Cerebral haemodynamic response to somatosensory stimulation in newborn lamb.
Cerebral haemodynamic response to somatosensory stimulation in newborn lamb.
复制标题
新生羔羊对体感刺激的脑血流动力学反应。
DOI：
10.1113/jp274244
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Wong FY.
中科院分区：
文献类型：
--
作者：
Nakamura S;Walker DW;Wong FY.
神经刺激引起的脑血流动力学反应已在成人中得到广泛研究，但胎儿和新生儿脑的血流动力学反应却知之甚少，本研究采用近红外光谱技术测量了新生羔羊对体感刺激的脑血流动力学反应，与最近在胎羊中的发现相比。新生羔羊脑中的脑血流动力学反应可以涉及氧合血红蛋白（oxyHb）的增加，或氧合血红蛋白减少，表明灌注和氧合减少。在新生儿中发现氧合血红蛋白变化与平均动脉血压之间正相关，但在胎羊中没有发现，这表明结果不太可能单独归因于不成熟的自动调节。与成人研究相反，高碳酸血症增加了大多数羔羊对体感刺激的脑血流和氧合血红蛋白的变化。摘要神经血管耦合反应已经被定义为成人脑，但在新生儿中，使用近红外光谱或血氧水平依赖性功能性磁共振成像对局部脑灌注进行无创测量产生了可变和不一致的结果，包括提示灌注减少和局部组织缺氧的阴性反应。此外，在新生儿管理中允许性高碳酸血症（> 50 mmHg）对体感输入脑血管反应的影响尚不清楚。采用近红外光谱技术检测8只麻醉新生羔羊脑组织氧合血红蛋白和脱氧血红蛋白（ΔoxyHb、ΔdeoxyHb）的变化，研究刺激左正中神经1.8、4.8和7.8s的脑血流动力学功能反应。刺激总是产生体感诱发反应，和表层皮质灌注激光多普勒血流仪测量主要增加正中神经刺激。然而，在1.8 s刺激下，对侧半球的oxyHb反应为阳性（即oxyHb增加）、阴性或不存在;在4.8和7.8 s刺激下，观察到阳性和阴性反应。高碳酸血症增加了基线oxyHb和总Hb，与脑血管舒张一致，7只试验羔羊中有6只在7.8 s刺激后显示出增加的Δ总Hb反应，其中4只羔羊也显示出增加的ΔoxyHb反应。在三只羔羊中的两只中，负ΔoxyHb反应在高碳酸血症期间变为阳性模式。这些结果表明，而不是功能性充血，体感刺激可以引起负（减少氧合血红蛋白，总血红蛋白）的功能反应，在新生儿脑提示减少局部灌注和血管收缩，和高碳酸血症产生基线高灌注和增加功能性充血。
Key pointsCerebral haemodynamic response to neural stimulation has been extensively studied in adults, but little is known about cerebral haemodynamic response in the fetal and neonatal brain.The present study describes the cerebral haemodynamic response measured by near infrared spectroscopy to somatosensory stimulation in newborn lambs, in comparison to recent findings in fetal sheep.The cerebral haemodynamic responses in the newborn lamb brain can involve an increase in oxyhaemoglobin (oxyHb), or a decrease of oxyHb suggestive of reduced perfusion and oxygenation.Positive correlations between changes in oxyHb and mean arterial blood pressure were found in newborn but not fetal sheep, which suggests the result is unlikely to be due to immature autoregulation alone.In contrast to adult studies, hypercapnia increased the changes in cerebral blood flow and oxyHb in most of the lambs in response to somatosensory stimulation.AbstractThe neurovascular coupling response has been defined for the adult brain, but in the neonate non‐invasive measurement of local cerebral perfusion using near infrared spectroscopy or blood oxygen level‐dependent functional magnetic resonance imaging have yielded variable and inconsistent results, including negative responses suggesting decreased perfusion and localized tissue tissue hypoxia. Also, the impact of permissive hypercapnia ( > 50 mmHg) in the management of neonates on cerebrovascular responses to somatosensory input is unknown. Using near infrared spectroscopy to measure changes in cerebral oxy‐ and deoxyhaemoglobin (ΔoxyHb, ΔdeoxyHb) in eight anaesthetized newborn lambs, we studied the cerebral haemodynamic functional response to left median nerve stimulation using stimulus trains of 1.8, 4.8 and 7.8 s. Stimulation always produced a somatosensory evoked response, and superficial cortical perfusion measured by laser Doppler flowmetry predominantly increased following median nerve stimulation. However, with 1.8 s stimulation, oxyHb responses in the contralateral hemisphere were either positive (i.e. increased oxyHb), negative, or absent; and with 4.8 and 7.8 s stimulations, both positive and negative responses were observed. Hypercapnia increased baseline oxyHb and total Hb consistent with cerebral vasodilatation, and six of seven lambs tested showed increased Δtotal Hb responses after the 7.8 s stimulation, among which four lambs also showed increased ΔoxyHb responses. In two of three lambs, the negative ΔoxyHb response became a positive pattern during hypercapnia. These results show that instead of functional hyperaemia, somatosensory stimulation can evoke negative (decreased oxyHb, total Hb) functional responses in the neonatal brain suggestive of decreased local perfusion and vasoconstriction, and that hypercapnia produces both baseline hyperperfusion and increased functional hyperaemia.