The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia; Department of Paediatrics, Monash University, Melbourne, Australia.
The Ritchie Centre, The Hudson Institute of Medical Research, Melbourne, Australia; School of Health & Biomedical Sciences, RMIT University, Melbourne, Australia.
Exp Neurol. 2021 Jul;341:113687. doi: 10.1016/j.expneurol.2021.113687. Epub 2021 Mar 10.
In the adult brain, increases in neural activity lead to increases in local blood flow. However, in the preterm neonate, studies of cerebral functional haemodynamics have yielded inconsistent results, including negative responses suggesting decreased perfusion and localised tissue hypoxia, probably due to immature neurovascular coupling. Furthermore, the impact of vasoactive medications, such as dopamine and dobutamine used as inotropic therapies in preterm neonates, on cerebrovascular responses to somatosensory input is unknown. We aimed to characterise the cerebral haemodynamic functional response after somatosensory stimulation in the preterm newborn brain, with and without dopamine or dobutamine treatment.
We studied the cerebral haemodynamic functional response in 13 anaesthetised preterm lambs, using near infrared spectroscopy to measure changes in cerebral oxy- and deoxyhaemoglobin (ΔoxyHb, ΔdeoxyHb) following left median nerve stimulation using stimulus trains of 1.8, 4.8 and 7.8 s. The 4.8 and 7.8 s stimulations were repeated during dopamine or dobutamine infusion.
Stimulation always produced a somatosensory evoked response. Majority of preterm lambs demonstrated positive functional responses (i.e. increased ΔoxyHb) in the contralateral cortex following stimulus trains of all durations. Dopamine increased baseline oxyHb and total Hb, whereas dobutamine increased baseline deoxyHb. Both dopamine and dobutamine reduced the evoked ΔoxyHb responses to 4.8 and 7.8 s stimulations.
Somatosensory stimulation increases cerebral oxygenation in the preterm brain, consistent with increased cerebral blood flow due to neurovascular coupling. Notably, our results show that dopamine/dobutamine reduces oxygen delivery relative to consumption in the preterm brain during somatosensory stimulations, suggesting there may be a risk of intermittent localised tissue hypoxia which has clear implications for clinical practice and warrants further investigation.
在成人大脑中，神经活动的增加会导致局部血流量的增加。然而，在早产儿中，对脑功能血液动力学的研究得出了不一致的结果，包括负反应表明灌注减少和局部组织缺氧，这可能是由于不成熟的神经血管耦合。此外，血管活性药物（如多巴胺和多巴酚丁胺）作为早产儿的正性肌力治疗药物，对躯体感觉输入引起的脑血管反应的影响尚不清楚。我们旨在描述早产儿脑在有或没有多巴胺或多巴酚丁胺治疗的情况下，躯体感觉刺激后的脑血流动力学功能反应。
我们使用近红外光谱法测量 13 只麻醉早产儿左正中神经刺激后大脑氧合和脱氧血红蛋白的变化（ΔoxyHb，ΔdeoxyHb），以测量大脑血流动力学功能反应。使用 1.8、4.8 和 7.8 s 的刺激序列进行刺激。在多巴胺或多巴酚丁胺输注期间重复 4.8 和 7.8 s 的刺激。
刺激总是产生躯体感觉诱发电位。大多数早产儿在所有刺激持续时间后，对侧皮质都表现出正的功能反应（即增加ΔoxyHb）。多巴胺增加基线氧合血红蛋白和总血红蛋白，而多巴酚丁胺增加基线脱氧血红蛋白。多巴胺和多巴酚丁胺都降低了 4.8 和 7.8 s 刺激的诱发ΔoxyHb 反应。
躯体感觉刺激增加了早产儿大脑的氧合，这与神经血管耦合导致的大脑血流增加一致。值得注意的是，我们的结果表明，多巴胺/多巴酚丁胺减少了早产儿大脑在躯体感觉刺激期间的氧输送与消耗的关系，这表明可能存在间歇性局部组织缺氧的风险，这对临床实践有明确的影响，需要进一步研究。
