Intraocular Pressure Changes Associated with Intubation with the Intubating Laryngeal Mask Airway Compared with Conventional Laryngoscopy

This open, prospective, randomised study was designed to evaluate the changes in intra-ocular pressure and haemodynamics after tracheal intubation using either the intubating laryngeal mask airway (ILMA) or direct laryngoscopy. Sixty adult patients, ASA physical status 1 or 2 with normal intra-ocular pressure were randomly allocated to one of the two techniques. Anaesthesia was induced with propofol followed by rocuronium. Tracheal intubation was performed using either the ILMA or Macintosh laryngoscope. Intra-ocular pressure, heart rate and blood pressure were measured immediately before and after tracheal intubation and then minutely for five minutes. In the laryngoscopy group there was a significant increase in intra-ocular pressure (from 7.2+/-1.4 to 16.8+/-5.3 mmHg, P<0.01), which did not return to pre-intubation levels within five minutes, and also in mean arterial pressure after tracheal intubation, which returned to baseline levels after five minutes. In the ILMA group there were no significant changes in intra-ocular pressure (from 7.6+/-1.8 to 10.4+/-2.8 mmHg, P >0.05) or mean arterial pressure after tracheal intubation. Time to successful intubation was longer with the ILMA, 56.8+/-7.8 seconds, compared with the laryngoscopy group, 33+/-3.6 seconds (P<0.01). Mucosal trauma was more frequent with the ILMA (eight of 30) compared with the laryngoscopy group (three of 30) (P<0.01). The postoperative complications were comparable. In terms of minimising increases in intra-ocular pressure and blood pressure, we conclude that the ILMA has an advantage over direct laryngoscopy for tracheal intubation.