INFLUENCE OF ALBUMIN CONCENTRATION ON THE RELATION BETWEEN THE CONCENTRATION OF IONIZED CALCIUM AND TOTAL CALCIUM IN CANINE BLOOD

Based on the results of 367 healthy dogs of different age, it could be demonstrated that the concentration of ionized calcium corrected to t he pH-value of 7,4 ([Ca-i(7,Ca-4)]) as well as the concentration of to tal calcium ([Catot]) clearly decreased with increasing age. The most obvious changes were found during the first four months. The [Ca-i(7.4 )] was not influenced distinctly by sex or by breed. The reference ran ge (2,5-97,5 % quantil) for [Ca-i(7,Ca-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 i n dogs older than one year, corresponding to a proportion of Ca-i to C a-tot of 44,9-54,9 %. A moderately close correlation existed between [ Ca-i(7,Ca-4)] and the [Ca-tot] (r = 0,754) (n = 393 adult dogs: 180 he althy animals and 213 unselected patients). A similar correlation coef ficient was found between the concentrations of Ca-tot and albumin (r = 0,718) or total protein (r = 0,617), respectively. The proportion of Ca-i to Ca-tot decreased with an increasing concentration of albumin, whereas [Ca-i(7,Ca-4)] tended to increase. The correction of the [Ca- tot] for albumin did not lead to an increased correlation coefficient for the relation with [Ca-i(7,Ca-4)] (r = 0,676). In addition to album in concentration, the relation between [Ca-i(7,Ca-4)] and the Ca-tot i s primarily influenced by complex-forming ions. This became clear by t he transient citrate-induced decrease of [Ca-i(7,Ca-4)] whereas [Ca-to t] increased after infusion of fresh frozen plasma in dogs suffering f rom diarrhea. This investigation shows the limits of the estimation of calcium homoeostasis on the basis of the [Ca-tot].