A Practical Protocol: Identifying Thyroidectomy Patients at Low Risk for Significant Hypocalcemia

CHICAGO, ILL. – Researchers from Johns Hopkins School of Medicine have identified a means of detecting thyroidectomy patients who can safely be discharged early after surgery, with little risk of developing significant hypocalcemia.

The research was sparked because there are an increased number of thyroid operations in the U.S. and around the world, began Tarik Y. Farrag, MD, Department of Otolaryngology-Head & Neck Surgery, Division of Endocrinology and Metabolism, Johns Hopkins School of Medicine, Baltimore, Md. We thought it was important to develop a protocol to help identify those patients who are at risk for developing significant hypocalcemia. This protocol could then be used to shorten length of stay for hospitalized patients at low risk, thus saving costs. Dr. Farrag outlined the protocol and the research that led to it in his Triological Society presentation at the Combined Otolaryngological Spring Meetings (COSM), A Safe and Cost Effective Short Hospital Stay Protocol to Identify Patients at Low Risk for the Development of Significant Hypocalcemia following Total Thyroidectomy.

Hypocalcemia is considered the most common complication following bilateral thyroidectomy, reported Dr. Farrag. Significant hypocalcemia can be life-threatening and may not manifest until after the patient is discharged from the hospital. The literature says two things, said Dr. Farrag, to monitor all patients for 48 hours before discharge, and to discharge patients after 24 hours, and send them home with calcium and vitamin D supplements. There is no consensus agreement on identifying the risk of hypocalcemia.

Therefore, Dr. Farrag and his colleagues set out to develop an algorithm that could identify patients at low risk for hypocalcemia, who can be considered suitable for earlier discharge.

Calculating the Risk of Hypocalcemia

We performed a retrospective chart review of 135 patients, explained Dr. Farrag. All charts were from 2001 to 2005, and included 45 males and 90 females. Researchers examined clinical notes and compared serum calcium (Ca) levels for each patient at 6 hours and at 12 hours after surgery.

Patients were divided into two groups: those with positive calcium slope and those with non-positive, said Dr. Farrag. Positive slope refers to an increased rate of change of serum Ca levels between the two time periods; non-positive describes no change or a decreased rate of change over the same period.

The number of patients in each group (positive slope and non-positive slope) who experienced significant hypocalcemia was then compared in order to assess whether the rate of change in the serum Ca level over time could predict significant hypocalcemia.

Fifty of the 135 subjects showed positive slope, and none of those subjects showed significant hypocalcemia at 12 hours.

Of the 85 patients in the non-positive slope group, 70% showed no significant hypocalcemia. Sixty-one had a serum Ca level of at least 8 mg/dl at 12 hours. In this subgroup, eight patients (13%) showed significant hypocalcemia. Seven saw an onset within 24 hours, and one between 24 and 48 hours. There were no readmissions and no necessity of permanent calcium supplements for this subgroup, said Dr. Farrag.

In the 24 non-positive slope patients with a serum Ca level below 8 mg/dl, 18 (75%) showed significant hypocalcemia. Four saw an onset within 24 hours, and 14 between 24 and 48 hours. There were two readmissions and two patients needed permanent calcium supplements.

Dr. Farrag and his colleagues also evaluated patient age, gender, and indication for total thyroidectomy (cases included 81 for cancer, 17 for adenoma, 12 for inflammatory disease, and 25 for goiter) and whether central neck dissection occurred. None of these factors had an impact on the algorithm.

Definitive Results

The results of the research seem clear: Patients who developed significant hypocalcemia had a non-positive slope 100 percent of the time, concluded Dr. Farrag. The researchers concluded that patients with a non-positive slope between 6 and 12 hours postoperatively, with a serum Ca level greater than 8 mg/dl at 12 hours, can be safely discharged from the hospital after 24 hours, as long as they are sent home with patient education and oral calcium supplements. Using the algorithm to identify these patients will eliminate an extra day, possibly longer, in the hospital, thus saving money and making that bed available for the next admission.

The slope of postoperative serum Ca levels is an easy, cost effective, and reliable predictor of who will develop significant hypocalcemia following thyroid surgery, said Dr. Farrag. Our management algorithm safety identifies those patients that can be confidently sent home within a 24-hour period after surgery. It also identifies those who need further hospitalization and are at risk for significant hypocalcemia.

Tarik Y. Farrag, MD

©2006 The Triological Society