| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
* From the Department of Anaesthesia, Pain Clinic, and Clinical Toxicology,Mito Saiseikai General Hospital, Ibaraki, Japan; and
the Department of Anesthesia, James Cook University, Cairns Base Hospital, Cairns, Australia.
Address correspondence to: Dr. Joseph R. Brimacombe, Department of Anesthesia, James Cook University, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia. Fax: 61-7-40506854; E-mail: jbrimaco{at}bigpond.net.au
 |
Abstract |
|---|
 TOP Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Methods: 193 patients (ASA I–II, 18–80 yr) were studied in a non-crossover, randomized fashion. Manual-in-line stabilization was applied and the best laryngoscopic view obtained. For the CMS, the primed tracheal tube was advanced under direct vision if Cormack-Lehane grade 1/2, placed behind the epiglottis and advanced blindly if grade 3, and intubation was not attempted if grade 4. For the FOS, the primed tracheal tube was advanced under the direct vision if grade 1/2 and under fibreoptic vision if grade 3/4.
Results: Intubation was successful more frequently (P = 0.02) and required fewer attempts (P = 0.003) with the FOS than the CMS. Intubation with the FOS was successful more frequently (P = 0.02) and required fewer attempts (P = 0.007) than the CMS if grade 3/4. For both stylets, intubation required fewer attempts (P < 0.007) and was quicker (P 
0.0001) for grade 1/2 than 3/4. Esophageal intubation occurred more frequently with the CMS (14 vs 0, P = 0.0001).
Conclusion: Tracheal intubation is more successful, requires fewer attempts and esophageal intubation is less frequent with the FOS than the CMS during cervical spine immobilization using manual-inline axial stabilization. The FOS is a more effective intubation instrument compared to the CMS in patients with simulated cervical spine immobilization.
|
Introduction |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
). Kitamura et al.,1 the inventors of the FOS, reported a 100% intubation success rate in 32 patients with simulated Cormack-Lehane grade 3, and Kitamura and Yamada2 reported a 100% intubation success rate in 11 patients without laryngoscopy. In the following randomized study, we compare the performance of the FOS with a Satin SlipTM conventional metal stylet (CMS; Mallincrodt Medical, Glens Falls, NY, USA) during simulated difficult airway management with manual-in-line stabilization in terms of ease of intubation, hemodynamic changes, and frequency of hypoxia, esophageal intubation, tissue trauma and postoperative pharyngolaryngeal complaints.
|
|
Methods |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
All patients were fasted for at least eight hours and premedicated with diazepam 5 mg and roxatidine 75 mg 100 min pre-induction. Modified Mallampati score,3 thyromental, sternomental4 and inter-incisor distances (with head extension)4 were measured at the preanesthetic visit. Monitoring included an electrocardiograph, pulse oximeter, gas analyzer, non-invasive blood pressure (BP) monitor (BP508, Nippon Colin Co., Ltd., Tokyo, Japan) and peripheral nerve stimulator. The patient was in the supine position with the head on a standard pillow 7 cm in height. Oxygen was administered via a face mask for five minutes. Lidocaine 0.5 mg•kg–1 was given iv with a venous tourniquet inflated to prevent pain on injection of propofol. Thirty seconds later, the tourniquet was released and anesthesia was induced with propofol 2 mg•kg–1 and fentanyl 2 µg•kg–1, and maintained with sevoflurane 2% in oxygen 33% and nitrous oxide. Muscle relaxation was obtained with vecuronium 0.1 mg•kg–1. Patients were ventilated via a face mask for five minutes until the train-of-four count was zero. Face mask ventilation was graded as easy (Guedel airway not required), moderately easy (Guedel airway required), difficult (Guedel airway plus jaw thrust required) and failed (failure to ventilate, alternative technique required).
Immediately pre-intubation, the pillow was removed, the head and neck placed in the neutral position, and manual-in-line stabilization applied by a trained assistant by holding the patient’s temple and applying counter traction against the intubator to maintain the neutral head-neck position. A curved PVC tracheal tube (7.0-mm internal diameter) was primed with the randomized stylet. A single experienced anesthesiologist (> 3,000 conventional laryngoscope-guided tracheal intubations, including > 100 with each stylet) obtained the best possible view of the glottis without laryngeal pressure using a #3 Macintosh laryngoscope. In the CMS group, if the glottic view5 was Cormack-Lehane grade 1 or 2, the tracheal tube was advanced into the trachea under direct vision. If the glottic view was Cormack-Lehane grade 3, the tracheal tube was placed behind the epiglottis and advanced towards the glottis; however, if tactile resistance was encountered, the primed tracheal tube was removed and the angle of the stylet adjusted into a ‘hockey stick’ shape, as judged by the anesthesiologist. If the glottic view was Cormack-Lehane grade 4, tracheal intubation was not attempted and considered failed. In the FOS group, if the glottic view was Cormack-Lehane grade 1 or 2, the primed tracheal tube was advanced into the trachea under direct vision with the angle of the tip being adjusted by manipulation of the lever, as necessary. If the glottic view was Cormack-Lehane grade 3 or 4, intubation was attempted under fibreoptic vision as follows: 1) the primed tracheal tube was advanced behind the epiglottis under direct vision (Cormack-Lehane grade 3) or fibreoptically (Cormack-Lehane grade 4); 2) the glottis was identified under fibreoptic vision by manipulation of the tip; and 3) the primed tracheal tube was advanced into the trachea. A maximum of three attempts was permitted. A failed attempt was defined as removal of the primed tracheal tube from the mouth. Laryngoscopy was maintained throughout the intubation attempts. If intubation failed after three attempts or was Cormack-Lehane grade 4 in the CMS group, manual-in-line stabilization was released and intubation was attempted without manual-in-line stabilization.
The following data were collected by an unblinded observer: ease of face mask ventilation; number of intubation attempts; reason for failure (CMS; Cormack-Lehane grade 4, tactile resistance; esophageal intubation; FOS; failure to locate glottis; view obstructed by secretions or fogging; esophageal intubation); intubation time (from insertion of the laryngoscope to confirmation of tracheal intubation by capnography); mucosal trauma (blood seen on the laryngoscope); lip or dental injury; and hypoxia (SaO2 < 95%). Non-invasive BP and heart rate were recorded immediately pre-induction, immediately pre-intubation, and one minute after successful intubation. End-tidal sevoflurane and CO2 concentrations were recorded immediately pre-intubation.
Pharyngolaryngeal morbidity was assessed 18 to 24 hr postoperatively by an investigator blinded to the method of intubation. Sore throat and hoarseness were graded on an established four-point scale.6 Sore throat was graded as: 0 = no sore throat; 1 = less severe than with a cold; 2 = similar to that noted with a cold; 3 = more severe than with a cold. Hoarseness was graded as: 0 = no hoarseness; 1 = noted by a patient; 2 = obvious to observer; 3 = aphonia.
Sample size was selected to detect a projected difference of 20% between groups for a type I error of 0.05 and a power of 0.8 with respect to intubation success rate in Cormack-Lehane grade 3/4 patients (based on a 60% incidence of grade 3/4 with manual-in-line stabilization).7 Descriptive data were tested using a two-tailed independent t test. Categorical data were tested by Chi-square test. The Mann Whitney U test was used for scored data. Unless otherwise noted, data are presented as mean ± SD. Significance was taken as P < 0.05.
|
Results |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
). Face mask ventilation was graded as easy in all patients. Intubation was successful more frequently (P = 0.02) and required fewer attempts (P = 0.003) with the FOS than the CMS, but duration of intubation was similar (Table II). Intubation was always successful at the first attempt with the FOS if grade 1/2; two patients required three attempts with the CMS (Table III). Intubation with the FOS was successful more frequently (P = 0.02) and required fewer attempts (P = 0.007) than the CMS if grade 3/4 (Table III). Intubation was successful more frequently in patients who were grade 1/2 than 3/4 for the CMS (P = 0.004), but not for the FOS (Table III). For both stylets, intubation required fewer attempts (P < 0.007) and was quicker (P 0.0001) for grade 1/2 than 3/4 (Table III). The reasons for failure (at the first, second or third attempt) with the CMS were Cormack-Lehane grade 4 (n = 2), esophageal intubation (n = 14) and tactile resistance (n = 39). The reasons for failure (at the first, second or third attempt) with the FOS were failure to locate glottis (n = 13) and view obstructed by persistent secretions (n = 3) or fogging (n = 1). Esophageal intubation occurred more frequently with the CMS (14 vs 0, P = 0.0001). Hemodynamic variables (Table IV) and the frequency of hypoxia, bleeding, lip and dental trauma, and postoperative pharyngolaryngeal complaints were similar between groups (Table V) and were unaffected by Cormack-Lehane grading within groups.
|
|
|
|
|
|
Discussion |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Three techniques have been used to simulate the difficult airway: 1) intentional insufficient laryngoscopy,9 2) manual-in-line stabilization plus laryngeal pressure,10–13 and 3) use of a rigid neck collar.13 Intentional insufficient laryngoscopy runs the risk of inter-observer bias because the grade of laryngeal exposure is primarily decided by the effort of the intubator. The rigid neck collar method solves this problem, but puts the patient at risk of hypoxia since face mask ventilation may be difficult due to poor fit against the face. The frequency of Cormack-Lehane grade 3/4 using manual-in-line stabilization plus laryngeal pressure is 22 to 39%10–13 and using a rigid collar is 64 to 65%.13–15 We found that the frequency of Cormack-Lehane grade 3/4 using manual-in-line stabilization without laryngeal pressure was 66% and that there were no episodes of hypoxia. This technique should allow smaller sample sizes than manual-in-line stabilization with laryngeal pressure and hypoxia may be less likely than with a rigid collar.
We found no difference in hemodynamic responses, or the frequency of trauma and postoperative pharyngolaryngeal complaints between stylets. This suggests that the additional attempts with the CMS were relatively unstimulating and atraumatic. It is possible that more trauma would have occurred with the CMS if the two Cormack-Lehane grade 4 patients were included. We did not attempt intubation in these patients because we felt the risk of trauma was too high. The study findings would not have been influenced by the inclusion of these patients. The hemodynamic responses, frequency of trauma and postoperative pharyngolaryngeal complaints were similar to conventional laryngoscopy and tracheal intubation.16
Our study has two limitations. Firstly, an experienced user conducted all intubations and our results may not be applicable to inexperienced personnel. Secondly, the intraoperative data were collected by an unblinded observer, a potential source of bias.
We conclude that tracheal intubation is more successful, requires fewer attempts and esophageal intubation is less frequent with the FOS than the CMS during cervical spine immobilization using manual-inline axial stabilization. The FOS is a more effective intubation instrument compared to the CMS in patients with simulated cervical spine immobilization.
|
|
Footnotes |
|---|
Accepted for publication March 16, 2004. Revision accepted September 10, 2004.
|
References |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
2 Kitamura T, Yamada Y, Du HL, Hanaoka K. An efficient technique for tracheal intubation using the StyletScope alone (Letter). Anesthesiology 2000; 92: 1210–1.[Medline]
3 Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487–90.[Medline]
4 Benumof JL. Management of the difficult adult airway. With special emphasis on awake tracheal intubation. Anesthesiology 1991; 75: 1087–110.[Medline]
5 Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 1105–11.[Medline]
6 Stout DM, Bishop MJ, Dwersteg JF, Cullen BF. Correlation of endotracheal tube size with sore throat and hoarseness following general anesthesia. Anesthesiology 1987; 67: 419–21.[Medline]
7 Asai T, Murao K, Tsutsumi T, Shingu K. Ease of tracheal intubation through the intubating laryngeal mask during manual in-line head and neck stabilisation. Anaesthesia 2000; 55: 82–5.[Medline]
8 Gataure PS, Vaughan RS, Latto IP. Simulated difficult intubation. Comparison of the gum elastic bougie and the stylet. Anaesthesia 1996; 51: 935–8.[Medline]
9 Goldberg JS, Bernard AC, Marks RJ, Sladen RN. Simulation technique for difficult intubation: teaching tool or new hazard? J Clin Anesth 1990; 2: 21–6.[Medline]
10 Smith CE, Pinchak AB, Sidhu TS, Radesic BP, Pinchak AC, Hagen JF. Evaluation of tracheal intubation difficulty in patients with cervical spine immobilization. Fiberoptic (WuScope) versus conventional laryngoscopy. Anesthesiology 1999; 91: 1253–9.[Medline]
11 Laurent SC, de Melo AE, Alexander-Williams JM. The use of the McCoy laryngoscope in patients with simulated cervical spine injuries. Anaesthesia 1996; 51: 74–5.[Medline]
12 Nolan JP, Wilson ME. Orotracheal intubation in patients with potential cervical spine injuries. An indication for the gum elastic bougie. Anaesthesia 1993; 48: 630–3.[Medline]
13 Heath KJ. The effect of laryngoscopy of different cervical spine immobilisation techniques. Anaesthesia 1994; 49: 843–5.[Medline]
14 MacQuarrie K, Hung OR, Law JA. Tracheal intubation using a Bullard laryngoscope for patients with a simulated difficult airway. Can J Anesth 1999; 46: 760–5.
15 Gabbott DA. Laryngoscopy using the McCoy laryngoscope after application of a cervical collar. Anaesthesia 1996; 51: 812–4.[Medline]
16 Ng WS. Pathophysiological effects of tracheal intubation. In: Latto IP, Rosen M (Eds). Difficulties in Tracheal Intubation. London: W.B. Saunders Company Ltd.; 1997: 13–50.
This article has been cited by other articles:
 |
|
 |
|
  K. Sugiyama and K. Okushima Difficult Intubation in a Patient Without a Mandibular Body Anesth. Analg., February 1, 2008; 106(2): 677 - 678. [Full Text] [PDF]
|
|
|
|
 |
|
 O. Hung and J. A. Law Advances in airway management Can J Anesth, June 1, 2006; 53(6): 628 - 631. [Full Text] [PDF]
|
|
|
|
|
|
R. B.P. Stasiuk "Conventional stylet" intubation - a misunderstood and misused concept Can J Anesth, August 1, 2005; 52(7): 780 - 780. [Full Text] [PDF]
|
|
|
|
 |
|
 Intubation in C-Spine Injury: Is a Fiberoptic Stylet Better? Journal Watch Emergency Medicine, April 13, 2005; 2005(413): 7 - 7. [Full Text]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
