An anterior cervical and mediastinal mass causes “cannot intubate and cannot ventilate” after induction

doi:10.21203/rs.3.rs-3144548/v1

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An anterior cervical and mediastinal mass causes “cannot intubate and cannot ventilate” after induction

https://doi.org/10.21203/rs.3.rs-3144548/v1

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The perioperative management of a patient with a large anterior mediastinal mass is one of the major challenges for anesthesia care providers. If there is significant tracheal compression or the patient presents with difficult breathing, particularly in supine position, awake fiberscope intubation is usually indicated in order to avoid complete tracheal obstruction after induction. Here, we report a patient with a large anterior cervical and mediastinal mass, along with tracheal compression but no difficult breathing, even in the supine position. After intubation, nearly “cannot intubate and cannot ventilate” was encountered. This case demonstrates that absence of difficult breathing awake in the supine position in a patient with a large anterior mediastinal massdoes not rule out “cannot intubate and cannot ventilate” after induction. Very high inspiratory pressure during mask ventilation is needed to achieve effective mask ventilation.

airway obstruction

mediastinum

airway management

mask ventilation

tracheal intubation

A patient with a mediastinal mass, particularly located in the anterior or superior mediastinum, or both, presents unique challenges for the anesthesiologist.[1-4] Both mask ventilation and tracheal intubation after induction are often difficult due to complete airway collapse which can result in a “cannot intubate and cannot ventilate” situation after induction of general anesthesia.[5] It is well-known that awake intubation is the safest approach for these patients, but they frequently object and some patients even refuse awake fiberoptic intubation. Awake intubation is often reserved for patients with compromised breathing, particularly in the supine position.[6] Patients with no difficult breathing , even in the supine position, can still undergo tracheal intubation after induction of general anesthesia as an option.[7] Nevertheless, the safety of such an approach remains controversial.

Here, we report a case of a patient with a large anterior cervical and mediastinal mass, and tracheal compression shown on CT scan. However, the patient denied any difficult breathing in the supine position. The patient was induced with general anesthesia, but both mask ventilation and intubation were nearly impossible. Effective mask ventilation was only achieved with extraordinary high peak inspiratory airway pressures accompanied with a long inspiratory time.

A 37 year-old female, with a medical history of obesity and large multinodular goiter with substernal component, presented for total thyroidectomy. She denied any wheezing, stridor or difficulty in breathing, even in supine position. She was 167 cm tall and weighed 138 Kg (body mass index [BMI] = 49.5 kg/m²). Her airway examination revealed an oropharyngeal class III and with a large tongue and a short/thick neck. CT scan 3 months prior to the surgery showed a large mass within the neck. The mass began at the base of the mandible within the retropharyngeal space and continued caudally to the left substernal region. There was deviation of the trachea and esophagus to the right, with mild narrowing of the oral airway near the epiglottis level. Significant trachea compression was seen in the middle segment of trachea (Figure 1).

An awake fiberoptic intubation was strongly advised, but the patient refused this and preferred intubation after induction of general anesthesia. Routine ASA monitors were applied prior to induction. After adequate pre-oxygenation, induction was achieved with ketamine 50 mg IV, propofol 200 mg IV, succinylcholine 100 mg IV. Tracheal intubation was attempted with a McGrath videoscope, blade size of 3 and then 4, by an experienced CRNA and then by the attending anesthesiologist without success. The vocal view was grade 4. Then, mask ventilation was attempted with a two-hand mask-holding technique, after insertion of an oral airway and with the breathing bag at a peak inspiratory airway pressure of about 40 cmH₂O. Airway pressure reached the set pressure but no expired volume or CO₂ were observed. Immediately, peak inspiratory pressure was increased to about 65 cmH₂O with an inspiratory time to roughly 4 seconds. Then expired tidal volume of about 200ml was achieved and expired CO₂ was visible. During this period of time of about 3 minutes, the patient’s O₂ saturation went down to about 90% and quickly returned back to 98% once effective mask ventilation was achieved. Then, the surgeon performed intubation with a Dedo laryngoscope and a bougie. An endo-tracheal tube of size 6.0 was inserted over the bougie without difficulty. Correct placement of end tracheal tube was confirmed with normal end-tidal CO₂ trace and bilateral breathing sounds. Intra-operative sedation was maintained with a ketamine infusion (5 mcg/kg/min) and isoflurane 1% throughout the surgery. The tidal volume was 400 ml per breath after intubation with a peak inspiratory pressure around 38 cmH₂O and PEEP 8 cmH₂O. Hemodynamic and O₂ saturation remained in the normal range throughout the operation, which lasted about 4 and a half hours. At the completion of the surgery and following the confirmation of adequate spontaneous breathing, she was extubated awake. Post extubation, she remained adequate spontaneous breathing and was transferred to the PACU. She was discharged home on post operation day #1 without any complication associated with her procedure.

This case highlights two important learning points: 1) a large anterior cervical and mediastinal mass can cause complete airway obstruction up on induction of general anesthesia, even with a patient who denied having difficult breathing awake in the supine position; 2) complete airway obstruction with mask ventilation can be overcome with extraordinary inspiratory airway pressure and a longer inspiratory time.

Incomplete tracheal obstruction from direct compression of an anterior mediastinal mass, when a patient is awake, can end up with complete airway obstruction up on induction, particularly in supine position.[5] Because an emergency tracheostomy can be very challenging, if not impossible, intubation after induction may end up with a ‘cannot intubate and cannot ventilate’ scenario.[8] Therefore, ECMO or cardiopulmonary bypass should be on standby as the backup plan, if complete airway obstruction after induction is anticipated.[9–10]

The working hypothesis for this ‘cannot intubate, cannot ventilate’ scenario is that reduction in functional residual capacity caused by induction and/or muscle relaxation results in complete trachea collapse.[11, 12] This can render both mask ventilation and trachea intubation impossible. Tracheostomy can be extremely difficult and may not create a patent airway even if a tracheostomy is successful.[13] Therefore, airway management for such a patient has to be planned carefully. The main focus on stratification of the patients with mediastinal masses for general anesthesia, particularly for airway management, is based on the history of difficult breathing in the supine position and the degree of trachea compression observed on an imaging study. Awake fiberoptic intubation is the safest choice for these cases. Clinicians often believe that difficult breathing in supine position is an indication for an awake tracheal intubation.[7] Due to widely availability of the image studies, the degree of trachea compression is also used for stratification of airway management and making the decision of awake intubation vs. intubation after induction of general anesthesia. This patient denied difficult breathing in the supine position, but the reduction of cross section area of trachea was greater than 50% of that immediately below the glottis or above her carina, as shown in Fig. 1. She fell in the gray area between the category of ‘safe’ and ‘uncertain’.[6] The care team decided to intubate her after induction, primarily due to her refusal to undergo an awake intubation. In addition, the video laryngoscope (McGrath, Aircraft Medical Ltd, Edinburgh, UK) was used as a primary intubation approach and the surgical team was on standby with a Dedo laryngoscope(Pilling Co., Fort Washington, PA) and bougie. As a result, it was proven that both intubation using even the McGrath video laryngoscope and mask ventilation with insertion of an oral airway and inspiratory pressure up to 40 cmH₂O failed.

Management of intra-operative life-threatening airway compression in these patients should be approached as follows: 1) repositioning of the patient. this should be determined before induction if there is one side or position that causes less symptomatic compression);[14] or 2) rigid bronchoscopy and ventilation distal to the obstruction.[15] Beside these two recommended approaches, in this case, we observed that much higher airway pressures (close to 70 cmH₂O) and longer inspiratory times were effective for adequate mask ventilation. Since an oral airway was inserted and inspiratory airway pressures close to 40 cmH₂O failed, but pressure above 65 cmH₂O was successful, the obstruction was likely located in the trachea. We believe that an obstructed segment of trachea from compression of anterior mass after induction can reopen with high airway pressures. Therefore, such a maneuver should be attempted if the “cannot intubate and cannot ventilate” is encountered.

Regardless of the mechanism of airway obstruction, the high BMI may contribute significantly to her complete airway collapse. Because her BMI was close to 50, reduction of her functional residual capacity was likely profound comparing with non-obese patients. The threshold of an awake trachea intubation for such a patient with an anterior mediastinal mass and with a high BMI should be lower than one with a comparable trachea compression, but not obese. It is also possible that the difficulty of breathing due to trachea compression was masked by her large BMI and this made the history of difficult breathing unreliable. Clinicians may value the trachea compression noted on an image study more than the symptoms of difficult breathing in stratification of the options of trachea intubation. We do not believe that her requirement of very high inspiratory pressure for mask ventilation was due to extremely low respiratory compliance as her compliance was close to normal after trachea was intubated. Therefore, her extremely difficult mask ventilation was due to airway obstruction, which required very high pressure to break up.

In conclusion, complete trachea obstruction can occur from compression of an anterior mediastinal masses after induction of general anesthesia. Lack of difficult breathing in the supine position, when the patient is awake, cannot predict effective mask ventilation after induction of general anesthesia, particularly for obese patients.

Conflict of Interest statement: All of the authors have no conflict interest in the study.

Financial Disclosure statement: All of the authors have no financial disclosure related to this study.

Prior presentations: No presentation of the work at conference meetings.

Acknowledgments: The authors have no conflicting interests with any companies.

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No competing interests reported.

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An anterior cervical and mediastinal mass causes “cannot intubate and cannot ventilate” after induction

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