Fischer M, Bockhorst K, Hoehn-Berlage M, Schmitz B, Hossmann K A
Max-Planck-Institute for Neurological Research, Department of Experimental Neurology, Cologne, Germany.
Magn Reson Imaging. 1995;13(6):781-90. doi: 10.1016/0730-725x(95)00030-k.
The apparent diffusion coefficient (ADC) of water is a sensitive indicator of water and ion homeostasis of brain. Resuscitation of the brain after cardiac arrest, the most frequent reason for global cerebral ischemia under clinical conditions, depends critically on the reversal of disturbances of water and ion homeostasis. We, therefore, investigated whether ADC imaging can be used to monitor the development and reversal of ischemic brain injury during and after cardiac arrest. Ten adult mongrel normothermic cats were anesthetized with alfentanil and midazolam, immobilized with pancuronium, and mechanically ventilated with O2/N2O. Arterial, left ventricular, central venous, and intracranial pressures were monitored throughout the experiment. Magnetic resonance imaging was performed in a 4.7T MR scanner with a shielded gradient system. Diffusion-weighted images (DWI) were obtained by pulsed gradient spin echoes (diffusion weighting factor b: 0, 500, 1000, 1500 s/mm2). Quantitative ADC images were calculated from DWIs by fitting signal intensities against b-factors. Fifteen minute cardiac arrest was induced in the magnet by electrical fibrillation. Resuscitation was also carried out in the magnet, using a pneumatic vest for remotely controlled closed chest cardiac massage. Seven of 10 animals were resuscitated successfully and subsequently monitored for 3 h. During cardiac arrest, ADC declined from 678 +/- 79 x 10(-6) to 430 +/- 128 x 10(-6) mm2/s (63% of baseline). In the successfully resuscitated animals ADC returned to 648 +/- 108 x 10(-6) mm2/s within 30 min and remained at this level throughout the 3 h of recirculation. Regional evaluations of ADC revealed a transient overshoot in brainstem and basal ganglia to 114% of control at 15 min before returning to baseline values after 40 min. Failure of cardiac resuscitation prevented ADC normalization and led to its further decline to below 50% of control. Postcardiac arrest normalization of ADC maps correlated with homogeneous return of ATP, glucose, and lactate to near normal, whereas failure of ADC normalization was associated with depletion of ATP and glucose and severe lactate accumulation. In conclusion, our data indicate, that normalization of ADC is a reliable indicator of cerebral recovery after resuscitation from cardiac arrest.
水的表观扩散系数（ADC）是脑内水和离子稳态的敏感指标。心脏骤停后脑复苏是临床情况下全脑缺血最常见的原因，其关键取决于水和离子稳态紊乱的逆转。因此，我们研究了ADC成像是否可用于监测心脏骤停期间及之后缺血性脑损伤的发展和逆转。十只成年杂种正常体温猫用阿芬太尼和咪达唑仑麻醉，用泮库溴铵制动，并用O₂/N₂O进行机械通气。在整个实验过程中监测动脉压、左心室压中枢静脉压和颅内压。在带有屏蔽梯度系统的4.7T磁共振扫描仪中进行磁共振成像。通过脉冲梯度自旋回波获得扩散加权图像（DWI）（扩散加权因子b：0、500、1000、1500 s/mm²）。通过将信号强度与b因子拟合，从DWI计算定量ADC图像。在磁体中通过电除颤诱发15分钟心脏骤停。复苏也在磁体中进行，使用气动背心进行遥控闭式胸外心脏按压。10只动物中有7只成功复苏，随后监测3小时。心脏骤停期间，ADC从678±79×10⁻⁶降至430±128×10⁻⁶mm²/s（为基线的63%）。在成功复苏的动物中，ADC在30分钟内恢复到648±108×10⁻⁶mm²/s，并在整个3小时的再循环过程中保持在该水平。ADC的区域评估显示，脑干和基底神经节在15分钟时短暂超射到对照的114%，40分钟后恢复到基线值。心脏复苏失败阻止了ADC正常化，并导致其进一步下降至对照的50%以下。心脏骤停后ADC图的正常化与ATP、葡萄糖和乳酸均匀恢复至接近正常相关，而ADC正常化失败与ATP和葡萄糖耗竭以及严重乳酸积累相关。总之，我们的数据表明，ADC正常化是心脏骤停复苏后脑恢复的可靠指标。
