Roles of Fentanyl and Nitroglycerin in Prevention of Myocardial Ischemia Associated with Laryngoscopy and Tracheal Intubation in Patients Undergoing Operations of Short Duration

The purpose of this study was to evaluate intravenous nitroglycerin given during induction of anesthesia as a means for prevention of myocardial ischemia and hemodynamic changes associated with induction, laryngoscopy, and intubation, in patients with stable angina scheduled for vascular operations of moderate duration. Forty-six patients were randomly assigned to receive either fentanyl, 3 micrograms/kg (group 1, n = 6), fentanyl, 8 micrograms/kg (group 2, n = 20), or fentanyl 3 micrograms/kg plus a continuous intravenous nitroglycerin infusion, 0.9 microgram X kg-1 X min-1 (group 3, n = 20), in addition to thiopental-pancuronium anesthetic induction, prior to laryngoscopy and intubation. The criteria for recognizing myocardial ischemia were the following: horizontal or downsloping ST segment depression equal to or greater than 1 mV, and/or ventricular arrhythmia, on CM5 recording. In group 1, myocardial ischemia occurred during laryngoscopy and intubation in four patients, and mean blood pressure (MBP), heart rate, and mean pulmonary wedge pressure (PCWP) increased significantly (P less than 0.05). Despite greater stability in MBP and heart rate in group 2, myocardial ischemia still occurred in four patients (not significantly different from group 1). Nitroglycerin added to low-dose fentanyl (group 3) produced significant reduction in myocardial ischemia (1/20) when compared with group 1 (P less than 0.01), and significantly greater stability in PCWP during laryngoscopy and intubation in comparison to groups 1 and 2. In patients with stable angina undergoing operations of short duration, the use of nitroglycerin infusion and low-dose fentanyl significantly decreases the incidence of myocardial ischemia associated with induction of anesthesia and tracheal intubation.