Weigt H U, Kwok W M, Rehmert G C, Turner L A, Bosnjak Z J
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226, USA.
Anesth Analg. 1997 Feb;84(2):285-93. doi: 10.1097/00000539-199702000-00009.
Cardiac dysrhythmias during inhaled anesthesia are well documented and may, in part, involve depression of the fast inward Na+ current (INa) during the action potential upstroke. In this study, we examined the effects of halothane, isoflurane, and sevoflurane at clinically relevant concentrations on INa in single ventricular myocytes isolated enzymatically from adult guinea pig hearts. INa was recorded using standard whole-cell configuration of the patch clamp technique. Halothane at 0.6 mM and 1.2 mM produced significant (P < 0.05) depressions of peak INa of 12.3% +/- 1.8% and 24.4% +/- 4.1% (mean +/- SEM, n = 12), respectively. Isoflurane (0.5 mM, n = 12; 1.0 mM, n = 15) and sevoflurane (0.6 mM, n = 14; 1.2 mM, n = 12) were less potent than halothane, decreasing peak INa by 4.8% +/- 1.1% and 11.4% +/- 1.4% (isoflurane) and 3.0% +/- 0.7% and 10.7% +/- 3.9% (sevoflurane). The depressant effects on INa were reversible in all cases. For all anesthetics tested, the degree of block increased at more depolarizing potentials. Anesthetics induced significant shifts in the steady-state inactivation and activation of the channel toward more hyperpolarizing potentials. The present findings indicate that volatile anesthetics at clinical concentrations decrease the cardiac INa in a dose- and voltage-dependent manner. At approximately equianesthetic concentrations, the decrease of INa caused by halothane was twice that observed with isoflurane or sevoflurane.
吸入麻醉期间的心脏心律失常已有充分记录，并且可能部分涉及动作电位上升支期间快速内向Na⁺电流（INa）的抑制。在本研究中，我们研究了临床相关浓度的氟烷、异氟烷和七氟烷对从成年豚鼠心脏酶解分离的单个心室肌细胞中INa的影响。使用膜片钳技术的标准全细胞配置记录INa。0.6 mM和1.2 mM的氟烷分别使峰值INa显著降低（P < 0.05），降低幅度分别为12.3% ± 1.8%和24.4% ± 4.1%（平均值 ± 标准误，n = 12）。异氟烷（0.5 mM，n = 12；1.0 mM，n = 15）和七氟烷（0.6 mM，n = 14；1.2 mM，n = 12）的作用比氟烷弱，使峰值INa降低4.8% ± 1.1%和11.4% ± 1.4%（异氟烷）以及3.0% ± 0.7%和10.7% ± 3.9%（七氟烷）。在所有情况下，对INa的抑制作用都是可逆的。对于所有测试的麻醉剂，在更去极化的电位下，阻滞程度增加。麻醉剂使通道的稳态失活和激活显著向更超极化的电位偏移。目前的研究结果表明，临床浓度的挥发性麻醉剂以剂量和电压依赖性方式降低心脏INa。在大约等效麻醉浓度下，氟烷引起的INa降低是异氟烷或七氟烷的两倍。
