If present, these signs include pallor, weakness, lightheadedness, yawning, nausea, diaphoresis, hyperventilation, blurred vision, and impaired hearing immediately before the syncopal event.

• 晕厥发生前，可立即出现面色苍白、虚弱无力、头晕、打哈欠、恶心、出汗、过度通气、视力模糊和听力下降。