局麻药的急性耐受性：可能只是药物浓度降低的表现
Tachyphylaxis to local anesthetic may be the manifestation of drug concentration decrease

为了了解布比卡因在硬膜外腔的浓度变化情况，作者设定了估算条件，依此来计算硬膜外腔布比卡因 的浓度。从计算的结果发现：①给予常用浓度的维持量后，硬膜外腔布比卡因的浓度降低；维持肌肉松弛的时间 缩短。②提高维持量的浓度，硬膜外腔的布比卡因能维持较高的浓度，达到较好的肌肉松弛度。由此提出假说： ①局麻药的急性耐受性（tachyphylaxis/acute tolerance）是局麻药浓度降低的表现；②提高维持量的浓度可以克服 局麻药的急性耐受性。
To understand the concentration variation of bupivacaine in epidural space, the author designed estimation conditions and calculated the concentration of bupivacaine in epidural space. From the estimation results we found: ① The concentration of bupivacaine in epidural space decreases after giving routine dose of maintenance and the duration of maintaining muscle relaxation is shortened. ② If the dose of maintenance is up-regulated, the concentration of bupivacaine in epidural space can maintain a higher level and the degree of muscle relaxation is desirable. Based on the findings, we proposed hypotheses: ① Tachyphylaxis to local anesthetic is the manifestation that local anesthetic concentration decreases. ② Increasing the dose of maintenance can overcome the tachyphylaxis to local anesthetic