35.5.1 Can Intubation Be Performed in the Lateral Position?
While transfer of the patient to the supine position would be ideal, it could be difficult to achieve in a timely manner and is not without considerable risk to the patient depending on the situation. Therefore, it is desirable to have several alternative approaches for reestablishing tracheal intubation in this particularly difficult situation.
If it is feasible to place the patient in a lateral position, the left lateral decubitus is preferred by some practitioners for laryngoscopy and intubation, as gravity will help to displace the tongue to the left and facilitate visualization of the glottis.1 However, others prefer the right lateral decubitus position as in this position, the operator's left arm has more room to maneuver during the procedure. The tongue can still be easily displaced by the laryngoscope in the right lateral decubitus position. Nathanson et al found tracheal intubation of a manikin in the lateral position to be more difficult than in the supine position.12 The ease of intubation increased with each subsequent attempt, indicating that operator experience was a confounding factor.12 An assistant may be necessary to stabilize the head, neck, and body while performing an intubation in a patient in the lateral decubitus position.
Blind endotracheal intubation techniques using the intubating LMA (Fastrach™, LMA North America, San Diego) and the lighted stylet have also been described with a patient in the lateral position.13-15 Experience with these intubation techniques will improve the operator's chance of success. Blind techniques should only be attempted after direct visualization techniques have failed, as anatomic distortion may be present.
35.5.2 What Are the Options for Tracheal Intubation in the Prone Position?
Reintubation while the patient is still in the prone position would eliminate the inherent risks associated with turning the patient. In addition to direct laryngoscopic intubation, alternative intubating techniques can be considered. These include the use of a flexible bronchoscope (FB), an intubating LMA (LMA Fastrach™, LMA North America Inc, San Diego, CA), light-guided intubation using the Trachlight™ (Laerdal Medical Corp., Wappingers Falls, New York), and digital intubation. However, there is limited clinical information with regard to the effectiveness and safety of these techniques in patients in the prone position.
Baer performed endotracheal intubation under direct laryngoscopy in the prone position in 200 patients undergoing lumbar surgery.16 Two failed intubations occurred and these patients were then intubated in the lateral or supine positions, with difficulty.16 This experience emphasizes the importance of airway assessment and management in the supine position when difficulty is predicted. We believe that tracheal intubation of patients in the prone position should be reserved for rescue situations and that elective intubation of patients requiring prone positioning should be performed in the supine position as this is most familiar to the airway practitioner.
Intubation in the prone position may be necessary if:
Ventilation and oxygenation are ineffective using BMV, the LMA, or the Combitube™.
Ventilation using BMV, the LMA, or the Combitube™ is adequate but a definitive airway is desired (eg, prolonged case, risk of aspiration).
Transfer of the patient to the supine position is impossible, or associated with extreme risk.
35.5.3 How Can Endotracheal Intubation Be Performed in the Prone Position in the Patient Presented Here?
Airway control in this case scenario can be reestablished by one of several techniques.
An intact ETT can be reinserted into the trachea by simple advancement, as long as the tip of the ETT is still in the glottis. This can be facilitated if a throat pack had been placed following the initial intubation. The ability to ventilate the patient through the ETT confirmed by the presence of an appropriate end-tidal CO2 waveform indicates that simple advancement of the tube may be all that is required. If ventilation through the ETT is difficult, it may still be possible to advance the ETT into the trachea with the aid of a lighted stylet, FB, or a tube exchanger. When using a tube exchanger (airway exchange catheter), the intratracheal location of the tube exchanger should be verified by flexible bronchoscopy or by detecting an appropriate end-tidal CO2 waveform when ventilating through the tube exchanger.
The tracheal tube should be replaced if there is evidence of tube damage and a significant leak exists. Small air leaks may be overcome by increasing inspired gas flow, if the remaining surgical time is short. The benefits of continuing the case without further airway manipulation must be weighed against potential further airway compromise and operating room contamination with anesthetic gases. Therefore, the anesthetic technique should be changed to TIVA, if required, should the anesthesia practitioner decide to proceed with the case in the presence of a small ETT leak. Larger leaks can be attenuated by the insertion of a throat pack, if not already present. If a throat pack was in place around the original ETT, it may be possible to pass a new ETT with a deflated cuff into the trachea through the cast (or track) made by the throat pack or it may be possible to change the tube over an airway exchange catheter. If these measures fail and airway control is lost, the throat pack should be removed if present and ventilation of the patient must be reestablished as soon as possible.
Tracheal intubation by direct laryngoscopy can be performed in the prone patient by the airway practitioner who is positioned at the head of the patient facing caudad and who uses the right hand to insert the laryngoscope into the pharynx and exposes the glottis (Figure 35-1). Operating the laryngoscope with the right hand while the practitioner faces the prone patient allows the laryngoscope blade to displace the tongue in the usual manner—away from the right side of the patient's mouth. The practitioner then uses the left hand to insert the ETT into the trachea. Alternately, direct laryngoscopy and intubation can be performed in a more conventional manner from either side of the patient (Figure 35-2). An assistant can turn the patient's head to the right and elevate the right shoulder slightly to facilitate access to the mouth. The head and neck can also be placed in the familiar sniffing position. This technique of laryngoscopic intubation in prone patients has been shown to be effective (99% success rate) and safe.16
Laryngoscopic intubation of a manikin placed in the prone position: Laryngoscopic intubation can be performed from the front of the manikin with the right hand holding the laryngoscope. The inset shows the laryngoscopic view of this technique. The vocal cords (VC) and the arytenoid cartilages (AC) can be visualized easily.
Laryngoscopic intubation of a manikin placed in the prone position: Laryngoscopic intubation can also be performed from the side (right) of the manikin. The inset shows the laryngoscopic view of this technique. The vocal cords (VC) and the epiglottis (EG) can be visualized easily.
Agrawal et al17 described the successful use of the ILMA for tracheal intubation in a patient in the prone position who presented with injuries precluding supine positioning. The ILMA can also provide a conduit through which an ETT can be advanced into the trachea blindly, or with the aid of a lightwand, or the flexible bronchoscope (see Chapter 12). However, insertion of an intubating LMA (as compared to the LMA Classic™) can be difficult in the prone position. Alternatively, a 7.0 mm ETT could be passed through a classic LMA with FB guidance if the "aperture bars" are removed to allow easier passage of the ETT through the opening in the LMA.
35.5.4 Upon Turning the Patient into the Supine Position, Bag-Mask-Ventilation Is Easy, But Direct Laryngoscopy Reveals a Grade 3 View. What Is the Appropriate Airway Management?
A previously easy intubation may be difficult upon returning the patient to the supine position. Anatomic distortion of the airway can occur due to factors inherent to the surgical procedure, to the prone position, to trauma during the initial intubation, or to dislodgement of the ETT. Cervical vertebral fixation and surgical manipulation of oropharyngeal and neck tissues can alter airway anatomy. Bleeding into the airway and hematoma formation can be associated with neck surgery. Prolonged surgical procedures with significant blood loss may be associated with generalized edema due to fluid resuscitation. Direct pressure on facial and neck structures and a dependent position compromise venous drainage and contribute to edema formation. Airway edema can alter the appearance of laryngeal structures and can make visualization of the larynx difficult.18-20 Edematous tissues may also be more easily traumatized.
In this case scenario, the patient was placed in the supine position and direct laryngoscopy revealed a Grade 3 laryngoscopic view. The application of BURP21 may improve the Cormack/Lehane view.22 If BURP does not improve the view of the glottis, alternative intubating techniques can be used, as long as effective ventilation and oxygenation can be provided by BMV. These techniques include the use of an Eschmann Introducer, lightwand (Trachlight™), intubating LMA, Glidescope™ (Keomed, Minnetonka, MN), Bullard laryngoscope, or FB. As each intubation attempt will likely decrease the chance of success on subsequent attempts, it is critical that the practitioner employs the technique with which he/she is most experienced. In general, in the presence of an abnormal upper airway (edema), tracheal intubation should be performed under direct or indirect vision, if at all possible. Use of the Eschmann Introducer can be considered to be a logical extension of direct laryngoscopy and has a high success rate in the presence of a Grade 3 view.23 It is also helpful to use a smaller ETT and lubricate the inside and outside of the ETT to minimize the resistance to passage through the larynx and assist in passing the ETT over the introducer.
If a visual technique is unsuccessful but BMV is adequate, nonvisual intubation techniques may be used with great caution, while preparing the patient for a surgical airway.
The lightwand is an invaluable tool for airway management, but its utility in obese patients is limited. Furthermore, in this case scenario, the failed laryngoscopic intubation is probably secondary to airway edema and/or trauma. The use of a nonvisual intubating technique, such as the lightwand, would therefore likely be unsuccessful in this setting.
For the patient in this case scenario, BURP did not improve the glottic view (Cormack/Lehane Grade 3 view) and passage of an Eschmann Introducer was unsuccessful. Subsequent use of the Glidescope™ (Keomed, Minnetonka, MN) with a styletted endotracheal tube resulted in successful intubation and rest of the case proceeded uneventfully.