Saito T, Takeichi S, Tokunaga I, Nakajima Y, Osawa M, Yukawa N
Department of Forensic Medicine, Tokai University School of Medicine, Kanagawa, Japan.
Nihon Hoigaku Zasshi. 1997 Oct;51(5):388-95.
The effects of pentobarbital on electroencephalogram (EEG) and auditory brain-stem response (ABR) were evaluated in 13 Japanese white male rabbits, divided into two groups, 7 and 6, respectively. After baseline evoked responses were obtained, pentobarbital was infused intravenously at 60 mg/kg/h in both groups. EEGs and ABR were recorded with 15 min intervals. When the blood concentration of pentobarbital reached therapeutic levels (2.0-5.0 mg/dL), cortical and hippocampal EEGs became isoelectric. Although the appearance of ABR waves was significantly delayed, each wave was clearly observed in spite of isoelectric EEG levels. The rabbits in one group were killed at that time, and their brains were removed to determine the concentration of pentobarbital in the brain tissue. In another group, pentobarbital was additionally infused at the rate of 120 mg/kg/h. Although the waves (II-IV) of the ABR gradually disappeared with increasing dosage, wave I was present until just prior to cardiac arrest. It is considered that the persistency of ABR at high doses of barbiturates is characteristic of patients in deep barbiturate coma. Therefore, at the diagnosis of brain death, there is no necessity to consider the half-life of the barbiturate, even if an excessive amount of barbiturate remains in the brain. In this study, pentobarbital concentration in the brain was nearly equal to the concentration in the blood. However, it is estimated that a large amount of barbiturate is accumulated in the brain of a patient after brain death because the blood flow in the brain is stagnant.
在13只日本雄性白兔中评估了戊巴比妥对脑电图（EEG）和听觉脑干反应（ABR）的影响，这些兔子被分为两组，分别为7只和6只。在获得基线诱发反应后，两组均以60mg/kg/h的速度静脉输注戊巴比妥。每隔15分钟记录一次EEG和ABR。当戊巴比妥的血药浓度达到治疗水平（2.0 - 5.0mg/dL）时，皮层和海马EEG变为等电位。尽管ABR波的出现明显延迟，但尽管EEG处于等电位水平，每个波仍清晰可见。此时一组兔子被处死，取出它们的大脑以测定脑组织中戊巴比妥的浓度。在另一组中，以120mg/kg/h的速度额外输注戊巴比妥。尽管随着剂量增加ABR的波（II - IV）逐渐消失，但波I一直存在到心脏骤停前。据认为，高剂量巴比妥类药物时ABR的持续性是深度巴比妥类昏迷患者的特征。因此，在脑死亡诊断时，即使大脑中残留过量的巴比妥类药物，也无需考虑巴比妥类药物的半衰期。在本研究中，大脑中戊巴比妥的浓度几乎与血液中的浓度相等。然而，据估计，脑死亡后患者大脑中会积聚大量巴比妥类药物，因为大脑中的血流停滞。
