engleski

Effects of two different forms of heparin on ionized calcium concentration

Ionized calcium (Ca++) is the physiologically active form of calcium, which compprises aproximately 40 percent-50 percent of total calcium in plasma. It is essential for the contractility of smooth vascular muscle, and it plays a vital part in cardiovascular function. The aim of this study was to test the effect of two different forms of heparin on ionized Ca measurement. The analysis was performed on a Ciba Corning 865 automatic system (Ciba Corning, Medfield, MA, USA). The instrument is used for determination of pH, blood gases, sodium, potassium, Cl, and Ca++ concentration, and makes an adjustment for pH (only when pH at 37 0C is between 7.2 and 7.7), glucose, lactate, tHb and hemoglobin derivatives in arterial, venous and capillary whole blood samples. Two different types of capillaries were used: disposable capillaries for gas analysis heparinized with 80 U/ml Na-heparin , 175 l, (Vitrex, Denmark), and Multi Cap containing 130- 200 U/ml Na+, Li+, Ca++ heparin titrated with KCl (Chiron Diagnostic Corp. East Walpole, MA, USA), 140 l. The measurements of actual ionized calcium referred to the actual patient pH and adjustment of ionized calcium to standard pH at pH 7.4 was done in whole capillary blood samples of 100 subjects. Results were statistically processed by the normality test. Significance of differences was caculated by the Wilcoxon signed rank test for pair data and Passing Bablok non- parametric regression procedure. Results of the comparison showed statistically significant differences between median Ca++ values measured in two different capillaries at actual pH as well as at adjusted pH (p is less than 0.001). The Passing Bablok analysis also yielded significant differences between the two types of capilaries (correlation coefficient r=0.953, p is more than 0.05). Results the both for slope and intercept showed statistically significant differences. According to the results, we conclude that heparin binds calcium and significantly reduces free calcium, and should not be used for Ca++ determination, while capillaries containing a coating of balanced heparin, designed to eliminate heparin-binding of ions, provide the precise results.

different forms of heparin; ionized calcium; Passing Bablock; Ciba Corning 865

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