Permalink : http://hdl.handle.net/2115/65490

KEYWORDS : target controlled infusion（TCI）;intravenous sedation;target-controlled infusion;propofol;prediction of optimal sedation level;young people;静脈内鎮静法;プロポフォール;至適鎮静予測;若年者

一般に，鎮静薬に対する感受性は個人差が大きく，静脈内鎮静法において個々の症例の術中至適投与量を事前に予想することは困難である．過量投与では管理の安全性が損なわれる可能性があり，術中至適投与量の事前予想が可能であれば，管理上大変有益である． 　我々は，以前，target controlled infusion（TCI）ポンプを用いたプロポフォール鎮静管理に際し，導入時に患者個々の感受性を読み取り，至適鎮静が得られた時点で，目標血中濃度をその際の予測脳内濃度と同じ値に再設定する方法（以下，本法）を考案し，14例の個々の症例に見合った術中の至適鎮静度を導入期のうちにわずかな誤差幅で予測でき，有用であると報告した．しかし，症例を重ねるにつれ，「導入期至適鎮静時の予測脳内濃度」と「術中に臨床徴候を指標に徴調整した目標血中濃度」との最大較差（以下，「最大較差」）が大きい症例も経験した． 　そこで，本法を用いたプロポフォール静脈内鎮静法併用局所麻酔下口腔外科手術が施行された82例を対象に，既報と同様の後ろ向き観察を行い，「最大較差」の大きい症例のその要因について検討した． 　「最大較差」が0.5μg/ml以上だった症例が９例あった．これらと「最大較差」が0.1μg/ml以下だった11例とを比較検討したところ，前者では有意に平均年齢が低かった｛23.7±7.4（16～37）VS 37.5±14.2（17～57）歳，mean±SD（最小値～最大値），p＜0.05｝．性別，body mass index，歯科治療恐怖や基礎疾患の有無，局所麻酔薬追加やフェンタニル併用の有無などに有意差はなかった． 　本法に用いたTCIポンプでは年齢がシミュレーション値に反映されず，したがって，若年患者への本法適用においては，実際値との間に差が出やすいことを考慮すべきと思われた.
Sensitivity to sedative medication varies greatly from individual to individual. Therefore, it is difficult to predict the optimal dosage of a sedative during intravenous sedation for each case. 　In a previous study on 14 patients, the authors investigated the usefulness of a new management method for intravenous propofol sedation using a target-controlled infusion pump, in which the estimated effect-site concentration of propofol at optimal sedation during induction was measured. The target blood concentration was reset to that value. The results showed that this method enabled the prediction of optimal intraoperative target blood concentrations of propofol for each individual with a minimal error range. However, some cases with a large error range during maintenance were observed. 　We enrolled 82 patients who underwent oral surgery under local anesthesia using this method in the present study. Cases with a large maximum difference between estimated effect-site concentration of propofol at optimal sedation during induction and target blood concentration at each point during surgery (hereafter, ‘maximum difference’) were investigated. A search for the expanding factor of ‘maximum difference’ was performed. 　The number of patients whose ‘maximum difference’ was 0.5μg/ml or greater (‘maximum difference ≧0.5’ group) and 0.1μg/ml or smaller (‘maximum difference ≦0.1’ group) was 9 and 11, respectively. The mean age of the ‘maximum difference ≧0.5’ group was significantly younger than the ‘maximum difference ≦0.1’ group {23.7±7.4 (minimum-maximum values, 16-37) vs. 37.5±14.2 (minimum-maximum values, 17-57) years, ｐ<0.05}. 　Our results suggest that we should be mindful of the potential discrepancy between estimated and actual measured values of target blood concentrations of propofol when the above sedation method is applied to younger patients.