Muscle relaxant effects on insertion efficacy of the laryngeal mask ProSealA® in anesthetized patients: a prospective randomized controlled trial

Anesthesiologists often encounter LMA-ProSeal(A (R)) (ProSeal) insertion difficulty due to its large cuff size. We performed a randomized clinical trial to examine how insertion efficacy and sealing pressure of ProSeal are affected by muscle relaxant administration in anesthetized patients. Our adult patients were either administered rocuronium (0.9 mg kg(-1)) as a muscle relaxant (R group; 40 patients) or not (C group; 40 patients). Anesthesia was induced with propofol and fentanyl. We compared the two groups with regard to the number of attempts required for successful insertion, sealing pressure, and subjective difficulty for insertion. Total insertion attempts required for successful ventilation in the two groups were one (R group, 38 patients; C group, 28 patients), two (R group, one patient; C group, seven patients), and three (R group, one patient; C group, five patients), revealing a significant difference between groups (p < 0.001). Sealing pressure was significantly higher in the R group than in the C group (R group, 27.4 +/- A 5.4 cmH(2)O; C group, 21.2 +/- A 5.2 cmH(2)O; p < 0.001). Leakage volume by mechanical ventilation was significantly smaller in the R group than in the C group (R group, 17.4 +/- A 29.1 ml; C group, 46.8 +/- A 45.5 ml; p < 0.001). Subjective difficulty of insertion was significantly lower in the R group than in the C group (R group, 12.3 +/- A 23.1 mm; C group, 39.4 +/- A 31.9 mm; p < 0.001). Muscle relaxation appears to facilitate ProSeal insertion efficacy by enabling higher successful insertion rates, higher sealing pressure, lower leakage volume, and lower subjective difficulty of insertion in anesthetized patients.