La determinación de PTH intraquirúrgica por quimioluminicncia predice la hipocalcemia en el postoperatorio de la tiroidectomia en niños.

FREIRE ANALÍA; CHIESA ANA; ACHA O; GRINSPON R; BRASLAVSKY D; TROIANO MARINA; BALLERINI G; MORINI M; ROPELATO MG; GRUÑEIRO DE PAPENDIECK L

Revista del Hospital de Niños Ricardo Gutierrez

Hospital Gutierrez

Lugar: Buenos Aires; Año: 2010 vol. 52 p. 442 - 448

0521-517X

Introduction: Hypocalcemia after thyroidectomy develops because of hypoparathyroidism secondary to parathyroid trauma or their inadvertent removal during thyroid resection. Due to its short half-life, PTH was reported as a useful monitor of postsurgical hypoparathyroidism in adults but there are no studies within a pediatric population. Objective: To evaluate the diagnostic accuracy of intra and postoperative PTH to predict the risk of hypocalcemia in children undergoing total thyroidectomy. Methods: We performed a prospective blind longitudinal cohort study. Twenty patients (3-17y) undergoing total thyroidectomy were included. Intact PTH was measured by ICMA (IMMULITE, Siemens, CVs <5.4 %, functional sensitivity=8pg/ml). Peripheral PTH measurements at 5 min after thyroid removal (intraoperative) and 60 min after thyroid removal (postoperative) were considered the predicting variables. The end-point variable was the postsurgical outcome: hypocalcemia was defined as total calcium (TCa)<8 mg/dL and/or ionized calcium (iCa)<0.8 nmol/L. Surgeons and endocrinologists ignored PTH levels. Signs or symptoms of hypocalcemia TCa and/or iCa were monitored regularly for 48 h after surgery. Treatment (calcium and active vitamin D3) were given to hypocalcemic patients.ROC curves were used to identify the PTH level that provided the best prediction of postsurgical hypocalcemia according to their sensitivity (S), specificity (Sp) diagnostic efficiency (DEf) and positive predicted value (PPV). Relative risk (RR) was calculated by Fisher’s test.  Results: 10/20 patients developed hypocalcemia whereas 3/10 were symptomatic.  Serum calcium dropped throughout the first 6 h in 40% of patients and at 24 h in 40%. None of the patients presented hypocalcemia after 36 h post surgery. Intraoperative PTH<14 pg/mL predicted hypocalcemia with S:80%, Sp:100%, DEf:90% (95%CI,72-100) and PPV:100%, while postoperative PTH<14 pg/mL showed S:80%, Sp:90%, DEf:82% (95%CI,63-100) and PPV:80%.  An intra or postoperative serum PTH<14 pg/mL bear a RR of 9 for developing hypocalcemia after thyroidectomy. Conclusion: Intra and postoperative PTH is an accurate tool for predicting hypocalcemia after thyroidectomy in children. Routine use of it would avoid unnecessary controls in patients identified as low-risk of hypocalcemia and allow the introduction of timely prophylactic calcium treatment in high-risk patients. This strategy would reduce morbidity as well as length and costs of hospitalization.