Predictability of hypocalcemia using early postoperative serum calcium levels

In operations involving the thyroid or parathyroid glands, postoperative serum calcium levels are one contributing factor to patients' length of hospital stay. In this study, we wanted to determine whether early postoperative serum calcium levels could be used to predict hypocalcemia following operations of the thyroid or parathyroid glands.

A retrospective chart review was performed on 203 patients who had undergone operations involving risk to the parathyroid glands. This included patients who had bilateral thyroid operations or those who had one or more parathyroid glands removed for various disease processes. Postoperative calcium levels were plotted as a function of time, and the slope between the first two levels was examined. Both serum calcium levels were drawn within 12 hours after the operation.

A positive slope predicted normocalcemia in 100% of patients undergoing thyroid or parathyroid procedures. A negative slope was predictive in magnitude. Patients who developed hypocalcemia had an average slope two to three times more negative than those remaining normocalcemic.

It appears that early serum calcium levels may be predictive for postoperative hypocalcemia in operations that put the parathyroid glands at risk.