D. S. Kim1, A. E. Barber1, R. C. Wang1 1University Of Nevada School Of Medicine,Division Of Otolaryngology-Head And Neck Surgery, Department Of Surgery,Las Vegas, NV, USA
Introduction:
Intraoperative parathyroid hormone (iPTH) assay is frequently employed as a predictive marker for postoperative hypocalcemia in total thyroidectomy and as an outcome measure in parathyroidectomy for primary hyperparathyroidism. However, studies have shown that, while parathyroid hormone (PTH) is primarily regulated by serum calcium levels, it is also partly influenced by alpha-adrenergic stimulation. In fact, the induction of general anesthesia with laryngoscopy and endotracheal intubation has been shown to increase catecholamine secretion significantly, thus causing a surge in PTH. At this time, the implication of these findings is not well understood in head and neck endocrine surgery. The aims of this study were to investigate the effect of anesthesia on iPTH in total thyroidectomy and parathyroidectomy and to understand the implications of the relationship in using iPTH as a surgical outcome parameter.
Methods:
This was a prospective cohort study with chart review. Thirty-seven patients undergoing total or completion thyroidectomy and seventeen patients undergoing parathyroidectomy for primary hyperparathyroidism at a tertiary level academic center and a community hospital between November 2014 and July 2015 were enrolled. PTH was measured at least at four time-points: pre-anesthesia (immediately prior to surgery), pre-incision (following anesthesia induction but before skin incision), post-excision (following complete excision of a thyroid or parathyroid gland) and post-operative (12 hours and beyond). Normal intact PTH was defined as 11.1 – 79.5 pg/ml.
Results:
iPTH increased globally following anesthesia induction and endotracheal intubation. In the total and completion thyroidectomy group, the mean pre-anesthesia and pre-incision PTH were 55.9 ± 15.2 pg/ml and 138 ± 42.2 pg/ml, respectively. The mean percentage increase from pre-anesthesia to pre-incision PTH was 149 ± 92.7% (range: 42 – 494%). In the parathyroidectomy group, the mean pre-anesthesia and pre-incision PTH were 176 ± 179 pg/ml and 254 ± 300 pg/ml, respectively. The mean percentage increase from pre-anesthesia to pre-incision PTH was 30.3 ± 38.6 % (range: 1 – 129%). The differences in PTH increases between two groups were significant (p<0.05). PTH normalized postoperatively in all patients in both groups. No incidence of postoperative vocal cord paresis or paralysis was observed.
Conclusion:
Parathyroid hormone rises following anesthesia induction and endotracheal intubation in total thyroidectomy and parathyroidectomy. However, the response is significantly blunted in patients undergoing parathyroidectomy compared to the total thyroidectomy group. Both phenomena should be taken into consideration when using iPTH as a therapeutic or predictive marker in head and neck endocrine surgery.