A 50-year-old male presents with a 6-month history of progressive paraparesis. He had sustained a fall at work about 12 months ago and has complained of back pain since that time. He also complains of difficulty with urination and constipation over the past several weeks. Magnetic resonance imaging (MRI) reveals disc herniation at T10-11 and spinal cord compression. He has been scheduled for T11 vertebrectomy, spinal cord decompression, and spinal instrumentation via a left thoracotomy. He is otherwise healthy. His medications include acetaminophen, and dexamethasone which has recently been added.

On examination, he is 173 cm (5 ft 8 in) tall and weighs 77 kg (170 lb). His vital signs are: BP 140/80 mm Hg, HR 69 beats per minute and regular, RR 16 breaths per minute, temperature 36.9°C, and oxygen saturation is 99% on room air. Examination of the lower extremities reveals 3/5 motor power in the left leg and 5/5 in the right leg. Sensation is altered below T11. The chest is clear to auscultation and heart sounds are normal.

Airway examination reveals a Mallampati II classification, thyromental distance of 5 cm, mouth opening of 5 cm, mandibular mobility of 2 cm, normal cervical spine extension, and full dentition.

Is This Patient Fit for Anesthesia?

The patient has spinal cord compression with slowly progressive neurologic symptoms and requires surgery. He has no significant comorbidities and needs no additional preoperative medical optimization.

What Anesthetic Technique Is Required?

General anesthesia is required. Lung separation has been requested by the surgeon to optimize the surgical exposure.

How Can One Lung Ventilation or Lung Separation be Achieved?

Double lumen tubes (DLTs) have been considered to be the gold standard for lung separation.^1–4 However, recently introduced bronchial blockers (BBs) have been shown to provide equivalent surgical exposure when compared to the DLT.^5–13 A DLT is preferred over BBs when lung isolation is required to protect the non-diseased lung from contamination with blood or pus, in the presence of a bronchopleural or bronchopleural cutaneous fistula, and to perform unilateral pulmonary lavage.¹ A contralateral DLT is preferred when a sleeve resection, or lung transplant is performed.^5,14 However, there are many clinical situations in which a DLT may not be the best primary choice.² The indications for the use of a BB include the difficult airway, the patient already intubated, distorted bronchial anatomy, small adults or young children, the presence of a tracheotomy, when nasal intubation or lobar blockade is required, and to avoid the need for a tube exchange.^1,3 Currently available BBs include the Univent Torque Control Blocker, the Arndt Wire-Guided Endobronchial Blocker, the Cohen Flexitip Endobronchial Blocker, the Fuji Uniblocker, the HS (Hospital Service) Endoblocker, the Coopdech Endobronchial Blocker,^{3,5,12,15–23} and the EZ-Blocker.^9,10,11,24

One lung ventilation using a DLT is planned.

In the operating room (OR), basic monitors are applied and a left radial arterial catheter is placed under local anesthesia. Following denitrogenation, general anesthesia is induced with propofol 175 mg, sufentanil 15 µg, and rocuronium 50 mg. Bag-mask-ventilation (BMV) is easily performed. Direct laryngoscopy (DL) with a #4 Macintosh blade reveals a Grade 4 Cormack–Lehane view (soft palate only). Cystic tissue is noted to be present at the posterior aspect of the tongue.

Is This a “Difficult Airway”?

The term “Difficult Airway” has been used when conventional DL reveals a Cormack–Lehane (CL) Grade 3 (epiglottis only) or Grade 4 (soft palate only) view.^14,25–27 Tracheal intubation by DL can certainly be more difficult in the presence of CL 3 or 4 direct laryngoscopic view and this clinical setting may be more appropriately defined as a “difficult intubation.” The ASA Task Force on Management of the Difficult Airway defines difficult airway as the clinical situation in which a conventionally trained anesthesiologist experiences difficulty with face-mask ventilation, endotracheal intubation, or both.²⁸ The difficult airway can also be defined as one in which an experienced practitioner anticipates or encounters difficulty with any or all of face-mask ventilation, direct or indirect (e.g., video) laryngoscopy, tracheal intubation, extraglottic device (EGD) use, or surgical airway.²⁹ Contextual issues such as anticipated safe apnea time, aspiration risk, presence of obstructing pathology, availability of skilled help and clinical inexperience can also contribute to the degree of difficulty.³⁰ DLTs and the Univent tube have been termed “difficult tubes” as they can be more difficult to insert due to their increased outside diameter (OD), shape, lack of a bevel at the tip, and increased overall rigidity which impedes optimal shaping of the tubes.^5,25,27 The criteria for difficult DLT insertion have not been well defined.^1,2 However, difficulty can be encountered in the presence of a CL II (partial glottis) view¹⁴ and it has been shown that placement of a DLT may be challenging in an airway that can be easily intubated with a single lumen tube (SLT).² The Univent is an SLT with an enclosed channel along its concave (anterior) aspect which contains a movable BB.^31,32 The OD of the Univent is relatively large as compared to a conventional polyvinyl chloride SLT and it has increased stiffness.^3,32 It can be problematic to insert in the setting of a difficult intubation.³

What Are the Options for Airway Management in This Patient?

Mask ventilation has been demonstrated to be easy but DL is difficult. The patient’s position should have been optimal before induction. If not, then it should be optimized. Head lift and external laryngeal manipulation should be considered part of best DL technique. A blade change can be considered if it is anticipated that a specific anatomic problem can be overcome. Placement of a DLT is best accomplished with a curved blade as it leaves more space in the pharynx through which to pass the relatively bulky DLT.¹⁴ An Eschmann Tracheal Introducer (ETI, commonly known as “bougie”) is unlikely to succeed in the presence of a CL Grade 4 view and may produce trauma.

When a patient with a difficult direct laryngoscopy requires lung separation, airway management options include: placement of an SLT and utilization of a BB; placement of a Univent tube; or placement of a DLT. The decision to use an SLT as opposed to a Univent or a DLT is based on the degree of difficulty anticipated with the more difficult tube, which in turn is a function of the available airway management equipment such as video-laryngoscopes, the airway anatomy/geometry, and the expertise of the airway practitioner. In addition, the anticipated post-operative clinical course must be considered. If postoperative ventilation is possible or probable based on the length and extent or type of surgery, anticipated fluid shifts and transfusion requirements, hemodynamic stability, or marginal respiratory reserve, placement of a DLT may require a tube changer at the end of the case.^1,2,14 Exchange of a DLT for an SLT at the end of the case is not without risk.² Edema, secretions, and trauma from the initial intubation^1,2,3,14,27 may make reintubation at the end of surgery more difficult. Optimal positioning for intubation at the end of surgery may also be more difficult to achieve. Reintubation at the end of surgery may be extremely difficult and a highly dangerous maneuver³ with potential loss of airway control.¹ Aspiration and airway trauma can also occur.¹

The decision to proceed with intubation with an SLT, a Univent, or a DLT is a matter of clinical judgment, taking into consideration the technical and airway anatomical issues as well as the anticipated clinical course. The requirement for lung separation must also be evaluated. The absolute indications for lung separation include massive bleeding or abscess in which the non-diseased lung must be protected from contamination, unilateral air leak from bronchopleural or bronchopleural cutaneous fistula, or unilateral pulmonary lavage for alveolar proteinosis or cystic fibrosis.^1,3,14,27 Video-assisted thoracoscopic surgery (VATS) has also been included as an absolute indication for lung separation.^1,27 Other indications for lung separation are relative and are to improve surgical exposure.^3,27 Although many surgical procedures are more easily performed with the lung collapsed, if placement of a DLT or BB is problematic, the need for lung separation as well as the safety of the technique must be considered.¹⁴

Intubation techniques that can be used as an alternative to DL include flexible bronchoscopic intubation under general anesthesia, intubation using a video-laryngoscope, or intubation through an EGD. Intubation of the unconscious patient using the flexible bronchoscope is a widely accepted technique. Jaw thrust and tongue traction can be used to open the pharynx and facilitate passage of the scope. Minimizing the discrepancy between the OD of the bronchoscope and the internal diameter (ID) of the ensleeved endotracheal tube (ETT) will minimize the risk that the tube will meet obstruction as it is passed through the larynx into the trachea over the scope.

In the setting of predicted difficult DL, awake flexible bronchoscopic intubation has historically been considered to be the safest means to secure the airway¹⁴ and is still recommended as the preferred technique in the elective setting.³ However, with the introduction of devices that are proving to be useful in the difficult intubation, protocols are changing¹⁴ and video-laryngoscopes are challenging bronchoscopy as the first choice for accessing the difficult airway.^14,33–35

Flexible bronchoscopic intubation using a Univent tube can be more difficult than with a conventional ETT due to the fixed concavity of the Univent as well as its larger OD.^1,36 When performing a flexible bronchoscopic intubation with a DLT, the length of the tube relative to the length of the shaft of the scope limits the maneuverability of the scope.^27,37 The rigidity of the DLT also makes it harder to advance the tube over the scope, though it can be done (see section “Can Awake Flexible Bronchoscopic Intubation be Done with a DLT?” in this chapter).²⁷

Intubation with an SLT utilizing a video-laryngoscope, such as the GlideScope^®, is widely practiced in the setting of a predicted difficult intubation and is associated with a high degree of success.^38,39 In 2005, Hernandez and Wong⁴⁰ reported the successful placement of a DLT using the GlideScope in a patient with anticipated difficult airway. Bustamante et al.⁴¹ subsequently reported the successful placement of DLTs in a dozen patients with anticipated and unanticipated difficult DL using the GlideScope. The authors suggested that the distal aspect of the DLT be pre-curved to about 60 degrees, the stylet be removed when the glottis was engaged, and then the tube rotated 180 degrees to cannulate the trachea. In 2012, Bussieres et al.⁴² described the use of a customized GlideRite DLT Stylet to facilitate DLT placement using the GlideScope. The device was used successfully in 50 patients without a predicted difficult intubation and in “more than 15 patients” with anticipated or proven difficult intubation.⁴² In 2012, Hsu et al.⁴³ compared the GlideScope and the Macintosh laryngoscope for DLT insertion in a randomized controlled trial which included 60 patients without difficult intubation predictors. All intubations were performed by two anesthesiologists who had previously performed at least 300 tracheal intubations with each device. There was no difference in the first attempt success rate between the groups and the authors concluded that intubation was easier using the GlideScope.⁴³ In 2013, Russell et al.⁴⁴ reported a randomized controlled trial which compared the GlideScope and the Macintosh laryngoscope for DLT intubation in 70 patients with no predictors of difficult laryngoscopy. The majority of the anesthetists who took part in the study had limited experience with the GlideScope for DLT insertion. All 35 patients in the Macintosh group were successfully intubated within two attempts, whereas in the GlideScope group, 29 patients were intubated on the first attempt with the GlideScope and three on a second attempt. In the remaining three patients, the Macintosh laryngoscope was used for the second attempt and was successful. The investigators encountered difficulty with tube delivery and advancement into the trachea. They concluded that the GlideScope was more difficult to use than the Macintosh for DLT intubation.⁴⁴ Failure of DLT intubation using the GlideScope has also been reported.⁴⁵ Shulman and Connelly⁴⁶ used the Bullard laryngoscope in a group of 29 patients scheduled for general anesthesia and lung separation. A DLT was successfully passed into the trachea in 28 of the 29 patients. Hirabayashi and Seo⁴⁷ used the Airtraq laryngoscope to place #35 or 37 DLTs in 10 patients. Nine of the 10 patients had a CL Grade 1 to 2 view on DL with a Macintosh blade. Suzuki et al.⁴⁸ reported the successful intubation of a patient with a #39 DLT using the Pentax AirwayScope with a modified blade. Poon and Liu⁴⁹ used the AirwayScope to place an airway exchange catheter (AEC) into the trachea and then railroaded a #37 DLT over the catheter under visual control using the scope. Intubation with a DLT using the Bonfils Intubation Fiberscope,⁵⁰ the Wu scope,⁵¹ the CEL-100 video-laryngoscope (Connell Energy Technology Co. Ltd., Shanghai, China),⁵² and the X-Lite (Rusch Tuttlingen, Allemagne)⁵³ have also been reported.

Retrograde intubation is an option in the clinical scenario presented here if the equipment and expertise are available.^54,55 Intubation with an SLT or AEC through a Laryngeal Mask Airway (LMA) or an Intubating Mask Airway (ILMA) is also an option.⁵⁶

Intubation by transillumination utilizing a lighted stylet is a nonvisual technique and is not recommended in the presence of pharyngeal masses or anatomic abnormalities of the upper airway.^57,58 However, successful placement of DLTs using a lighted stylet under general anesthesia in patients with predictors of difficult DL but without airway pathology has been reported.^36,59,60

In the case presented here, a flexible bronchoscopic intubation under general anesthesia was attempted but the vocal cords could not be visualized. The glottis was visualized with the GlideScope but the larynx was noted to be “extremely anterior” and neither a “bougie” nor an ETT could be passed through the glottis because of the acute angle that needed to be negotiated up into the larynx. An ILMA was placed and satisfactory ventilation was achieved. The flexible bronchoscope was passed through the ILMA but the vocal cords could not be identified. The patient was ventilated through the ILMA until the muscle relaxation could be reversed and then awakened.

What Should be the Next Steps in This Patient’s Management?

The patient requires urgent surgery. He was transported to the post-anesthesia care unit (PACU) for a period of observation. An explanation of the airway difficulty was provided to the patient, an antisialogogue was administered, and the patient was returned to the OR about 2 hours later for an awake flexible bronchoscopic intubation.

Awake flexible bronchoscopic intubation using an adult bronchoscope and an 8.5-mm ID SLT was performed under topical anesthesia (see Chapter 3). A remifentanil infusion was used to attenuate airway reflexes. The awake intubation was uneventful and was followed by the controlled induction of general anesthesia.

Can Awake Flexible Bronchoscopic Intubation be Done with a DLT?

Successful awake flexible bronchoscopic intubation with a DLT has been reported by Patane et al.³⁷ The laryngeal and carinal stimulation produced by the DLT can be intense and profound anesthesia of the airway is required.^4,37 When the bronchial lumen of a DLT is ensleeved over the bronchoscope, only a short segment of the insertion cord of the scope remains outside the tube and maneuverability is therefore limited.^27,37 Once the DLT has been placed in the trachea, general anesthesia can also be induced before advancing the DLT into the mainstem bronchus under flexible bronchoscopic control. Since modern BBs have become available, awake flexible bronchoscopic intubation with a DLT or Univent is rarely performed.⁶¹

What Are the Options for Lung Separation in This Case Now That an SLT Has Been Placed?

The options for one lung ventilation include use of a BB passed through the SLT or exchange of the SLT for either a Univent tube or a DLT using an AEC under visual control utilizing a video-laryngoscope.^2,14,26,45

In the case presented, it was decided to proceed with the placement of a BB and not to exchange the SLT for a DLT. This decision was based on the degree of difficulty anticipated with the tube change and the risk associated with this maneuver, as well as the possibility of the requirement for postoperative ventilatory support. A Fuji Uniblocker (Fuji Systems, Tokyo) was chosen and placed uneventfully in the left mainstem bronchus. The cuff was inflated under bronchoscopic control.

The choice of BB is largely a matter of personal preference. The Fuji Uniblocker is made of silicone,⁵ is 66.5 cm long, has an angled tip, and a spherical high-volume low-pressure cuff (cuff volume of 5–8 mL).³ The adult blocker is 9 Fr and has a 2 mm lumen.³ It is maneuvered by rotation in a similar manner to a bougie. Narayanaswamy et al.⁸ compared the Arndt wire-guided BB (Cook Critical care, Bloomington, IN), the Cohen Flexitip BB (Cook Critical care, Bloomington, IN), the Fuji Uniblocker, and the left DLT (Mallinckrodt Medical, Cornamaddy, Athlone, Westmeath, Ireland) in a randomized trial that included 104 patients undergoing left video or open thoracotomy. The three BBs provided surgical exposure equivalent to the left DLT, although the blockers required more time to position and required intraoperative repositioning more often.⁸ In a randomized trial that compared the Coopdech blocker, the Arndt, the Univent tube, and the left DLT, Zhong et al.¹² reported that surgical exposure was similar among the groups. The first clinical use of a new BB, the EZ-Blocker (AnaesthetIQ, Rotterdam, The Netherlands), was reported in 2010 by Mungroop et al.²⁴ The blocker has a 4 cm bifurcated tip each limb of which is fitted with a cuff. The blocker is positioned with one cuff in each mainstem bronchus and the cuff on the side to be blocked inflated. Lung collapse using the EZ-Blocker has been shown to be equivalent to that achieved with a DLT^9,11 and the Cohen BB.¹⁰

The surgical procedure required 8 hours to complete. The estimated blood loss was 8000 mL. Eleven units of packed red blood cells, 1500 mL of plasma, eight units of platelets, 6000 mL of crystalloid, and 1500 mL of colloid were administered. At the end of the case, edema of the face and tongue was evident.

Should This Patient be Extubated?

Airway edema can occur as a result of fluid resuscitation and trauma associated with the initial intubation. The presence of airway edema will almost certainly make reintubation conditions even less favorable than they were at the beginning of the case. In addition, the patient has undergone an extensive surgical procedure and the risk of respiratory failure in the immediate postoperative period is significant. The placement of an epidural catheter for postoperative analgesia was not done on consideration of the preexisting neurological deficit and the planned spinal surgery. Placement of a paravertebral catheter could have been considered as an alternative.