Application of Calcium in Acute Care Medicine
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Cardiac automaticity depends on the calcium ion, for the initial depolarizing current in sinus atrial and atrioventricular nodal cells is carried principally by the calcium ion.
The calcium ion reprents a universal coupling factor between excitation and response in many different cells. Best known examples of transmission of signals at the cell surface to the cell interior include excitation-contraction coupling and excitation-secretion coupling.
The calcium ion influences neuronal transmission: it influences the membrane permeability of nerve cells and thereby the resting potential of excitable membranes, by controlling the rate and duration of the sodium and potassium exchange across the cell membrane. For example, at low extracellular [Ca + +] levels, the membrane permeability for sodium and potassium is increased, and therefore, the depolarization threshold for initation of the action potential lowered. Characteristically, therfore, low calcium is associated with increased neuromuscular irritability.
KeywordsMassive Transfusion Calcium Infusion Hemodynamic Function Calcium Therapy Sinus Atrial
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