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* From the Department of Anesthesiology and
The Neurosurgery Division, Centre Hospitalier de l’Université de Montréal, Hôpital Notre-Dame, Montréal, Québec, Canada.
Address correspondence to: Dr. François Girard, Department of Anesthesiology, CHUM, Hôpital Notre-Dame, 1560 Sherbrooke East, Montreal, Quebec H2L 4M1, Canada. Phone: 514-890-8000, ext. 26876; Fax: 514-412-7653; E-mail: francois.girard.chum{at}ssss.gouv.qc.ca
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Abstract |
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Methods: After Institutional Review Board approval, data were collected from the charts of all the patients with spasmodic torticollis who underwent selective peripheral denervation at our institution between 1988 and 2001. The intubation grade was determined using the Cormack and Lehane laryngoscopic classification. The best laryngeal view was recorded.
Results: Data from 342 patients were available for analysis. Fourteen patients had a difficult airway. In two patients, intubation was difficult with three attempts at laryngoscopy in one patient and use of fibreoptic bronchoscopy in the other. Twelve (3.5%) patients presented with laryngoscopic grades of III or IV. The combined prevalence of laryngoscopic view grade III and IV and difficult intubation was 4.4%.
Conclusions: This study assesses the frequency of difficult intubation in patients suffering from spasmodic torticollis. When compared to the general population, these patients do not appear to have a higher frequency of difficult airway or difficult intubation.
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Methods |
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The intubation grade was determined using the Cormack and Lehane classification of the laryngoscopic view:3 full laryngeal view (grade I), visualization of only the posterior portion of laryngeal aperture (grade II), visualization of only the epiglottis (grade III), and visualization of only the soft palate (grade IV). Cormack and Lehane’s classification has been systematically used in our centre for many years and this information was readily available on the anesthetic record. We recorded the best laryngeal view regardless of the direct laryngoscopic technique used. For example, a grade II view obtained with the help of laryngeal pressure was effectively recorded as Cormack’s grade II.4–6 We defined a difficult airway as a grade III or grade IV laryngeal view or tracheal intubation requiring more than two direct laryngoscopies or the use of an alternative to direct laryngoscopy.
Data were compiled on an ExcelTM database. Results are presented as absolute number and percentages, except when stated otherwise. Differences in demographical and surgical characteristics of patients with difficult airway were compared to those of the study population with normal laryngoscopic views using Fisher’s exact test and unpaired Student’s t test when appropriate. All comparisons were two-tailed. A P < 0.05 was considered significant.
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Results |
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); two patients had a difficult intubation. Three attempts at laryngoscopy were required in one patient and fibreoptic bronchoscopy was used in another patient with limited mouth opening. There were no failed intubations in this series of patients. In 14 other patients, application of external laryngeal pressure improved visualization to grade II and enabled tracheal intubation without difficulty. There was no difference in terms of the demographical and surgical data between patients with difficult airway and patients with a normal airway (Table II).
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Discussion |
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This study is the first to assess the frequency of a difficult airway in patients with ST. We found a prevalence of 4.4% of difficult airway which is comparable to the 4.7% prevalence in a prospective cohort of 18,500 patients requiring general anesthesia in a single general hospital over a two-year period.8 The combined prevalence of grade III and IV view was 3.5% in our study. This prevalence is somewhat lower than that reported by El-Ganzouri et al.9 in a study evaluating the predictive value of preoperative assessment of the airway on difficult intubation. The authors prospectively studied the frequency of laryngoscopic views III and IV in 10,507 patients using the Cormack and Lehane classification, with optimal head and neck positioning, forceful anterior elevation of the laryngoscope blade or external laryngeal displacement when required. They found a combined prevalence of 6.1% for grade III (5.1%) and grade IV (1.0%) laryngeal views.
Because of the contorted head posture, the airway of patients with ST, is difficult to evaluate accurately. Although muscle relaxants are used to facilitate tracheal intubation, the muscle spasm sometimes remains fixed because of the prolonged dystonia. Even after surgery, in some patients the direction of abnormal head posture does not change immediately. Reasons for this include cervical spine ankylosis and muscle atrophy or fibrosis. In these patients, the degree of abnormal dystonic head rotation and tilt is usually improved three to 12 months after surgery.12 Despite this, and based on the result of the present study, tracheal intubation of patients with ST do not appear specially challenging compared to the general population. A possible explanation could be that the adverse influence of one or two factors (head rotation, limitation of extension) may be offset by other favourable factors (adequate mouth opening, edentulous mouth). In addition, most of these patients will respond at least partially to muscle relaxants leading to better than anticipated intubating conditions. Because of the retrospective nature of our study and the heterogeneous information on preoperative evaluation of the airway in the charts, we could not examine these factors. In our case series, patients with a difficult airway had similar demographical and surgical features when compared to patients with a normal airway. Thus, no risk factor for difficult tracheal intubation could be identified in the ST population.
This study has some limitations. A retrospective study can be contaminated by unrecognized biases. In this study we relied on the written record of the evaluation of the airway performed by different anesthesiologists over a long period of time; thus our study is susceptible to reporting bias and changes in airway evaluation over time. Predefined criteria for the evaluation of a difficult airway in a well designed prospective study might yield to a different prevalence depending on the criteria used. However, because of the rarity of surgery performed in patients with ST, even in a specialized centre, such a study would be very difficult to conduct.
In conclusion, this study assesses the prevalence of difficult tracheal intubation and difficult laryngoscopy in patients with ST. Contrary to our stated hypothesis, patients with ST do not appear to have a higher frequency of difficult airway and intubation than that of the general population, despite the abnormal head postures.
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2 Girard F, Ruel M, McKenty S, et al. Incidences of venous air embolism and patent foramen ovale among patients undergoing selective peripheral denervation in the sitting position. Neurosurgery 2003; 53: 316–20.[Medline]
3 Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 1105–11.[Medline]
4 Wilson ME, Spiegelhalter D, Robertson JA, Lesser P. Predicting difficult intubation. Br J Anaesth 1988; 61: 211–6.
5 Krantz MA, Poulos JG, Chaouki K, Adamek P. The laryngeal lift: a method to facilitate endotracheal intubation. J Clin Anesth 1993; 5: 297–301.[Medline]
6 Benumof JL, Cooper SD. Quantitative improvement in laryngoscopic view by optimal external laryngeal manipulation. J Clin Anesth 1996; 8: 136–40.[Medline]
7 Bellhousse CP, Dore C. Criteria for estimating likelihood of difficulty of endotracheal intubation with the Macintosh laryngoscope. Anaesth Intensive Care 1988; 16: 329–37.[Medline]
8 Rose DK, Cohen MM. The airway: problems and predictions in 18,500 patients. Can J Anaesth 1994; 41: 372–83.
9 El-Ganzouri AR, McCarthy RJ, Tuman KJ, Tanck EN, Ivankovich AD. Preoperative airway assessment: predictive value of a multivariate risk index. Anesth Analg 1996; 82: 1197–204.[Abstract]
10 Adnet F, Baillard C, Borron SW, et al. Randomized study comparing the "sniffing position" with simple head extension for laryngoscopic view in elective surgery patients. Anesthesiology 2001; 95: 836–41.[Medline]
11 Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429–34.[Medline]
12 Munchau A, Palmer JD, Dressler D, et al. Prospective study of selective peripheral denervation for botulinum-toxin resistant patients with cervical dystonia. Brain 2001; 124: 769–83.
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