通过血液氧合水平依赖性(BOLD)MRI测量,人脑中的局部脑血管反应性(rCVR)对潮气末CO2和O2的变化具有很大的变化。
我们在精心控制的潮气末气体浓度下检查了清醒的参与者,以评估局部CVR变化如何与麻醉中常见的潮气末气体变化有关。
观察性研究。
三级护理中心,温尼伯,加拿大。该研究的成像发生在2019年。
12名健康成人受试者。
在两种潮气末气体范式下研究了大脑BOLD反应。第一次潮气末氧气(ETO2)保持稳定,而ETCO2从低碳酸血症到高碳酸血症(CO2斜坡)逐渐增加;第二个ETCO2保持稳定,而ETO2从常氧到高氧(O2斜坡)增加。BOLD图像是通过将潮气末气体序列分为两个相等的部分进行建模的,以检查区域CVR。
以成对方式比较低碳酸血症与轻度高碳酸血症和轻度高氧(平均FIO2=0.3)与明显高氧(平均FIO2=0.7)的体素分布(P<0.005以达到体素显示阈值)。此外,对CO2斜坡数据进行了类型分析。这根据分割将对CO2斜坡的BOLD响应分为四类CVR斜率(A型;+/+斜率:正常响应,类型B+/-,C型-/-颅内盗血,类型D-/+。)类型B至D代表对CO2刺激的反应改变。
两种潮气末气体的区域响应性差异。在检查的0.3%的体素中,低碳酸血症区域CVR比高碳酸血症CVR更为明显(P<0.005,成对比较);相反的情况发生在2.3%的体素中。对于O2,与较高的高氧相比,轻度高氧在0.2%的体素中具有更明显的CVR;相反的发生在0.5%的体素中。根据类型分析,所有受试者的区域CO2反应均发生了变化,范围为4±2%至7±3%的体素。
在清醒的受试者中,观察到CVR的区域差异和异常,以及麻醉过程中常见的潮气末气体的变化.根据这些发现,可以考虑通过严格控制接近个体静息值的潮气末气体来最大程度地减少神经系统并发症风险患者的局部CVR波动。
Regional cerebrovascular reactivity (rCVR) is highly variable in the human brain as measured by blood oxygenation level-dependent (BOLD) MRI to changes in both end-tidal CO 2 and O 2 .
We examined awake participants under carefully controlled end-tidal gas concentrations to assess how regional CVR changes may present with end-tidal gas changes seen commonly with anaesthesia.
Observational
study.
Tertiary care centre, Winnipeg, Canada. The imaging for the
study occurred in 2019.
Twelve healthy adult subjects.
Cerebral BOLD response was studied under two end-tidal gas paradigms. First end-tidal oxygen (ETO 2 ) maintained stable whereas ETCO 2 increased incrementally from
hypocapnia to hypercapnia (CO 2 ramp); second ETCO 2 maintained stable whereas ETO 2 increased from normoxia to hyperoxia (O 2 ramp). BOLD images were modeled with end-tidal gas sequences split into two equal segments to examine regional CVR.
The voxel distribution comparing
hypocapnia to mild hypercapnia and mild hyperoxia (mean F I O 2 = 0.3) to marked hyperoxia (mean F I O 2 = 0.7) were compared in a paired fashion ( P < 0.005 to reach threshold for voxel display). Additionally, type analysis was conducted on CO 2 ramp data. This stratifies the BOLD response to the CO 2 ramp into four categories of CVR slope based on segmentation (type A; +/+slope: normal response, type B +/-, type C -/-: intracranial steal, type D -/+.) Types B to D represent altered responses to the CO 2 stimulus.
Differential regional responsiveness was seen for both end-tidal gases. Hypocapnic regional CVR was more marked than hypercapnic CVR in 0.3% of voxels examined ( P < 0.005, paired comparison); the converse occurred in 2.3% of voxels. For O 2 , mild hyperoxia had more marked CVR in 0.2% of voxels compared with greater hyperoxia; the converse occurred in 0.5% of voxels. All subjects had altered regional CO 2 response based on Type Analysis ranging from 4 ± 2 to 7 ± 3% of voxels.
In awake subjects, regional differences and abnormalities in CVR were observed with changes in end-tidal gases common during the conduct of anaesthesia. On the basis of these findings, consideration could be given to minimising regional CVR fluctuations in patients-at-risk of neurological complications by tighter control of end-tidal gases near the individual\'s resting values.