Kohn C W, Brooks C L
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Ohio State University, Columbus 43210.
Am J Vet Res. 1990 Aug;51(8):1206-10.
Blood, serum, and plasma total calcium concentrations and plasma and serum ionized calcium concentrations were anaerobically determined by use of a calcium-specific electrode for samples obtained from 39 healthy horses. Mean (+/- SD) serum ionized calcium concentration was 6.6 +/- 0.3 mg/dl (1.6 +/- 0.1 mmol/L) and the mean serum ionized calcium percentage was 58.2 +/- 3.4%. Serum ionized calcium percentage was not significantly correlated with serum pH. Plasma ionized calcium percentage was weakly correlated with plasma pH (r = -0.480; P less than or equal to 0.05). Ionized calcium concentration was determined in serum samples manipulated in vitro by additions of 1 to 80 microliters of 0.1N hydrochloric acid or sodium hydroxide to yield 6 to 10 pH values between 6.8 and 8.2. In all horses, the relationship between serum ionized calcium percentage and serum pH at these pH values was then examined by use of a repeated-measures multiple regression analysis. Correlations between serum ionized calcium percentage and adjusted serum pH value for each horse were highly significant (P less than or equal to 0.05); however, analysis of pooled data from all horses indicated that a statistically significant relationship between serum pH and ionized calcium percentage did not exist. Lack of a significant relationship between these variables was most likely attributable to heterogeneity of variance of ionized calcium percentage among horses, reflecting variation in undefined biochemical constituents of serum that affect the equilibrium of calcium binding. When it is essential to evaluate the calcium status of a horse, direct measurement of serum ionized calcium concentration is recommended.
对从39匹健康马匹采集的样本，使用钙特异性电极厌氧测定血液、血清和血浆中的总钙浓度以及血浆和血清中的离子钙浓度。平均（±标准差）血清离子钙浓度为6.6±0.3mg/dl（1.6±0.1mmol/L），平均血清离子钙百分比为58.2±3.4%。血清离子钙百分比与血清pH无显著相关性。血浆离子钙百分比与血浆pH呈弱相关（r = -0.480；P≤0.05）。在体外处理血清样本，加入1至80微升0.1N盐酸或氢氧化钠，使pH值在6.8至8.2之间产生6至10个值，然后测定离子钙浓度。在所有马匹中，随后使用重复测量多元回归分析检查这些pH值下血清离子钙百分比与血清pH之间的关系。每匹马血清离子钙百分比与校正后血清pH值之间的相关性高度显著（P≤0.05）；然而，对所有马匹的汇总数据进行分析表明，血清pH与离子钙百分比之间不存在统计学上的显著关系。这些变量之间缺乏显著关系很可能归因于马匹之间离子钙百分比的方差异质性，反映了影响钙结合平衡的血清中未定义生化成分的变化。当必须评估马匹的钙状态时，建议直接测量血清离子钙浓度。
