Positive pressure ventilation with the laryngeal mask airway in non-paralysed patients: comparison of sevoflurane and propofol maintenance techniques

Abstract

We have compared anaesthetic maintenance and emergence characteristics of propofol and sevoflurane with the laryngeal mask airway (LMA) at commonly used doses in 185 ASA I-II patients, in a randomized, prospective study. Anaesthesia was induced with propofol 2.5-3.5 mg kg-1 and fentanyl 1-3 micrograms kg-1. Neuromuscular blocking agents were not used. All patients underwent positive pressure ventilation (PPV) with tidal volumes of 6-8 ml kg-1 to maintain normal end-tidal carbon dioxide concentration. Anaesthesia was maintained with 66% nitrous oxide in oxygen and infusion of propofol 6 or 8 mg kg-1 h-1, or 1% or 1.5% end-tidal sevoflurane. There were no failed insertion attempts and adequate ventilation was achieved in all patients. During emergence, there was a greater incidence of excitatory phenomena with 1% and 1.5% sevoflurane (95% confidence intervals (CI) 4-19%) compared with propofol (95% CI 0-4%). Sevoflurane 1.0% (95% CI 37-71%) was associated with the greatest overall incidence of respiratory and haemodynamic problems. This was significantly higher compared with propofol 6 mg kg-1 h-1 (95% CI 19-36%). Shorter times to LMA removal were observed with 1% and 1.5% sevoflurane compared with propofol (P < 0.0002). Postoperative problems did not differ between groups. We conclude that propofol 6-8 mg kg-1 h-1 and 1.5% sevoflurane were suitable for maintenance of anaesthesia for musculoskeletal surgery in non-paralysed ASA I-II patients undergoing PPV with the LMA. Emergence was more rapid with sevoflurane, but was associated with more excitatory phenomena.