Department of Neurosurgery.
Department of Neurosurgery, University Hospital Essen, Essen.
J Neurosurg Anesthesiol. 2022 Apr 1;34(2):193-200. doi: 10.1097/ANA.0000000000000713.
Early detection of cerebral ischemia and metabolic crisis is crucial in critically ill subarachnoid hemorrhage (SAH) patients. Variable increases in brain tissue oxygen tension (PbtO2) are observed when the fraction of inspired oxygen (FiO2) is increased to 1.0. The aim of this prospective study was to evaluate whether a 3-minute hyperoxic challenge can identify patients at risk for cerebral ischemia detected by cerebral microdialysis.
Twenty consecutive severe SAH patients undergoing continuous cerebral PbtO2 and microdialysis monitoring were included. FiO2 was increased to 1.0 for 3 minutes (the FiO2 challenge) twice a day and PbtO2 responses during the FiO2 challenges were related to cerebral microdialysis-measures, ie, lactate, the lactate-pyruvate ratio, and glycerol. Multivariable linear and logistic regression models were created for each outcome parameter.
After predefined exclusions, 274 of 400 FiO2 challenges were included in the analysis. Lower absolute increases in PbtO2 (∆PbtO2) during FiO2 challenges were significantly associated with higher cerebral lactate concentration (P<0.001), and patients were at higher risk for ischemic lactate levels >4 mmol/L (odds ratio 0.947; P=0.04). Median (interquartile range) ∆PbtO2 was 7.1 (4.6 to 12.17) mm Hg when cerebral lactate was >4 mmol/L and 10.2 (15.76 to 14.24) mm Hg at normal lactate values (≤4 mmol/L). Median ∆PbtO2 was significantly lower during hypoxic than during hyperglycolytic lactate elevations (4.6 vs. 10.6 mm Hg, respectively; P<0.001). Lactate-pyruvate ratio and glycerol levels were mainly determined by baseline characteristics.
A 3-minute FiO2 challenge is an easy to perform and feasible bedside diagnostic tool in SAH patients. The absolute increase in PbtO2 during the FiO2 challenge might be a useful surrogate marker to estimate cerebral lactate concentrations and might be used to identify patients at risk for impending ischemia.
在重症蛛网膜下腔出血（SAH）患者中，早期发现脑缺血和代谢危机至关重要。当吸入氧分数（FiO2）增加到 1.0 时，脑组织氧张力（PbtO2）会出现可变增加。本前瞻性研究旨在评估 3 分钟高氧挑战是否可以识别通过脑微透析检测到脑缺血风险的患者。
连续纳入 20 例接受连续脑 PbtO2 和微透析监测的严重 SAH 患者。每天两次将 FiO2 增加到 1.0 进行 3 分钟（FiO2 挑战），并将 FiO2 挑战期间的 PbtO2 反应与脑微透析测量值（即乳酸、乳酸-丙酮酸比值和甘油）相关联。为每个结果参数创建多变量线性和逻辑回归模型。
在预先设定的排除标准后，400 次 FiO2 挑战中有 274 次被纳入分析。FiO2 挑战期间 PbtO2 （△PbtO2）的绝对值较低与较高的脑乳酸浓度显著相关（P<0.001），且患者发生缺血性乳酸水平>4mmol/L 的风险更高（比值比 0.947；P=0.04）。当脑乳酸>4mmol/L 时，△PbtO2 的中位数（四分位数范围）为 7.1（4.6 至 12.17）mm Hg，而乳酸值正常（≤4mmol/L）时为 10.2（15.76 至 14.24）mm Hg。△PbtO2 在缺氧时明显低于高糖酵解性乳酸升高时（分别为 4.6 和 10.6mm Hg，P<0.001）。乳酸-丙酮酸比值和甘油水平主要由基线特征决定。
3 分钟 FiO2 挑战是一种简单易行的床边诊断工具，可用于 SAH 患者。FiO2 挑战期间 PbtO2 的绝对增加可能是一种有用的替代标志物，用于估计脑乳酸浓度，并可能用于识别即将发生缺血的风险患者。
