proportion of Cai to Catot of 44.9-54.9%. A moderately close correlation existed between [Cai (7.4)] and the [Catot] (r = 0.754) (n = 393 adult dogs: 180 healthy animals and 213 unselected patients). A similar correlation coefficient was found between the concentrations of Catot and albumin (r = 0.718) or total protein (r = 0.617), respectively. The proportion of Cai to Catot decreased with an increasing concentration of albumin, whereas [Cai (7.4)] tended to increase. The correction of the [Catot] for albumin did not lead to an increased correlation coefficient for the relation with [Cai (7.4)] (r = 0.676). In addition to albumin concentration, the relation between [Cai (7.4)] and the Catot is primarily influenced by complex-forming ions. This became clear by the transient citrate-induced decrease of [Cai (7.4)] whereas [Catot] increased after infusion of fresh frozen plasma in dogs suffering from diarrhea. This investigation shows the limits of the estimation of calcium homoeostasis on the basis of the [Catot].