LARYNGEAL MASK AIRWAY AND INCIDENCE OF GASTROESOPHAGEAL REFLUX IN PARALYZED PATIENTS UNDERGOING VENTILATION FOR ELECTIVE ORTHOPEDIC-SURGERY

We have studied the incidence of gastrooesophageal reflux associated w ith the laryngeal mask airway (LMA) in 82 paralysed patients undergoin g ventilation for elective orthopaedic surgery. Anaesthesia was manage d by skilled LMA users. A pH-sensitive probe was passed nasally into t he 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. Neur omuscular block was produced with vecuronium and the train-of-four cou nt 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 a ll patients. There were no adverse airway events. Mean oesophageal pH values during each phase of anaesthesia were: before insertion 5.88 (S D 0.77), placement 5.85 (0.74), maintenance 5.89 (0.73), emergence 5.7 1 (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 vent ilation for elective orthopaedic surgery when antagonism of neuromuscu lar block is avoided. The validity of these findings for unskilled LMA users is unknown.