SAT-278 Changes in Biochemical and Electrocardiographic Findings During Insulin Tolerance Test

BACKGROUND : The insulin tolerance test (ITT) is the most sensitive test for evaluation of growth hormone and cortisol deficiency. However, this test has risks of hypoglycemia and its associated complications. Therefore, it is limitedly performed in pediatric patients in clinical practice. This study investigated the changes of serum levels of electrolytes and calcium, and findings on electrocardiography (EKG) during ITT. Methods : We recruited 88 short stature patients who hospitalized the Severance Children’s Hospital for combined pituitary function test between July 2017 and June 2018. The changes in EKG and serum level of electrolytes and calcium were analyzed when the patients were in hypoglycemia during ITT. Results : The mean age of patients at evaluation was 6.33±2.58 years. The height of all patients were below the 3 rd percentile on the Korean children and adolescents growth standard, and mean yearly growth rate was 4.5±1.5cm/yr. Hypoglycemia (serum glucose level of <50 mg/dL) increased heart rate (90.82/min at euglycemia; 109.82/min at hypoglycemia; p <0.001) and corrected QT (QTc) interval (427 ms at euglycemia; 445 ms at hypoglycemia; p <0.001). Hypokalemia was observed in 53 (61.63%) of patients at hypoglycemia and the serum level of potassium decreased from 4.32±0.35 mmol/L to 3.34±0.60 mmol/L (p<0.001). The serum level of calcium did not show any difference. Therefore, additional subgroup analysis was performed to compare the prolongation of QTc in patients with normokalemia and hypokalemia during ITT. The number of patients with prolonged QTc interval (>500ms) was found to be statistically increased in the hypokalemic group compared to the normokalemic group (45.83%(n=22) vs 19.35%(n=6), p=0.016). Among 88 patients, cardiac arrhythmia (1st degree atrioventricular block) was found in 2 patients during hypoglycemia CONCLUSION : Statistically significant differences were noted in serum level of potassium and QTc interval before and after ITT. This study also showed the relationship between prolonged QTc interval (>500ms) and decreased serum level of potassium. Therefore it is important to monitor the changes in EKG continuously during ITT and perform electrolyte tests before and after ITT to ensure the pediatric patient’s safety.