Ionized calcium and the heart. Elucidation of in vivo concentration-response relationships in the open-chest dog.

Publisher Website
Google Scholar
Abstract
Pharmacological relationships between Ca2+ and cardiac electric and mechanical parameters were explored in the open-chest dog. A technique that allows determination of reliable, repeatable concentration-response relationships in vivo was developed. This method consists of alternating infusions of sodium citrate and calcium gluconate and direct measurement of serum Ca2+ by an ion-specific electrode. With this technique, 4 consecutive curves for Ca2+ vs. the 1st derivative of the left ventricular pressure (dP/dt) were essentially superimposable within limits of 2-10 mg/100 ml. Relationships between Ca2+ and the ECG interval measured from the end of the S wave to the peak of the T wave (SaTc) proved to be superior to other ECG measurements as a correlate of Ca2+. Ca2+ correlated better than total Ca with physiological function in several situations. Postsurgical Ca2+ levels (4.92 .+-. 0.10 mg/100 ml) were consistently higher than preanesthetic values (4.57 .+-. 0.07 mg/100 ml, P < 0.025), whereas total Ca measurements were not significantly different (.hivin.X = 5.3 .+-. 0.10 meq/l, .hivin.X = 5.1 .+-. 0.10 meq/l, P < 0.1). This difference in Ca2+ apparently was able to account for significant alterations in dP/dt, suggesting that fluctuations in Ca2+ may be involved in regulation of the contractile state of the heart.

This publication has 11 references indexed in Scilit: