Propofol静脈麻酔による機能的脳神経外科手術の術中モニタリング

Intraoperative monitoring for functional neurosurgery during intravenous anesthesia with propofol

I．はじめに

　てんかん外科，微小血管減圧術，定位脳手術などの機能的脳神経外科手術に際しては，術中の皮質脳波，誘発電位などの電気生理学的モニタリングがその成功に重要な役割を果たしている．しかし，従来の吸入麻酔薬による全身麻酔下では術中モニタリングに多大な影響と様々な制限が加えられる．

　最近の新しい静脈麻酔薬の出現により，欧米ではtot—al intravenous anesthesia（TIVA）という言葉が麻酔科領域で注目されつつある．その静脈麻酔薬の1つであるpropofolが1995年11月に本邦でも発売された．Prop—ofolは作用時間が極めて短く，反復投与でも体内蓄積が少ないことから，比較的手術時間が長い脳神経外科手術でも多く用いられ，術後の覚醒が良好であったと言う^{13,22,23,29）}．

We studied the effects of propofol on electrophysiolo-gic monitoring for functional neurosurgery. In six pa-tients with intractable epilepsy, electrocorticograms (ECoGs) were monitored for epilepsy surgery, and in two of them, somatosensory evoked potentials (SEPs) were monitored because of the focus adjacent to the central sulcus. In four patients with hemifacial spasm, brain stem auditory evoked potentials (BAEPs) and abnormal muscle responses (AMRs) were monitored during microvascular decompression (MVD). In two patients with Parkinson's disease and in one patient with post-traumatic tremor, neural noise levels were re-corded from microelectrodes during posteroventral pal-lidotomy and Vim thalamotomy.

In each case of epilepsy surgery, during intravenous anesthesia with propofol, spike activity was recordable enough to identify the resective area and the residual spikes. SEP phase reversal was obtained in two pa-tients and an exact determination of the central sulcus was possible. BAEPs and AMRs were obtained in all MVDs. To record neural noise levels, the infusion of propofol was decreased in two cases of posteroventral pallidotomy, and it was stopped in one case of Vim tha-lamotomy. In these patients, neural noise levels were recorded and were useful for identifying the target. Propofol is a potentially useful anesthetic agent for electrophysiologic monitoring during functional neuro-surgery.