Liem K D, Hopman J C, Oeseburg B, de Haan A F, Festen C, Kollée L A
Department of Pediatrics, University Hospital Nijmegen, The Netherlands.
Pediatrics. 1995 Apr;95(4):555-61.
To investigate cerebral oxygenation and hemodynamics in relation to changes in some relevant physiologic variables during induction of extracorporeal membrane oxygenation (ECMO) in newborn infants.
Twenty-four newborn infants requiring ECMO were studied from cannulation until 60 minutes after starting ECMO. Concentration changes of oxyhemoglobin (cO2Hb), deoxyhemoglobin (cHHb), total hemoglobin (ctHb), and (oxidized-reduced) cytochrome aa3 (cCyt.aa3) in cerebral tissue were measured continuously by near infrared spectrophotometry. Heart rate (HR), transcutaneous partial pressures of oxygen and carbon dioxide (tcPO2 and tcPCO2), arterial O2 saturation (saO2), and mean arterial blood pressure (MABP) were measured simultaneously. Intravascular hemoglobin concentration (cHb) was measured before and after starting ECMO. In 18 of the 24 infants, mean blood flow velocity (MBFV) and pulsatility index (PI) in the internal carotid and middle cerebral arteries were also measured before and after starting ECMO using pulsed Doppler ultrasound.
After carotid ligation, cO2Hb decreased whereas cHHb increased. After jugular ligation, no changes in cerebral oxygenation were found. At 60 minutes after starting ECMO, the values of cO2Hb, saO2, tcPO2, and MABP were significantly higher than the precannulation values, whereas the value of cHHb was lower. There were no changes in cCyt.aa3, tcPCO2, and HR, whereas cHb decreased. The MBFV was significantly increased in the major cerebral arteries except the right middle cerebral artery, whereas PI was decreased in all measured arteries. Cerebral blood volume, calculated from changes in ctHb and cHb, was increased in 20 of 24 infants after starting ECMO. Using multivariate regression models, a positive correlation of delta ctHb (representative of changes in cerebral blood volume) with delta MABP and a negative correlation with delta tcPO2 were found.
The alterations in cerebral oxygenation after carotid artery ligation might reflect increased O2 extraction. Despite increase of the cerebral O2 supply after starting ECMO, no changes in intracellular O2 availability were found, probably because of sufficient preservation of intracellular cerebral oxygenation in the pre-ECMO period despite prolonged hypoxemia. The increase in cerebral blood volume and cerebral MBFV may result from the following: (1) reactive hyperperfusion, (2) loss of autoregulation because of prolonged hypoxemia before ECMO and/or decreased arterial pulsatility, or (3) compensation for hemodilution related to the ECMO procedure.
研究新生儿体外膜肺氧合（ECMO）启动过程中脑氧合及血流动力学与一些相关生理变量变化的关系。
对24例需要ECMO的新生儿从插管开始至ECMO启动后60分钟进行研究。通过近红外分光光度法连续测量脑组织中氧合血红蛋白（cO2Hb）、脱氧血红蛋白（cHHb）、总血红蛋白（ctHb）和（氧化 - 还原）细胞色素aa3（cCyt.aa3）的浓度变化。同时测量心率（HR）、经皮氧分压和二氧化碳分压（tcPO2和tcPCO2）、动脉血氧饱和度（saO2）和平均动脉血压（MABP）。在ECMO启动前后测量血管内血红蛋白浓度（cHb）。在24例婴儿中的18例中，还使用脉冲多普勒超声在ECMO启动前后测量颈内动脉和大脑中动脉的平均血流速度（MBFV）和搏动指数（PI）。
颈动脉结扎后，cO2Hb降低而cHHb升高。颈静脉结扎后，未发现脑氧合有变化。在ECMO启动后60分钟，cO2Hb、saO2、tcPO2和MABP的值显著高于插管前的值，而cHHb的值较低。cCyt.aa3、tcPCO2和HR无变化，而cHb降低。除右侧大脑中动脉外，主要脑动脉的MBFV显著增加，而所有测量动脉的PI均降低。根据ctHb和cHb的变化计算得出，24例婴儿中有20例在ECMO启动后脑血容量增加。使用多元回归模型，发现δctHb（代表脑血容量变化）与δMABP呈正相关，与δtcPO2呈负相关。
颈动脉结扎后脑氧合的改变可能反映了氧摄取增加。尽管ECMO启动后脑氧供应增加，但未发现细胞内氧可用性有变化，这可能是因为尽管存在长时间低氧血症，但在ECMO前阶段细胞内脑氧合得到了充分保留。脑血容量和脑MBFV的增加可能是由于以下原因：（1）反应性高灌注，（2）由于ECMO前长时间低氧血症和/或动脉搏动性降低导致的自动调节丧失，或（3）对与ECMO程序相关的血液稀释的代偿。
