PubMed1999
STUDY OBJECTIVES: To compare the respiratory depressant effects of propofol and sevoflurane used to facilitate the placement of the cuffed oropharyngeal airway (COPA), and to evaluate the effectiveness of the COPA in supporting positive pressure ventilation during anesthetic-induced apnea. DESIGN: Randomized, single-blinded study. SETTING: University hospital. PATIENTS: 60 ASA physical status I and II adult patients scheduled for elective surgery with general anesthesia. INTERVENTIONS: Patients were induced either with spontaneous inhalation of 5% sevoflurane or with propofol 2.0 mg/kg intravenously (i.v.) followed by a continuous infusion of 170 micrograms kg-1 min-1. If the propofol patient had a tight jaw in 90 seconds, additional propofol (0.5 mg/kg) was administered and the infusion rate was increased to 200 micrograms kg-1 min-1. The COPA was placed as soon as the jaw was sufficiently relaxed to allow its insertion into the mouth. MEASUREMENTS AND MAIN RESULTS: The median (range) time to the COPA placement were 90 seconds (30 to 150 sec) and 120 seconds (60 to 210 sec) with propofol and sevoflurane, respectively (p = 0.07, Mann-Whitney U-test). Unacceptable responses to the placement (3 or more coughs, vigorous or persistent [> 30 sec] movements) occurred in 23% and 17% of those who received propofol and sevoflurane, respectively, (p = 0.35. Chi-square test). All these responses were easily suppressed by additional doses of the assigned induction drug. After placement of the COPA, 53% (16/30) of the propofol patients had apnea lasting at least 30 seconds. Notably, the positive airway pressure at which a leak occurred in the mouth (pharyngeal leak pressure) was lower during this propofol-induced apnea than after the return of spontaneous breathing [9 (5 to 20) cmH2O vs. 15 (5 to 20) cmH2O, p < 0.01, Wilcoxon's signed-rank test]. In contrast, at no time were the sevoflurane patients apneic, and their pharyngeal leak pressure immediately following the placement was 12 (10 to 20) cmH2O. CONCLUSIONS: Propofol and sevoflurane are equally effective in facilitating the placement of the COPA. However, propofol often induces apnea, which is complicated by a less effective seal of the airway by the COPA against positive pressures. Because sevoflurane induction allows spontaneous respiration to continue and provides an adequate pharyngeal seal immediately following the placement of the COPA, it may be advantageous when apnea is not desired.