A comparison of corrected serum calcium levels to ionized calcium levels among critically ill surgical patients.

BACKGROUND: Aberrations in calcium homeostasis are common in critically ill patients. The proper method to evaluate this issue in surgical patients has not been completely defined.

METHODS: Medical records of patients admitted to a university-affiliated, tertiary-care surgical intensive care unit were retrospectively reviewed. Calcium status was evaluated by ionized levels and as a function of serum calcium levels corrected for albumin aberrations.

RESULTS: Corrected serum calcium values failed to accurately classify calcium status in 38% of cases. The sensitivity and specificity of the corrected serum calcium formula to evaluate hypocalcemia were 53% and 85%, respectively. Corrected serum values underestimated the prevalence of hypocalcemia and overestimated the prevalence of normocalcemia. No factors were able to discern which patients could be evaluated by corrected serum calcium levels.

CONCLUSIONS: Calcium homeostasis should be evaluated by ionized calcium levels rather than as a function of serum calcium and albumin levels.