The ions of calcium, magnesium, potassium, and sodium may be involved singly or in combination in the alteration of neuromuscular irritability in infants and children. Of these the role of magnesium in the neonatal period has received the least attention.
Although hypocalcemia is generally considered the most important factor responsible for initiating tetany, the level of other cations may under certain conditions influence the production of tetanic manifestations. It has been demonstrated by several investigators that for normal neuromuscular activity a certain ratio of the concentrations of serum potassium and calcium should exist. Harrison et al1,2 reported that when their patients with sprue had hypokalemia they showed none of the manifestations of tetany even though hypocalcemia was present. Engle et al3 demonstrated that administration of potassium salts to asymptomatic hypocalcemic and hypokalemic patients may induce active tetany. Harbaugh and Dennis4,5 noted, in their studies in cattle with