Z. F. Khan1, R. Teo1, M. L. Mao1, J. C. Farrá1, J. I. Lew1 1University Of Miami,Division Of Endocrine Surgery, DeWitt Daughtry Family Department Of Surgery, University Of Miami Leonard M. Miller School Of Medicine,Miami, FL, USA
Introduction:
Parathyroidectomy (PTX) guided by intraoperative parathormone (ioPTH) monitoring for primary hyperparathyroidism (pHPT) confirms removal of all hyperfunctioning parathyroid glands. A >50% ioPTH drop criterion at 10 minutes after abnormal parathyroid gland excision predicts operative success in 98% of patients. However, ioPTH levels may be influenced by gland manipulation and PTH half-life variability between patients. This study evaluates the utility of an additional 20 minute ioPTH measurement when a 10 minute value has not dropped by >50% during PTX in patients with pHPT.
Methods:
A retrospective review of prospectively collected data of 739 patients with pHPT confirmed by elevated serum calcium and PTH levels who underwent ioPTH monitoring guided PTX at a single institution was performed. When a >50% ioPTH drop from the highest either pre-incision or pre-excision level was achieved after 10 minutes, PTX was completed. If this >50% ioPTH drop criterion was not met, however, bilateral neck exploration (BNE) was performed, or an additional 20 minute ioPTH measurement was obtained. Operative success was defined as eucalcemia ≥6 months whereas recurrence was defined as calcium and PTH levels above normal range >6 months after successful PTX. Multiglandular disease (MGD) was defined as persistently elevated PTH and calcium levels despite removal of one hypersecreting gland at the initial operation, or when removal of a single gland resulted in operative failure.
Results:
Of 739 patients with a mean follow up of 41 months, overall operative success was 98.5% with a recurrence rate of 1.1%. Within this group, 79 (11%) patients did not meet the >50% ioPTH drop at 10 minutes criterion. Of these patients, 63% (50/79) patients underwent immediate further exploration, while a 20 minute ioPTH measurement was drawn in 37% (29/79). There were no significant differences in preoperative calcium, PTH or creatinine in these two groups. Of patients with a 20 minute ioPTH level with no further exploration, 38% (11/29) had a >50% ioPTH drop at 20 minutes, and 62% (18/29) did not. There were no significant differences between operative success, failure, recurrence or MGD between patients who had a 20 minute ioPTH measurement and those who underwent immediate further exploration. Of the 79 patients that did not meet the >50% ioPTH drop criterion at 10 minutes, there was a statistically significant lower rate of BNE in the group with a 20 minute ioPTH level measured compared to the group that underwent immediate further exploration (38% 11/29 vs. 64% 32/50, p<0.05). By obtaining a 20 minute ioPTH level, BNE was avoided in 38% (11/29) of patients that had a ≤50% ioPTH drop at 10 minutes.
Conclusion:
A 20 minute ioPTH measurement is useful in preventing unnecessary BNE and its associated risk for complications in patients with a delayed >50% ioPTH drop due to parathyroid gland manipulation and PTH half-life variability during PTX.