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© 1999 International Anesthesia Research Society
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Abstract |
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We conducted this feasibility study using the intubating laryngeal mask airway (ILMA) and a polyvinyl chloride tracheal tube to compare success rates, hemodynamic effects, and postoperative morbidity with two methods of tracheal intubation. After ethics approval and informed consent, 90 healthy ASA physical status I or II women with normal airways were enrolled in the randomized, controlled study. After a standardized inhaled anesthesia induction protocol, tracheal intubations using ILMA with fiberoptic guidance (ILMA-FOB) and ILMA inserted blindly without fiberoptic guidance (ILMA-Blind) were compared with the control group of direct laryngoscopy (laryngoscopy group). All 90 patients were successfully ventilated. For tracheal intubation, success rates were equal in all three groups (97%). Total intubation times were longer for the ILMA-FOB group (77 s versus 48.5 s for laryngoscopy and 53.5 s for ILMA-Blind). The laryngoscopy group had a larger increase in mean arterial blood pressure to tracheal intubation. There were no differences in postoperative sore throat or hoarseness among the groups. In conclusion, success rates are equally high for tracheal intubation using ILMA-Blind and ILMA-FOB techniques in women with normal airways.
Implications: The intubating laryngeal mask airway (ILMA) can be used as a primary airway for oxygenation and ventilation. Both methods of tracheal intubation using the ILMA were equally successful. Postoperative morbidity in the ILMA groups was similar to that in the laryngoscopy group. For women with normal airways, both the ILMA inserted blindly and the ILMA with fiberoptic guidance are suitable alternatives to laryngoscopy for tracheal intubation.
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Introduction |
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The intubating laryngeal mask airway (ILMA) is a new, modified laryngeal mask airway specifically designed for guided tracheal intubations (1). Compared with the conventional laryngeal mask airway, the ILMA is shorter and wider. This allows for a larger tracheal tube (TT), up to 8 mm in internal diameter, and for easy removal after tracheal intubation. The epiglottic elevator bar at the mask aperture and the rigid (stainless steel), anatomically curved shaft have also been added to optimize placement of the TT into the trachea.
Studies of the use of the ILMA for tracheal intubation are limited. The objective of this feasibility study was to evaluate two methods of tracheal intubation using the ILMA with a polyvinyl chloride (PVC) TT. ILMA with fiberoptic guidance (ILMA-FOB) and ILMA without fiberoptic guidance (ILMA-Blind) were compared with the control group of direct laryngoscopy (laryngoscopy group). Variables studied were overall success rate for oxygenation and ventilation with the ILMA as a primary airway, success rates for tracheal intubation using the ILMA, times for airway insertion and tracheal intubation, hemodynamic responses, and postoperative sore throat and hoarseness.
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Methods |
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After obtaining institutional ethics approval and informed consent, 90 ASA physical status I or II women scheduled for elective laparoscopy or laparotomy were enrolled in the study. Exclusion criteria included patients with known or suspected difficult airways and patients at risk of gastroesophageal reflux. Patients were randomized into one of the three groups using a closed envelope method with predetermined group numbers and then single-blinded. All patients were anesthetized and tracheally intubated by the primary investigator or by a resident under the supervision of the primary investigator. At the start of the study, the primary investigator’s experience with the ILMA was limited, with approximately 25 successful uses for tracheal intubation.
After the placement of routine monitors, patients were given 10–20 mL/kg isotonic sodium chloride solution through an 18-gauge IV catheter. General anesthesia with spontaneous ventilation was induced with 1 mg/kg propofol and 8% sevoflurane with 50% N2O at a flow rate of 6 L/min (2). Inhaled induction of anesthesia was continued for 3 min. At this time, the airway was topically anesthetized with 100 mg of 10% lidocaine, which was sprayed with a curved nozzle into the posterior pharynx to decrease coughing with tracheal intubation. An oropharyngeal airway was then inserted into the pharynx of patients in the laryngoscopy group, and the ILMA was inserted into the pharynx of patients in the ILMA-FOB and the ILMA-Blind groups. A size 3, 4, or 5 ILMA was used at the discretion of the attending anesthesiologist, depending on the overall size of the patient. If ventilation with CO2 confirmation could not be established, the airway was removed and a different sized airway was inserted. Inhaled anesthesia was continued for 5 min longer.
Patients in the laryngoscopy group were tracheally intubated using a size 3 Macintosh blade. The first attempt was made without a stylet and without laryngeal manipulation. If needed, the second attempt was made with a stylet and laryngeal manipulation.
Patients in the ILMA-FOB group were tracheally intubated with the ILMA using a 5-mm fiberoptic bronchoscope (medium size), which was passed 2 cm beyond the TT for guidance. Oxygenation and spontaneous ventilation were continued through the TT as bronchoscopy was performed. Fiberoptic view of the airway was graded as either full, partial, or no view of the vocal cords before tracheal intubation was attempted. If the first tracheal intubation attempt failed, the ILMA was removed, and the following protocol was initiated. When the initial fiberoptic view showed a down-folded epiglottis, the same size ILMA was reinserted with a jaw thrust to avoid the down-folding of the epiglottis. When the view showed the esophagus, a smaller size ILMA was used. When the view showed the tip of the epiglottis, a larger size ILMA was used. A second attempt at tracheal intubation was then performed with fiberoptic guidance through the reinserted ILMA.
The ILMA-Blind group was intubated blindly, using tactile sensation. The use of force on the airway was avoided to minimize airway trauma. If resistance was felt, the attempt was deemed a failure. If the first tracheal intubation attempt failed, the ILMA was removed, and the intubation failure protocol was followed (3). When resistance to TT advancement was felt 1.5 cm past the epiglottic elevating bar of the ILMA with the first attempt, a down-folded epiglottis was assumed, and the same size ILMA was reinserted with a jaw thrust to avoid down-folding the epiglottis. When resistance was felt at 0 or 5 cm, the ILMA was deemed to be too large, with esophageal impingement or intubation, and a smaller size ILMA was reinserted. When resistance was felt at 3 cm, tracheal advancement into the vallecula was assumed, and a larger size ILMA was reinserted. A second attempt at tracheal intubation was then performed without fiberoptic guidance through the ILMA.
All groups were tracheally intubated using a 7-mm inner diameter PVC TT. In the ILMA groups, the TT was inserted backward, such that the concave bend was facing down (Figure 1). Airway insertion time was defined as the time from removal of the face mask to the time ventilation was established through the airway with CO2 confirmation. Tracheal intubation time was defined as the time from loss of CO2 due to disconnection of the circuit for tracheal intubation to the time of reappearance of the CO2 from the tracheal tube with no evidence of cuff leak with positive pressure ventilation. Total induction time was defined as the time from the administration of propofol for induction of anesthesia to the time of successful tracheal intubation. Immediately after successful tracheal intubation, patients were paralyzed by 0.3 mg/kg IV rocuronium. Two minutes after successful tracheal intubation, the ILMA was removed using a 6-mm TT as a pusher/conduit. The 6-mm TT was connected into the lumen of the in situ 7-mm TT, and the ILMA was passed over this conduit for removal.
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Failed tracheal intubation with any of the groups was defined as more than two tracheal intubation attempts or >5 min for overall tracheal intubation attempts. Patients with failed tracheal intubation in the laryngoscopy group were intubated with ILMA-FOB. Patients with failed tracheal intubations in the ILMA-FOB and ILMA-Blind groups were tracheally intubated with direct laryngoscopy. Heart rate and oxygen saturation were measured continuously, and blood pressure was measured at 1-min intervals from the start of induction to 5 min after successful tracheal intubation. Sore throat and hoarseness were measured 2 h after surgery (Day 0) and 1 day after surgery (Day 1) using a visual analog scale (VAS), 0 being no pain or hoarseness and 10 being the worst pain or hoarseness that the patient could imagine. Sore throat and hoarseness data from patients with failed tracheal intubations were excluded.
The results were analyzed by using a one-way analysis of variance (ANOVA) and one-way ANOVA on ranks for nonparametric data. Dunn’s method and Student-Newman-Keuls method were used for all pairwise comparisons. Blood pressures and heart rates were analyzed using a two-way split-plot ANOVA and multiple comparison post hoc tests with adjustments for multiple comparisons. A P value of <0.05 was considered significant.
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Results |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Patients had similar demographic data, and similar surgeries were performed (Table 1). Oropharyngeal airway insertion in the laryngoscopy group was successful in all 30 patients with one attempt. ILMA was successful as a primary airway for oxygenation and ventilation in 57 of 60 patients (95%) with one attempt and in 60 of 60 with two attempts. Overall success rates for tracheal intubation were equal at 97% (Table 2). First attempt success rates for tracheal intubation were also similar, ranging from 87% for ILMA-Blind to 93% for ILMA-FOB. The tracheas of all patients in the ILMA-FOB group with partial or full views of the vocal cords via the bronchoscope were successfully intubated, and if the cords could not be identified, tracheal intubation was not successful. One failure occurred in each of the three groups. The tracheas of these patients were successfully intubated using the designated alternative methods. The failures in the ILMA-FOB and ILMA-Blind groups occurred when a size 4 ILMA was used in both attempts. It was presumed at that time that the patient’s down-folded epiglottis could not be corrected. All failures occurred while the primary investigator was the primary intubator. Most patients (90%) were intubated using a size 4 ILMA.
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There were no episodes of desaturation (SpO2 < 90%), and mean oxygen saturation was similar in all three groups (97%–98%). Time for airway insertion was faster for the oropharyngeal airway in the laryngoscopy group (Table 3). Time for tracheal intubation, excluding airway insertion time, was fastest for the ILMA-Blind group, followed by the laryngoscopy and the ILMA-FOB groups. Total time from induction to successful tracheal intubation was longer for the ILMA-FOB group. Hemodynamic responses after airway insertion were similar. Inhaled induction of anesthesia resulted in a decrease in mean arterial pressure in all groups. Increases in mean arterial blood pressure after tracheal intubations were less in the ILMA groups compared with the laryngoscopy group (Figure 2). VAS scores for sore throat and hoarseness were not different.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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The results of this feasibility study have shown that, for women with normal airways, the ILMA can be successfully used for oxygenation and ventilation. For tracheal intubation, the ILMA-FOB and ILMA-Blind techniques were both equally successful with similar postoperative morbidity. Not surprisingly, times for tracheal intubations were longer for the ILMA-FOB group because of the time required to manipulate the FOB.
Our success rates for tracheal intubation with the ILMA were higher than those in similar studies in which failure was defined as more than two attempts at tracheal intubation (97% vs 69%–96%) (4–8). We attribute our high success rates and the absence of complications to our uniform population, as all patients were women with normal airways; experience with the ILMA, as all tracheal intubations were either performed or supervised by the primary investigator; and careful insertion techniques. We also inserted the PVC TT backward, with the concave surface down. Inserted backward, the PVC TT seems to follow a more anatomical direction compared with conventional insertion of a PVC TT into the ILMA. We postulate that if the PVC TT had been inserted conventionally, with the concave surface up, success rates would have been lower, and sore throat scores would have been higher, because of the steep curvature of the PVC TT as it exits the ILMA.
Our reasons for using a PVC TT were that they were disposable, more readily accessible, and less expensive (<$2 vs >$100 CDN for a reusable silicone TT). The PVC TT has been abandoned by Dr. Brain, the inventor of the ILMA, because of concerns regarding lower success rates, higher incidences of sore throats and the possibility for airway damage due to its stiffness, especially when a blind technique is chosen. However, with backward insertions of the PVC TT, we had high success rates with low morbidity in our study. Caution must be used with this new technique, and the use of force must be avoided to prevent airway trauma. We suggest repositioning the ILMA or changing the ILMA size if any resistance is felt. We also advocate the use of the FOB whenever difficulty is encountered during tracheal intubation with the ILMA.
The total time for tracheal intubation was longer for the ILMA-FOB group. However, the time difference was <2 min, which may not be clinically important. The FOB has the theoretical advantages of guiding the TT into the trachea to avoid trauma associated with wrongful placement, increasing success rates by correctly identifying optimal ILMA size required before tracheal intubation is attempted, and confirming correct placement of the tracheal tube. The main disadvantage of the FOB is the cost associated with its acquisition and maintenance.
The ILMA has been advocated for use in patients with difficult airways by the distributor. There are a limited number of case reports of successful tracheal intubations with the ILMA on patients with difficult airways (9–11). There are no formal, randomized, controlled studies of the success of the ILMA in patients with proven difficult airways for ventilation or for tracheal intubation. Therefore, we cannot advocate or oppose the use of the ILMA in patients with difficult airways until more evidence is available on its effectiveness. We do, however, suggest that one familiarize oneself with the use of the ILMA on patients with normal airways before attempting to use the ILMA in patients with difficult airways.
In conclusion, it is feasible to use both ILMA-Blind and ILMA-FOB as alternatives to direct laryngoscopy for tracheal intubation in women with normal airways. This study has also shown the usefulness of the ILMA as a primary airway for oxygenation and ventilation. Whether the ILMA will be most useful as a primary airway, an intubating device, or both is yet to be determined in a diverse population.
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Acknowledgments |
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The authors acknowledge the support and encouragement of the Department of Obstetrics and Gynaecology.
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Footnotes |
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This study was presented in abstract form at the annual meeting of the Canadian Anaesthetists’ Society, Toronto, Ontario, Canada, June 15, 1998.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Brain AI, Verghese C, Addy EV, Kapila A. The intubating laryngeal mask. I. Development of a new device for intubation of the trachea. Br J Anaesth 1997;79:699–703.
[Abstract/Free Full Text] - Muzi M, Robinson BJ, Ebert TJ, O’Brien TJ. Induction of anesthesia and tracheal intubation with sevoflurane in adults. Anesthesiology 1996;86:536–43.
- Brimacombe JR, Brain AIJ, Berry AM. Future directions. In: The laryngeal mask airway: a review and practical guide. Philadelphia:WB Saunders, 1997:227–47.
- Ferson DZ, Supkis DE, Rahlfs TF. Evaluation of the intubating laryngeal mask as a primary airway device and a guide for blind tracheal intubation [abstract]. Anesthesiology 1997;87:A485.
- Cross AM, Colombani . Preliminary study of intubation with a new laryngeal mask for difficult intubation [abstract]. Anesthesiology 1997;87:A481.
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Kapila A, Addy EV, Verghese C, Brain AI. The intubating laryngeal mask airway: an initial assessment of performance. Br J Anaesth 1997;79:710–3.
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Brain AI, et al. The intubating laryngeal mask. II. A preliminary clinical report of a new means of intubating the trachea. Br J Anaesth 1997;79:704–9.
[Abstract/Free Full Text] - Langenstein H, Moller F. Intubating laryngeal mask airway: Fastrach. Anaesthesist 1998;43:311–9.
- Joo H, Rose DK. Fastrach: a new intubating laryngeal mask airway—successful use in patients with difficult airways. Can J Anaesth 1998;45:253–6.[Web of Science][Medline]
- Brimacombe JR. Difficult airway management with the intubating laryngeal mask. Anesth Analg 1997;85:1173–5.[Web of Science][Medline]
- Parr MJ, Gregory M, Baskett PJ. The intubating laryngeal mask: use in failed and difficult intubation. Anaesthesia 1998;53:343–8.[Web of Science][Medline]
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