Different formulae for flexible laryngeal mask airway size selection in endoscopic sinus surgery for China adult male

Abstract

Objective The objective of this study is to evaluate weight and height-based formulae for selecting the appropriate size of flexible laryngeal mask airway(FLMA) for China adult male in endoscopic sinus surgery(ESS). Methods One hundred adult male patients (ASA class Ⅰ or Ⅱ, age≥18 years) were randomly allocated in group A (weight-based formulae: size 3 for weight<50 kg, size 5 for weight≥70 kg, size 4 for the rest) and group B (weight and height-based formulae: size 3 for weight<50 kg and height<150 cm, size 5 for weight≥70 kg or height≥170 cm, and size 4 for the rest). An experienced user inserted the FLMA after rapid induction. FLMA location was estimated by auscultation, ventilation peak pressure and oropharyngeal leak pressure. Intermittent positive pressure ventilation and total intravenous anesthesia were performed during operation. The primary outcome was concordant with FLMA size used according to the weight-based manufacturers' recommendations or the weight and height-based formulae. The secondary outcome was success rate of the first insertion, attempts of FLMA insertion, ventilation peak pressure, oropharyngeal leak pressure, fiberoptic bronchoscopy score(FOB), FLMA inner contamination by blood and postoperative sore throat score. Measurements of height, weight, the size of the oral opening, Mallampati grades and random grouping were accomplished by the same anesthesia doctor. FLMA insertion and intraoperative and postoperative data collection were accomplished by another anesthesia doctor blindly. Results FLMA was used in 95 patients (50 in group A and 45 in group B) for ventilation during anesthesia. FLMA size 4 was used in 24 patients and size 5 in 71 patients. There were 5 cases (2 in group A and 3 in group B) switched to endotracheal intubation because of dissatisfaction with FLMA location. In group A, 23/27 cases were supposed to be used FLMA size 4/5, actually 15/35 cases were used FLMA size 4/5, the concordance in group A was 72.0%. In group B, 11/34 cases were supposed to be used FLMA size 4/5, actually 9/36 cases were used FLMA size 4/5, the concordance in group B was 91.1%, which was higher than that in group A (P 0.05). Conclusions Weight and height-based formula for the FLMA size selection is more effective than the manufacturer's weight-based formula in ESS for China adult males. These formulae predict FLMA size more accurately and improve the success rate for FLMA insertion. Key words: Flexible laryngeal mask airway; Endoscopic sinus surgery; Adult male; China