Sones, Donald A.

Abstract Our experiences with the automatic titration method of quantitating serum calcium and magnesium are presented. In addition, modifications of the original procedure to allow determination of intraerythrocyte concentrations of magnesium are described. It appears that adoption of a separate magnesium standard in addition to the calcium standard, plus certain other minor modifications designed to minimize the variables inherent in the procedure, provides a significant increase in accuracy and reproducibility of results. Values for intraerythrocyte magnesium concentration in 9 normal dogs were found to range from 4.69 to 5.77 mg./100 ml. Values for 4 dogs that received long-term administration of chlorothiazide also fell within this normal range.

A study has been made at the Mayo Clinic of the results of treatment in 28 hypertensive patients receiving thiazide diuretics. The use of these agents produced a significant but very temporary reduction in plasma volume in most patients. The plasma volume reverted to or toward normal after the first week of treatment; therefore, hypovolemia could not explain the prolonged hypotensive effect of these drugs. Administration of thiazide diuretics did not deplete the body of its sodium stores, as measured by isotope studies in five patients on an unrestricted diet. Therapy with thiazides did not produce a persistent increase in urinary aldosterone excretion in the nine patients studied for this possibility.