Monash Biomedicine Discovery Institute and Department of Medical Imaging and Radiation Sciences, Monash University, Clayton, VIC, Australia.
Monash Biomedical Imaging, Monash University, Clayton, VIC, Australia.
PLoS One. 2017 Dec 6;12(12):e0188737. doi: 10.1371/journal.pone.0188737. eCollection 2017.
Injurious mechanical ventilation causes white matter (WM) injury in preterm infants through inflammatory and haemodynamic pathways. The relative contribution of each of these pathways is not known. We hypothesised that in vivo magnetic resonance imaging (MRI) can detect WM brain injury resulting from mechanical ventilation 24 h after preterm delivery. Further we hypothesised that the combination of inflammatory and haemodynamic pathways, induced by umbilical cord occlusion (UCO) increases brain injury at 24 h.
Fetuses at 124±2 days gestation were exposed, instrumented and either ventilated for 15 min using a high tidal-volume (VT) injurious strategy with the umbilical cord intact (INJ; inflammatory pathway only), or occluded (INJ+UCO; inflammatory and haemodynamic pathway). The ventilation groups were compared to lambs that underwent surgery but were not ventilated (Sham), and lambs that did not undergo surgery (unoperated control; Cont). Fetuses were placed back in utero after the 15 min intervention and ewes recovered. Twenty-four hours later, lambs were delivered, placed on a protective ventilation strategy, and underwent MRI of the brain using structural, diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) techniques.
Absolute MRS concentrations of creatine and choline were significantly decreased in INJ+UCO compared to Cont lambs (P = 0.03, P = 0.009, respectively); no significant differences were detected between the INJ or Sham groups and the Cont group. Axial diffusivities in the internal capsule and frontal WM were lower in INJ and INJ+UCO compared to Cont lambs (P = 0.05, P = 0.04, respectively). Lambs in the INJ and INJ+UCO groups had lower mean diffusivities in the frontal WM compared to Cont group (P = 0.04). DTI colour mapping revealed lower diffusivity in specific WM regions in the Sham, INJ, and INJ+UCO groups compared to the Cont group, but the differences did not reach significance. INJ+UCO lambs more likely to exhibit lower WM diffusivity than INJ lambs.
Twenty-four hours after injurious ventilation, DTI and MRS showed increased brain injury in the injuriously ventilated lambs compared to controls. DTI colour mapping threshold approach provides evidence that the haemodynamic and inflammatory pathways have additive effects on the progression of brain injury compared to the inflammatory pathway alone.
机械通气引起的损伤可通过炎症和血流动力学途径导致早产儿的脑白质（WM）损伤。目前尚不清楚这些途径中哪一种的贡献更大。我们假设，在早产儿分娩后 24 小时，活体磁共振成像（MRI）可以检测到机械通气引起的 WM 脑损伤。此外，我们假设通过脐带结扎（UCO）诱导的炎症和血流动力学途径的联合作用会增加 24 小时时的脑损伤。
妊娠 124±2 天的胎儿接受暴露、仪器操作，并在脐带完整（INJ；仅炎症途径）或结扎（INJ+UCO；炎症和血流动力学途径）的情况下使用高潮气量（VT）损伤性策略进行 15 分钟通气。将通气组与接受手术但未通气的羔羊（Sham）以及未接受手术的羔羊（未经手术对照；Cont）进行比较。15 分钟干预后，胎儿被放回子宫内，母羊恢复。24 小时后，分娩羔羊，给予保护性通气策略，并使用结构、扩散张量成像（DTI）和磁共振波谱（MRS）技术对大脑进行 MRI 检查。
与 Cont 组相比，INJ+UCO 组的绝对 MRS 肌酸和胆碱浓度明显降低（P=0.03，P=0.009）；INJ 或 Sham 组与 Cont 组之间未检测到显著差异。与 Cont 组相比，INJ 和 INJ+UCO 组内囊和额 WM 的轴向弥散度降低（P=0.05，P=0.04）。INJ 和 INJ+UCO 组的额 WM 平均弥散度低于 Cont 组（P=0.04）。DTI 彩色图显示，与 Cont 组相比，Sham、INJ 和 INJ+UCO 组的特定 WM 区域的弥散度较低，但差异无统计学意义。INJ+UCO 组比 INJ 组更有可能表现出较低的 WM 弥散度。
损伤性通气后 24 小时，与对照组相比，DTI 和 MRS 显示损伤性通气的羔羊脑损伤增加。DTI 彩色图阈值方法提供的证据表明，与炎症途径相比，血流动力学和炎症途径的联合作用对脑损伤的进展具有附加作用。
