Tanaka S, Tsuchida H, Nanba H, Fujita S, Namiki A
Department of Anesthesiology, Sapporo Medical University, School of Medicine.
Masui. 1994 Nov;43(11):1659-64.
Isoflurane often produces tachycardia during clinical anesthesia. We examined the effect of a stepwise increase of isoflurane concentration on hemodynamic parameters in the absence or presence of nitrous oxide (N2O). After induction with thiamylal (3 mg.kg-1), isoflurane in oxygen or in 66% N2O-oxygen was administered with mask ventilation. Inspired isoflurane concentration was increased in a stepwise fashion (1, 2, 3 and 4%) every 5 minutes and manual ventilation was performed to maintain ETCO2 within 35-40 mmHg. Blood pressure (BP), heart rate (HR) and cardiac output (CO) were measured before and at every minute after isoflurane administration until 20 minutes. Systolic BP decreased gradually with increasing isoflurane concentration, but was transiently elevated for 3%. HR increased in a dose-related manner. CO decreased significantly at 1-3%. N2O and this seemed to magnify the isoflurane-induced decrease in BP and increase in HR at 1% and 2%. CO increased from baseline at 4%. Isoflurane tended to increase HR in a dose-related manner and induced a hyperdynamic response during rapid increasing of isoflurane concentration. This response may have beed caused by the irritating effect of isoflurane on the airways. Addition of N2O attenuated this response because it increases the speed of induction and the depth of anesthesia.
异氟烷在临床麻醉期间常引起心动过速。我们研究了在有或无氧化亚氮（N₂O）存在的情况下，异氟烷浓度逐步增加对血流动力学参数的影响。用硫喷妥钠（3mg·kg⁻¹）诱导后，通过面罩通气给予氧气中的异氟烷或66% N₂O - 氧气中的异氟烷。每5分钟逐步增加吸入异氟烷浓度（1%、2%、3%和4%），并进行人工通气以维持呼气末二氧化碳分压（ETCO₂）在35 - 40 mmHg之间。在给予异氟烷之前及之后每分钟测量血压（BP）、心率（HR）和心输出量（CO），持续20分钟。随着异氟烷浓度增加，收缩压逐渐下降，但在3%时短暂升高。心率呈剂量相关增加。在1% - 3%时心输出量显著下降。N₂O似乎在1%和2%时放大了异氟烷引起的血压下降和心率增加。在4%时心输出量从基线增加。异氟烷倾向于以剂量相关方式增加心率，并在异氟烷浓度快速增加期间诱发高动力反应。这种反应可能是由异氟烷对气道的刺激作用引起的。添加N₂O减弱了这种反应，因为它增加了诱导速度和麻醉深度。
