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William Stewart CEO Vitaid (Canadian distributors of the LMA™) E-mail: [email protected] Accepted for publication August 24, 2007. References 1 Wong DT, McGuire GP. Fractured laryngeal mask airway (LMA) (Letter). Can J Anesth 2000; 47: 716. 2 Jee RA, van Hasselt GL. Manufacturer’s response to a defective cuff in a disposable laryngeal mask airway (Letter). Can J Anesth 2007; 54: 681–2.

Verification of vocal cord function using the Pentax-AirwayScope®

FIGURE Panel A) Photo of LMA-Unique™ identifiers; Panel B) Photo of LMA-Unique™ size 3 showing “clamshell” cuff protector.

highlighted in the Journal seven years ago.1 Thirdly, single use products are subject to extreme storage and transportation stresses. LMA™ single use products have a protective “clamshell” to protect against cuff deformity during storage and transport (Figure, panel B). All LMA™ devices have features to protect against inadvertent contact with the epiglottis. The device described by Drs. Jee and van Hasselt does not. Single use LMA™ devices have a protective and removable valve ‘stent’ to allow escape of gases used in sterilization. Injecting air into the cuff to add shape, as suggested in the letter,2 may not allow this gas to vent properly. In addition, the air will diffuse through the silicone cuff reducing the desired effect. CAN J ANESTH 54: 12

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To the Editor: The Pentax-AirwayScope® (AWS; Pentax, Tokyo, Japan) is a new rigid indirect video laryngoscope for tracheal intubation. It consists of a charge-coupled device camera, built-in colour liquid crystal device monitor and an anatomically shaped disposable introducer (Pblade®) through which the camera cable passes. When the epiglottis is lifted with the tip of the Pblade®, the camera provides a view of the glottis on the monitor. The tracheal tube set in the Pblade® is easily inserted into the trachea after adjusting the centre of the target mark in the monitor to the glottic opening.1,2 As a consequence of its structural features, the AWS improves the glottic view over the conventional Macintosh blade.3 Also, patients can comfortably tolerate conscious intubation, due to the anatomically shaped blade configuration.4 We recently used the AWS to verify the vocal cord function in 56-yr-old female with suspected bilateral recurrent laryngeal nerve injury following a subtotal thyroidectomy. General anesthesia was induced and maintained with propofol, remifentanil and fentanyl. The patient’s trachea was intubated after obtaining muscle relaxation with vecuronium. At the end of the operation, the surgeon identified the possibility of bilateral recurrent laryngeal nerve injury and requested examination of vocal cord function. The propofol and remifentanil infusions were discontinued. At the point during emergence when the patient could follow simple instructions such as ‘take a deep breath’, the AWS, with the rescue tube set in the channel, was inserted in the patient’s mouth and a clear view of the patient’s vocal cords was easily achieved (Figure, panel 1). The tracheal tube was then carefully withdrawn and the patient was first asked to breath hold (Figure, panel 2) and then inhale deeply (Figure, panel 3). Normal vocal cord mobility was observed, and the

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4 FIGURE Lar yngeal view obtained from the Air wayScope during extubation 1) The vocal cords and endotracheal tube prior to extubation. 2) Post-extubation, the vocal cord appearance using the Air wayScope with breath holding. 3) Vocal cord appearance using the Air wayScope during deep inhalation.

respiratory maneuvers displayed on the sleeve monitor connected to the AWS could be seen simultaneously by the anesthesiologist and surgeon. The patient was discharged from the operating room without reporting any pain or discomfort. This case highlights several advantages of the AWS to assess vocal cord function. First, because the CCD camera is located 2.5 cm from the glottis, an unobstructed, clear glottic view is obtained. Second, several observers can watch the procedure simultaneously. Third, re-intubation, if necessary, can be performed very easily with the tube set in the channel just 3 cm proximal to the glottis. Finally, since the Pblade® is anatomically shaped, the procedure is easily tolerated by the patient, as minimal lifting force is required to expose the glottis. As this device is used for intubation when the patient is conscious,5 it is considered to be less invasive during extubation, requiring minimal sedation. We conclude that the AWS is a useful device to evaluate vocal cord function at the time of tracheal extubation. Chika Kikuchi MD Akihiro Suzuki MD PhD Hiroshi Iwasaki MD PhD Asahikawa Medical College, Hokkaido, Japan E-mail: [email protected] Accepted for publication September 11, 2007. References 1 Koyama J, Aoyama T, Kusano Y, et al. Description and first clinical application of AirWay Scope for tracheal CAN J ANESTH 54: 12

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intubation. J Neurosurg Anesthesiol 2006; 18: 247– 50. Hirabayashi Y. Airway Scope®: initial clinical experience with novice personnel. Can J Anesth 2007; 54: 160–1. Suzuki A, Toyama Y, Katsumi N, et al. The PentaxAWS® improves laryngeal view compared with Macintosh blade during laryngoscopy and facilitates easier intubation (Japanese). Masui 2007; 56: 464–8. Suzuki A, Hayashi D, Toyama H, Minami S, Iwasaki H. Use of the Pentax-AWS® in a patient with Cormack 3a difficult airway (Japanese). Masui 2007; 56: 341–4. Suzuki A, Kunisawa T, Takahata O, Iwasaki H, Nozaki K, Henderson JJ. Pentax-AWS® (Airway Scope) for awake tracheal intubation (Letter). J Clin Anesth 2007 (in press).

Recurrent postoperative deep vein thrombosis in a patient with obstructive sleep apnea and malignant hyperthermia susceptibility To the Editor: We recently managed a patient with known malignant hyperthermia susceptibility (MHS) who had a concurrent history of obstructive sleep apnea (OSA), recurrent deep vein thrombosis (DVT) and past history of pulmonary thromboembolism (PTE). A 67-yr-old male (ASA physical status III) was diagnosed with adenocarcinoma of the sigmoid colon and was scheduled to undergo anterior resection. In the past, he had had three uneventful general anesthetics for unrelated surgeries, but on each occasion had developed bilateral leg DVT and documented PTE once. Since then he was on prophylactic anticoagulation with dalteparin sodium 11,000 IU sc bid. The diagnosis of OSA had been made based on sleep studies. Because of a family history of unexplained death under anesthesia, he had undergone in vitro testing and a diagnosis of MHS was confirmed. His grandmother had died unexpectedly during an operation many years before and this had prompted the testing. To facilitate epidural catheter insertion for this surgery, anticoagulation had been omitted the evening before. In the operating room, recommended MH preparations and precautions were taken and intravenous access and monitoring were instituted. An epidural catheter was inserted at T9/10 without complication and appropriately tested. After preoxygenation, anesthesia was