June 1, 2011
by Naveen Eipe, MBBS, MD (Anesthesiology) and Taylor McGuire, DDS, MSc, FRCD(C), Dip. ABOMS
INTRODUCTIONAirway management for maxillofacial trauma is often complicated by distortion of the airway from the injury, emergent management for impending compromise, and other serious co-existing injuries. While traditionally the use of nasal intubations and tracheostomies are preferred, we discuss the use of retromolar and submental intubation techniques as alternative airway management strategies. Additionally, we will also discuss simple innovations with nasal airways that are specifically designed to aid fiberoptic intubation.
RETROMOLAR INTUBATIONSurgical treatment in maxillofacial injuries often requires reduction and stabilization of maxillary and mandibular fractures by placing the patient’s teeth in proper occlusion. The presence of an oral (tracheal) tube significantly impedes this wiring of the jaw and therefore Inter- Maxillary Fixation (IMF) precludes conventional oro-tracheal intubation. Martinez1 first described retromolar route for intubation in 1998 as an alternative to conventional airway management techniques in maxillofacial trauma. In retromolar intubation, the orotracheal tube is positioned behind the last molar so that it rests in the retromolar space. Adequacy of retromolar area for this tracheal tube accommodation can be judged preoperatively by asking the awake patient to close his or her mouth slowly while an alternative tracheal tube is placed in the retromolar space. In most patients this should not interfere with dental occlusion and or cause crushing of the tube.
To perform retromolar intubation as a technique of tube fixation, first anesthesia is induced appropriately and then tracheal intubation is carried out with a reinforced tube by suitable technique. After satisfactory ventilation is confirmed, the reinforced tracheal tube is moved laterally along the gingivo- buccal sulcus into the vestibule of the mouth. It is then secured beyond the last molar tooth into the retromolar trigone and fixed between the molars with the help of an interdental wire or suture ligature. After this, once again satisfactory ventilation is reconfirmed both with and without simulated dental occlusion, surgery can then proceed. After completion of IMF, tracheal extubation may be performed from the retromolar space. When compared to nasal intubation, this technique of retromolar placement of orotracheal tube is easier to perform, less traumatic and requires less time. With limited retromolar space as the only relative contraindication to this technique, this can be performed in children. This technique can be considered in selected cases of maxillofacial trauma and for cleft surgery specifically to avoid nasal intubations.2
Retromolar intubation can be performed as a technique of tracheal intubation with a retromolar scope-the Bonfils. The Bonfils is a 40cm long, semi-rigid optical stylet with an external diameter of 5.0mm and a fixed anterior tip curvature of 40 degrees and can accommodate 6.5mm endotracheal tubes or larger. The eyepiece can also be converted to project the image onto a remote monitor to provide better visualization and enhance teaching.3 There is an adaptor “slide cone” for fixation of the endotracheal tube. This adaptor has a side port that allows oxygen insufflation or instillation of local anesthetic. The Bonfils has been successfully used to intubate patients with normal airways, as well as patients with difficult airways (expected or unexpected), including those who failed direct laryngoscopic intubation. It may also useful in patients with limited neck mobility, patients with cervical spine injuries and for those with limited mouth opening due to reflexive trismus from maxillofacial injuries.
SUBMENTAL INTUBATION Hernandez-Altemir4 first described submental tracheal intubation in 1986, specifically to avoid tracheostomy in maxillofacial trauma cases. This method has now become widely established for airway management in adults with midfacial fractures especially when long term ventilation is not anticipated. Advantage of this route is that while it avoids potential complications associated with nasal intubation and tracheostomy, it allows an unobstructed surgical field for adequate reduction and fixation of midfacial, panfacial or combined nasal, maxillary and mandibular fractures. Submental intubation is also indicated in non-trauma patients-in those undergoing elective orthognathic surgeries where mandibular advancement and rhinoplasty are done together or in cleft lip & palate patients undergoing complex rotational flaps.
To perform this technique, the trachea is intubated orally with armored tracheal tube. An important consideration for the selection of these tubes is that they should have a detachable universal (15mm machine-end) connector and this may not be possible with all reinforced tubes]. Aseptic preparation of the skin of the neck, lower face and end of the tube is done. A 1.5cm skin incision is made in submental region, just medial to the lower border of mandible, approximately one third of the way from symphysis to the angle of mandible. Avoiding the digastric triangle prevents damage to the facial vessels, sublingual glands and hypoglossal and lingual nerve. A medium size hemostat is introduced through submental incision and pierces the floor of the mouth cephalad through the myelohyoid muscle, where the intraoral incision is made. It should emerge anterior to the opening of the submandibular duct. The pilot balloon is deflated and taken through the submental incision and then re-inflated. The tip of the artery forceps is re-inserted through the submental incision and after the universal connector of the tube is disconnected and the tube is passed through the submental incision. The universal connector is reattached and satisfactory ventilation is ensured. The tube is then secure to the skin with sutures. After completion of the operation, tube is again disconnected from breathing circuit; pilot cuff is pulled back in the oral cavity followed by endotracheal tube. Tube is again connected to the breathing circuit and the anesthetic and surgery can proceed (Fig. 1).
During the procedure, the tube may kink in the floor of the mouth. Therefore, reinforced tubes have to be been used. The tube may migrate (endobronchial intubation or tracheal extubation) with jaw movements. It should be secured to the skin with suitable sutures. It may be useful to maintain spontaneous respiration during both the transfer to the tube out and back in. The ability to remove the connector from the tube and passage of the pilot balloon before the tube is important. Submental intubation is a simple surgical airway technique associated with a low morbidity and has been used for a variety of craniofacial surgeries.5 Adequate mouth opening is a prerequisite requirement for this procedure. Complications of the submental intubation are infrequent and include: superficial infection of the submental wound, orocutaneous fistula, abscess formation and hypertrophic scarring. But if prolonged surgery, postoperative ventilation or the requirement for prolonged access to the airway is anticipated then a preoperative tracheostomy may be considered.
MODIFICATIONS OF NASAL AIRWAYS-MODIFIED NASAL TRUMPET (MNT) AND SPLIT NASO-PHARYNGEAL AIRWAY (SNPA)
Modified Nasal Trumpet (MNT)A modified nasal trumpet (MNT) is prepared by inserting a 15mm universal connector tracheal tube (from a 7.0mmID or 8.0mmID) into the flanged end of a nasal airway (adult sizes from 28 to 34Fr). These can be softened by placing in warm water and lubricated with lidocaine or EMLA gel prior to insertion into the nares. The purpose of the universal connector is to allow for the connection of the nasopharyngeal airway to the anesthetic breathing circuit (or Ambu Bag). We usually use this in spontaneously breathing patients, where the volumetric measurements and capnographic monitoring of ventilation are possible. The use of the MNT for assisted and
controlled ventilation has also been described.6
The MNT is useful in difficult airway management as it can be used for simultaneous uninterrupted oxygen delivery and fiberoptic oral or nasal intubation while also allowing for oropharyngeal suctioning (simulated in Fig. 2). This is a useful adjunct in the obese, patients with OSA and others sedated under regional anesthesia. We have found this invaluable in the post anesthetic care unit for patients recovering from anesthesia after dental and maxillofacial surgery patients. We recommend that all patients with their jaws wired (IMF), should have a MNT while they are being monitored in the early postoperative period.
Split Naso- Pharyngeal Airway (SNPA)The Split Naso-Pharyngeal Airway (SNPA) is another innovative modification of the nasal airway that was first described to facilitate atraumatic naso-gastric tube placement7. We have used it specifically to aid nasal fiberoptic intubation. This is created by cutting the soft rubber nasal airway of appropriate size longitudinally. We suggest that the split be performed spirally as cutting it straight through tends to make the SNPA collapse in the nasopharynx.
If the SNPA is adequately prepared (warm, soft and lubricated with local anesthetic gel), it allows for nasal fiberoptic endoscopy to be performed with little distress to the patient. It requires a much lighter plane of sedation and or anesthesia, if any. Most importantly, since the SNPA can be peeled off the bronchoscope, it facilitates atraumatic tracheal intubation to be performed. In some patients the SNPA additionally allows improves the visualization of the larynx and it can be advanced or withdrawn and rotated. When compared to direct nasal endoscopy, the SNPA may require less anesthetic depth and affords for the procedure to repeated atraumatically if required, which may be important in the teaching or training scenario (simulated in Fig. 2).
This is very useful adjunct in both elective and emergency maxillofacial surgery where fiberoptic nasal intubation is often required and bleeding during airway management is frequent. With the SNPA, fiberoptic intubation can be performed and teaching is possible. We also recommend the use of the SNPA in fiberoptic evaluation of postoperative patients with stridor in the post anesthetic care unit.
CONCLUSIONRetromolar and submental intubation techniques are useful alternatives in selected cases of maxillofacial surgery and may avoid some of the complications associated with nasal intubation and tracheostomy respectively. Nasal airways may be modified to facilitate airway management and facilitate fiberoptic intubations during airway management for maxillofacial trauma. OH
Naveen Eipe, MBBS, MD (Anesthesiology), Staff Anesthesiologist, The Ottawa Hospital (TOH) & Assistant Professor, Department of Anesthesiology, University of Ottawa. Email: firstname.lastname@example.orgTaylor P. McGuire, DDS, MSc, FRCD(C), Dip. ABOMS, Staff Surgeon, The Ottawa Hospital (TOH) & Private Practice-Argyle Associates in Oral & Maxillofacial Surgery Ottawa, Ontario, Canada. (www.argyleassociates.com)
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