Risk stratification for outpatient parathyroidectomy and predictors of postoperative complications

The mainstay of treatment for primary hyperparathyroidism is surgery. Hypocalcemia after parathyroidectomy is common and poses a significant challenge, leading to increased patient morbidity and health care costs. While several groups have found predictor factors for hypocalcemia, none have created a risk stratification model. Here, we recognize important factors and optimal cut-off values that can allow risk stratification of patients.

A single-institution retrospective chart review of 339 patients that underwent parathyroidectomy from 2009 to 2012 was conducted. Pre-operative, intra-operative, and post-operative data were collected. A non-routine outcome was defined as post-operative admission, outpatient hypocalcemia-related complication, or inpatient hypocalcemia-related complication. The preoperative or intraoperative factors of patients that experienced a non-routine outcome were compared to those that did not. Optimal cut-off values were determined for preoperative and intraoperative factors and a risk stratification method was created.

A total of 39 patients experienced a non-routine outcome including 24 postoperative admissions, 2 inpatient hypocalcemia-related complications, and 17 outpatient hypocalcemia-related complications. Patients with a non-routine outcome displayed a trend toward preoperative hypercalcemia (calcium >11.0mg/dL) than not (p=0.0543). The median preoperative parathyroid hormone (PTH) level was significantly higher among patients with a non-routine outcome (p=0.0037). Furthermore, the median percent decrease in PTH at 20min intraoperatively among patients with a non-routine outcome was significantly higher compared to those that did not (p=0.0421). The optimal cut-off value for preoperative PTH was 129pg/mL and for median percent decrease in intraoperative PTH at 20min was 90.7% for predicting a non-routine outcome. A risk stratification model was created based on these data.

Our analysis reveals that patients with larger intraoperative decrease in PTH levels (greater than 90.7% drop at 20min), higher preoperative hypercalcemia (greater than 11mg/dL), and higher preoperative PTH levels (greater than 129pg/mL) are more likely to experience a non-routine outcome during outpatient parathyroidectomy. Patients can be risk stratified based on this criteria.