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Department of Anesthesia, University of Basel/Kantonsspital, Basel, Switzerland
Address correspondence and reprint requests to Thomas Erb, MD, Department of Anesthesiology, Duke University Medical Center, PO Box 3094, Durham, NC 27710. Address e-mail to ERB00003 @mc.duke.edu.
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Abstract |
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Implications: Fiberoptic intubation under spontaneous respiration is a well established technique for management of difficult airways. Our study demonstrates the feasibility and safety of a novice training program for fiberoptic intubation under general anesthesia, not only in paralyzed patients but also in those breathing spontaneously.
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Introduction |
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Methods |
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Five residents in their first or second year of anesthesia training participated in the study. None of the study participants had any previous experience in fiberoptic airway instrumentation. Before the start of the study, all participants completed a short structured fiberoptic training program as follows: First, an instructional videotape, demonstrating both handling of the instrument and various FOI techniques, was shown to the trainees. Second, the trainees received the opportunity to practice FOI on an intubation mannequin with and without airway endoscopy mask (VBM, Sulz am Neckar, Germany) (12) under the supervision of an instructor.
A block-randomization was used to assign each trainee 10 spontaneously breathing patients (Group A: sevoflurane anesthesia via an airway endoscopy mask) and 10 paralyzed apneic patients (Group B: total IV anesthesia and full neuromuscular blockade) in a randomized order.
Oral premedication consisted of ranitidin 300 mg the night before and midazolam 7.5 mg 1 h before the start of anesthesia. Routine monitoring was used. In Group A, the pharynx was sprayed with 4–6 puffs of lidocaine aerosol. Then, inhaled induction of anesthesia was started with sevoflurane 8% in 100% oxygen (fresh gas flow 6 L/min) via an airway endoscopy mask. After 3 min, the inspiratory concentration of sevoflurane was reduced to 5%. An Ovassapian fiberoptic intubating airway (Kendall, Irvine, CA) was inserted as soon as deemed appropriate (13). Depth of anesthesia was assessed and was considered adequate for FOI when pupils were miotic, no eyeball activity was noted, and when a vigorous anterior displacement of the mandible did not evoke a motor response. The bronchoscope was then inserted through the silicon membrane of the endoscopy mask. When the tip of the bronchoscope was positioned immediately above the epiglottis, topical anesthesia of the larynx was applied through the suction channel of the bronchoscope using 2 mL of lidocaine 4%. Advancement of the fiberscope into the trachea was withheld for 60 s to allow for the drug’s anesthetic effect.
In Group B, all patients received lidocaine 30 mg IV in an attempt to blunt pain on injection of propofol. Anesthesia was induced with fentanyl 3 µg/kg and propofol 1 mg/kg IV. Anesthesia was maintained with continuous infusion of propofol 10 mg · kg-1 · h-1. Muscle relaxation was performed with atracurium 0.5 mg/kg, and the lungs were manually ventilated with 100% O2 via a regular face mask.
In both groups, fiberoptic airway instrumentation was performed with the patient’s mandible anteriorly dislocated at the temporomandibular joint by the supervisor in order to open the retropharyngeal space. A plastic endotracheal tube, size 7.5, attached to a Olympus BF P20D fiberbronchoscope (Olympus Optical Company, Tokyo, Japan) was used in all patients. Duration of intubation was defined as the time from introducing the bronchoscope into the patient’s mouth until end-tidal carbon dioxide was recorded after resumption of ventilation via endotracheal tube.
Inhaled induction under spontaneous ventilation or intubation attempts were discontinued if SpO2 decreased below 95%; in this case, patients were ventilated manually via face mask for 3 min before the next attempt. If the trainee failed to intubate within two attempts, the patient’s trachea was intubated by the supervisor.
Postoperatively, patients were asked for side effects of tracheal intubations, such as sore throat.
Data were analyzed using the 
2 test or Fisher’s exact test, and the unpaired Student’s t-test, as appropriate. Time to complete intubation was further analyzed using the log-rank (Mantel-Cox) test and, in addition, comparing the first five intubations with the subsequent intubations within each group using the Wilcoxon’s rank sum test. A P value of <0.05 was considered significant.
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Results |
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Discussion |
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However, available data on FOI under spontaneous respiration are limited. Smith et al. (9) reported desaturation episodes (SpO2 < 90%) with an incidence as high as 30% in patients with expected difficult intubation when breathing halothane and nitrous oxide in 50% oxygen via a Mathias oral airway. Furthermore, in that study, desaturation episodes were associated with difficulties in maintaining a patent airway and, as a result, in maintaining an adequate depth of anesthesia.
In our study, fiberoptic airway instrumentation never had to be interrupted because of hypoxemia (SpO2 < 95%) in Group A. We suggest that this favorable outcome compared with previous studies (8,9) may, at least in part, result from differences in airway management. First, we used a specifically designed airway endoscopy mask that fits tightly to the patient’s face and, therefore, not only enables the administration of 100% oxygen during fiberoptic airway instrumentation but also prevents loss of anesthetic gases (12). Second, we used sevoflurane as an anesthetic whose physicochemical properties, along with lack of pungency, allows a rapid and smooth induction when delivered via a face mask (16). Third, the use of topical anesthesia in Group A may have contributed to a more profound blunting of airway reflexes in nonparalyzed patients. Fourth, our patients had normal airway anatomy, whereas Smith et al. (9) studied individuals with predicted difficult intubation. Of note, however, 17/18 patients in Smith et al.’s study with hypoxemic episodes (SpO2 < 90%) presented a glottic visible at Cormack and Lehande grade I or II at direct laryngoscopy (17), which suggests that abnormal airway anatomy was not a major contributing factor in the development of hypoxemia in these patients. Finally, our patients received 100% oxygen via a face mask, a fact which might have improved a patient’s tolerance for possibly inadequate alveolar ventilation during airway instrumentation.
The overall percentage of successful intubation by our novices in FOI was high (Table 2). Nonetheless, the time necessary to perform successful intubation decreased with an increasing number of FOIs in both groups, thereby demonstrating a significant learning effect. Duration of intubation was increased in Group A (Figure 1) and reflects, in part, the time needed to apply local anesthetics through the bronchoscope and the delay of 60 seconds to allow for the desired drug effect. In addition, coughing and, more important, time to overcome impingement of the tube on the larynx accounts for prolonged FOI in certain subjects. However, we suggest that this had no untoward effect on patients’ safety in Group A because all patients in this study were at low risk of regurgitation and, furthermore, none of the patients in this group sustained critical decreases in SpO2 values (Table 2).
In conclusion, in addition to a fiberoptic training program in apneic patients, a training program with spontaneously breathing patients may allow the acquisition of additional skills required when dealing with awake patients with difficult airways. Our data suggest that such a training program can be safely performed without significant untoward effects to spontaneously breathing patients under general anesthesia with sevoflurane. However, we emphasize the fact that our data cannot be extrapolated to patients with difficult airways, although the successful use of sevoflurane anesthesia has been reported in small number of such patients (18,19). Therefore, further studies are required to demonstrate the safety and feasibility of FOI of patients with difficult airways under general anesthesia.
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Footnotes |
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This article has been cited by other articles:
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  H. Kohase, H. Sehata, H. Inada, Y. Ikeda, and M. Umino Endotracheal Intubation Device with a Charge Couple Device Camera Anesth. Analg., February 1, 2003; 96(2): 432 - 434. [Abstract] [Full Text] [PDF]
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 V. K. Durga, J. P. Millns, and J. E. Smith Manoeuvres used to clear the airway during fibreoptic intubation Br. J. Anaesth., August 1, 2001; 87(2): 207 - 211. [Abstract] [Full Text] [PDF]
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C. M. B. Heard, B. Gunnarsson, and J. E. Fletcher Teaching Fiberoptic Intubation in the Pediatric Patient Anesth. Analg., October 1, 2000; 91(4): 1044 - 1044. [Full Text] [PDF]
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