Rhondali Ossam, André Caroline, Pouyau Agnès, Mahr Aurélie, Juhel Simon, De Queiroz Mathilde, Rhzioual-Berrada Khalid, Mathews Sylvain, Chassard Dominique
Department of Pediatric Anesthesia, Hôpital Mère-Enfant, Lyon, France; Department of Pediatric Anesthesia, Hôpital Sainte Justine, Montréal, QC, Canada.
Paediatr Anaesth. 2015 Feb;25(2):180-5. doi: 10.1111/pan.12512. Epub 2014 Sep 16.
OBJECTIVE/AIM: To assess the impact of sevoflurane and anesthesia-induced hypotension on brain perfusion in children younger than 6 months.
Safe lower limit of blood pressure during anesthesia in infant is unclear, and inadequate anesthesia can lead to hypotension, hypocapnia, and low cerebral perfusion. Insufficient cerebral perfusion in infant during anesthesia is an important factor of neurological morbidity. In two previous studies, we assessed the impact of sevoflurane anesthesia on cerebral blood flow (CBF) by transcranial Doppler (TCD) and on brain oxygenation by NIRS, in children ≤2 years. As knowledge about consequences of anesthesia-induced hypotension on cerebral perfusion in children ≤6 months is scarce, we conducted a retrospective analysis to compare the data of CBF and brain oxygenation, in this specific population.
We performed a retrospective analysis of data collected from our two previous studies. Baseline values of TCD or NIRS were recorded and then during sevoflurane anesthesia. From a database of 338 patients, we excluded all patients older than 6 months. Then, we compared physiological variables of TCD and NIRS population to ensure that the two groups were comparable. We compared rSO2 c and TCD measurements variation according to MAP value during sevoflurane anesthesia, using anova and Student-Newman-Keuls for posthoc analysis.
One hundred and eighty patients were included in the analysis. TCD and NIRS groups were comparable. CBF velocities (CBFV) or rSO2 c reflects a good cerebral perfusion when MAP is above 45 mmHg. When MAP is between 35 and 45 mmHg, CBFV variation reflects a reduction of CBF, but rSO2 c increase is the consequence of a still positive balance between CMRO2 and O2 supply. Below 35 mmHg of MAP during anesthesia, CBFV decrease and rSO2 c variation from baseline is low. For each category of MAP and for the two groups, etCo2 and expired fraction of sevoflurane (FeSevo) were comparable (anova P > 0.05).
In a healthy infant without dehydration, with normal PaCO2 and hemoglobin value, scheduled for short procedures, MAP is a good proxy of cerebral perfusion as we found that CBF assessed by CBFV and rSO2 c decreased proportionally with cerebral perfusion pressure. During 1 MAC sevoflurane anesthesia, maintaining MAP beyond 35 mmHg during anesthesia is probably safe and sufficient. But when MAP decreases below 35 mmHg, CBF decreases and rSO2 c variation from baseline is low despite CMRO2 reduction. In this situation, cerebral metabolic reserve is low and further changes of systemic conditions may be poorly tolerated by the brain.
评估七氟醚及麻醉诱导的低血压对6个月以下儿童脑灌注的影响。
婴儿麻醉期间血压的安全下限尚不清楚，麻醉不足可导致低血压、低碳酸血症和脑灌注不足。婴儿麻醉期间脑灌注不足是神经功能障碍的重要因素。在之前的两项研究中，我们通过经颅多普勒（TCD）评估了七氟醚麻醉对2岁及以下儿童脑血流（CBF）的影响，并通过近红外光谱（NIRS）评估了对脑氧合的影响。由于关于麻醉诱导的低血压对6个月及以下儿童脑灌注影响的知识较少，我们进行了一项回顾性分析，以比较这一特定人群中CBF和脑氧合的数据。
我们对之前两项研究收集的数据进行了回顾性分析。记录TCD或NIRS的基线值，然后在七氟醚麻醉期间进行记录。在338例患者的数据库中，我们排除了所有6个月以上的患者。然后，我们比较了TCD和NIRS人群的生理变量，以确保两组具有可比性。我们使用方差分析和Student-Newman-Keuls进行事后分析，比较七氟醚麻醉期间根据平均动脉压（MAP）值的rSO2 c和TCD测量值的变化。
180例患者纳入分析。TCD组和NIRS组具有可比性。当MAP高于45 mmHg时，CBF速度（CBFV）或rSO2 c反映了良好的脑灌注。当MAP在35至45 mmHg之间时，CBFV变化反映了CBF的降低，但rSO2 c升高是脑氧代谢率（CMRO2）与氧供应之间仍为正平衡的结果。麻醉期间MAP低于35 mmHg时，CBFV降低，rSO2 c相对于基线的变化较小。对于每一类MAP以及两组，呼气末二氧化碳分压（etCo2）和七氟醚呼出分数（FeSevo）具有可比性（方差分析P>0.05）。
在无脱水、动脉血二氧化碳分压（PaCO2）和血红蛋白值正常、计划进行短时间手术的健康婴儿中，MAP是脑灌注的良好指标，因为我们发现通过CBFV和rSO2 c评估的CBF与脑灌注压成比例下降。在1个最低肺泡有效浓度（MAC）七氟醚麻醉期间，麻醉期间维持MAP高于35 mmHg可能是安全且足够的。但是当MAP降至35 mmHg以下时，CBF降低，尽管CMRO2降低，但rSO2 c相对于基线的变化较小。在这种情况下，脑代谢储备较低，全身状况的进一步变化可能难以被大脑耐受。
