Are we ready for submental diversions?

In patients with maxillofacial injuries, airway management technique is selected to ensure it does not interfere with surgical access. Trachea can be intubated through orotracheal, nasotracheal, retromolar and submental route or the patient can be subjected to tracheostomy.

Nasotracheal intubation is the most preferred technique; nevertheless it is usually avoided in patients with panfacial fracture, skull base fracture, and naso-orbito-ethmoid complex fracture as there is a danger of accidental passage of the tracheal tube into the cranial cavity which can lead to major complications like meningitis, sepsis, and cerebrospinal fluid leakage.[1,2] Elective tracheostomy is a traditional method for airway access in these patients. Tracheostomy is an invasive procedure and may be associated with greater morbidity, at times causing tracheal stenosis, internal emphysema, damage to the laryngeal nerves, tracheoesophageal fistula and scarring.[3,4] Tracheostomy may not be possible in patients with associated cervical spine injury and neck mass.

The submental diversion of orotracheal intubation is one such technique that provides an unobstructed surgical access with minimal trauma as compared to nasotracheal intubation and tracheostomy. Indications for submental intubation are maxillofacial injuries with associated fractures of nasal bone and skull base,[5] patients requiring use of temporary intermaxillary fixation in patients where nasotracheal intubation is not possible, orthognathic surgeries and elective aesthetic face surgeries. Some of the other indications include repair of congenital malformations, skull base surgery, multiple or complex facial osteotomies, transfacial oncologic procedures of the cranial base, and pedunculated craniofacial surgeries.

Many authors have use the term “Submental Intubation” to describe this technique including the article in the current issue of IJA by Banerjee PK et al.[6] The technique refers to conventional oral tracheal intubation followed by intraoral diversion of the proximal end of the “wire reinforced” endotracheal tube (WR-ETT) through the anterior floor of the mouth into the submental region. Hence, a more appropriate terminology should be “submental diversion”. It is important to understand that submental diversion is not an option for management of difficult airway. It is usually performed in a patient with normal airway where conventional orotracheal intubation is possible. Submental diversion is only an intermediate step that offers surgical access in specific surgeries where temporary intraoperative occlusion of teeth that is, intramaxillary and maxillomandibular fixation is needed to check the alignment of the fracture fragments. It is applicable only in patients in whom anatomy is expected to become normal after the surgery, and long term post-operative ventilation is not anticipated.

There are certain issues that need attention when submental diversion is contemplated. It is mandatory to use WR-ETT to avoid kinking, as tube takes an acute bend when diverted through the submental region. Secondly, once the tube is disconnected from the anaesthesia circuit and the proximal end of the WR-ETT is handed over to the surgeon to negotiate through the submental region patient cannot be ventilated if paralyzed. One should ensure that the opening created by the surgeon is 1 cm more than the external diameter of the WR-ETT for passage of the tube and to keep the patient spontaneously breathing under inhalational anaesthesia during the time of diversion to prevent desaturation. Since the proximal end is unsterile there is always a possibility of infection at the local site when proximal end exchanges hands between anaesthesiologist and the operating surgeon. A disposable sterile anaesthesia circuit can be used along with sterile WR-ETT. In addition, anaesthesiologist should take precautions to keep the proximal end of WR-ETT sterile. An able assistant who takes care of the proximal end of WR-ETT (wearing sterile gloves) and hands it over to the surgeon is a useful option. Such precautions can help to reduce the infection rate at local site.

Several modifications have been suggested to submental diversion with an expectation of improved outcome. Gadre and Waknis[7] suggested the trans-mylohyoid approach where the WR-ETT can be passed through the mylohyoid muscle anywhere between the first mandibular molars of either side anterior to the masseter muscle. Use of two WR-ETT (one anterograde and the other retrograde) is claimed to be superior because there is less chance of hypoxia if there is difficulty in retrieval and no need of detaching the connector[8]. One serious drawback of the retrograde technique is that it may result in the introduction of infection to lower airways. Hanamoto et al. used sterile polypropylene cylinder of the 10 ml syringe, through the submental incision into the oral cavity for re-routing the orotracheal tube without compromising ventilation.[9] Lima et al.[10] utilized surgical glove finger to cover the proximal end of the WR-ETT, which helped in preventing the entry of blood and soft tissue during its passage through the orocutaneous tunnel.

Tube exchangers can also be used for submental diversion as suggested by Drolet et al.[11] Nyarady et al. suggested “Rule of 2-2-2” – 2 cm long incision, 2 cm away from the midline, 2 cm medial to the mandibular margin along with a Nylon guiding tube to avoid injury to the associated structures.[12] Some reinforced tracheal tubes are manufactured with no detachable connectors, so one should make sure that the connectors are detachable before planning a submental diversion. A 100% silicon wire reinforced tube primarily intended for intubation through intubating laryngeal mask airway (ILMA) is a better option as it has an easily removable universal connector.[13] Mahmood and Lello[14] performed submental intubation using preformed Sheridan tube. The preformed curvature helps in the positioning of the tube as it conforms to the anatomy of the region.

At the end of surgery, it is prudent to bring back the tube to the oral route before extubation. Although few authors have recommended extubation directly through the submental route[15] there is every chance that it can lead to trauma to the contralateral side vocal cord. Extubation through the submental route will cause straightening of the acute angle of the distal end of WR-ETT while it is exiting the glottis is held back at the lower portion of the contralateral vocal ligament. The pulling or traction of the contralateral vocal cord can thus sustain injury if direct submental extubation is attempted. It is wise to bring back the WR-ETT to the oral route where the normal curvature is maintained to avoid injury to the glottic structure during extubation. If there is intermandibular wiring and fixation, then the tube should be redirected to the retromolar space and brought out through the oral cavity before extubation.

To conclude, when indicated, submental diversion is a useful technique that can help avoid tracheostomy and decrease airway morbidity.