Chapter 36. Lung Separation in the Patient with a Difficult Airway

A 50-year-old man 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-T11 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: blood pressure (BP) 140/80 mm Hg, heart rate (HR) 69 beats per minute (bpm) and regular, respiratory rate (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 the 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.

36.2.1 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 preoperative medical optimization.

36.2.2 What Anesthetic Technique Is Required?

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

36.2.3 How Can One Lung Ventilation or Lung Separation Be Achieved?

Double lumen tubes (DLT) 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.5-8 The DLT is preferred when lung isolation is required to protect the nondiseased 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.5,9 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 bronchial blocker include the difficult airway, distorted bronchial anatomy, the presence of a tracheostomy, when a nasal intubation is required, and to avoid the need for a tube exchange. 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 Endoblocker, and the Coopdech Endobronchial Blocker.3,5,10-13

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 ug, and rocuronium 50 mg. Bag-mask-ventilation 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.

36.3.1 Is This a Difficult Airway?

The term "difficult airway" has been used when conventional direct laryngoscopy reveals a Cormack/Lehane (C/L) Grade 3 (epiglottis only) or Grade 4 (soft palate only) view.9,14-16 Certainly, tracheal intubation can be more difficult in this clinical setting. 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."17 The other dimensions of airway management (ventilation by extraglottic device and surgical access to the airway) as outlined by Murphy et al must also be considered when estimating the magnitude of airway difficulty.18 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) and increased overall rigidity which impedes optimal shaping of the tubes.14,16 The criteria for difficult DLT insertion have not been well defined.1,2 However, difficulty can be encountered in the presence of a Cormack/Lehane II (partial glottis) view.9

36.3.2 What Are the Options for Airway Management in This Patient?

Mask ventilation has been demonstrated to be easy but direct laryngoscopy 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 the best direct laryngoscopy 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.9 An Eschmann tracheal introducer (bougie) is unlikely to succeed in the presence of a CL Grade 4 view and may produce trauma.

In the patient who has a difficult direct laryngoscopy and who requires lung separation, the airway management options include placement of a single tube (SLT) and utilization of a bronchial blocker, 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 is a function of the available airway management equipment (eg, video laryngoscope), the airway anatomy/geometry, and the expertise of the airway practitioner, as well as the anticipated postoperative clinical course. 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, then placement of a DLT may require a tube change at the end of the case.1,2,9 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 intubation1-3,9,16 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 can be 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 nondiseased 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.1,3,9,16 Video-assisted thoracoscopic surgery (VATS) has also been included as an absolute indication for lung separation.1,16 Other indications for lung separation are relative and are to improve surgical exposure.3,16 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.9

Intubation techniques that can be used as an alternative to DL include flexible bronchoscopic intubation under general anesthesia, intubation using a video laryngoscope (Glidescope, McGrath, Pentax AirwayScope, Bullard, or Stortz VMAC), or intubation through an LMA or ILMA.

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 hypopharynx 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 airway9, and in the elective, predicted difficult airway, is still recommended as the preferred technique.3 However, with the introduction of devices that are proving to be useful in the difficult intubation, protocols are changing9 and video laryngoscopes are challenging bronchoscopy as the first choice for accessing the difficult airway.9,19-21

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.1,22 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.16,23 The rigidity of the DLT also makes it harder to advance the tube over the scope.16

Intubation with an SLT utilizing the Glidescope is widely practiced and is associated with a high degree of success.24 Hernandez and Wong have reported the successful placement of a DLT using the Glidescope.25 Shulman and Connelly used the Bullard laryngoscope in a group of 29 patients scheduled for general anesthesia and lung separation.26 A DLT was successfully passed into the trachea in 28 of the 29 patients using the Bullard laryngoscope. Hirabayashi and Norimasa used the Airtraq laryngoscope to place #35 or #37 DLTs in 10 patients.27 Nine of the 10 patients had a CL Grade 1 to 2 view on DL with a Macintosh blade. Suzuki et al reported the successful intubation of a patient with a #39 DLT using the Pentax AirwayScope with a modified blade.28 Poon and Liu 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.29 Intubation with a DLT using the Bonfils intubation fiberscope30 and Wu scope31 have also been reported.

Retrograde intubation is an option in the clinical scenario presented here if the equipment and expertise are available.32,33

Intubation with an SLT or AEC through an LMA or ILMA is also an option.34 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.35,36 However, placement of DLTs using a lighted stylet under general anesthesia in patients with predictors of difficult DL but without airway pathology has been reported.22,37,38

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.

36.3.3 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.

36.3.4 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.23 The laryngeal and carinal stimulation produced by the DLT requires profound anesthesia of the airway.23 When 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.

36.3.5 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 bronchial blocker passed through the SLT or exchange of the SLT for either a Univent tube or a DLT using an AEC and under visual control utilizing a video laryngoscope.2,9,15,39,40

In the case presented here, it was decided to proceed with the placement of a bronchial blocker 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 post-op ventilation. An Arndt WEB was chosen and placed uneventfully.

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, 8 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.

36.4.1 Should This Patient Be Extubated?

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 BB was deflated and removed but the ETT was left in place. The patient was transported to the intensive care unit (ICU) in stable condition and electively ventilated. Twenty-four hours after the surgery the patient was awake and no longer required ventilatory support.

36.4.2 How Should the Patient Be Extubated at This Point in Time?

Whether the patient should be extubated in the ICU or in the OR is a matter of clinical judgment and to some extent dependent on the expertise and equipment available. Nasopharyngoscopy can be performed to determine the extent, if any, of airway edema, and the presence of an air leak around the tube may be reassuring.

Given the degree of difficulty experienced with the intubation, the patient was transported to the OR for extubation. Extubation was performed over an AEC, being careful to match the numbers on the catheter with the numbers on the SLT. A surgeon skilled in the performance of a surgical airway was present in the room and the equipment required was immediately available. Extubation was uneventful.

36.5.1 If the SLT Had Been Exchanged for a DLT after Induction, How Should This Be Done?

Tube exchange should be done utilizing an AEC and under visual control.2,3,15,41 If the glottis cannot be visualized by DL, then a video laryngoscope such as the Glidescope, McGrath, Pentax, or Stortz VMAC can be used.2,15 The AEC should be introduced no further than 24 to 26 cm from the teeth or lips in order to minimize the risk of trauma to the distal trachea and bronchi.3,9,15 The AEC should be at least 70 cm in length in order to permit control of the proximal end of the catheter with the DLT ensleeved.9 Utilization of an AEC at least 83 cm in length has also been recommended for a DLT exchange.15

36.5.2 If a DLT Had Been Used for Lung Separation, What Should the Appropriate Airway Management Have Been at the End of the Case? Can the Patient Go to ICU with a DLT in Place?

Intubation was difficult at the start of the case. Given the extent and duration of the surgery and the evidence of airway edema, exchange of the DLT for an SLT at the end of the case could be a highly dangerous maneuver.3 The view of the glottis was suboptimal with the Glidescope at induction and the angle into the larynx difficult to negotiate. The options then, are to leave the DLT in place, or perform a tracheotomy. If it is anticipated that the airway edema will recede in the immediate postoperative period and that prolonged ventilatory support will not be required, tracheotomy is not necessary at this time. Given the intraoperative course, placement of a BB through the SLT was a good decision and avoided the consideration of a potentially risky tube change at the end of the case.

A DLT can be used in the critical care setting for one lung ventilation or for postoperative two lung ventilation, if tube change to an SLT is considered to be too risky.9 However, ICU staff are generally less experienced in the management of a DLT16 and most ICU nurses are not comfortable with DLTs.1 If the DLT is left in an endobronchial position, malposition can occur and it has been recommended that in this setting neuromuscular blockade be employed.16 Alternatively, the DLT can be withdrawn such that the endobronchial lumen is above the carina and both lungs ventilated with both lumens with the bronchial cuff deflated.9 Suction is also more difficult through a DLT and secretions can be problematic.16

In the postoperative setting, extubation directly from the DLT can be performed when the condition of the upper airway and ventilatory function are satisfactory. If more prolonged but short-term ventilatory support is anticipated, tube exchange to an SLT can be performed when the upper airway is favorable. If longer-term ventilation is anticipated, tracheotomy without a tube change may be more appropriate.

36.5.3 What Would Have Been Appropriate Airway Management If the Surgery Had Been an Emergency and Could Not Be Postponed?

Intubation had failed by DL, Glidescope, flexible bronchoscope, and via the ILMA. The expertise to perform a retrograde intubation was not available and the likelihood of success was uncertain given the airway pathology. If the neurologic deficit had been acute, then a tracheotomy could have been performed under general anesthesia with the patient ventilated via the ILMA. A bronchial blocker could then be passed through an armored ETT or conventional tracheotomy cannula inserted into the tracheotomy stoma.9,15,42,43 If a wire-reinforced ETT is used, this can be changed for a tracheotomy cannula at the end of the case. A conventional DLT can be inserted through a tracheotomy stoma, or a DLT modified for use in tracheostomized patients (eg, Tracheopart or Naruke tube) can also be used.3,15,43-47 A conventional DLT placed through a tracheotomy stoma has been said to be prone to malposition15 as it is too long relative to the shortened upper airway and the tracheal cuff may be proximal to the stoma.16 Cohen has recommended that a rigid large diameter DLT not be passed through an old tracheotomy stoma.1 The Univent tube has also been inserted through a tracheotomy stoma to achieve one lung ventilation.48,49

36.5.4 If a "Cannot Intubate, Cannot Ventilate" Situation Had Occurred at Induction, What Would Have Been the Appropriate Management?

If ventilation by mask or extraglottic device had become impossible during the failed intubation attempts, emergency cricothyrotomy would have been indicated.3

The patient made an uneventful recovery. The diagnosis of lingual tonsillar hyperplasia (see Chapter 37) was subsequently confirmed by an ear, nose, and throat consultant. No treatment was required.

Lung separation can be achieved using a DLT, the Univent tube, or a bronchial blocker placed through an SLT. In the setting of a difficult airway, the decision to use a particular device must take into consideration the airway anatomy and geometry, the expertise and equipment available, and the anticipated postoperative clinical course. Airway management decisions will depend on whether the difficulty is predicted or unpredicted and whether the surgery is elective or emergency. In the management of the difficult airway, the first priority is to ensure adequate oxygenation and ventilation; one lung ventilation becomes a secondary objective.3