Shetty Anil N, Lucke Ashley M, Liu Peiying, Sanz Cortes Magdalena, Hagan Joseph L, Chu Zili D, Hunter Jill V, Lu Hanzhang, Lee Wesley, Kaiser Jeffrey R
Department of Obstetrics and Gynecology, Baylor College of Medicine, Texas Children's Hospital, Pavilion for Women, 6651 Main St., Houston, TX, 77030, USA.
Department of Pediatrics (Neonatology), Baylor College of Medicine, Houston, TX, USA.
Pediatr Radiol. 2019 Feb;49(2):224-233. doi: 10.1007/s00247-018-4283-9. Epub 2018 Nov 6.
Therapeutic hypothermia is the standard-of-care treatment for infants diagnosed with moderate-to-severe hypoxic-ischemic encephalopathy (HIE). MRI for assessing brain injury is usually performed after hypothermia because of logistical challenges in bringing acutely sick infants receiving hypothermia from the neonatal intensive care unit (NICU) to the MRI suite. Perhaps examining and comparing early cerebral oxygen metabolism disturbances to those after rewarming will lead to a better understanding of the mechanisms of brain injury in HIE and the effects of therapeutic hypothermia.
The objectives were to assess the feasibility of performing a novel T2-relaxation under spin tagging (TRUST) MRI technique to measure venous oxygen saturation very early in the time course of treatment, 18-24 h after the initiation of therapeutic hypothermia, to provide a framework to measure neonatal cerebral oxygen metabolism noninvasively, and to compare parameters between early and post-hypothermia MRIs.
Early (18-24 h after initiating hypothermia) MRIs were performed during hypothermia treatment in nine infants with HIE (six with moderate and three with severe HIE). Six infants subsequently had an MRI after hypothermia. Mean values of cerebral blood flow, oxygen extraction fraction, and cerebral metabolic rate of oxygen from MRIs during hypothermia were compared between infants with moderate and severe HIE; and in those with moderate HIE, we compared cerebral oxygen metabolism parameters between MRIs performed during and after hypothermia.
During the initial hypothermia MRI at 23.5±5.2 h after birth, infants with severe HIE had lower oxygen extraction fraction (P=0.04) and cerebral metabolic rate of oxygen (P=0.03) and a trend toward lower cerebral blood flow (P=0.33) compared to infants with moderate HIE. In infants with moderate HIE, cerebral blood flow decreased and oxygen extraction fraction increased between MRIs during and after hypothermia (although not significantly); cerebral metabolic rate of oxygen (P=0.93) was not different.
Early MRIs were technically feasible while maintaining hypothermic goal temperatures in infants with HIE. Cerebral oxygen metabolism early during hypothermia is more disturbed in severe HIE. In infants with moderate HIE, cerebral blood flow decreased and oxygen extraction fraction increased between early and post-hypothermia scans. A comparison of cerebral oxygen metabolism parameters between early and post-hypothermia MRIs might improve our understanding of the evolution of HIE and the benefits of hypothermia. This approach could guide the use of adjunctive neuroprotective strategies in affected infants.
治疗性低温是诊断为中重度缺氧缺血性脑病（HIE）婴儿的标准治疗方法。由于将接受低温治疗的重病婴儿从新生儿重症监护病房（NICU）转运至MRI室存在后勤保障方面的挑战，因此通常在低温治疗后进行MRI以评估脑损伤。或许检查并比较早期脑氧代谢紊乱与复温后的情况，将有助于更好地理解HIE脑损伤机制及治疗性低温的效果。
目的是评估在治疗过程早期，即治疗性低温开始后18 - 24小时，采用一种新型的自旋标记下T2弛豫（TRUST）MRI技术测量静脉血氧饱和度的可行性，提供一种无创测量新生儿脑氧代谢的框架，并比较低温治疗早期和后期MRI的参数。
对9例HIE婴儿（6例中度HIE和3例重度HIE）在低温治疗期间进行早期（低温开始后18 - 24小时）MRI检查。6例婴儿随后在低温治疗后进行了MRI检查。比较中度和重度HIE婴儿低温治疗期间MRI的脑血流量、氧摄取分数和脑氧代谢率的平均值；对于中度HIE婴儿，比较低温治疗期间和治疗后MRI的脑氧代谢参数。
出生后23.5±5.2小时进行首次低温MRI检查时，与中度HIE婴儿相比，重度HIE婴儿的氧摄取分数更低（P = 0.04）、脑氧代谢率更低（P = 0.03），脑血流量有降低趋势（P = 0.33）。对于中度HIE婴儿，低温治疗期间和治疗后MRI之间，脑血流量下降，氧摄取分数增加（尽管无显著差异）；脑氧代谢率无差异（P = 0.93）。
在维持HIE婴儿低温目标温度的同时进行早期MRI检查在技术上是可行的。重度HIE在低温治疗早期脑氧代谢紊乱更严重。对于中度HIE婴儿，低温治疗早期和后期扫描之间脑血流量下降，氧摄取分数增加。比较低温治疗早期和后期MRI的脑氧代谢参数可能会增进我们对HIE演变及低温治疗益处的理解。这种方法可为受影响婴儿辅助神经保护策略的应用提供指导。
