Airway Management in a Child with Large Frontonasal Encephalocele: Utility of a Small-sized Face Mask

The case presented by Mathew et al. in this issue of Anesthesia & Analgesia presents us with an opportunity to explore a broader view of difficult airway management: first, how a situation or context influences our approach to the problem; second, the “unwritten truth” of bronchoscopic intubation; and third, the importance of gas-exchange preservation over devices and techniques. In Chinese, the written word for “crisis,” “Wei Ji,” is formed by combining 2 separate words: “Wei” or “danger” and “Ji” or “opportunity.” This combination most likely originated from ancient teachings about how to live a life that thrives while responding to unpredictable mystical, political, and environmental forces. This frame of reference reflects a deep-seated philosophy of cultural survival. History provides a unique context that has resonance and reverberations in this day and age. In other words, although what we do today is often shaped by history and guided by evidence, our actions are frequently tempered by the circumstances (or “context”) in which we act. It has been said that we are in the midst of a medical-legal “crisis.” Perhaps, as the ancient Chinese did, we ought to seize this as an “opportunity,” though alert to the “danger” posed by this “crisis.” But in this modern context, the “opportunity” is shaped by evidence rather than mystical, environmental, and political forces. Caplan et al. first reported alarmingly poor outcomes related to the management of the difficult airway in their review of the American Society of Anesthesiologists (ASA) closed claims database in 1990. They reported that adverse outcomes associated with respiratory events constituted the single largest class of injury, and litigation, in anesthesia in the United States (34%). The review also identified that most of these airway management–related adverse respiratory outcomes were preventable. Recognizing that reversing this finding was paramount to our specialty, the ASA formed a task force to review the existing evidence and to recommend corrective airway management strategies. The ASA Difficult Airway Algorithm and Guidelines were published in 1993 and subsequently revised in 2003. Although there are limitations to the recommendations, the ASA guidelines provide clinicians with an evidence-based approach to the airway evaluation and management of patients about to undergo an anesthetic. Although it is difficult to assess the true impact of these guidelines on clinical outcomes, a recent review of the closed claims database showed that there are signs of improvement, with reduction in the number of adverse events (especially death and brain death) associated with airway management misadventures. Unfortunately, this improvement was limited to the management of the airway on induction of anesthesia, but not outside the operating room. Clearly, continuing efforts to increase awareness of the difficult airway and improve airway assessment and education, coupled with the enhancement of predictive and management strategies, are crucial to the difficult airway management approach in a controlled environment. The findings of Peterson et al. also suggest that a broader understanding and approach to airway management is needed to improve overall outcome. During the last 2 decades, many new airway devices and techniques have been developed, and these have changed the landscape of airway practice and management. In addition, there has been a major paradigm shift in airway management, emphasizing gas exchange (ventilation and oxygenation) over tracheal intubation. Clinicians use only 4 methods of ventilation and oxygenation: a bag mask, an extraglottic device (e.g., a laryngeal mask airway), a tracheal tube, and a surgical airway. Selection of one of these techniques to provide gas exchange depends not only on the devices best suited to the patient’s anatomy but also on the situation faced by the clinician. In other words, airway management is “context sensitive” in that it is heavily dependent on the clinical situation and the environment. If, for instance, a patient presents with a history or clinical features predictive of an “impossible” tracheal intubation using a laryngoscope, and also possesses predictors of difficult bag-mask ventilation and difficulty in using an extraglottic device, such as the laryngeal mask airway, it would be prudent for the clinician in the setting of an operating room to secure the airway awake, frequently utilizing a flexible fiberoptic bronchoscope. However, the management plan would be quite different if this same patient required airway management in the prehospital setting, in the emergency department, or in the magnetic resonance imaging suite where skill sets and limited resources play decisive roles. The selection of an airway approach might also be different if the patient requires immediate and rapid emergency airway intervention, if the patient is a small child who is extremely uncooperative, or if the patient is pregnant. There are From the Department of Anesthesia, Dalhousie University, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada.

We appreciate the interest of Miyasaka et al. in our recent letter1and applaud them for their comments.Miyasaka et al. demand the development of anesthesia-compatible magnetic resonance imaging (MRI) suites and monitoring techniques because conditions to provide anesthesia for patients in MRI suites are often far from optimal and provoke mistakes.In particular, the authors address difficulties achieving adequate monitoring within the MRI suite, especially in critically ill patients. Clearly, the problem is that monitors, ventilators, and infusion pumps either interfere with the MRI (evoking low quality images or artifacts) or the equipment contains ferromagnetic parts and may not work correctly in the presence of a strong magnetic field (which results in danger for the patient). At the same time demand for MRI diagnostic procedures in critically ill patients is increasing steeply. Thus, with present equipment the anesthesiologist often faces a “catch-22” situation.Accordingly, Miyasaka et al.' s points that MRI manufacturers should take anesthesiologists‘ comments regarding more comfortable and safe MRI suites seriously and that anesthesiologists should be involved in conceptual designs of MRI suites from the beginning are well taken. However, even if MRI suites become more anesthesia-compatible in the future, the main risk, i.e. , the presence of a very strong magnetic field with all its hazards, as reported in our letter, is inescapable.Furthermore, their well-taken comments do not only apply to MRI suites. In the near future, some operating rooms and advanced shock/trauma patient admission units will contain MRI equipment. Thus, the need for more high-tech MRI-safe ventilators and monitors in the future is obvious, and, as always, anesthesiologists should take part in developing and shaping their future work environment.* Klinik für Anästhesiologie und Intensivmedizin, Universitätsklinikum Essen, Essen, Germany. christian.zimmer@uni-essen.de

Sir, Non-operating room anaesthesia (NORA) procedures have increased tremendously over the last few years due to rapid technological developments and have resulted in improved outcomes and survival. The key to providing an optimal anaesthesia in NORA is based on the type of the procedure and the physiology of the patients. Providing anaesthesia in magnetic resonance imaging (MRI) suite poses several unique problems including limited patient access and visibility, absolute need to exclude ferromagnetic components and prevent malfunction of monitoring equipment.[1] Alternative approaches to general anaesthesia are gaining popularity which is being highlighted in the present case. A 35 year old male was admitted in our institute as a diagnosed case of lumbar disc prolapse with impending cauda equina syndrome [Figure 1]. Figure 1 Magnetic resonance imaging of lumbosacral spine of the patient His blood investigations and other parameters were normal. He was advised MRI for a precise diagnosis so as to plan an appropriate intervention. Due to severe back pain and muscle spasm, the patient was unable to lie down in supine position. Looking at the limited resources at MRI suite in our setup, he was given intravenous sedation and analgesic in the form of injection fentanyl, injection midazolam, injection haloperidol and injection dexmedetomidine infusion, but it proved inadequate and MRI could not be done. Hence, next sitting for MRI was planned under regional anaesthesia. After taking written consent and keeping nil orally for 6 h, the patient was taken to operation theatre (OT) with all necessary precautions. L2 –L3 epidural space was identified in the sitting position. After injecting 10ml of bupivacaine 0.25% admixed with clonidine (150 µg), the patient was made to lied own. Within 3 min he was relieved of pain. He remained stable and comfortable in the OT. After observing for 20 min, haemodynamic parameters remained stable, and he was shifted to MRI suite with running intravenous fluid and cordless pulse oximeter. In MRI suite, patient's vital parameters were monitored continuously while intravenous fluid was being administered by infusion. The patient lay supine on the table comfortably. MRI study was completed in 40 min in a single sitting and was uneventful. His blood pressure fell slightly with marginal bradycardia which did not require pharmacological support. The patient was shifted to the recovery room with specific instructions to monitor his vitals, was kept nil orally for another 2 h, and duration of analgesia and motor power in the lower limbs were observed. He received 2 L of intravenous fluids in perioperative period. His vitals were stable throughout the recovery period; pain started after 5 h of injection which was grade 3–4 on the visual analogue scale and motor power of lower limb returned to its previous state in 3 h. Lumbar disc prolapse leading to radiculopathy is a common clinical problem that results in significant disability.[2] Pain and other neurologic symptoms associated with this condition are likely as a result of mechanical compression and local inflammation of spinal nerve roots.[3] Radicular pain is so severe in nature that it may not be relieved by systemic analgesics which as in the present case. Neuraxial bupivacaine 0.25% leads to muscle relaxation with almost stable haemodynamic and good sensory blockade; to prolong the duration of analgesia we added 0.2 µg/kg of clonidine, as it is clinically used to treat neuropathy pain.[4] In addition to analgesia mediated by its action at α-2 adrenergic receptors located in the central and peripheral nervous system, clonidine may have anti-inflammatory activity that could influence pain by other mechanisms.[5] Clonidine acts as an analgesic and anti-inflammatory agent in the setting of peripheral nerve injury. Clonidine has demonstrated effects on reducing both nociceptive and neuropathic pain in experimental models and in clinical use. Studies done previously concluded that epidural clonidine results in functional improvement in radicular pain.[4] From the present case, it can be concluded that epidural clonidine provides significant pain relief, particularly in patients with neuropathic pain. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

The Non-Operating Room Anesthesia (NORA) Safety Project is an exploratory prospective cohort study examining the incidence of near-miss events in NORA settings. While adverse events are typically well captured because of quality improvement programs that exist in most major health settings, near-miss events are often not documented, and safety standards are not well established. We present the results of a dedicated forum for near-miss reporting, including the incidence and type of near-miss events, as a first step toward understanding NORA near misses. By providing granular data from a highly engaged audience, we aimed to highlight evidence-backed opportunities for improving safety culture in the procedural landscape. We surveyed all in-hospital NORA cases excluding pediatrics, those performed in the intensive care unit, or the peri-partum areas. The day of data collection was rotated weekly. Providers surveyed included anesthesiologists, nurse anesthetists, and anesthesiology residents. REDCap survey was sent via secure e-mail. If a near-miss event occurred, respondents were asked to classify their events in the following categories: patient, provider, and/or environment. Over a 42-week period, 1383 completed surveys were received in which 90 near-miss events were reported. Filtering for near misses reported on study data collection days and removing voluntary near misses from our total survey responses, our incidence rate was 3.22% (43/1336). The top near-miss locations were the magnetic resonance imaging suite (21/90 [23.3%]) and both neuro and body interventional radiology suites (15/90 [16.7%] and 11/90 [12.2%], respectively). The top near-miss category was environmental concerns (75/90 [83.3%]), and top subcategory was poor group dynamics (31/90 [34.4%]). Significant characteristics in the near-miss patients included older age (mean [±standard deviation {SD}] 60.8 [±16.9] vs 56.8 [±17.3] years [ P = .03]), male (52/90, 57.8% vs 586/1293, 45.3% [ P = .03]), higher American Society of Anesthesiologists (ASA) physical status (III and IV 65/90, 72.2% [ P < .001]), longer procedure (119.8 ± 108.9 minutes vs 63.1 ± 72.2 minutes [ P < .001]), emergent procedures (28/90, 31.1% vs 159/1293, 12.3% [ P < .001]), and involvement of resident providers (36/90, 40.0% vs 234/1293, 18.1% [ P < .001]). A Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression model confirmed a statistically significant relationship between the presence of a resident provider and near-miss events (odds ratio: 2.38 [ P = .02]). The NORA landscape is often remote in location, not as well-staffed or well-resourced, and with variable setups. With a systematic survey, we were able to capture near-miss events which would otherwise have been lost. These near-miss events cannot be evaluated in isolation. Future direction should focus on a systems-wide approach in safety surveillance that facilitates multidisciplinary collaboration and reporting. Our findings demonstrate near misses as an opportunity-to improve in-hospital access to care, promote quality assurance, and ultimately, make NORA a safer place.

This note presents a testing protocol developed to assess the suitability of a compact ultrasound (US) system for potential use inside a 1.5 T interventional magnetic resonance imaging (MRI) suite. Test results for specific commercial US and MRI systems in a particular clinical use case are also presented. The protocol consisted of safety testing and evaluations of image quality of both MRI and US systems at the proposed clinical use configuration. Safety tests included magnetic field measurements inside MRI suite, handheld magnet assessments of magnetic properties of the US system, and magnetic displacement force measurements. The safety tests were followed by direct assessments of US system components inside MRI suite. Each US system component was demonstrated to have no risk of displacement at the proposed locations with a large safety margin. No clinically relevant difference in US image quality was observed compared to images acquired outside MRI suite. While MR image quality met the American College of Radiology standards for clinical scanning, increases in noise levels and radiofrequency (RF) interference associated with the presence of US scanner in MRI suite were observed. The ‘sleep mode’ operating condition of the US system resulting in consistent absence of RF interference and minimal noise increase was identified and proposed for use during MRI scanning. Our results demonstrate the utility of our testing methods, and the suitability of this particular compact US system for safe use in our site-specific configuration inside the 1.5 T MRI suite. These results would be dependent on the specific test systems.

Difficult airway management (DAM) is a challenging aspect of anesthetic care. Although nearly all DAM episodes result in successful intubation, complications are common and clinical decision-making may be complex. In adults with anticipated DAM scheduled for nonemergent surgery, we prospectively observed clinical decisions made during DAM such as awake/sedated versus anesthetized, choice of initial and subsequent devices, case cancellation/postponement, conversions between awake and anesthetized approaches, and process complications such as multiple intubation/supraglottic airway (SGA) insertion attempts, difficult bag-mask ventilation (BMV), hypoxemia, and cardiovascular destabilization. From 2009 to 2014, we prospectively observed 1295 episodes of anticipated DAM in a convenience sample of 1245 adults scheduled for nonemergent surgery. Trained observers recorded airway management decisions and process complications during DAM. We described clinical decisions made during DAM and outcomes including number of attempts, need for BMV, hypoxemia, and cardiovascular destabilization. No cases were canceled/postponed for airway management failure and all intubations were eventually successful. Of the 1295 episodes of airway management in our study cohort, 166 (13%) were intubated awake. Patients intubated awake had more difficult airway indicators than those intubated anesthetized, their first-pass success rate was 49%, 30% required ≥3 attempts, 4% required a device change, 50% experienced hypoxemia, and 29% experienced cardiovascular destabilization. Among the 1129 patients intubated while anesthetized, first-pass success rate was 64% and 20% required ≥3 attempts, 11% required a device change, hypoxemia occurred in 30%, and cardiovascular destabilization in 20%. One patient (0.08%) was converted from an anesthetized to an awake approach. Patients with a failed anesthetized intubation attempt and difficult BMV between attempts were at high risk for multiple attempts (67%) and hypoxemia (100%). Airway management was successful in all patients and the incidence of process complications was higher than in routine airway management. Despite a high risk of DAM, 87% of patients were intubated anesthetized and conversions between awake and anesthetized approaches were rare. That patients intubated awake had more difficult airway indicators implies that clinicians reserve awake intubation for particularly difficult airways. The high incidence of multiple attempts, hypoxemia, and cardiovascular destabilization in patients intubated awake suggests that awake airway management remains challenging. We found no clear pattern in device choices after a first failed attempt. Patients with a first failed anesthetized intubation attempt and difficult BMV were at particularly high risk for hypoxemia.

With the expanding clinical application of magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU), acoustic field characterization of MR-HIFU systems is needed for facilitating regulatory approval and ensuring consistent and safe power output of HIFU transducers. However, the established acoustic field measurement techniques typically use equipment that cannot be used in a magnetic resonance imaging (MRI) suite, thus posing a challenge to the development and execution of HIFU acoustic field characterization techniques. In this study, we developed and characterized a technique for HIFU acoustic field calibration within the MRI magnet bore, and validated the technique with standard hydrophone measurements outside of the MRI suite. A clinical Philips MR-HIFU system (Sonalleve V2, Philips, Vantaa, Finland) was used to assess the proposed technique. A fiber-optic hydrophone with a long fiber was inserted through a 24-gauge angiocatheter and fixed inside a water tank that was placed on the HIFU patient table above the acoustic window. The long fiber allowed the hydrophone control unit to be placed outside of the magnet room. The location of the fiber tip was traced on MR images, and the HIFU focal point was positioned at the fiber tip using the MR-HIFU therapy planning software. To perform acoustic field mapping inside the magnet, the HIFU focus was positioned relative to the fiber tip using an MRI-compatible 5-axis robotic transducer positioning system embedded in the HIFU patient table. To perform validation measurements of the acoustic fields, the HIFU table was moved out of the MRI suite, and a standard laboratory hydrophone measurement setup was used to perform acoustic field measurements outside the magnetic field. The pressure field scans along and across the acoustic beam path obtained inside the MRI bore were in good agreement with those obtained outside of the MRI suite. At the HIFU focus with varying nominal acoustic powers of 10-500W, the peak positive pressure and peak negative pressure measured inside the magnet bore were 3.87-68.67MPa and 3.56-12.06MPa, respectively, while outside the MRI suite the corresponding pressures were 3.27-67.32MPa and 3.06-12.39MPa, respectively. There was no statistically significant difference (P>0.05) between measurements inside the magnet bore and outside the MRI suite for the p+ and p- at any acoustic power level. The spatial-peak pulse-average intensities (ISPPA ) for these powers were 312-17816W/cm2 and 220-15698W/cm2 for measurements inside and outside the magnet room, respectively. In addition, when the scanning step size of the HIFU focus was increased from 100μmto 500μm, the execution time for scanning a 4×4mm2 area decreased from 210min to 10min, the peak positive pressure decreased by 14%, the peak negative pressure decreased by 5%, and the lateral full width at half maximum dimension of pressure profiles increased from 1.15mm to 1.55mm. The proposed hydrophone measurement technique offers a convenient and reliable method for characterizing the acoustic fields of clinical MR-HIFU systems inside the magnet bore. The technique was validated for use by measurements outside the MRI suite using a standard hydrophone calibration technique. This technique can be a useful tool in MR-HIFU quality assurance and acoustic field assessment.

Indications for using supraglottic airway devices have widened over time and they now hold a prominent role in guidelines for difficult airway management. We aimed to describe the use of supraglottic airway devices in difficult airway management. We included adult patients undergoing general anaesthesia registered in the Danish Anaesthesia Database from 2008 to 2012 whose airway management had been recorded as difficult, defined as: ≥3 tracheal intubation attempts; failed tracheal intubation; or difficult facemask ventilation. In the Danish Anaesthesia Database, a separate difficult airway management module requires the technique used in each successive airway management attempt to be recorded. The primary aim of the study was to describe the use of supraglottic airway devices in cases of difficult airway management. Secondary aims were to examine success rates of supraglottic airway devices in difficult airway management cases, and specifically in the cases of 'cannot intubate, cannot facemask ventilate'. Difficult airway management occurred in 4898 (0.74% (95%CI 0.72-0.76%)) of 658,104 records of general anaesthesia. Supraglottic airway devices were used or use was attempted in 607 cases of difficult airway management (12.4% (95%CI 11.5-13.3%)), and were successful in 395 (65.1% (95%CI 61.2-68.8%)) cases. In 'cannot intubate, cannot facemask ventilate' situations, supraglottic airway devices were used in 86 (18.9% (95%CI 15.6-22.8%)) of 455 records and were successful in 54 (62.8% (95%CI 52.2-72.3%)) cases. We found that supraglottic airway devices are not widely used in the management of the difficult airway despite their prominent role in difficult airway management guidelines.

Conducting a general anaesthetic within a magnetic resonance imaging (MRI) suite poses many problems for the anaesthetist. Ferromagnetic substances are contained in most anaesthetic and monitoring equipment. Their presence within the magnetic field may cause hazards and artifacts during imaging. This report describes the testing and use of a free-standing Fortec II vaporizer within an MRI suite. The Fortec II vaporizer's function was altered depending upon its distance from and orientation to the magnetic field. The MRI images were not affected by this vaporizer's presence within the MRI suite. We conclude that an inhalational anaesthetic can be administered, using a pretested free-standing anaesthetic vaporizer and a Bain circuit, within the magnetic field of a magnetic resonance imager.

Sir, Magnetic resonance imaging (MRI) poses challenges to the anaesthesiologists in providing adequate sedation without compromising the patient's airway or haemodynamics and ensuring rapid recovery. The additional challenges posed by remote locations make the highest level of vigilance essential during MRI study. Dexmedetomidine has been used as a sole agent or in combination with other drugs for sedation in radiology set up.[1,2] Seven-month-old male child, weighing 7 kg, with history of swelling in the floor of mouth was referred to our hospital for MRI scanning. On detailed history, the swelling was present since birth and was increasing in size. There was no feeding difficulty but sleep was disturbed. On examination, a 4 cm × 4 cm swelling completely pushing tongue to one side was seen [Figure 1a]. Rest of the clinical examination was normal. Need for Intensive Care Unit stay was explained to relatives. Equipment for difficult airway was kept ready. Plan was to sedate the child in the preparation room. All monitors (electrocardiogram [ECG], pulse oximetry, end-tidal CO2 [ETCO2]) were attached. In the MRI room, MRI-compatible anaesthesia workstation and multiparameter monitor were kept ready. Intravenous (i.v.) cannula was secured and glycopyrrolate 0.05 mg administered. Dexmedetomidine 7 µg was administered over 10 min as infusion. Sedation was assessed using Ramsay sedation score. Ketamine 10 mg i.v. was given as supplemental sedation after completion of dexmedetomidine infusion to achieve Ramsay sedation score of 6. Then patient was transferred to MRI table and all monitors (ECG, pulse oximetry, ETCO2) were attached. Stable capnogram was established before proceeding to scan. Oxygen supplementation was given with nasal cannula (2 L/min). Continuous monitoring of vital parameters was done. Procedure lasted for 45 min. No episode of apnoea, desaturation and bradycardia was noted. The child was immobile throughout the MRI scanning. After the procedure, the patient was transferred to recovery room and monitored till recovery. MRI imaging confirmed the extent of swelling, and the tumour was compressing trachea [Figure 1b]. Figure 1 (a) Large tumour in oral cavity pushing tongue; (b) magnetic resonance imaging scan showing tumour compressing trachea Dexmedetomidine is useful for paediatric sedation in many clinical situations. It is associated with rapid onset and offset and a natural, sleep-like state with minimal effect on respiration. During MRI, the patient needs to be still for good-quality image. Paediatric patients need sedation and sometimes general anaesthesia for MRI. Many drugs such as chloral hydrate, phenobarbital, ketamine, midazolam and propofol have been used in MRI setting.[1] Dexmedetomidine alone has been used for sedation in MRI suite with more than 90% success.[3] These studies noted no apnoea or respiratory depression with high dose of dexmedetomidine. As dexmedetomidine single dose gives adequate sedation for 45–60 min, MRI can be done without need for supplemental sedation. In a study comparing dexmedetomidine plus single bolus dose of midazolam and propofol, dexmedetomidine provided satisfactory condition for MRI and respiratory incidences were similar to the propofol group.[2] In another study of dexmedetomidine versus midazolam,[4] the quality of MRI was better with dexmedetomidine and need for rescue medication was less. Comparison of intramuscular (i.m.) ketamine, i.m. dexmedetomidine, and dexmedetomidine–ketamine combination showed that the combination was superior with regard to onset, haemodynamic and respiratory stability.[5] Quality of MRI and radiologist satisfaction regarding image quality was better in dexmedetomidine–ketamine combination group. The combination of dexmedetomidine and ketamine is useful as the risk of apnoea is minimal with this combination. In a case series of trisomy 21 patients for MRI, dexmedetomidine–ketamine combination provided effective sedation without haemodynamic and respiratory compromise.[6] We conclude that dexmedetomidine and ketamine combination is an option to manage children with difficult airway for sedation in MRI suite.

Sir, The number of diagnostic and therapeutic procedures performed outside the operation theatre has increased over the last decade and providing anaesthesia and sedation will be a real challenge to the anaesthetisiologists. Sedation for magnetic resonance imaging (MRI) procedures in children adds a substantial risk in younger children. This is more so in paediatric patients with difficult airway.[1] A 4 years male child weighing 16 kg presented to paediatric department with a huge swelling of tongue since birth. He had undergone resection of the same at 6 months of age which had recurred (size approximately around 6 cm × 4 cm). He had difficulty in speech and feeding, and, of course, cosmetic issue to his family and society. Paediatricians suspected venolymphatic malformation and to confirm the diagnosis child was advised MRI neck. During preanaesthetic evaluation, we noted the profusely enlarged tongue which was protruding out of oral cavity [Figure 1]. The child was unable to protrude his tongue as it was covering the entire oral cavity. Availability of all emergency drugs and difficult airway cart including fibreoptic bronchoscope were confirmed in the MRI suite. Figure 1 (a and b) Profusely enlarged and protruding tongue Parental consent was obtained, and the child was fasted for 6 h for solids and 2 h for clear liquids. Monitoring with pulseoximeter and electrocardiogram (ECG) were initiated, and baseline heart rate (HR), and blood pressure were recorded. Intranasal dexmedetomidine 1 μg/kg and eutectic mixture of lignocaine and prilocaine cream was applied 30 min before securing a 22 gauge intravenous cannula over dorsum of the left hand. Injection glycopyrrolate 10 μg/kg was administered. Oxygen through nasal prongs was delivered at 2 L/min. Injection dexmedetomidine 0.5 ΅g/kg (IV)was administered over 10 min. The sedated child was taken to MRI console (Ramsay sedation score of 5).[2] An MRI compatible monitor was used to monitor HR, ECG and oxygen saturation and respiration through a sidestream capnography continuously and patient remained stable throughout the procedure lasting for 20 min. In the recovery room, the child was made to lie in the left lateral position. Monitoring and oxygen supplementation were continued. The child made an uneventful recovery from sedation. Venolymphatic malformations are slow-flow lesions that are a combination of dilated lymphatic channels filled with proteinaceous fluid and large veins. These can be difficult to separate from other low flow lesions such as lymphatic malformations and haemangiomas on certain imaging, especially ultrasound. The presence at birth favours venolymphatic malformation, although the other two do occur at birth.[3] Computed tomography and MRI are used for volumetric analysis of haemangiomas and vascular malformations. Imaging resources are useful in both diagnostic differentiation and analysis of lesion features with regard to its size, extension and location, as well as for follow-up of lesions treated under a systemic therapy.[4] MRI suite is unlikely to be a favourable place to give sedation or anaesthesia for many reasons. Patient's distance from anaesthesiologist creates problems such as airway management, intravenous access, patient visualisation and monitor attachment.[5] MRI compatible machines and airway instruments are required and patients may suffer due to claustrophobia, noisy unfamiliar environment, hypothermia, and strong magnetic field. Children require moderate to deep sedation during MRI procedures to avoid movement and image distortion. The potential complications of deep sedation include hypoventilation, apnoea, airway obstruction, bradycardia and hypotension. An appropriate drug which causes minimal cardiorespiratory depression has to be used. Dexmedetomidine (a highly selective α2 -adrenoreceptor agonist) as a sedative agent will provide a controllable sedation and analgesia without cardiorespiratory depression.[6] An interesting feature regarding oral use of dexmedetomidine is that after oral administration for paediatric sedation, the absorption is to the extent of 82%.[7] Although dexmedetomidine and propofol provide adequate sedation in children, propofol provides more rapid rates of anaesthetic induction and recovery but dexmedetomidine better preserves mean arterial pressure and respiratory rate.[8] Thus, we conclude that drugs which provide a controlled sedation without cardiorespiratory depression like dexmedetomidine can be very useful for sedation in paediatric patients with difficult airway outside operation theatre. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Context:Induction of general anesthesia and mandatory low-ambient temperature in the magnetic resonance imaging (MRI) suite renders the pediatric patient prone to fall in core temperature. Previously done studies have shown mixed results with core temperature showing both rise and fall.Aims:The aim of this study is to evaluate which effect, hypothermia or hyperthermia, predominates in children anesthetized for MRI. Is the change in temperature the same across age groups and for different MRI scanners?.Settings and Design:Prospective, observational study in a tertiary care teaching hospital.Subjects and Methods:Two hundred and fifty children of age between 1 month and 16 years scheduled for MRI under propofol-based total intravenous anesthesia (TIVA) were recruited. A baseline core temperature (pre-scan) was recorded with the pediatric nasopharyngeal temperature probe after induction of anesthesia and also after the scan in the recovery room.Results:The study shows that there is a significant fall in temperature of 1.022°C (CI = 0.964, 1.081) following MRI (P < 0.001) but the difference across different age groups and type of MRI scanner used are not significant. There is a significant correlation between duration in the MRI room and a decrease in temperature (P value = 0.003). Using simple linear regression analysis, it is found that if there is a 1-min increase in the duration of MRI, there is a decrease of 0.006°C in temperature.Conclusion:Vigilant temperature preservation strategies have to be maintained during the time the anesthetized child is present in the MRI suite. MRI compatible active warming devices are warranted especially in high turnover centers.

(Grady) Fellow.(Perkins) Assistant Professor.Received from the Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota. Submitted for publication April 5, 1996. Accepted for publication December 18, 1996.Address reprint requests to Dr. Perkins: Department of Anesthesiology, Mayo Clinic, 200 First Street, SW, Rochester, Minnesota 55905.Anesthesia services in the magnetic resonance imaging (MRI) suite are increasing and require that the anesthetic equipment used is adequate to ensure patient safety, is MRI compatible, and has a negligible effect on image quality. We report a case in which the MRI scan quality was noticeably degraded by an unsuspected but commonly used piece of anesthesia equipment, the pilot balloon valve of a conventional endotracheal tube.A 17-yr-old trauma patient with a known L4burst fracture required general anesthesia for a detailed MR examination of the spine and paraspinous region. After successful induction of general anesthesia, the patient's trachea was intubated with a 7.0 cuffed endotracheal tube (Lo-Pro; Mallinkrodt Medical, St. Louis, MO). The initial T2-weighted, gradient recalled MR examination revealed gross image degradation in the sagittal and transverse sections of the cervical spine region. The image artifact was consistent with ferromagnetic interference. A search for a source of ferromagnetic interference was initially unsuccessful. A radiology technician reported that similar interference had been observed in the past and was related to the position of the pilot balloon. Repositioning the pilot balloon 5 cm away from the surface of the neck area eliminated the distortion in a repeated MR scan. Subsequent inspection of the pilot balloon revealed a ferromagnetic spring that closes the pilot balloon valve.The strength of the magnetic field and the nature of the signal needed to generate the image requires that the anesthesiologist use nonferromagnetic materials in the MRI suite. It has long been known that ferromagnetic materials can interfere with the magnetic field generated by the MRI scanner. [1,2]This case illustrates how even a very small ferromagnetic object can severely distort a magnetic resonance image in an adult patient. Brenn and Saldutti [3] reported a similar episode of ferromagnetic interference during an MRI scan in a 6-month-old infant. The larger body size of the adult and the greater distance from the skin and pilot balloon to the internal structures to be examined does not appear to offer any significant protection of MRI quality. Pilot balloon springs of oral RAE tubes and laryngeal mask airways have also been implicated in MRI degradation. [4,5] The spring within the pilot balloon valve apparatus (Bespak PVC Medical Check Valve, Tenax Corporation, Apex, NC) is made of stainless steel and causes the image distortion. Image degradation only occurs when the pilot balloon valve containing this spring lies directly on the area of the head or neck to be scanned (Figure 1). According to the manufacturer (Tenax Corporation), this spring is present in all biomedical pilot balloon valves. Although plastic versions have been used in the past, the spring is best made of stainless steel because of its small size and the need for highly reliable operation. The risk for direct patient injury via induced heat production or dislocation of the valve spring is insignificant. The type of image distortion described by this report is easily avoided by placing the pilot balloon as far from the area to be examined as possible. We have found it convenient to secure the pilot balloon near the y-connector of the anesthesia circuit, thereby separating the pilot balloon from the skin surface by at least 3 cm and preventing image distortion.

The coronavirus disease 2019 (COVID-19) disease, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), often results in severe hypoxemia requiring airway management. Because SARS-CoV-2 virus is spread via respiratory droplets, bag-mask ventilation, intubation, and extubation may place health care workers (HCW) at risk. While existing recommendations address airway management in patients with COVID-19, no guidance exists specifically for difficult airway management. Some strategies normally recommended for difficult airway management may not be ideal in the setting of COVID-19 infection. To address this issue, the Society for Airway Management (SAM) created a task force to review existing literature and current practice guidelines for difficult airway management by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. The SAM task force created recommendations for the management of known or suspected difficult airway in the setting of known or suspected COVID-19 infection. The goal of the task force was to optimize successful airway management while minimizing exposure risk. Each member conducted a literature review on specific clinical practice section utilizing standard search engines (PubMed, Ovid, Google Scholar). Existing recommendations and evidence for difficult airway management in the COVID-19 context were developed. Each specific recommendation was discussed among task force members and modified until unanimously approved by all task force members. Elements of Appraisal of Guidelines Research and Evaluation (AGREE) Reporting Checklist for dissemination of clinical practice guidelines were utilized to develop this statement. Airway management in the COVID-19 patient increases HCW exposure risk. Difficult airway management often takes longer and may involve multiple procedures with aerosolization potential, and strict adherence to personal protective equipment (PPE) protocols is mandatory to reduce risk to providers. When a patient's airway risk assessment suggests that awake tracheal intubation is an appropriate choice of technique, and procedures that may cause increased aerosolization of secretions should be avoided. Optimal preoxygenation before induction with a tight seal facemask may be performed to reduce the risk of hypoxemia. Unless the patient is experiencing oxygen desaturation, positive pressure bag-mask ventilation after induction may be avoided to reduce aerosolization. For optimal intubating conditions, patients should be anesthetized with full muscle relaxation. Videolaryngoscopy is recommended as a first-line strategy for airway management. If emergent invasive airway access is indicated, then we recommend a surgical technique such as scalpel-bougie-tube, rather than an aerosolizing generating procedure, such as transtracheal jet ventilation. This statement represents recommendations by the SAM task force for the difficult airway management of adults with COVID-19 with the goal to optimize successful airway management while minimizing the risk of clinician exposure.

Chapter 16 - Airway Management