Propofol-containing sedatives increase levels of parathyroid hormone

Effect of general anesthesia and intubation on parathyroid levels in normal patients and those with hyperparathyroidism

BACKGROUND

Induction of general anesthesia and endotracheal intubation may precipitate parathyroid hormone (PTH) elevation in patients with primary hyperparathyroidism (HPT). The purposes of this study were to revisit this observation and to study its impact in healthy patients.

METHODS

Patients with primary HPT who underwent parathyroidectomy were retrospectively studied. The PTH was sampled and compared: before, immediately after general anesthesia and endotracheal intubation, and 15 minutes after parathyroidectomy. Healthy adults who underwent elective operations were prospectively studied. The PTH was sampled before general anesthesia and endotracheal intubation, immediately after, and 15 minutes later.

RESULTS

Thirty-one patients, aged 28-89 years (mean 60.1 ± 13 years), were retrospectively studied. The PTH was significantly elevated after general anesthesia and endotracheal intubation (P = .014). Fifty patients, aged 21-86 years (mean 54 ± 15 years), were prospectively studied. The PTH elevation after general anesthesia and endotracheal intubation was not significant.

CONCLUSION

General anesthesia and endotracheal intubation causes an immediate, steep, and significant PTH elevation in patients with primary HPT but only a minor change in healthy adults. The difference may be attributed to an impaired adrenergic response in patients with primary HPT.

Transient increases in intraoperative parathyroid levels related to anesthetic technique

BACKGROUND

Parathyroid hormone (PTH) secretion is partially regulated by circulating catecholamines. We examined the effect of different anesthetic techniques on intraoperative PTH (IOPTH) levels in patients undergoing parathyroidectomy for primary hyperparathyroidism.

METHODS

We prospectively studied 132 patients divided into 3 anesthetic cohorts: monitored anesthetic care (MAC; n = 45), general anesthesia with laryngeal mask airway (LMA; n = 43), or general endotracheal anesthesia (GETA; n = 39). IOPTH levels were drawn before induction and at defined intervals postinduction.

RESULTS

All anesthetic techniques increased IOPTH levels from preinduction to 3 minutes postinduction (MAC, 28%; LMA, 45%; GETA, 65%; P < .001). Temporal trends in postinduction IOPTH levels were similar in patients receiving general anesthesia, characterized by a peak effect at 6 minutes. Using a multivariate logistic regression analysis, GETA was >7 times more likely to increase the preinduction IOPTH by ≥ 50% at 3 minutes postinduction compared with MAC (P < .0001). Using immediate postinduction IOPTH levels in surgical decision making would have led to failed surgery in 2 of 6 patients with multiple gland disease receiving GETA.

CONCLUSION

Preincision IOPTH samples should be drawn before induction to avoid incorporation of potentially misleading anesthetic-related IOPTH elevations into surgical decision making.

Contemporary and practical uses of intraoperative parathyroid hormone monitoring

OBJECTIVE

To describe the evolution and current applications of intraoperative parathyroid hormone (PTH) monitoring along with a detailed description of intraoperative protocol and assay methodology.

METHODS

Review of the literature regarding the role of intraoperative PTH monitoring in parathyroidectomy, controversies associated with its use in the treatment of hyperparathyroidism, and outcomes using this operative approach. The technologies currently available for "quick" PTH measurement are summarized.

RESULTS

Since its inception, intraoperative PTH monitoring has become an essential tool in the endocrine surgeon's armamentarium for treatment of sporadic primary hyperparathyroidism. Intraoperative PTH monitoring changed the operative approach to this disease from bilateral neck exploration with identification of all parathyroid glands and excision based on size, to a highly successful procedure achieved with a limited dissection and gland excision guided by hormone hypersecretion instead of morphologic characteristics. Intraoperative PTH monitoring accuracy is directly associated with the intraoperative criteria used. Although controversy exists regarding the best intraoperative PTH monitoring criteria to be used, most specialized centers have shown excellent results with this intraoperative guidance. Currently, most parathyroid surgeons use intraoperative PTH monitoring, selectively or routinely, during parathyroidectomy.

CONCLUSION

Parathyroidectomy guided by intraoperative PTH monitoring to treat sporadic primary hyperparathyroidism is a highly successful and less-invasive approach associated with lower risks than bilateral neck exploration, and it has become the surgical treatment of choice for this disease.

Effects of propofol on intraoperative parathyroid hormone monitoring in patients with primary hyperparathyroidism undergoing parathyroidectomy: a randomized control trial

PURPOSE

Serial measurements of parathyroid hormone (PTH) serum concentrations aid parathyroidectomy surgery. There are concerns that propofol may increase PTH concentrations and/or interfere with PTH assays. The primary purpose of this study is to determine the effects of propofol on PTH concentrations in patients with primary hyperparathyroidism and to determine its effect on PTH assays.

METHODS

Thirty patients with primary hyperparathyroidism were assigned randomly to induction and maintenance with either propofol or sevoflurane. Blood samples for PTH assays were obtained pre-induction, immediately after induction, ten minutes after induction, and after excision of parathyroid adenoma. The primary endpoint was the PTH concentration at ten minutes after induction. This endpoint was compared between groups using analysis of covariance adjusting for pre-induction PTH. An in vitro study was performed with four different pools of PTH concentrations that were spiked with increasing concentrations of propofol. Serum PTH was measured in duplicate in each sample and analyzed using repeated measures analysis of variance.

RESULTS

At ten minutes after induction, PTH concentrations did not differ significantly between groups (least square mean difference -7.0 pg·mL(-1); 95% confidence interval, -34.2 to +20.2). The PTH level in vitro did not change significantly with increasing propofol concentrations.

DISCUSSION

Parathyroid hormone concentrations in patients with primary hyperparathyroidism were not affected by the type of anesthesia (propofol vs sevoflurane). Furthermore, propofol was found not to interfere with PTH assays at clinically relevant concentrations. There is no evidence to support the avoidance of a propofol anesthetic for parathyroid surgery.

Article Commentary: Current Applications of the Intraoperative Parathyroid Hormone Assay in Parathyroid Surgery

Parathyroid hormone measurement using a two-site immunochemiluminometric assay has allowed for a rapid and accurate technique that has found its way into the operative armamentarium of some parathyroid surgeons. It can be used to assess the completeness of parathyroid gland resection and allow for a minimally invasive parathyroidectomy. This operative approach has become a popular marketing tool, providing patients with confidence in their surgical outcome. The purpose of this review is to provide the surgeon with the practical points and pitfalls of the use of intraoperative parathyroid hormone in the treatment of parathyroid disease.

Does propofol anesthesia affect intraoperative parathyroid hormone levels? A randomized, prospective trial

BACKGROUND

Intravenous propofol (2,6-diisopropylphenol) infusion is used commonly for sedation/anesthesia during operations. Several authors have reported that propofol can interfere with intact parathyroid hormone (PTH) testing in vitro. Therefore, many surgeons avoid propofol during parathyroidectomy.

METHODS

To determine whether propofol affects intraoperative PTH levels in vivo, we randomly assigned 34 patients (80% power; alpha < .05) with secondary hyperparathyroidism to undergo surgery for dialysis access. Patients were assigned randomly to local anesthesia with either propofol (n = 17 patients) or midazolam (n = 17 patients) sedation. PTH values were obtained before the procedure and at 10 minutes and 30 minutes after the start of the propofol or midazolam.

RESULTS

Median preoperative serum PTH and calcium levels were 175 pg/mL (range, 27-2646 pg/mL) and 9.2 mg/dL (range, 8.1-10.8 mg/dL), respectively. There was no statistically significant difference between the PTH levels in the 2 groups at each of our time points. There was also no difference in the percentage of change from baseline in the PTH values between our 2 groups. No patient in either group had a sustained drop in their PTH level of greater than 50%.

CONCLUSIONS

Intravenous propofol infusion does not alter PTH levels significantly during the operation. Therefore, we believe the intraoperative PTH assay can be used safely during propofol sedation when parathyroid surgical procedures are being performed.

Measurement of parathyroid hormone and application of parathyroid hormone in intraoperative monitoring

There has been a clear progression in assays for the analysis of PTH and its clinical applications. This includes the innovative use of PTH as a point-of-care assay as an intraoperative measure of the success of parathyroid surgery. The rapid PTH assay has served as a model for the development of other rapid hormone assays, such as for adrenocorticotropic hormone,although the clinical usefulness of these other applications is less well established. Knowledge of the circulating forms of PTH continues to progress. Information about the biologic and immunologic activities of these forms will aid in the interpretation and clinical use of current assays and in the development of new assays with improved specificities. The clinical laboratory will continue to play a vital role in providing testing and support for this important mediator of mineral metabolism.

Assessment and management of patients with abnormal calcium

Calcium is essential for homeostasis, and normocalcemia should be maintained strictly during the perioperative period. The biochemistry of calcium equilibrium results from the calcium-sensing receptors on the parathyroid glands, which detect changes in calcium concentrations and initiate the proper response. Asymptomatic hypercalcemia is a common metabolic derangement that is often discovered on routine serum screening. The most common etiologies are primary hyperparathyroidism and cancer. Increasingly, parathyroidectomy is the preferred therapy for primary hyperparathyroidism. Severe hypercalcemia ("hypercalcemic crisis") should be managed aggressively with a combination of intravenous fluids, steroids, bisphosphonates, and calcitonin. Some of these patients may require an urgent parathyroidectomy for calcium control. Hypocalcemia needs to be verified, as many cases of hypocalcemia are the artifact of hypoalbuminemia. Severe hypocalcemia occurs after subtotal or total parathyroidectomy with auto transplantation as well as after massive resuscitation or blood transfusion. Strategies aimed at correcting calcium concentrations depend on the severity of symptomatology. If symptoms are mild, oral calcium supplementation can be given; otherwise, intravenous calcium should be administered.