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Important considerations for the evaluation of the Glidescope as a new airway device
- Marc J Capon, Dr G Kessell (7 December 2006)
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Severe ankylosing spondylitis without patent nasal route
- Berrin Gunaydin, Berrin Gunaydin, Irfan Gungor, Nesrin Yigit, and Hulya Celebi (4 September 2006)
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Marc J Capon, Medical Student University of Dundee and Anaesthetics dept JCUH, Dr G Kessell
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Dear Sir, We read with interest the recent article Lai et al in which they attempted to compare the laryngoscopic views found using a Mactintosh laryngoscope with those obtained using the Glidescope® in a group of patients with ankylosing spondylitis(1). They also appear to have had a subsidiary aim of observing the effectiveness of preoperative evaluation tests in predicting difficult intubations. Unfortunately, although their results are in favour of the Glidescope® we have a number of concerns about the study design. Although they explicitly state the experience of the anaesthetist using the Glidescope® there is no similar information about the anaesthetist using the Macintosh laryngoscope. It is well established that an experienced anaesthetist will observe a better view. They also fail to state whether the first anaesthetist is the same throughout the study. An inexperienced anaesthetist performing direct laryngoscopy will introduce a bias in favour of the Glidescope®. The authors do not state whether either of the anaesthetists making the observations were blinded to the aim of the study. Clearly, if the authors of the paper are involved in the assessment this would again introduce significant bias in favour of the Glidescope®. In most difficult airway research the best laryngoscopic grade is recorded for the view obtained with the use of airway manoeuvres such as cricoid pressure, BURP and bimanual manipulation (2). Though by definition this should be the case, it is not stated whether any airway manoeuvres were used by either anaesthetist. The effect of any such manoeuvres can greatly affect the view achieved and therefore the results and significance of the study. There is ambiguity regarding, which preoperative evaluation tests were used to predict possible difficult intubations. After preoperative evaluation they identified 12 patients to be potential difficult intubations. However, if they used thyromental distance less than 6.5cms there would be 14 patients rather than 12 they state. Although not clearly stated, it appears they have used a combination of Modified Mallampati and thyromental distance as defined by Frerk et al (3). It would seem unwise to draw conclusions about prediction of difficult intubations without being more specific about the criteria used. Although it is necessary to evaluate new airway management devices the subjective nature of the observations demands rigorous attention to study design. Unfortunately, in this instance it is not possible to be confident that conclusions are valid. Yours Faithfully Marc Capon, Dr G Kessell Anaesthetics Department, James Cook University Hospital, Cheriton House, Middlesbrough, Cleveland, TS4 3BW, England. References 1. H. Y. Lai IHC, A. Chen, F. Y. Hwang and Y. lEE. The use of the Glidescope for tracheal intubation in patients with ankylosing spondylitis. Bri J of Anaesth 2006;3:419-422. 2. R. M. Levitan WCK, W. J. Levin, W. W. Everett. Laryngeal view during laryngoscopy: A randonized trial caomparing cricoid pressure, backwards- upwards-rightward pressure, and bi-manual laryngoscopy. Ann of Emerg Med 2006;47(6):548- 555. 3. Frerk CM. Predicting difficult intubation. Anaesthesia 1991;46(12):1005 -1008. Conflict of Interest:None declared |
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Berrin Gunaydin, MD, PhD Department of Anesthesiology, Gazi University - Faculty of Medicine, Berrin Gunaydin, Irfan Gungor, Nesrin Yigit, and Hulya Celebi
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Dear editor, after reading the article on the use of the Glidescope® for tracheal intubation in patients with ankylosing spondylitis (AS) by Lai et al (1), we had an opportunity of using Glidescope® Video Laryngoscope in a patient with AS with predicted difficult intubation on preoperative evaluation. A 43 year-old male patient (weight=40 kg and height=160 cm) with AS + rheumatoid arthritis was scheduled to undergo for removal of infected hip protesis. In his medical history he had total hip replacement surgery for left and right sides with 6-month intervals 17 years ago and bilateral total knee replacement 6 years ago. In his current preoperative airway assessment; Mallampati classification was III, thyromental distance was 4cm, interincisor gap was 2 cm and the atlanto-occipital extension was completely limited. We initially planned neuroaxial anesthesia. Unfortunately our attempts failed and we could not succeed to perform central blockade, so we cancelled the operation. On the next day, we prepared all the required equipment for difficult airway and intubation we had in our department. In the operating room, heart rate, noninvasive blood pressure and peripheral oxygen saturation were monitored. After efficient preoxygenation, the patient received iv 1 µg kg-1 of fentanyl and 2 mg kg-1 of propofol. Following full neuromuscular relaxation with 1.5 mg kg-1 of succinylcholine, Machintosh (Heine, Germany) laryngoscope with a size 3 blade was used for initial direct laryngoscopy. Laryngeal view was graded as IV according to Cormack Lehane grading system and glottic opening was not viewed, so it was recorded as zero. For the second trial, McCoy laryngoscope was used but also failed. Then we attempted to use Glidescope®. Since cervical spine was totally immobile and fixed, neither extension nor the flexion of the neck was possible to manipulate the handle of the Glidescope®. We could hardly place it into the mouth. Although we could not obtain a better laryngoscopic view, we blindly inserted orotracheal tube. Soon after confirming that it was not in the correct place, we removed it. Meanwhile patient started to breathe spontaneously. Fiberoptic intubation was attempted but failed since nasal route was not patent. Then the patient received additional propofol for placing an alternative airway device. Initially, combitube was placed but peripheral oxygen saturation started to decline. For that reason it was removed and we placed LMA Fastrack followed by the connection of the capnograph. The patient was ventilated with 50 % oxygen-air mixture in approximately 1-1.5% sevoflurane and remifentanil infusion of 0.2 µg-1 kg- 1 min was added. Infected hip protesis was removed in 30 min by surgeons. When the operation finished, the patient was spontaneously breathing but it was not safe enough to remove the LMA Fastrack. He was tranquil but able to obey verbal commands such as opening his eyes. During the waiting period of achieving effective spontaneous breathing strength by manual ventilation, his cooperation was suddenly ceased. We immediately attached the electrodes of the bispectral index (BIS) monitor on the forehead for assessing the hypnotic level and cannulated radial artery for blood gas analysis. BIS value was 30 and the corresponding PaCO2 in the blood gas analysis was 135 mmHg. We started to hyperventilate the patient and the next measurements of BIS and PaCO2 were 50 and 72 mmHg twenty minutes later. Consecutive BIS and PaCO2 were 90 and 45 mmHg, respectively. End tidal CO2 also showed a similar declining pattern to the PaCO2 throughout this period. The patient was transferred to ICU. Blood gas analysis on admission to the ICU (pH = 7.23, PCO2 =43.2 mmHg, PO2 = 49.5 mmHg, HCO3= 18.6 mmol L-1 and BE= -7.9 during receiving 4 L min-1 oxygen) demonstrated a reasonably remarkable improvement before transporting the patient to the ward (pH = 7.49, PCO2 =20.9 mmHg, PO2 = 127.3 mmHg, HCO3= 16.2 mmol L-1 and BE= -5.7 during receiving 4 L min-1 oxygen). Anesthesia for patients with AS is challenging since failure of central blockades might necessitate general anesthesia as reported by Ahmad et al (2) as it was in our case. It has been reported that Glidescope® improved better laryngeal view and provided better glottic exposure in patients with simulated difficult airway and in patients requiring general anesthesia for elective surgery without difficult airway, respectively (3, 4). On the contrary to these studies we experienced that Glidescope® could not provide successful intubation by the oral route in a patient with AS and a documented difficult airway. Lai et al (1) successfully performed nasotracheal intubation by Glidescope® in 8 of 11 difficult laryngoscopy patients with AS. Since our patient’s nasal route was not patent, we cannot comment on our outcome like Lai et al (1). Regarding our patient’s previous operations under general anaesthesia, AS could have probably progressed and worsened during the years. Therefore we could neither perform central blockade nor intubate the patient. Another issue concerning this patient was the difficulty in removing the LMA fastrack and waking up the patient. We suggest that BIS should be monitored from the beginning of the operation in recognized difficult airway and intubation to overcome an unexpected hypnotic state. Consequently, patients with severe AS having difficult airway and insufficient nasal access still remain problematic in the regard of using either Glidescope® or fiberoptic intubation. RERERENCES 1.Lai HY, Chen IH, Hwang FY, Lee Y. The use of the Glidescope for tracheal intubation in patients with ankylosing spondylitis. Br J Anaesth 2006; 97 (3): 419-22. 2.Ahmad N, Channa AB, Mansoor A, Hussain A. Management of difficult intubation in a patient with ankylosing spondylitis- a case report. Middle East J Anaesthesiol 2005; 18: 379-84. . 3.Lim Y, Yeo SW. A comparison of the Glidescope with the Macintosh laryngoscope for tracheal intubation in patients with simulated difficult airway. Anaesth Intensive Care 2005; 32: 243-7 4.Hsiao WT, Lin YH, Wu HS, Chen CL. Does a new videolaryngoscope (glidescope) provide better glottic exposure? Acta Anaesthesiol Taiwan 2005; 43: 147-151 Conflict of Interest:None declared |
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