van Dijk J Gert, van Rossum Ineke A, Thijs Roland D
Department of Neurology, Leiden University Medical Centre, Leiden, Netherlands.
Stichting Epilepsie Instellingen Nederland, Heemstede, Netherlands.
Front Cardiovasc Med. 2020 Mar 13;7:36. doi: 10.3389/fcvm.2020.00036. eCollection 2020.
Syncope usually lasts less than a minute, in which short time arterial blood pressure temporarily falls enough to decrease brain perfusion so much that loss of consciousness ensues. Blood pressure decreases quickest when the heart suddenly stops pumping, which happens in arrhythmia and in severe cardioinhibitory reflex syncope. Loss of consciousness starts about 8 s after the last heart beat and circulatory standstill occurs after 10-15 s. A much slower blood pressure decrease can occur in syncope due to orthostatic hypotension Standing blood pressure can then stabilize at low values often causing more subtle signs (i.e., inability to act) but often not low enough to cause loss of consciousness. Cerebral autoregulation attempts to keep cerebral blood flow constant when blood pressure decreases. In reflex syncope both the quick blood pressure decrease and its low absolute value mean that cerebral autoregulation cannot prevent syncope. It has more protective value in orthostatic hypotension. Neurological signs are related to the severity and timing of cerebral hypoperfusion. Several unanswered pathophysiological questions with possible clinical implications are identified.
晕厥通常持续不到一分钟，在这段短时间内，动脉血压会暂时下降到足以显著减少脑灌注，从而导致意识丧失。当心脏突然停止泵血时，血压下降最快，这发生在心律失常和严重的心脏抑制性反射性晕厥中。意识丧失在最后一次心跳后约8秒开始，循环停止在10 - 15秒后发生。在体位性低血压导致的晕厥中，血压下降要慢得多。站立时血压随后可稳定在低值，常导致更细微的体征（即无法行动），但通常不会低到足以导致意识丧失。当血压下降时，脑自动调节试图保持脑血流量恒定。在反射性晕厥中，血压快速下降及其较低的绝对值意味着脑自动调节无法预防晕厥。它在体位性低血压中有更大的保护价值。神经学体征与脑灌注不足的严重程度和时间有关。确定了几个未解决的具有潜在临床意义的病理生理问题。
