Mitchell M M, Prakash O, Rulf E N, van Daele M E, Cahalan M K, Roelandt J R
Department of Anesthesiology, University of California, San Diego 92103.
Anesthesiology. 1989 Oct;71(4):526-34. doi: 10.1097/00000542-198910000-00008.
Despite evidence from animal experiments to the contrary, nitrous oxide (N2O) reportedly does not induce myocardial ischemia when used as an adjunct to fentanyl anesthesia in patients with coronary artery disease who have well-preserved left ventricular (LV) function. However, the incidence of ischemia with N2O administration in similar patients with poor LV function may be different. The effects of N2O on segmental LV function, as determined by two-dimensional transesophageal echocardiography, changes in the ST-segment of the electrocardiogram were compared with the effects of an equal concentration of nitrogen (N2) (crossover design) in 70 patients who required elective coronary artery bypass grafting. Of these patients, 24% had left ventricular ejection fraction (LVEF) less than or equal to 40%. Myocardial ischemia was diagnosed in 14 patients during the study: four while awake, seven during induction of anesthesia and tracheal intubation, and four during the remainder of the study (one during N2O and three during 100% oxygen; one patient had two distinct periods of ischemia). No value for LVEF could be found that would distinguish between patients who did or did not have ischemia during the study. Patients treated with beta-adrenergic blocking drugs preoperatively were less likely to develop ischemia (P less than 0.05). Preoperative calcium channel blockers made no such differences. Onset of ischemia was not closely associated with hemodynamic changes. Thus, N2O does not induce clinically detectable myocardial ischemia in patients who have coronary artery disease, and poor LV function in situations in which the effects of deepening anesthetic depth and mild depression of global myocardial function are deemed desirable or harmless.
尽管动物实验得出了相反的证据，但据报道，在左心室（LV）功能良好的冠心病患者中，一氧化二氮（N2O）用作芬太尼麻醉的辅助药物时，并不会诱发心肌缺血。然而，在左心室功能较差的类似患者中，使用N2O导致缺血的发生率可能有所不同。本研究采用交叉设计，通过二维经食管超声心动图测定N2O对左心室节段功能的影响，并将其与等浓度氮气（N2）的影响进行比较，同时观察心电图ST段的变化。研究对象为70例需要择期冠状动脉搭桥术的患者，其中24%的患者左心室射血分数（LVEF）小于或等于40%。研究期间，14例患者被诊断为心肌缺血：4例在清醒时，7例在麻醉诱导和气管插管期间，4例在研究的其余阶段（1例在使用N2O期间，3例在使用100%氧气期间；1例患者有两个不同的缺血期）。未发现LVEF值可用于区分研究期间发生或未发生缺血的患者。术前接受β-肾上腺素能阻滞剂治疗的患者发生缺血的可能性较小（P<0.05）。术前使用钙通道阻滞剂则无此差异。缺血的发生与血流动力学变化并无密切关联。因此，在认为加深麻醉深度和轻度抑制整体心肌功能的影响是可取或无害的情况下，N2O不会在患有冠心病且左心室功能较差的患者中诱发临床可检测到的心肌缺血。
