Yu Jing Yuan

Oxygen flush is an effective means to eliminate obscured vision by fogging during intubation using the Airtraq® optical laryngoscope

To the Editor, The Airtraq optical laryngoscope (Airtraq) (Prodol Meditec S.A., Vizcaya, Spain) is a new disposable tracheal intubation device with an anatomically-shaped blade that contains two parallel channels, the optical channel and the guiding channel, which accommodates the endotracheal tube (ETT). The image is transmitted to a proximal viewfinder, and the distal viewing lens allows visualization of the larynx and advancement of the ETT. In addition, the Airtraq has a warming element at the blade tip. According to the manufacturer’s manual, the Airtraq light should be turned on at least 30 sec before use to allow heating of the viewing lens and to prevent fogging. Despite the Airtraq’s anti-fog mechanism, we have observed that visualization of the laryngeal inlet can be obscured by fogging on the viewing lens, especially when tracheal intubation time is prolonged in patients with difficult airways. To resolve this issue, and in view of previous experience with another optical laryngoscope (Truview laryngoscope, Truphatek International Ltd, Netanya, Israel) and the fibreoptic laryngoscopes, we tested the effectiveness of using highflow oxygen to eliminate fogging during laryngoscopy and tracheal intubation using the Airtraq. After receiving local ethics committee approval and written informed consent, we recruited 321 children (aged three months to 17 yr) and 283 adults (aged 18-75 yr) into the study. All of the patients were American Society of Anesthesiologists’ physical status I-II patients who were scheduled for elective plastic surgery in our hospital from March 2009 to June 2010. All procedures called for general anesthesia requiring tracheal intubation. Exclusion criteria included patients with a limited mouth opening that precluded insertion of the Airtraq and refusal to participate in the study. All intubations were performed by anesthesiologists who had been trained in the use of an Airtraq in a short-term airway management program and who had performed tracheal intubations using this device in more than 20 patients prior to this study. Induction and maintenance of anesthesia were not standardized but were left to the discretion of the staff anesthesiologist to use either a propofol or sevofluranebased technique with or without neuromuscular blockade. Before orotracheal intubation, an appropriately-sized ETT was loaded into the guiding channel of the Airtraq, and the ETT tip was positioned at the right side of the viewing lens. When performing nasotracheal intubation, the ETT was inserted via the pre-selected nostril until its tip passed through the posterior naris. The Airtraq was then passed into the patient’s airway over the tongue in the midline. Once the Airtraq blade tip was positioned in the vallecula with the glottis in the centre of the viewfinder, the ETT was passed by the glottis and advanced downwards into the trachea. Obscured vision during laryngoscopy and intubation was defined as fogging on the viewing lens that impeded continuous observation for airway structures and ETT advancement. Whenever this problem occurred, an assistant immediately attached the anesthesia circuit to the ETT. By intermittently pushing the oxygen flush valve of an anesthesia machine, a high oxygen flow was transported via the ETT to the distal end of the Airtraq to eliminate the fogging (Figure). The efficiency of de-fogging was assessed using a three-point scale (inefficient = no Fu Shan Xue, Jian-Hua Liu contributed equally to this work.

Facilitating tracheal intubation in pediatric patients with the Airtraq® optical laryngoscope

To the Editor, The Airtraq optical laryngoscope (Airtraq) (Prodol Meditec S.A., Vizcaya, Spain) is a relatively new disposable tracheal intubation device with an anatomically shaped blade that has two parallel channels, the optical channel and the guiding channel, which accommodates the endotracheal tube (ETT). The Airtraq incorporates a guiding channel to the right of the viewing axis to solve the challenge of passing the ETT through the glottis. However, delivering the ETT through the gap between the end of the guiding channel tube to the glottis may not be straightforward. The guiding channel tube and viewing axis are somewhat incongruent, because the direction of ETT advancement from the guiding channel is defined by the configuration of the guiding channel tube and the ETT angulation. When attempting to advance the ETT through the laryngeal aperture with the Airtraq during tracheal intubation, it has been reported that a posterior tube tip location can be problematic, especially for pediatric patients. On the basis of our cumulated experience with the Airtraq, which includes more than 500 pediatric patients to date, another possible difficulty in advancing the ETT through the glottis, especially in infants and young children with smaller airways, is a left tube tip location. This potential problem arises because the Airtraq is designed with the guiding channel at the right of the viewing axis, and a left-oriented slope at the right side of the distal opening of the guiding channel is devised to direct the tube tip into the glottis in the midline (Figure, Panel A). This design results in ETT advancement from the guiding channel towards the left. Consequently, during advancement of the ETT, the tube tip may move across the midline (Figure, Panel B) towards either the left vocal cord or the left laryngeal vestibule rather than align the ETT towards the midline of the glottis (Figure, Panel C). Whenever this problem arises, our practice has been to withdraw the ETT by approximately 0.5 cm and to exercise one of four available options: 1) slightly rotate the Airtraq in a clockwise direction; 2) advance the Airtraq downwards; 3) gently apply leftwards laryngeal pressure with external laryngeal manipulation, then re-attempt ETT advancement; and 4) in the very rare occasions the above measures fail, withdraw the ETT from the guiding channel and introduce a pediatric bougie into the visualized glottis via the guiding channel. The ETT is then railroaded along the bougie through the larynx, and the Airtraq is used to monitor the progress of the ETT advancement. Over the previous two years, we have used these maneuvers quite successfully to facilitate advancing the ETT into the glottis with the Airtraq device in pediatric patients with uncomplicated and difficult airways alike.

Endotracheal intubation with Airtraq® optical laryngoscope in the pediatric patients

1 Jagannathan N, Kho MF, Kozlowski RJ et al. Retrospective audit of the air-Q intubating laryngeal airway as a conduit for tracheal intubation in pediatric patients with a difficult airway. Pediatr Anesth 2011; 21: 422–427. 2 Markakis D, Sayson S, Schreiner M. Insertion of the laryngeal mask airway in awake infants with the Robin sequence. Anesth Analg 1992; 75: 822–824. 3 Stricker P, Budac S, Fiadjoe J et al. Awake laryngeal mask insertion followed by induction of anesthesia in infants with the Pierre Robin sequence. Acta Anaesthesiol Scand 2008; 52: 1307–1308.

Performance of GlideScope(®) videolaryngoscope for nasotracheal intubation in children.

not have either one of these pumps or remifentanil infusion rate table, some simple methods have been described (1). Here is an other practical method to calculate the dose quickly in milliliter per hour for pediatric patients. In our institute, we usually start remifentanil at 0.5 lgÆkgÆmin infusion rate for induction of balanced general anesthesia of pediatric patients and decrease the rate to 0.25–0.1 lgÆkgÆmin after intubation (approximately 4–6 min after initial rate), thus the patient is administered a 2–3 lgÆkg loading dose. According to our protocol, you can prepare 30 lgÆml remifentanil (usually 1500 lg drug in 50ml syringe), and then you can start the infusion at the numeric value of the patient’s weight in milliliter per hour. For example, if the patient’s weight is 17 kg, we start the infusion at 17 mlÆh and decrease the rate to half or 1/5 of it (8.5 or 3.4 mlÆh) for maintenance. As remifentanil is still an expensive drug, you may not want too much remaining waste drug (for short procedures and little children). In an operating room with a high turnover, you can prepare this 30 lgÆml solution in a 100 ml mediflex and obtain the appropriate volume according to patient’s weight and estimated surgery time. Also you can prepare the concentration 10 lgÆml (500 lg drug in 50-ml syringe), then for a 17 kg weight child, the rate will be 3 · 17 mlÆh for 0.5 lgÆkgÆmin infusion. More diluted solutions will prevent inadvertent bolus injections of high doses during inset of syringe to the pump or removal. Once the basic formula is memorized, multiplication or division can calculate higher or lower rates with higher or lower concentrations according to preferences. Standardization will reduce the incidence of mistakes during preparation of drugs.

Comments on comparison of the combined Airtraq ® laryngoscope and a fiberoptic bronchoscope with the Airtraq ® alone for tracheal intubation

To the Editor: The recent article of Nishikawa et al. [1] comparing tracheal intubation by combined use of the Airtraq laryngoscope (Airtraq) and a fiberoptic bronchoscope (FOB) with use of the Airtraq alone in a manikin study was of great interest to us. They found that in comparison with Airtraq alone, the combined use of the Airtraq and a FOB provided more rapid tracheal intubation in difficult airway scenarios. This finding suggests that a combination of the Airtraq and a FOB may be more effective for managing difficult airways compared with the use of the Airtraq alone. However, there are several aspects of this study that should be clarified. First, the purpose of this study was to evaluate the efficacy of the combined use of the Airtraq and a FOB for tracheal intubation in simulated airway scenarios when the glottic view could not be optimized in the middle of the viewfinder of the Airtraq. However, in the results, the authors did not provide the glottic view obtained by the Airtraq in all airway scenarios. When the tracheal intubation was performed with the Airtraq alone in this study, we would like to know whether the glottis was positioned in the middle of the viewfinder of the Airtraq (i.e., grade 1 view of the Airtraq) with or without optimization maneuvers [2]. In this position, the endotracheal tube (ETT) will be advanced toward the glottis under a predetermined angle, defined by the configuration of the tube conduit and the ETT angulation [3, 4], whereas a partial or total glottic view that is off center, i.e., grade 2 view of the Airtraq, is suboptimal for tracheal intubation with the Airtraq alone [2]. Second, in the results, the authors described that, to successfully intubate the trachea with the Airtraq alone, the requirement for optimization maneuvers increased with the level of difficulty of the tongue edema scenario. However, they did not state what optimization maneuvers were used. On the basis of our accumulated experience with the Airtraq, other than external laryngeal manipulation, adjusting the position of the entire device in the mouth and pharynx is often required to optimize the glottic position before attempting to intubate. Third, three and two participants failed to intubate the trachea with the Airtraq alone in the tongue edema scenarios simulating grade 3 and 4, respectively. In the cervical immobilization scenarios, two and one participants failed with the Airtraq and the combined use, respectively. However, the authors did not provide the reasons for these failed intubations. When the tracheal intubation is performed with the Airtraq alone, our experience suggests that a posterior tube tip location is a most common cause of failed intubation, particularly in patients with tongue edema, micrognathia, short neck, or limited head and neck movement. To solve this issue, the operator can withdraw the Airtraq 1–2 cm away from the glottis and lift the device up [4]; this allows the tube tip to move upward toward the glottis with further advancement after its initial posterior movement [3]. If the larynx is simultaneously pushed down, the posterior tube tip location may often be corrected. Also, the Endoflex ETT with a built-in flexing mechanism and a friction lock is a useful choice to overcome a posterior tube tip location [5]. Fourth, the combined use of the Airtraq and a FOB can enable rapid intubation in managing a difficult airway, but F. S. Xue (&) J. H. Liu Y. J. Yuan X. Liao Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 33 Ba-Da-Chu Road, Shi-Jing-Shan District, Beijing 100144, People’s Republic of China e-mail: fruitxue@yahoo.com.cn

Airway management in pediatric patients with a rigid external distractor in situ.

SIR—External distraction is a technique commonly used for multistage maxillary reconstruction associated with severe craniomaxillofacial anomalies in the older children and adolescents (1). Because the rigid external distractor (RED) or RED frame used to apply distraction forces to the maxilla includes a halo device anchored to the cranium, a vertical midline facial bar, and a horizontal bar anchored to the maxilla by the transcutaneous infranasal wires (2), it can significantly interfere with the ability to ventilate with a facemask or perform a direct laryngoscopy (Figure 1a). Moreover, such pediatric patients often have abnormal airways, which can further increase the difficulty in airway management. To secure the airway safely, several schemes of airway management for the patients with a RED, such as awake fiberoptic intubation, removal of the vertical bar and distraction wires before anesthesia induction to allow facemask ventilation and unobstructed direct laryngoscopy, and fiberoptic nasal intubation under anesthesia, have been reported (2,3). However, awake fiberoptic intubation is not a suitable option for children because of inability to cooperate. Also, a fiberoptic bronchoscope is not always available in every institution, and the skill of using the fiberscope in pediatric patients with difficult intubation may not be widespread enough to guarantee the effective and timely use of this device (4). In addition, when emergent airway control is necessary in the early postoperative period, removal of the RED frame before anesthesia induction has a risk of causing surgical failure, because force applied to the maxilla during facemask ventilation and laryngoscopic intubation can cause relapse of the unsupported segments (2). Thus, alternative methods need to be assessed. Recently, we have evaluated the ability of a modified facemask ventilation method and performance of the Airtraq optical laryngoscope (Airtraq; Prodol Meditec S.A., Vizcaya, Spain) for endotracheal intubation in children with a RED in situ. Here, we would like to report our experience. After children entered the operating room, an intravenous cannula was inserted, and the routine monitors were used. Based on the method described by Tong et al. (2), a small-size, rounded facemask that could adequately cover the child’s mouth below the horizontal bar of RED was selected for preoxygenation. To ensure the child’s safety, appropriate screwdrivers and wire cutters to remove the vertical bar of RED and traction wires were always available at all times and the assigned caretaker was instructed in their proper use. Then, anesthesia was induced using either a propofolor sevoflurane-based technique with or without neuromuscular blockade according to the preoperative airway evaluation and the discretion of the staff

A simple measure to facilitate use of a preformed oral tube for tracheal intubation using the Airtraq® laryngoscope in children

Did you receive our preoperative information leaflet when your child was booked for their operation? Question 2 Did your child cooperate with the anaesthetic doctor and nurse when going asleep for their operation? Question 3 Did your child go asleep with the mask or with an injection? Question 4 Was your child upset in the anaesthetic room? Question 5 Did your child have to be held securely while going asleep? Question 6 Did you hold your child while they were going asleep or were they on the bed? Question 7 If your child needed to be restrained while going asleep, would you prefer to hold them or have a member of hospital staff hold them? Question 8 Instead of being restrained, would you prefer a sedative medication to be given to your child before coming to the operating department? Question 9 What do you think your child remembers about going asleep for their operation today? Question 10 Would you change any part of your experience and your child’s experience of going asleep for surgery today? Thank you for participating in this study. If you do not want to answer these questions, but would like to speak to a member of the team about the issues raised in the questions, please ask the dayward sister to page the Consultant Anaesthetist attending the Children’s Theatre today.

Insertion of the ProSeal™ laryngeal mask airway with the 90° rotation technique

To the Editor, We were greatly interested in the recent article by Jeon et al. that described insertion of the ProSeal laryngeal mask airway (PLMA) with the 90 rotation technique. In this study, an extension of their previous work, the authors provided a simple and useful insertion technique for the PLMA that has a high success rate and a low incidence of pharyngeal mucosal trauma. However, several design aspects of this study should be clarified. The evaluation criteria for an effective airway differ from the previous study. In the former article, they evaluated gas leakage and the lowest limitation of peak airway pressure during manual ventilation. In their most recent study, the authors considered normal thoracoabdominal movement and capnography to indicate proper placement, with the possibility that obvious gas leakage was present. Also, a failed insertion attempt was not defined clearly. A three-point ventilation score that Keller et al. described is a useful method to assess the quality of ventilation through the PLMA. Using this score, inadequate quality of ventilation with minimal chest expansion and considerable gas leakage is often considered as the failed insertion attempt. The orogastric tube placement through the PLMA drainage tube was not performed. In fact, the presence of a drainage tube to provide a channel for regurgitated fluid and placement of an orogastric tube is one of the important design modifications of this device. Also, passage of a lubricated orogastric tube via the drainage tube and aspiration of gastric fluid is an essential test to determine correct placement. Difficult placement of the orogastric tube often suggests obstruction of the drainage tube caused, for example, by the device folding over. This situation may put the patient at increased risk of gastric insufflation and aspiration during airway maintenance with the PLMA. In this study, the postoperative sore throat was assessed as a side effect of the two insertion methods. However, the authors did not compare the use of opioid drugs between groups during anesthesia maintenance. Also, standardization of postoperative analgesia should be a crucial component of study design. The type and dose of analgesia and the timing of its administration in relation to the assessment of sore throat should have been described. In the absence of a comparison of opioid dosages during anesthesia and a postoperative analgesic protocol, the secondary outcome findings and their subsequent conclusions should be interpreted with caution, as they may have been determined using incomplete methodology.

Comments on use of a Parker Flex-Tip tube® to facilitate intubation with the Pentax-AWS®

To the Editor: The recent article of Ohmura et al. [1] regarding use of a Parker Flex-Tip tube to facilitate intubation when the Pentax-AWS (AWS) fails to reach the larynx was of great interest to us. Although they provided a useful method to improve success rate of intubation with the AWS, there are several aspects that have to be clarified. In their case report, the PBlade tip of the AWS was not able to be advanced beneath the epiglottis but was inserted into the vallecula. The epiglottis was indirectly elevated, and the laryngeal exposure was approximately 80% of the glottic opening. Actually, the design of the AWS PBlade is to be inserted posterior to the epiglottis, directly elevating it out of the way (Miller-type approach) [2, 3]. Also, the target mark on the monitor is designated for a preformed, curved endotracheal tube (ETT) [4]. In this way, the curved ETT advanced from the guiding channel tends to travel forward for a short distance almost in line with and align with the glottis [2]. However, when the AWS PBlade is inserted into the vallecula (Macintosh-type approach), intubation often fails because of ETT impingement on the epiglottis [2]. According to our experience and the available literature, difficulty in inserting the PBlade tip into the posterior surface of the epiglottis really is a common troublesome problem during intubation with the AWS, particularly at patients with micrognathia, a short neck, or limited head and neck movement. In patients with simulated restricted neck mobility, this issue had resulted in multiple intubation attempts in 42% of patients [3]. It is easily corrected by partially withdrawing the device, and with a subsequent scooping movement of the PBlade, lifting the epiglottis, and advancing the ETT into the trachea. A second solution is to insert a bougie through the ETT and into the trachea and then railroad the ETT over the bougie via the glottis. In their mannequin study, the AWS PBlade was deliberately inserted into the vallecula (Macintosh-type approach). In this case, the epiglottis can indirectly be elevated by the AWS PBlade, and most of the glottic opening may be viewed on the monitor. This approach does not differ from the condition in which the AWS PBlade fails to reach the larynx; the latter occurs because the distance from the mouth to the larynx of the patient is longer than the designed length of the PBlade [4]. In this situation, the epiglottis cannot indirectly be left by the AWS PBlade, and the pendulous epiglottis may obstruct the laryngeal view and interfere with alignment of the ETT tip with the glottis. Based on the findings of this mannequin study, therefore, we believe it would be more appropriate to conclude that the use of the Flex-Tip tube allows for successful intubation when the AWS PBlade is inserted by a Macintosh-type approach. One of the most important features of the AWS that facilitates intubation is a target mark on the monitor, which indicates the direction of travel of the ETT as it advances from the guiding channel [5]. Before advancing the ETT, the glottis must be positioned at the center of the target mark. In panels b and d of fig. 1 of this article, however, the glottis seems to be at the left side of the target mark, rather than the center of the target mark. We would like to know whether a different orientation relationship of the An answer to this letter to the editor is available at doi: 10.1007/s00540-010-1057-4.

Can 8% lidocaine spray 10 min prior to endotracheal intubation reduce the incidence of postoperative sore throat?

To the Editor: The recent article of Honma et al. [1] on the effects of lidocaine spray administered 10 min prior to intubation on postoperative sore throat (POST) was of great interest to our group. Based on the results of their randomized clinical study, the authors reported that 8% lidocaine spray was able to significantly reduce the incidence of POST when sprayed on laryngopharyngeal structures 10 min prior to endotracheal intubation. They attributed the beneficial effect of lidocaine pretreatment on POST to be primarily due to its anti-inflammatory effects. However, we feel that there are several aspects of the methods and results of this study that need to be clarified. First, regarding the methods, the authors do not clearly describe the criteria of inclusion and exclusion of patients. We noted that most of the study subjects were elderly patients—based on the reported mean age of[60 years for all patients in the different groups. It has been demonstrated that patients’ ages are related to the occurrence of POST and that the incidence of POST increases in younger patients between the ages of 30 and 39 years [2]. In addition to the patient characteristics listed in Table 1 of their article, the authors should also explain whether the different treatment groups were comparable with respect to the other well-known risk factors of POST, such as surgical site, use of the stylet and cricoid pressure during intubation, use of nitrous oxide during anesthesia, control of intracuff pressure during surgery, among others [3]. Although the actual causes of POST are not yet clear, a number of factors, including those mentioned above, have been implicated. Thus, we suggest that a comparison of these factors among the different treatment groups would facilitate an objective interpretation of the results of this study. Secondly, the authors do not clearly explain how they ensure that the 8% lidocaine spray is targeted exactly on the laryngopharyngeal structures 10 min prior to endotracheal intubation. Was the lidocaine sprayed under direct laryngoscopy? Furthermore, they should provide the ingredients of the 8% lidocaine and 2% lidocaine gel used in this study. The high-concentration lidocaine solution used for metered-dose pump spray often contains ethanol, polyethylene glycol 400, menthol, saccharin, and macrogolum as additives in the solvent. Also, methylparaben is commonly used as an ingredient in lidocaine gel. In fact, it is these chemical additives in the lidocaine preparations—not lidocaine itself—that can irritate airway mucosa, potentially causing airway mucosa damage, thus leading to increased incidence and severity of POST [4, 5]. Third, in this study, the POST was only evaluated at one time point, i.e., 24 h following extubation. Also, it is not clear whether POST is evaluated by an investigator who is blinded to the patient’s group allocation. The incidence and severity of POST are known to be variable at different observed points after extubation, with the highest incidence of POST reported to occur 6 h post-extubation [5]. Thus, we believe that the use of a single time point to evaluate POST may have missed the effects of different treatments on the highest incidence of POST. It would have been perhaps more informative to provide data comparing the incidence of POST at more time points among the different groups. An answer to this letter to the editor is available at doi:10.1007/s00540-011-1156-x.