AUSTRALASIAN ANAESTHESIA 2017 AUSTRALASIAN ANAESTHESIA 2017 Invited papers and selected continuing education lectures Editor: Richard Riley Department of Anaesthesia and Pain Medicine Royal Perth Hospital Pharmacology and Anaesthesiology Unit School of Medicine and Pharmacology University of Western Australia Contents Airway Awake videolaryngoscopy 3 Vazira Moosajee, Scott Douglas, Iljaz Hodzovic Airway management after cervical spine surgery: A review of the literature 13 Jonathan Nicholson, William Bradley, Tish Stefanutto, Glen Downey, Lauren Berkow Tracheostomy crisis management 21 James Anderson, Travis Leahy Breathing / Ventilation Perioperative lung protective ventilation 31 Simon Wong, Ajay Kadaliparambil, Hergen Buscher Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE) technique in paediatric 43 anaesthesia practice Susan Humphreys, Derek Rosen, Andreas Schibler Circulation Heart failure with preserved ejection fraction: Diastole is important too! 53 Kate Drummond Extra corporeal membrane oxygenation: Anaesthetic perspectives 63 Elizabeth Winson, Matthew Brain Coagulation Introducing viscoelastic haemostatic assay-guided blood product transfusion into your hospital 77 Megha Jain, Erin Chamberlen, Kathryn Santifort, Surbhi Malhotra, Catherine Downs Rotational thromboelastometry (ROTEM®) in obstetrics 95 Julie Lee, Kerstin Wyssusek, Jeremy Cohen, Andre Van Zundert Fibrinogen concentrate for acquired hypofibrinogenaemia 105 Hamish Mace, Mansi Khanna Evidence, new methods and current practice of point-of-care coagulation testing in major haemorrhage 117 Michael C Reade, James Winearls Intraoperative cell salvage 135 Laura Willington, Michelle Roets Published in 2017 by: Australian and New Zealand Regional College of Anaesthetists 630 St Kilda Road What is the role of thoracic epidural analgesia in contemporary anaesthesia practice? 147 Melbourne, Victoria 3004 Andrew Deacon, Jennifer Hartley Australia Dissecting epidural failure in the obese parturient: Time to carefully consider the lumbar 159 ISBN 978-0-9945075-5-6 interspinous ligament Copyright © 2017 by the Australian and Sue Lawrence, Adrian Langley, David Sturgess New Zealand College of Anaesthetists, Abdominal wall blocks – steps to quality assurance and managing risk 169 all rights reserved. None of the contents of James Griffiths this publication may be reproduced, stored in a retrieval system or transmitted in any form, by any means without the prior written Pain permission of the publisher. Recent insights into the mechanism of opioid tolerance and withdrawal: Implications for the use 179 Please note that any views or opinions of remifentanil expressed in this publication are solely those David A Jarvis of the author and do not necessarily represent those of ANZCA. Lidocaine infusions: The golden ticket in postoperative recovery? 185 Martin Bailey, Andrew Toner, Tomas Corcoran Printed by: Ellikon Caution with ketamine 197 384 George Street David A Jarvis Fitzroy, Victoria 3065 Australia Brain / Neuro Acute management of stroke 209 Candice Delcourt, Pierre Janin Decompressive craniectomy in the management of neurological emergencies: An inconvenient truth? 221 Stephen Honeybul, Kwok Ho, Grant Gillett Adenosine for transient cardiac standstill in neurovascular surgery: A heart-stopping moment 229 Shona Osborn Liver / Metabolic Anaesthesia for patients with liver disease 241 Tom Fernandez, Chris Nixon Perioperative hyperglycaemia – epiphenomenon or therapeutic target 253 Faculty and Regional Sub-Editors Alexandra Skubala, Tomas Corcoran Malignant hyperthermia – “Keeping things cool” 263 Professor Thomas Bruessel Sinéad O’Keeffe, Philip Nelson, Mark Davis Australian Capital Territory Dr Brenda Cassidy Paediatrics Faculty of Pain Medicine Hypnosis and communication in paediatric peri-operative care 273 Associate Professor Alicia Dennis Rob Laing, Allan Cyna Victoria Postoperative behaviour change in children 281 Dr Thomas Fernandez Paul Lee-Archer, Michael Reade, Britta Regli-von Ungern-Sterberg, Deborah Long New Zealand Dr Adrian Langley Assessment Queensland Epigenetics and anaesthesia 291 Dr Priya Nair Christopher Bain, Kiymet Bozaoglu College of Intensive Care Medicine Associate Professor Richard Riley Education Western Australia Preparing candidates for the ANZCA primary examination vivas 301 Dr Sharon Tivey Andrew Gardner, Ross Macpherson New South Wales Trainee mentoring – Tips to setting up a program and issues encountered along the way 309 Dr Gerald Toh Ian Balson South Australia Free open access online education in anaesthesia 317 Dr Maurice Vialle Ryan Juniper Tasmania It’s more complicated than that: Complexity and anaesthesia 325 Dave Gillespie, Rod Peadon, John Neal Management Informed consent in the age of peri-operative medicine: Is it possible? 335 Scott Simmons, Allan M Cyna The anaesthetist as a leader and manager: Priorities, dilemmas and solutions 343 Debra SA Coleman A guide to the electronic roster 355 Peter Mulrooney AUSTRALASIAN ANAESTHESIA 2017 Preface Welcome to the 2017 edition of Australasian Anaesthesia. I continue to be surprised at the depth and breadth of talent in our fields. Although there is some emphasis in several topics, it is always gratifying that we are able to produce a wide range of areas that reflects the diversity of practice in anaesthesia and pain medicine. Airway management, regional anaesthesia, coagulation and cardiac function will always be topical. Articles on education and management also feature to make this edition well-rounded and deserving of your attention. In this edition we also welcome the inclusion of several chapters focusing on intensive care medicine. I hope that you will be similarly impressed to read about some of these developments that our ICU colleagues are leading. Further, a chapter on outcomes following decompressive craniectomy for severe traumatic brain injury is timely and thought-provoking. Having a family member undergo such an operation years ago made it especially poignant. Several years back a keynote speaker at an international simulation in healthcare meeting described the reluctance of many senior clinicians to ask for feedback on their own clinical and teaching practices. As a practicing surgeon, and clinical educator, he decided to embrace the principles of adult education and began to seek feedback from his surgical trainees. Thus, at the completion of each day’s operating, he now asks the trainee, “How’d I do today?” It was a little confronting at first but it became part of his embedded practice and he now welcomes it. The speaker exhorted us to follow his example and seek feedback from our juniors; irrespective of their level of training. He suggested that we might be surprised at the feedback. To follow on this theme, I can let you know that I typically receive one complaint and one to two compliments for each edition of Australasian Anaesthesia, but this is hardly enough. Thus, if you have bouquets or brickbats about the “Blue Book”, I would encourage you to give us feedback. An email address below is provided to facilitate this. Finally, I wish to thank the authors, the regional editors and ANZCA’s Publications Manager Liane Reynolds for their work and support in producing this edition. Please take the opportunity to thank our authors personally when you can and also consider writing yourself for a future edition. Associate Professor Richard Riley Editor, Australasian Anaesthesia 2017 [email protected] Airway Awake videolaryngoscopy Vazira Moosajee, Scott Douglas, Iljaz Hodzovic Airway management after cervical spine surgery: A review of the literature Jonathan Nicholson, William Bradley, Tish Stefanutto, Glen Downey, Lauren Berkow Tracheostomy crisis management James Anderson, Travis Leahy Awake videolaryngoscopy 3 Awake videolaryngoscopy VAZIRA MOOSAJEE, MBBS BSc (Hons) FRCA Senior Registrar, Department of Anaesthesia and Pain Medicine, Royal Perth Hospital, Western Australia. Dr Moosajee graduated from Imperial College, London. She completed her anaesthetic training in London and Wales with subspecialty training in regional and airway anaesthesia. She is currently a Fellow at Royal Perth Hospital, in Western Australia. SCOTT DOUGLAS, MBBS (Hons) FANZCA Consultant Anaesthetist, Department of Anaesthesia and Pain Medicine, Royal Perth Hospital, Western Australia. Dr Douglas is a Consultant Anaesthetist at Royal Perth Hospital (RPH) in Perth, Western Australia. His interests include difficult airway management, airway management education, airway surgery, apnoeic oxygenation and obstetric anaesthesia, and he is the Director of Audit at RPH. He regularly teaches “Cannot Intubate Cannot Oxygenate” rescue techniques, is an Advanced Life Support and Effective Management of Anaesthetic Crisis (EMAC) instructor, and is co-author of the new EMAC Airway chapter. ILJAZ HODZOVIC, MD FRCA Consultant Anaesthetist and Senior Lecturer at Cardiff University; Royal Gwent Hospital, Wales, United Kingdom. Following his graduation from Belgrade Medical School, Dr Hodzovic’s career took him to the United Kingdom where he became a Fellow of the Royal College of Anaesthetists and Senior Lecturer at Cardiff University. His main clinical interests are major otolaryngological cancer surgery and anaesthesia for gastrointestinal surgery. He has published in the field of difficult airway management and is an invited reviewer for national and international peer reviewed anaesthesia journals. He chairs the All Wales Airway Group and is a member of the Innovation Committee of the Aneurin Bevan University Health Board. INTRODUCTION Awake direct laryngoscopy has historically been used in patients with compromised airways, in whom asleep airway management was anticipated to be difficult. The technique may be tolerated by a moribund patient without topicalisation or sedation, but the stimulation may still induce airway reflexes making intubation difficult, if not impossible, and cause undesirable autonomic sequelae. Patients with a preserved level of consciousness are generally unable to tolerate unmedicated awake direct laryngoscopy. The key advantages of performing awake intubation are the maintenance of upper airway tone and spontaneous respiration. When anaesthesia is induced, apnoea frequently occurs and airway obstruction may worsen. The Royal College of Anaesthetists Fourth National Audit Project highlighted inexperience as the main reason for underuse of awake intubation techniques in the United Kingdom1,2. Effective topical local anaesthetic (LA) and sedation strategies, along with recent technological advances in airway equipment, has renewed interest in awake laryngoscopy. The introduction of videolaryngoscopes, particularly those with hyper-angulated blades, has reduced the degree of stimulation required to perform awake laryngoscopy. Video laryngoscopy (VL) is now firmly embedded within the anaesthetic airway management armamentarium. This is reflected by the inclusion of the technique in “Plan A” of the 2015 Difficult Airway Society (DAS) guidelines flowchart for the management of unanticipated difficult tracheal intubation in adults3. Similarities between indirect VL and conventional laryngoscopy have led to faster attainment of proficiency in the skill by novices4,5 and experienced operators demonstrated no difference in technical difficulty, patient discomfort and time to orotracheal intubation between Awake Video Laryngoscopy (AVL) and Awake Flexible Bronchoscopic Intubation (AFBI) in patients with an anticipated difficult airway6. AFBI is the preferred term of the authors as many intubating bronchoscopes are either hybrids of fibreoptic and digital technology or have no fibreoptics at all. VL’s ease and usability has had the desirable secondary effect of multi-disciplinary familiarity with the technique and the advent of AVL as an alternative strategy for awake intubation. The authors of this paper recognise that AVL is an evolving technique and those finessing it encounter many pitfalls and challenges. We do not claim to be in any way experts in the field of AVL, but we recognise, and in this article will consider, its evolving role in contemporary airway management practice. IS THERE A NEED FOR AVL? A key objective of airway management is to predict difficulties and thereby prevent adverse clinical outcomes. In the face of an anticipated difficult intubation, it is widely acknowledged that techniques which maintain spontaneous breathing are the safest1. In cases where mouth opening is preserved and oral intubation is essential, there is an emerging interest in using AVL as an alternative to AFBI, the current “gold standard”, AVL may be perceived (rightly or wrongly) as being simpler and more familiar than AFBI, and in some institutions equipment for AVL may be more readily available. There is also a growing body of case reports which cite the successful use of AVL in preference to AFBI, or where AFBI has failed (table 1). 4 Australasian Anaesthesia 2017 Awake videolaryngoscopy 5 Airway oedema The Tomahawk Technique Several case reports of AVL involve significant macroglossia and laryngeal inlet oedema. These patients Awake intubation in the face-to-face upright position can mitigate some of the disadvantages associated with presented in extremis with stridor. AFBI and nasendoscopy failed due to mucosal swelling. AVL displaced the the traditional laryngoscopy position, especially in those with a threatened airway. Upright AVL is best performed oedematous tongue and provided glottic access with less base of tongue force (5-14 N) compared to conventional with a hyperangulated blade, inserted handle down in the “tomahawk” position. This method has been found laryngoscopy. Use of a channelled VL was especially advantageous, as it negated the need for an introducer to produce Cormack-Lehane grade one or two views in less than 30 seconds. Optimisation of those glottic device, hence avoiding the “cork in bottle” effect7,8,9. views was then achieved with only minor adjustments to the patient’s sitting position. Note that if a non- channelled scope is employed, the hyperangulated blade necessitates the use of a preformed introducer20,21. An additional case report documents rescue AVL in a patient where successful awake insertion of a Flexible Intubating Bronchoscope (FIB) was followed by failure to pass the endotracheal tube (ETT). The FIB did not WHAT ARE THE LIMITATIONS OF AVL? allow the glottis to be visualised during passage of the ETT and hence identification and rectification of hold-up was a peripherally blind process above the carina. AVL provided a widescreen view which allowed guidance Not all VLs are equal and it is important to acknowledge their limitations. of the ETT through the glottis without hold-up10. Incorrect size/shape to match airway anatomy Fixed or immobilised cervical spine Any laryngoscope blade with a fixed length and curvature, video or otherwise, will not suit all mouth to larynx AVL has facilitated timely intubation in patients with unstable cervical spines, without the need to remove distances and shapes at the extremes of anatomical variability. immobilisation devices, and also for patients with a fixed neck deformity. The ability of hyperangulated VLs to Difficult insertion provide laryngeal visualisation while maintaining anatomical alignment has been increasingly exploited in trauma Insufficient mouth opening scenarios11,12. Although the exact amount varies, for any particular VL there will be a minimum mouth opening distance required Secretions to insert and manipulate the VL, and (if the VL is unchanneled) insert and manipulate an ETT separately from Airway secretions may impede the view of any device relying on a transmitted image. AVL may be more forgiving the VL. Extremely limited mouth opening may necessitate AFBI via the nasal approach. than AFBI in the presence of secretions in the airway, especially when using VLs with a designated suction Difficult/impossible insertion due to neck/chest wall relationship channel or that permit the passage of large bore suction devices via the intubating channel13. In those with fixed flexion deformities or prominent breast tissue, obstruction due to the chest wall may make Airway stenosis and obstruction it impossible to insert the VL. Introducing the blade with 90 degrees of rotation before returning to the normal Rescue AVL was described in a morbidly obese patient with a massive multi-nodular goitre with pressure alignment may overcome this problem. For VLs with blades and handles that can be detached from one another, symptoms. Perioperative work up revealed a displaced trachea and a compressed airway with a diameter of introducing the blade alone without the handle attached may also be of assistance11. 2 mm at the glottis. AFBI failed due to the size of the ETT being limited by the diameter of the FIB and extensive Traumatic insertion mucosal hypertrophy, which prevented the FIB advancement. AVL provided a Cormack-Lehane grade two During VL the operator’s visual attention is directed toward the screen, which can result in damage to soft glottic view on screen and allowed a Frova airway intubation catheter (Cook Medical) to be inserted into the tissues or ETT cuff. It is essential that the VL blade is inserted into the mouth under direct observation and not trachea14. while looking at the screen. Experienced VL operators have similar minor complication (bleeding and sore throat) AFBI was considered of limited appeal in managing a case of laser excision of a ball-valving laryngeal mass. rates to FIB intubation. However, there are reports of VL related palatopharyngeal arch injury requiring surgical Potential further obstruction was possible from inadvertent trauma caused by the “blind” advancement of the repair in patients with abnormal upper airway anatomy, prior airway surgery and/or previous radiotherapy22. ETT over the FIB in the presence of pathologically friable tissue. AVL was considered advantageous, allowing Channelled or unchannelled? continuous visualisation of the airway and guidance of the ETT past the friable mass. Importantly, with the entire Channelled VLs eliminate the need for an ETT introducer, avoiding the “cork in a bottle” phenomenon, reducing team able to follow events, immediate expert advice was provided in real time15. the risk of trauma during insertion of the ETT, simplifying the technique, and creating a protected conduit for Morbid obesity the ETT, however they usually require a greater degree of mouth opening. Unchannelled VLs may require less AVL has been successfully used to intubate tracheas in morbidly obese patients presenting with a potentially mouth opening, but do require an ETT introducer. This is important, as the smallest internal diameter of an ETT difficult airway. It was found to be comparable in this group to AFBI in terms of time to awake tracheal intubation, that can be used with a preformed GlideRite® stylet is 5 mm15. number of intubation attempts and glottic view achieved16,17. Pharyngeal hyperreflexia AVL is not simply a skill hybrid of AFBI and VL. Exaggerated gag responses are the most commonly cited reason Table 1. Case reports where AVL was used preferentially over AFBI for failure of AVL. This can be understood after consideration of the physical differences between the techniques. VLs have evolved from the Macintosh blade. The pressure of the blade on the tongue and in the vallecular provokes Airway oedema/swelling 7,8,9,10 discomfort and the gag reflex in otherwise well-topicalised airways that are likely to have tolerated AFBI. Immobilised neck and fixed neck deformities 11,12 The intermittent failure to tolerate AVL has contributed to the use of the “awake look” technique. If a Cormack- Lehane grade of one or two is transiently seen during AVL, conversion to a GA technique occurs. Extreme Airway stenosis and obstruction 14,15 caution is recommended with this approach, as grade of laryngoscopy may deteriorate with loss of muscle Morbid obesity 16,17 tone, and a clear laryngoscopy does not guarantee a straight forward intubation! SUPPRESSION OF THE GAG REFLEX Cost Within our specialty there is a belief that dense airway topicalisation alone, particularly of the mucosal surfaces Although the exact values will vary by location and device, the cost of single use VL blades and sterilising supplied by the glossopharyngeal nerve, can improve AVL outcomes. reusable VL blades is usually significantly cheaper than the cost of single use FIBs or sterilising reusable FIBs. It is hypothesised that those with a persistent gag reflex have deeper submucosal pressure receptors less amenable to a topicalisation. Therefore, some authors advocate bilateral glossopharyngeal nerve blocks. They NOVEL TECHNIQUES are performed using a spinal needle to inject lidocaine at the bases of the palatoglossal folds. Patient refusal The Combination Technique or disease burden may render this technique inappropriate23. AVL can be used in combination with AFBI. This technique aims to limit the individual disadvantages of the FIB and VL. Two operators are required to monitor the entire process of intubation. The VL is inserted first and the There is considerable evidence to demonstrate multifactorial aetiology underlying the gag response. Those best possible screen view is obtained. If Cormack-Lehane grade one or two views are obtained on the VL, the pursuing a completely sedation-free AVL technique are now turning their interest towards alternative management FIB is used like a stylet with a controlled flexible tip. If grade three or four views are obtained the VL is used to strategies. These include patient selection, behavioural, pharmacological and complimentary therapies24. open the oropharynx and guide (or act as a conduit, if a channelled scope) the FIB to the point where the glottis can be visualised by the FIB operator. Appropriate views are then maintained on the VL and FIB monitors, independently, by both operators. This technique offers a wider field of view and a reduced need for ETT manipulation. It can also be used in the presence of oedema to displace tissue18,19. 6 Australasian Anaesthesia 2017 Awake videolaryngoscopy 7 Patient selection In dental practices, it is applied using a nasal mask. Patients are pre-oxygenated and nitrous oxide is introduced The gag reflex is well recognised within the dental community, where an exaggerated response results in some in 10 per cent increments. No more than a 50 per cent mix is administered, with an optimal effect noted to patients self-limiting their treatment. The Gagging Severity Index was developed as a predictive scoring system occur at between 30-40 per cent. It is reversed within two to three minutes with 100 per cent oxygen29. which takes no more than five minutes to complete and score. This may help anaesthetists minimise negative AVL experiences for patients most at risk25. COMPLEMENTARY THERAPY Pharmacological adjuncts Acupressure and acupuncture The benefits of conscious sedation during awake intubation were recognised as early as 1975. However, an Acupressure and acupuncture are employed by dentists globally to control the gag reflex. In the UK, the British ideal elixir for conscious sedation remains elusive26. Dental Acupuncture Society offers courses for general practice dentists and dental care professionals. It has been shown to reduce the duration and intensity of the gag reflex on insertion of a Berman airway. Acupuncture Drugs commonly used for sedation are either anxiolytic or analgesic. Appropriate levels of “sedation” for safe uses needling to activate small myelinated nerve fibers in muscle, the midbrain and the pituitary hypothalamus awake intubation are difficult to standardise, especially as the pharmacodynamics of sedation using opioids via the spinal cord. Enkephalin, beta-endorphin, dynorphin, serotonin and noradrenaline are also all involved and hypnotics are not directly comparable. Operator preferences tend to lack a firm evidence base. The authors in this process30,31. of this paper would advocate the use of easily reversible drugs, and strongly suggest having their antagonists readily available. The horizontal mento-labial groove approximately midway between chin and lower lip is used as an acupuncture and acupressure site. To control the gag reflex, an acupuncture needle is inserted 0.3-0.5 mm and rotated for The relative requirements of anxiolysis and analgesia will vary with the anatomical and physiological condition five seconds, or sustained increasing digital pressure is applied for five minutes24. of patients and also with the urgency of the situation. The use of sedation is often employed by anaesthetists who are also mindful to avoid significant morbidity or mortality that over sedation can bring1,27. THE FUTURE ROLE OF AVL Midazolam It is the opinion of the authors that no single technique will always work and as such AVL is a useful technique Midazolam is a benzodiazepine sedative agent with a rapid onset and short duration of action. It is most to learn. AVL may also confer an advantage over AFBI, in specific situations, such as: commonly used in combination with an opioid. It is usually administered as intermittent boluses of 0.5-1 mg IV, with a recommended maximum limit of 0.05 mg/kg−1. The technique is often favoured by anaesthetists 1. Unavailability of a FIB. because of their widespread familiarity with the drug. 2. Unfamiliarity of the anaesthetist with AFBI. The main benefits for the patients are its anterograde amnesia and acute reversibility with flumazenil. 3. Critically stenosed airways, to avoid the “cork in bottle” effect. Disadvantages of the technique lie in the potential cumulative effect of multiple intermittent boluses resulting 4. Friable supraglottic pathology, to provide a panoramic view for passing the ETT. in unpredicted over-sedation27. Fentanyl 5. Supraglottic oedema, to displace tissue and form a path for passing of the ETT. Fentanyl is a synthetic phenylpiperidine derivative opioid. It is primarily an analgesic with rapid onset and short THE AUTHORS APPROACH TO AVL duration of action. It is administered as 10-25 mcg intermittent boluses IV up to a maximum of 1.5 µg kg−1. It Preparation for the procedure: Setup and equipment is also associated with mild hypnosis and an antitussive effect. Airway instrumentation provokes an intense nociceptive response, especially during the passing of the tracheal tube, and fentanyl can help mitigate the AVL equipment should be ergonomically placed to ensure optimal viewing and working conditions. We effects of inadequate topicalisation. It is also acutely reversible with naloxone. The main risks of it use are recommend a semi-recumbent patient with their head in the neutral position. This allows the operator’s eyes, respiratory depression, nausea, vomiting and, very rarely, chest wall rigidity27. the patient’s opened mouth, and the video display to all be aligned in one line of sight. Remifentanil Pre-procedural oxygenation can then commence and be maintained during the procedure via the buccal route We advocate the use of remifentanil as an adjunct to topicalisation for awake intubation. It is an ultra-short- or nasally32. Standard monitoring is applied as per ANZCA guidelines and topical anaesthesia (as described acting opioid with an elimination half-time of six minutes which is dependent only on hydrolysis by non-specific below) ± sedation are administered. plasma and tissue esterases. Target-controlled infusion (TCI) administration allows a stable level of sedation The intubator stands above the head of the patient holding the VL in their left hand. The semi-recumbent position to be titrated and maintained. Better tracheal tube tolerance during intubation has been attributed to the ensures efficient performance of laryngoscopy, requiring only a movement of 30-60 degrees against the plane antitussive and analgesic properties of remifentanil. A testament to its effectiveness is the emergence and of gravity33. uptake of it as a sole agent, for a two-person AFBI technique. In addition to standard anaesthetic room equipment, nasal and oral Mucosal Atomisation Devices (MADs) As a single agent with no airway topicalisation, remifentanil is infused to achieve a predicted effect site concentration [Teleflex Medical Europe Ltd. Ireland], 4 per cent lidocaine in 5 mL syringes and 2 per cent lidocaine in a 2 mL of 1 ng mL−1 and then titrated upwards in 0.5 ng mL−1 increments. Effect site concentrations of 6.3 (3.87 SD) ng syringe should be prepared. Appropriately-sized ETTs should be selected, any flexometallic ETT should be mL− 1 for nasal endoscopy and 8.06 (3.52 SD) ng mL−1 for tracheal intubation provided good conditions with no placed in warm sterile saline or water to soften tube. The patient will need a kidney dish to expectorate into serious adverse events28. When used in combination with midazolam or propofol, a remifentanil effect site and also some tissues. concentration of 3-5 ng mL−1 was considered sufficient27. Rosenstock et al found they gave a median remifentanil Oral anaesthesia infusion of 0.13 mcg/kg-1 min-1 during AVL intubation, compared to 0.12 mcg/kg-1 min-1 for AFBI, in conjunction with airway topicalisation, including transtracheal injection, using a maximum dose of 3 mg/kg lidocaine 6. Lidocaine is the agent most commonly used for topicalisation of the airway. Published maximum doses for airway topicalisation range from 4-9 mg/kg-1. The maximum dose should not be exceeded to avoid adverse Propofol effects such as arrhythmias and convulsions34. Propofol is an alkylphenol derivative hypnotic sedative and that can be administered as boluses, simple infusion, Sensory innervation of the oral and oropharyngeal mucosa is supplied by branches of the glossopharyngeal, or as a TCI. Its relatively narrow therapeutic index for sedation makes its safe use demanding. TCI administration vagus and facial nerves. Anaesthesia for AVL targets the glossopharyngeal and vagus nerves in particular (table is more pharmacodynamically consistent and may allow for a more predictable level of sedation to be maintained. Current evidence would suggest that propofol only TCI is used with effect site concentrations ≤3 mcg/mL−1 27, 2). The rest of this section will focus on various methods this can be topically achieved. or ≤1 mcg/mL−1 when used in conjunction with benzodiazepines and/or opioids. Combining TCI propofol with Table 2. Sensory innervation of oropharyngeal mucosa other sedatives may help minimise the side effects and improve efficacy, though may also paradoxically increase the risk of excessive sedation. TOPICAL ANAESTHESIA TARGET SITE SENSORY INNERVATION Nitrous oxide NO is commonly used in dental patients and has been shown to significantly increase tolerance of intrusive 2 Oropharynx, posterior tongue Glossopharyngeal nerve oropharyngeal stimulation. Other beneficial effects include reducing secretions and anxiolysis. Rapid onset and offset allows easy titration of the nitrous oxide to ensure patients remain fully conscious. It is contraindicated Larynx Vagus nerve in patients with chronic lung disease pregnancy (first trimester), previous ear or eye surgery and previous bleomycin therapy (when co-administered with increased concentrations of oxygen)29.