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目的评价近红外光谱仪(NIRS)脑氧合指标与新生猪脑血流的相关性,以寻找能最好反映脑血流变化及脑血管自主调节功能的 NIRS 指标。方法 10头出生前1～3d 新生猪随机分为两组:正常对照组(6头)、低血压组(4头)。人为动脉放血造成血压及脑血流的改变。应用 NIRS 连续监测脑组织氧合血红蛋白(△HbO_2)与还原血红蛋白(△HHb)的动态变化,计算二者之和△tHb(△tHb=△HbO_2+△HHb)及二者之差△HbD(△HbD=△HbO_2-△HHb)。同时应用彩色微球技术定量测定脑血流的变化,并对测定结果进行线性回归分析。结果对 NIRS 测定的△tHb、△HbD 和彩色微球定量测得的全脑(GCBF)以及大脑皮层脑血流(CBFc)之间的关系进行线性回归分析。正常生理条件下,△HbD 和△tHb 与 GCBF 存在显著相关,相关系数分别为 r_(la)=0.409和 r_(lb)b=0.440,P 均<0.05;△HbD 和△tHb 与 CBFc 也存在显著相关,相关系数分别为 r_(2a)=0.394和 r_(2b)=0.400,P 均<0.05。低血压条件下,新生猪仅在 MABP 降至35mmHg(1mmHg=0.133kPa)时脑血流才显著降低(P<0.05),而随着血压的逐渐降低,△HHb逐渐增高(P<0.01),△HbO_2和△tHb 先有升高趋势(P<0.05),然后在 MABP 降至35 mm Hg 时才显著降低(P<0.01),△HbD 与 GCBF、CBFc 采用线性回归分析所得的相关系数 r_(3a)=0.890、r_(3b)=0.887差异有统计学意义,P 均<0.01;而△tHb 与 GCBF、CBFc采用线性回归分析所得的相关系数 r_(4a)=0.395、r_(4b)=0.375差异均无统计学意义,P 均>0.05,△HbD与脑血流的变化趋势相同,二者密切相关;而△tHb 与脑血流的变化未存在相关。新生猪 MABP>35mmHg 时脑血流与血压不相关,提示自主调节功能完整,将调节功能完整的新生猪脑血流、△HbD 与相应的 MABP 值行线性回归分析显示相关系数<0.5;MABP<35 mmHg 时脑血流与血压相关,提示自主调节功能受损,将调节功能受损的新生猪脑血流、△HbD 与相应的 MABP 值行线性回归分析显示相关系数>0.5。结论正常生理及低血压条件下,△HbD 均能很好反映出脑血流的动态变化;△tHb仅在正常生理条件下能用来反映脑血流的动态变化。1～3d 新生猪脑血管自主调节的下限为35 mmHg,NIRS 氧合指标△HbD 与 MABP 的相关性可以反映新生猪的脑血管自主调节状态。
Objective To evaluate the relationship between cerebral oxygenation index (NIRS) and cerebral blood flow of newborn piglets in near infrared spectroscopy (NIRS) in order to find NIRS index which can best reflect the cerebral blood flow changes and the autonomic regulation of cerebral blood vessels. Methods Ten newborn piglets 1 ~ 3 days before birth were randomly divided into two groups: normal control group (6 heads), hypotension group (4 heads). Arterial blood loss caused by blood pressure and cerebral blood flow changes. The changes of △ HbO_2 and △ HHb in brain tissue were monitored continuously by NIRS, and the difference △ HbD (△ HbD △ HbD △ HbD △ HbD = ΔHbO_2 - ΔHHb). At the same time, the color microsphere technique was used to quantitatively measure the change of cerebral blood flow, and the linear regression analysis of the determination results was carried out. Results Linear regression analysis was performed on the relationship between △ tHb, △ HbD and quantitative GCBF and cerebral cortical cerebral blood flow (CBFc) measured by NIRS. Under normal physiological conditions, △ HbD and △ tHb were significantly correlated with GCBF, the correlation coefficients were r la (a) = 0.409 and r (b) b = 0.440 respectively, P <0.05; △ HbD, △ tHb and CBFc were also significant The correlation coefficients were r_ (2a) = 0.394 and r_ (2b) = 0.400 respectively, P <0.05. Hypobaric blood pressure decreased significantly (P <0.05) in neonatal pigs when MABP was reduced to 35mmHg (1mmHg = 0.133kPa), while △ HHb increased gradually with the decrease of blood pressure (P <0.01) △ HbO_2 and △ tHb firstly increased (P <0.05), then decreased significantly when MABP decreased to 35 mm Hg (P <0.01). Correlation coefficients of △ HbD with GCBF and CBFc using linear regression analysis showed that r_ ( (4a) = 0.395, r 4b (4b) = 0.375, the correlation coefficients of △ tHb, GCBF and CBFc were linear regression analysis There was no significant difference between the two groups (P> 0.05). The trend of △ HbD was the same as that of cerebral blood flow, and there was no significant difference between △ tHb and cerebral blood flow. The newborn pig MABP> 35mmHg cerebral blood flow is not related to blood pressure, suggesting that autonomic regulatory function is complete, the regulation of functional intact neonatal pig blood flow, △ HbD and corresponding MABP values ?? linear regression analysis showed that the correlation coefficient <0.5; MABP < Cerebral blood flow was associated with blood pressure at 35 mmHg, suggesting that autonomic dysfunction was impaired. Linear regression analysis of brain blood flow, △ HbD, and corresponding MABP values in impaired neonatal pigs showed a correlation coefficient of> 0.5. Conclusion △ HbD can reflect the dynamic changes of cerebral blood flow under normal physiological and hypotensive conditions. △ tHb can only reflect the dynamic changes of cerebral blood flow under normal physiological conditions. The lower limit of cerebral vascular autonomic regulation in newborn pigs aged 1 ~ 3d was 35 mmHg. The correlation between △ HbD and MABP of NIRS oxygenation index could reflect the autonomic regulation of cerebrovascular in newborn pigs.