Abstract: 　Objective　To explore early detection and timely treatment of positive reactions and complications of neurally mediated syncope (NMS) children during head-up tilt test (HUTT). Methods　Clinical data of children with NMS diagnosed with HUTT positive examination were retrospectively analyzed. Results　In 201 NMS patients, there were 95 males and 106 females, aged from 7.33 to 9.75 years old. Of them, 98 cases were postural tachycardia syndrome, and 103 cases were vasovagal syncope (VVS). In HUTT test, 5 (2.5%）cases had syncope who were all VVS, 200 (99.5%）cases have complications including 182 (90.5%) with sinus tachycardia and 38 (18.9% ) with sinus bradycardia. In all cases with sinus tachycardia and sinus bradycardia, there were 20 cases (10.0%) with sudden rise and drop in heart rate, 2 (1.0%) with cardiac arrest, 2 (1.0%) with junctional escape beat, 1(0.5%) with II° atrioventricular block, 1 (0.5%) with atrial prematuem beats, 2 (1.0%) with convulsions, and 2 (1.0%）with temporary aphasia. By lying down immediately, once reached positive reaction, oxygen supply, raising and massaging both lower extremities if syncope occurs, compressing chest if cardiac arrest occurs, partial patients given oral milk after wakefulness, and the manifestations above in all the patients disappeared quickly, consciousness, heart rate, blood pressure, ECG return to normal, and no sequela and death. It showed 90.0% (181/201） presyncope in HUTT, and 53.7%（108/201） had presyncope, after then reached positive response, 95%（103/108） of these patients had reached positive response after presyncope in 8 min. There were 23.4% (47/201）presyncope and positive response occurred simultaneously. Conclusion　NMS children have risk during HUTT. The key to reduce the risk of test is to recognize and manage the positive reaction and complications in time.

Key words: 　syncope;　head-up tilt test;　positive reaction;　complications;　child