Camara A K, Turner L A, Bosnjak Z J
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
Acta Anaesthesiol Scand. 2001 Aug;45(7):885-92. doi: 10.1034/j.1399-6576.2001.045007885.x.
Halothane is known to potentiate catecholamine-induced depression of conduction velocity in Purkinje fibers but not endocardial muscle fibers. The purpose of this study was to examine the interactions of halothane with epinephrine and isoproterenol on canine epicardial conduction velocity at moderately elevated extracellular potassium concentration ([K]0).
Epicardial muscle strips (10x10x2 mm) were superfused with Tyrode's solution containing 4 or 8 mM [K]0 in the presence of 5 microM epinephrine or 1 microM isoproterenol with or without 0.8 mM halothane. Conduction velocity in the longitudinal and transverse directions relative to epicardial fiber orientation was recorded during alternate stimulation in each direction.
In the presence of halothane, a change from 4 to 8 mM [K]0 decreased (P< or =0.05) longitudinal and transverse conduction velocities by 26% and 21%, respectively. Isoproterenol alone at 4 and 8 mM [K]0 depressed (P<0.05) both longitudinal and transverse conduction velocities. However, the depression of longitudinal conduction velocity by isoproterenol at 4 mM [K]0 was attenuated by halothane. Epinephrine with or without halothane depressed (P<0.05) both longitudinal and transverse conduction velocities at 8 but not at 4 mM [K]0.
The results do not support a synergistic interaction between halothane and epinephrine on myocardial conduction but do demonstrate depression of conduction by epinephrine at 8 mM [K+]0, a potassium ion concentration comparable to those reported following epinephrine infusions.
已知氟烷可增强儿茶酚胺诱导的浦肯野纤维传导速度减慢，但对心内膜肌纤维无此作用。本研究的目的是在细胞外钾浓度适度升高（[K]0）的情况下，研究氟烷与肾上腺素和异丙肾上腺素对犬心外膜传导速度的相互作用。
将心外膜肌条（10×10×2 mm）在含有4或8 mM [K]0的台氏液中进行灌流，同时存在5 μM肾上腺素或1 μM异丙肾上腺素，有无0.8 mM氟烷。在每个方向交替刺激期间，记录相对于心外膜纤维方向的纵向和横向传导速度。
在氟烷存在的情况下，[K]0从4 mM变为8 mM时，纵向和横向传导速度分别降低（P≤0.05）26%和21%。单独使用异丙肾上腺素在4和8 mM [K]0时均降低（P<0.05）纵向和横向传导速度。然而，在4 mM [K]0时，异丙肾上腺素对纵向传导速度的降低作用被氟烷减弱。无论有无氟烷，肾上腺素在8 mM [K]0时均降低（P<0.05）纵向和横向传导速度，但在4 mM [K]0时则无此作用。
结果不支持氟烷与肾上腺素在心肌传导方面存在协同相互作用，但确实表明在8 mM [K+]0（与肾上腺素输注后报道的钾离子浓度相当）时，肾上腺素可降低传导速度。
