Kurth C Dean, McCann John C, Wu Jun, Miles Lili, Loepke Andreas W
Department of Anesthesiology, Cincinnati Children's Hospital, University of Cincinnati College of Medicine, Cincinnati, Ohio 45229-3039, USA.
Anesth Analg. 2009 Apr;108(4):1268-77. doi: 10.1213/ane.0b013e318196ac8e.
Detection of cerebral hypoxia-ischemia (H-I) and prevention of brain injury remains problematic in critically ill neonates. Near-infrared spectroscopy (NIRS), a noninvasive bedside technology could fill this role, although NIRS cerebral O(2) saturation (Sc(O2)) viability-time thresholds for brain injury have not been determined. We investigated the relationship between H-I duration at Sc(O2) 35%, a viability threshold which causes neurophysiological impairment, to neurological outcome.
Forty-six fentanyl-midazolam anesthetized piglets were equipped with NIRS and cerebral function monitor (CFM) to record Sc(O2) and electrocortical activity (ECA). After carotid occlusion, inspired O(2) was adjusted to produce H-I (Sc(O2) 35% with decreased ECA) for 1, 2, 3, 4, 6 or 8 h in different groups, followed by survival to assess neurological outcome by behavioral and histological examination.
For H-I lasting 1 or 2 h, ECA and Sc(O2) during reperfusion rapidly returned to normal and neurological outcomes were normal. For H-I more than 2-3 h, ECA was significantly decreased and Sc(O2) was significantly increased during reperfusion, suggesting continued depression of tissue O(2) metabolism. As H-I increased beyond 2 h, the incidence of neurological injury increased linearly, approximately 15% per h.
A viability-time threshold for H-I injury is Sc(O2) of 35% for 2-3 h, heralded by abnormalities in NIRS and CFM during reperfusion. These findings suggest that NIRS and CFM might be used together to predict neurological outcome, and illustrate that there is a several hour window of opportunity during H-I to prevent neurological injury.
在危重新生儿中，脑缺氧缺血（H-I）的检测及脑损伤的预防仍然存在问题。近红外光谱（NIRS）是一种无创床边技术，可能发挥这一作用，尽管尚未确定脑损伤的NIRS脑氧饱和度（Sc(O2)）生存时间阈值。我们研究了在导致神经生理损伤的生存阈值Sc(O2) 35%时，H-I持续时间与神经学转归之间的关系。
46只接受芬太尼-咪达唑仑麻醉的仔猪配备了NIRS和脑功能监测仪（CFM），以记录Sc(O2)和皮层电活动（ECA）。在颈动脉闭塞后，调整吸入氧以在不同组中产生H-I（Sc(O2) 35%且ECA降低）1、2、3、4、6或8小时，随后存活，通过行为和组织学检查评估神经学转归。
对于持续1或2小时的H-I，再灌注期间的ECA和Sc(O2)迅速恢复正常，神经学转归正常。对于超过2 - 3小时的H-I，再灌注期间ECA显著降低，Sc(O2)显著升高，提示组织氧代谢持续抑制。随着H-I超过2小时增加，神经损伤发生率呈线性增加，约每小时15%。
H-I损伤的生存时间阈值是Sc(O2) 35%持续2 - 3小时，再灌注期间NIRS和CFM出现异常可预示。这些发现表明NIRS和CFM可能联合用于预测神经学转归，并说明在H-I期间有几个小时的机会窗口来预防神经损伤。
