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Ionized calcium: serum levels during symptomatic hypocalcemia

M Sorell, J F Rosen

    The Journal of Pediatrics
    |July 1, 1975
    PubMed

    Insights

    Symptomatic hypocalcemia occurs when serum ionized calcium levels drop below 2.50 mg/dl. Direct measurement of ionized calcium is crucial for diagnosing hypocalcemia, as other serum levels do not correlate reliably.

    Area of Science:

    • Biochemistry
    • Clinical Chemistry
    • Endocrinology

    Background:

    • Hypocalcemia, a condition of low calcium levels, can arise from various causes.
    • Accurate assessment of calcium status is vital for patient management.

    Purpose of the Study:

    • To investigate the critical threshold for ionized calcium in symptomatic hypocalcemia.
    • To evaluate the reliability of indirect methods for estimating ionized calcium.

    Main Methods:

    • Direct measurement of serum ionized calcium ([Ca-++]) in nine patients with symptomatic hypocalcemia.
    • Correlation analysis with serum total calcium and phosphate levels.
    • Comparison with predicted [Ca-++] values from the McLean-Hastings nomogram.

    Main Results:

    • All nine patients exhibited serum [Ca-++] ≤ 2.50 mg/dl.
    • No significant correlation was found between [Ca-++] and total calcium or phosphate.
    • The McLean-Hastings nomogram did not accurately predict measured [Ca-++].

    Conclusions:

    • Symptomatic hypocalcemia is associated with serum [Ca-++] near or below 2.50 mg/dl.
    • Direct measurement of serum ionized calcium is essential for confirming hypocalcemia.
    • Indirect measures and nomograms are unreliable for assessing ionized calcium in hypocalcemic patients.

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