Evaluation of the pH of secretions in the hypopharynx during gynaecological laparoscopy. Is the use of a laryngeal mask airway safe?
Background and Goal of Study: We evaluated the safety of using a ProSeal laryngeal mask airway during gynaecological laparoscopy, assessing the risk of regurgitation of gastric contentes by measuring the pH of secretions in the hypopharynx during the anaesthetic/surgical procedure.
Materials and methods: In total, 80 patients were evaluated who were under general anaesthesia for gynaecological laparoscopy in which airway access was maintained using a ProSeal laryngeal mask airway. Secretions in the hypopharynx were collected by aspiration using an oesophageal drainage tube to measure their pH at various times during the anaesthetic/surgical procedure. We used pH test strips, pH 2-9 (Merck, Darmstadt, Germany), and in case of any doubts, a pH meter was also used. A pH of ≤ 4.0 was considered positive for the regurgitation of gastric contents. 
Results and discussion: None of the pH measurements of analysed secretions in the hypopharynx had a pH of ≤ 4.0. The mean pH of the secretions varied from 6.34 for the lower means to 6.50 for the higher means when measured at different time points, which are comparable to the normal pH of saliva. 
Conclusion(s): From these results, we conclude that the ProSeal laryngeal mask airway is a safe alternative for anaesthesia during laparoscopic surgery for patients without risk factors for the regurgitation of gastric contents. 
References: 
1) Brain AIJ, Verghese C, Strube PJ. The LMA ´ProSeal´ - a laryngeal mask with an oesophageal vent. Br J Anaesth 2005; 49: 275-80.
2) Cook TM, Lee G, Nolan JP. The ProsealTM laryngeal mask airway: a review of the literature. Can J Anaesth 2005; 52: 739-60. 
3) Ambi U, Koppal R, Joshi C, Prakashappa DS, Iyer H. LMA Classic and LMA Proseal: a comparative study in paralyzed anaesthetized patients. J Clin Diagn Res 2011; 5: 940-3.