Flexible Lightwand-Guided Intubation Using the Intubating Laryngeal Mask Airway??? in the Supine, Right, and Left Lateral Positions in Healthy Patients by Experienced Users

Tracheal intubation is usually performed with the patient in the supine position; however, it is occasionally required in the lateral position if there is loss of airway control during surgery in the lateral position, if patients cannot be moved from the lateral position because of pain, if patients are trapped in the lateral position, or perhaps to reduce the risk of aspiration at the induction in the presence of oropharyngeal bleeding. Laryngoscope-guided tracheal intubation is more difficult in the lateral than the supine position because airway anatomy is distorted, and the practitioner is in an unfamiliar posture (1), but there is prospective evidence that the classic laryngeal mask airway is easy to insert in the lateral position in patients with normal airways (2) and anecdotal evidence that it is easy to insert in emergency situations where other airway devices have failed (3,4). Our group described two cases where the intubating laryngeal mask airway™ (ILMA; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) was successfully used as a rescue ventilatory device and aid to lightwand-guided intubation in two patients in the lateral position (5). In the following study, we compare flexible lightwand-guided intubation using the ILMA in the supine, right, and left lateral positions by experienced users. Methods After ethical committee approval and written informed consent, 120 fasted consecutive ASA physical status I–III patients scheduled for elective orthopedic surgery and requiring tracheal intubation were studied. Patients were excluded if they were <18 yr old, had respiratory tract pathology, gastroesophageal reflux, or were considered otherwise unsuitable for the ILMA. Patients were randomized for ILMA insertion and flexible lightwand-guided intubation in the supine, right, or left lateral positions. Anesthetic management was standardized according to the following protocol: Monitoring was applied preinduction and included an electrocardiograph, pulse oximeter, gas analyzer, noninvasive blood pressure monitor, peripheral nerve stimulator, tidal volume monitor, and airway pressure monitor. The induction of anesthesia was in the supine position with fentanyl 1 μg/kg and propofol 1.5–3.0 mg/kg, cisatracurium 0.15 mg/kg for muscle relaxation, and face mask ventilation with 100% oxygen and sevoflurane 2% until the train-of-four count was 0. Patients either remained in the supine position or were moved into the right or left decubitus position. The head and neck were maintained in the neutral position using a pillow behind the occiput for the supine position and with a pillow beneath the dependant side of the head and neck and a hand behind the occiput for the lateral position. ILMA insertion (size 4, ≤70 kg; size 5, >70 kg) and cuff inflation were performed according to the manufacturer’s recommendations (6). After successful ILMA placement, a 7- to 8-mm well-lubricated straight silicone tracheal tube, preloaded with the flexible lightwand, was inserted into the ILMA tube and advanced beyond the epiglottic elevating bar while observing the glow in the neck. Room lighting was reduced. If a glow could not be seen, the skin over the neck was stretched or the neck flexed and head extended to increase the thyrosternal distance. Whenever slight tactile resistance was felt, a predetermined sequence of adjusting maneuvers was instituted depending on the location of the glow (Table 1) (7). When the tube easily advanced 8 cm beyond the ILMA, the anesthesiologist judged whether the esophagus or trachea had been intubated by capnography. If esophageal intubation occurred, the ILMA was partially withdrawn and the handle extended before a second attempt. If this failed, the ILMA was partially withdrawn and reinserted before a further attempt. The maximum number of adjusting maneuvers and intubation attempts allowed was four and five, respectively. Successful ILMA placement was defined as a tidal volume of 7 mL/kg without an audible oropharyngeal leak at peak airway pressures ≤20 cm H2O. An insertion attempt was defined as rotation of the ILMA towards the pharynx. An intubation attempt was defined as a forward and backward movement of the tracheal tube through the ILMA. The time taken from the ILMA entering the mouth to successful intubation was noted. All ILMA insertions and intubations were conducted by experienced ILMA users (>100 uses with blind technique before the start of the study), although they had no specific training with insertion in the lateral position. An unblinded observer collected data. Sample size was selected to detect a projected difference of 20% between the groups with respect to insertion time for a type I error of 0.01 and a power of 0.8. Statistical analysis was with the unpaired t-test and χ2 test. Significance was taken as P < 0.05.Table 1: Light-guided Intubation via the Intubating Laryngeal Mask Airway™ (ILMA) Using the Flexible Lighted Catheter: Probable Cause of Resistance and Appropriate Management Strategy Depending of the Location of the Glow on the NeckResults Data are presented in Table 2. There were no differences in demographic data. The ILMA was successfully inserted in all patients at the first attempt. Flexible lightwand-guided intubation was successful in all patients. There were no differences in time, the number of insertion attempts, the number of adjusting maneuvers, or the number of accidental esophageal intubations.Table 2: Demographic Data, Insertion Times, Number of Insertion Attempts, Number of Intubation Attempts, and Adjusting Maneuvers for Intubating Laryngeal Mask Airway™ Insertion in the Right Lateral and Supine PositionDiscussion Flexible lightwand-guided intubation using the ILMA was equally successful in the supine and lateral positions. This is probably because anatomic distortion is minimized because ILMA insertion is a blind technique, and practitioner posture is unimportant. Success rates were similar for the right and left lateral positions because the ILMA is a symmetric airway device, unlike the conventional right-sided laryngoscope blade that probably favors intubation in the left lateral position (8). Interestingly, the first time insertion success rate in the lateral position was higher than in a previous study describing insertion of the classic LMA in the lateral position (2) (100% versus 70%). We speculate that the ILMA may be easier to insert than the classic LMA in the lateral position. The high success rate for flexible lightwand-guided intubation using the ILMA suggests that it would be a reasonable alternative to face mask ventilation and laryngoscope-guided intubation in the lateral position. Interestingly, flexible lightwand-guided intubation using the ILMA has a high success rate in the failed intubation scenario (9). A limitation of our study is that experienced users inserted the ILMA, and our results may not be applicable to inexperienced users. However, there is evidence for rapid skill acquisition for flexible lightwand-guided intubation using the ILMA in the supine position by nurses (10). We conclude that flexible lightwand-guided intubation with the ILMA is equally effective in the supine, right, and left lateral positions in healthy patients by experienced users.