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Ketamine-Induced Spontaneous Breathing Intubation With Airway Topicalization: A Case Report of Airway Obstruction in Retrieval Care

Published:October 20, 2021DOI:https://doi.org/10.1016/j.amj.2021.09.007

      Abstract

      A LifeFlight Retrieval Medicine air medical team was tasked to a rural facility 200 km away to manage and retrieve a 73-year-old woman with evolving airway obstruction. Resources at the referring site included a general practitioner with anesthetic skills training but no access to otorhinolaryngology (ear, nose, and throat) or flexible fiberoptic airway devices. On arrival of the LifeFlight Retrieval Medicine, the patient became agitated, with deterioration in her airway patency. A clinical diagnosis of Ludwig's angina with evolving airway obstruction was made. Using a technique of ketamine-facilitated, spontaneous breathing tracheal intubation with a video laryngoscope, the retrieval team was able to safely secure the patient's airway before transporting her to a regional hospital with ear, nose, and throat surgical services. Computed tomographic imaging revealed an oropharyngeal abscess with spread into the larynx, which subsequently underwent surgical drainage. This case report outlines the technique of awake laryngoscopy with relevance to the retrieval physician and discusses some of the challenges and potential complications associated with it.
      A LifeFlight Retrieval Medicine (LRM) team was tasked to a 73-year-old woman who presented to the emergency department of a small, rural hospital with a 10-hour history of jaw and neck swelling with associated dyspnea, dysphagia, voice changes, and an inability to tolerate the supine position. Further history revealed a dental abscess and molar extraction 24 hours before her presentation. Her relevant past medical history included atrial fibrillation, for which she was taking rivaroxaban.
      On LRM arrival, she was agitated and distressed. Her vital signs revealed a sinus tachycardia at 100 beats/min, respiratory rate of 16 breaths/min, oxygen saturation of 98% on room air, Glasgow Coma Scale score of 15, temperature of 37.1°C, and blood pressure of 133/90 mm Hg. Airway examination revealed a tender and firm swelling of the left mandible and anterior neck externally and no soft tissue compliance to the floor of the mouth internally. Mallampati grading was 4, and mouth opening was limited to 3 cm. There were no palpable anatomic structures that could guide front-of-neck surgical airway access. The following clinical signs concerning for airway obstruction were present: stridor, hoarseness of voice, drooling, and the need to remain in a seated position for airway patency. Over 15 minutes, she developed increased work of breathing with a new cough. A diagnosis of Ludwig's angina with evolving airway obstruction was made. A situation report was conveyed to Retrieval Services Queensland medical coordinator.
      We anticipated the need for intubation and considered the staffing and skill mix available on-site, the urgency, and the equipment and medications available. The local medical officer was a general practitioner with previous anesthetic skills training, whereas the retrieval medical officer was a fellow of the Australasian College for Emergency Medicine. At the referring hospital, no specialist anesthetics or otolaryngologist were available. The equipment to manage difficult airways was limited to video laryngoscopy and supraglottic airway devices. Flexible fiberoptic devices were not available and are not part of the standardized kit carried by LRM. The local anesthetic agents within the LRM kit are limited to 80 mg lidocaine 2% and 200 mg ropivacaine 1%.
      A plan was made for an awake laryngoscopy to preserve the patient's spontaneous respiratory efforts as opposed to rapid sequence induction (RSI) with the potential for failure to oxygenate in the setting of a difficult intubation. Plans for failure and indications for moving to an emergency surgical airway were discussed.
      The patient became increasingly agitated, and the likely cause of agitation was hypoxia. To facilitate preoxygenation and physiological monitoring, ketamine was administered in 20-mg aliquots to a total of 100 mg. This resulted in a dissociative state with preserved respiratory effort. Preoxygenation was achieved using a standard nasal cannula underneath a self-inflating bag-valve-mask device with a good seal, both with flow rates at 15 L/min. The patient's airway was anesthetized using a locally sourced 10% lidocaine pump with a nozzle, delivering a 10-mg dose per spray, in a sequential “spray-as-you-go” manner. Lidocaine was sprayed on the anterior surface of the patient's tongue, tonsillar pillars, and posterior oropharynx in a progressive manner during inspiration. A total of 10 sprays were delivered to the oropharynx. The gag reflex tested negative with the spraying nozzle; after which, gentle insertion of a McGrath video laryngoscope with a size 4 Macintosh blade along the anesthetized portion of the airway was performed. Before insertion, both sides of the blade of the video laryngoscope were sprayed with lidocaine, and the camera eye was wiped after. While viewing the video laryngoscope screen, the operator sprayed further onto the laryngeal surfaces, including the vallecular, vocal cord mucosa, and through the vocal cords. After each spray, the bag-mask-valve device was reapplied for 60 seconds to continue preoxygenation before the next spray was delivered. During laryngoscopy, there was no gag reflex, cough, agitation, or patient movement, indicating adequate anesthesia of the supraglottic structures. The direct view revealed a Cormack-Lehane (CL) grade of 4, whereas video images revealed a percentage of glottic opening score of 0%. External laryngeal manipulation improved the direct view to a CL grade of 3 and the video view to a percentage of glottic opening score of 10%. A CL grade of 3 or 4 is associated with a difficult intubation rate of 16.2%, with difficult intubation being defined by American Society of Anesthesiologists as 3 or more attempts.
      • Koh W
      • Kim H
      • Kim K
      • Ro YJ
      • Yang HS.
      Encountering unexpected difficult airway: relationship with the intubation difficulty scale.
      The glottic opening was sprayed generously with lidocaine to a total of 210 mg (3 mg/kg). A bougie was passed beyond the glottis with tactile feedback provided by the assistant providing ELM as well as the primary airway operator. A size 7.0 endotracheal tube was advanced over the bougie, with confirmation of tracheal intubation by end-tidal capnography waveform. A size 6.0 endotracheal tube was available in case of failure to advance the former. The patient was then fully anesthetized with 50 mg ketamine and 100 mg rocuronium.
      The patient was transported by helicopter to a hospital with ear, nose, and throat services with a 45-minute flight time. A computed tomographic scan revealed extensive stranding and soft tissue edema at the floor of the mouth and within the supra- and infrahyoid neck, suggestive of an oropharyngeal abscess with spread into the larynx (Figure 1, Figure 2). She underwent drainage in the operating room and was extubated 2 days after.
      Figure 1
      Figure 1Left parapharyngeal and masticator space soft tissue swelling displaces the oropharynx, endotracheal tube, and nasogastric tube to the left (arrow).
      Figure 2
      Figure 2The site of a recent tooth extraction and likely source of infection (*). Left parapharyngeal and masticator space soft tissue swelling displaces the oropharynx (arrow).

      Discussion

      Managing difficult airways poses a great level of physical, mental, and psychological stress, even for experienced clinicians; limitations imposed by air medical and retrieval environments add further complexity to this. The following discussion highlights some of the considerations in intubating a patient in a similar manner relevant to the retrieval physician.

      Staffing

      Access to specialist staff and equipment and operating room environments contribute to safely dealing with airway obstruction. These staff and resources are often not found in rural hospitals or, if present, may be infrequently exposed to such scenarios. LRM clinicians are critical care specialists and trainees supported by critical care paramedics. This small team rehearses airway drills on a daily basis to help improve actions and decision making around airway management. As the most experienced airway clinician and with familiarity in this technique, the LRM clinician was the primary airway operator with close assistance provided by the critical care paramedic. A second clinician can maintain situational awareness as well as being attuned to task fixation or failure by the airway operator while being alert to any change in clinical status.

      RSI or Not?

      The decision to not perform RSI warrants discussion. RSI aims to swiftly achieve optimal intubating conditions, thereby minimizing the time available for potential aspiration of gastric contents. The patient was agitated and intolerant of preoxygenation attempts—a key component to safely performing RSI. Adequate preoxygenation extends the duration of safe apnea and increases the time available for intubation before the patient's oxygen saturation drops to critical levels.
      • Wallace C
      • McGuire B.
      Rapid sequence induction: its place in modern anaesthesia.
      The perceived difficulty with intubation, rescue ventilation, and emergency front-of-neck access in this poorly preoxygenated patient required us to consider alternative techniques. Delayed sequence induction is well recognized in the emergency medicine literature to help improve preoxygenation before airway instrumentation.
      • Weingart SD
      • Seth Trueger N
      • Wong N
      • Scofi J
      • Singh N
      • Rudolph SS
      Delayed sequence intubation: a prospective observational study.
      We performed delayed sequence induction using ketamine to allow preoxygenation, establish placement of physiological monitoring, and calm the agitated patient while preserving the patient's native respiratory effort. An important risk is an aspiration event compromising an already threatened airway.
      • Weingart SD
      • Seth Trueger N
      • Wong N
      • Scofi J
      • Singh N
      • Rudolph SS
      Delayed sequence intubation: a prospective observational study.
      Anticipating and considering strategies to deal with this should be factored in during the planning phase.
      Regardless of the approach chosen, a “cannot intubate, cannot oxygenate” situation needs to be anticipated, and a plan for an emergency surgical airway must be decided on. The LRM team rehearsed rapid shift from awake laryngoscopy in settings of hemodynamic compromise, including preparing equipment and the patient's neck for a surgical airway.
      • Tonna JE
      • DeBlieux PM.
      Awake laryngoscopy in the emergency department.
      Given the distorted neck anatomy, ultrasound could have been used to identify the trachea and cricothyroid membrane.
      • Frerk C
      • Mitchell VS
      • McNarry AF
      • Mendonca C
      • Bhagrath R
      • Patel A
      • et al.
      Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults.

      Sedation

      The use of sedation in difficult airways is a contentious topic. Traditional teaching suggests that the fully awake technique is the safest option. This maximizes the “margin of safety” because muscle tone and reflexes are maintained and respiratory function is unaffected by anesthetic agents.
      • Wong P
      • Wong J
      • Mok MU.
      Anaesthetic management of acute airway obstruction.
      However, cautious use of sedation to facilitate securing the airway via an awake technique is well recognized. The fundamental principle is to maintain airway patency.
      • Evans A
      • Morton B
      • Groom P
      Difficult Airway Society guidelines for awake tracheal intubation in adults – is lidocaine topicalisation safe?.
      Benzodiazepines, opioids, alpha-2 agonists, propofol, and ketamine, among others, are used to alleviate discomfort and anxiety during awake intubations. However, sedation can be hazardous. The risk of laryngospasm, hypoxia, aspiration, loss of airway tone with worsening airway obstruction, and respiratory depression are reported complications.
      • Tonna JE
      • DeBlieux PM.
      Awake laryngoscopy in the emergency department.
      The literature suggests the choice of sedative agents among anesthetists is remifentanil, dexmedetomidine, and low-dose propofol.
      • El-Boghdadly K
      • Ahmad I
      Sedation strategies in awake tracheal intubation: a reply.
      We used ketamine because of the familiarity of LRM as well as its benefit in the preservation of airway reflexes and respiratory drive. Ketamine can precipitate laryngospasm and hypersalivation, which can be mitigated by early administration of glycopyrrolate.
      • Tonna JE
      • DeBlieux PM.
      Awake laryngoscopy in the emergency department.
      Key principles in choosing sedation are to ensure that a familiar agent is used, in the smallest dose necessary, and to observe possible complications including aspiration, loss of respiratory drive, and signs of airway obstruction. Sedation is not a substitute for inadequate airway topicalization. Real-time, end-tidal capnography should be used for monitoring, not just to confirm successful intubation of the trachea but also to detect apnea early on. A second source of capnography attached to the breathing circuit after intubation helps void erroneous interpretation of a pre-existing capnogram.

      Topicalization

      Effective topical anesthesia is crucial; without it, laryngoscopy is likely to stimulate patients to unsafe levels by causing agitation, laryngospasm, and airway trauma during laryngoscopy. Local anesthesia of the airway serves to anesthetize the branches of 3 nerves: the trigeminal, glossopharyngeal, and vagus nerves. The high level of heterogeneity in the literature suggests a range of methods are available to achieve this, including topical application (via atomized techniques or nebulizers) and sharp needle blocks. Topicalization is the simplest method; little knowledge of the larynx anatomy is required for successful implementation.
      • Tonna JE
      • DeBlieux PM.
      Awake laryngoscopy in the emergency department.
      Nebulized lignocaine 2% to 4% via a face mask for 15 to 30 minutes achieves anesthesia of the oropharynx and trachea, with the advantages being its simplicity and lack of patient discomfort. Lignocaine can also be applied directly to the mucosa by using a 10% spray supplied in pressurized bottles, as performed in our case. The atomized technique is highly effective and well tolerated.
      • Pani N
      • Kumar Rath S.
      Regional & topical anaesthesia of upper airways.
      Needle-based techniques, being less familiar, require good knowledge of anatomy and are less favored in the retrieval environment.
      Lignocaine is the most appropriate agent for airway topicalization. It is readily available, has relatively low neurologic and cardiac toxicity compared with other agents, reaches its peak effect within 2 to 5 minutes, provides a clinically useful duration of topical action (30-45 minutes), and can be administered to a maximum dosage of 9 mg/kg topically.
      • Pani N
      • Kumar Rath S.
      Regional & topical anaesthesia of upper airways.
      Caution must be exercised in patients with hepatic dysfunction.
      Antisialagogues such as glycopyrrolate and atropine, although not essential, can improve intubating conditions by reducing the salivary secretion load. Glycopyrrolate has an onset of action within 1 to 2 minutes and a peak effect around 30 to 60 minutes, whereas atropine has less antisialagogue action. A dry field ensures better quality of topical anesthesia by allowing local anesthetic to act on mucosal surfaces in appropriate concentrations.
      • Ramkumar V.
      Preparation of the patient and the airway for awake intubation.
      Cardiovascular side effects need to be considered alongside the patient's condition. Unwanted side effects such as tachycardia can sometimes make awake intubation more difficult as a result of increased patient anxiety secondary to tachycardia.
      • Leslie D
      • Stacey M.
      Awake intubation.
      A means of assessing the adequacy of topicalization is to provide the patient with a Yankauer suction catheter and asking the patient to clear any secretions from the back of his or her pharynx while examining for evidence of an intact gag reflex. This can also be done by the airway operator if the patient is unable to do so.

      Oxygenation Strategies

      Desaturation is a real and common complication during awake intubation techniques. The introduction of high-flow, humidified nasal oxygen is associated with significantly lower rates of desaturation.
      • Ahmad I
      • El-Boghdadly K
      • Bhagrath R
      • et al.
      Difficult Airway Society guidelines for awake tracheal intubation (ATI) in adults.
      Although it is possible to administer 100% oxygen in the operating room using an anesthesia machine, this cannot be done easily in the retrieval environment unless the patient is intubated. Effective preoxygenation is performed using an airtight mask fit over the patient's face. Various preoxygenation techniques include traditional tidal volume breathing for 3 to 5 minutes and 4 to 8 deep inspiratory capacity breaths, but the main determining factor remains the compliance of the patient to oxygen therapy (ie, the occurrence of agitation as in our case, which required sedation to facilitate preoxygenation).
      • Ramkumar V.
      Preparation of the patient and the airway for awake intubation.

      Equipment

      The equipment required to safely perform awake tracheal intubation is likely familiar to clinicians new to the technique. A suitable list of items is presented in Table 1.
      Table 1
      MonitoringElectrocardiography, noninvasive blood pressure, peripheral oxygen saturation, and capnography are required at a minimum.
      Airway devicesA video laryngoscope familiar to the airway operator, devices to assist in airway rescue including supraglottic airway aids and laryngeal  mask airway, and equipment to perform emergency front-of-neck access
      Intubating aidesA Frova bougie and a suitable checklist (for rapid sequence induction or 1 dedicated for awake intubation)
      Endotracheal tubesAn endotracheal tube including sizes smaller for when airway edema is greater than anticipated
      Oxygenation devicesA self-inflating bag-valve-mask ventilator, high-flow nasal oxygen (humidified, if available), nasal prong oxygen, and nonrebreather  oxygen mask (often superior to a self-inflating bag in spontaneous breathing patients)
      Topicalization devicesA flexible atomization device (eg, MADgic atomisation device) and a nebulizer
      Medications1% to 2% lignocaine nebulizer, lignocaine 10% atomizer, drugs to facilitate the induction of anesthesia and muscle relaxation, medications  to manage local anesthetic systemic toxicity (Intra-Lipid and adrenaline), and antagonist medication relevant to the sedation agent (eg, naloxone and flumazenil)
      Suction devicesTwo suction devices should be available in the event of soiling of the airway by vomitus, blood, or pus. The LifeFlight Retrieval Medicine  kit has 2 Yankauer devices.

      Conclusion

      Retrieval clinicians have a broad range of specialty training, including emergency medicine, intensive care, and anesthesiology. One should be aware of the limitations imposed by the air medical environment in managing airway obstruction. These are highly dependent on local resources, medication availabilities, and the skill set of the retrieval team. The airway operator should rely on techniques that are familiar and within one's expertise.
      Spontaneous breathing intubation is an advantageous option in safely securing a threatened airway. It requires little in the way of specialized equipment in resource-limited environments and can be safely performed with training and familiarity in the steps. There are several subtleties to intubating difficult airways in this manner, and this article addresses only some of them. Learning from experienced colleagues in disciplines such as anesthesia and ear, nose, and throat can shed light on many of these and make spontaneous breathing intubation a potentially viable technique in the retrieval environment.

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