Laryngeal mask airway and incidence of gastro-oesophageal reflux in paralysed patients undergoing ventilation for elective orthopaedic surgery

We have studied the incidence of gastrooesophageal reflux associated with the laryngeal mask airway (LMA) in 82 paralysed patients undergoing ventilation for elective orthopaedic surgery. Anaesthesia was managed by skilled LMA users. A pH-sensitive probe was passed nasally into the oesophagus before induction and recordings made during five phases of anaesthesia. Anaesthesia was induced with propofol and fentanyl and maintained with 0.5-1.5% isoflurane and nitrous oxide in oxygen. Neuromuscular block was produced with vecuronium and the train-of-four count maintained at less than or equal to 1. Towards the end of surgery, neuromuscular function was allowed to recover spontaneously. All LMAs were inserted at the first attempt and ventilation was successful in all patients. There were no adverse airway events. Mean oesophageal pH values during each phase of anaesthesia were: before insertion 5.88 (SD 0.77), placement 5.85 (0.74), maintenance 5.89 (0.73), emergence 5.71 (0.78) and removal 5.82 (0.75). There we re no reflux events (pH <4.0) during any phase of anaesthesia. We conclude that the incidence of gastro-oesophageal reflux is low in paralysed patients undergoing ventilation for elective orthopaedic surgery when antagonism of neuromuscular block is avoided. The validity of these findings for unskilled LMA users is unknown.