Calcium (Ionized and Total), Magnesium, Phosphorus, and Glucose in Plasma from Parturient Cows

Abstract

SUMMARY A calcium ion electrode system was used to assay ionized calcium (Ca ++ ) in plasma from 18 parturient cows, 9 of which developed hypocalcemic paresis and required treatment. Plasma Ca ++ concentration was 0.88 ± 0.13 mEq./L. (mean ± s.d. ) in 9 cows which had signs of parturient paresis, but 2 other cows did not develop paresis despite having plasma Ca ++ values of 0.9 and 1.0 mEq./L., respectively. In 277 samples, Ca ++ could be expressed as a function of total calcium (Ca T ): Ca ++ = 0.388 Ca T ± 0.225 mEq./L. This relationship remained consistent throughout the development and regression of hypocalcemia and after the intravenous infusion of calcium borogluconate. Although Ca ++ varied over a six- to sevenfold range (0.6 to 3.9 mEq./L.), 85% of the variation in Ca ++ could be explained by variation in Ca T . Correlations of plasma Ca ++ with plasma Ca T , Mg, P, and glucose cannot be used to explain the remaining 15% variation in Ca ++ . Magnesium concentration increased at parturition and during hypocalcemia, whereas phosphorus concentration was less than normal. High glucose concentrations were often seen immediately at parturition (maximum, 187 mg./100 ml.), whereas at the nadir of hypocalcemia, only moderate increases (maximum, 96 mg./100 ml.) occurred. Plasma glucose concentration decreased by 30 ± 5 mg./100 ml. in 55 to 270 minutes after calcium borogluconate was infused.