Abstract
This chapter gives a presentation of the major issues to consider in maxillofacial and dental surgery when sharing the airway with the surgeon. It is essential to have knowledge of the surgical population and procedures to plan the airway handling safely to avoid potential complications. Nasal intubation gives optimal access for the surgeon and is the gold standard but is accompanied with the risk of nasal trauma. Manoeuvres to minimise complications are given. There are different considerations to take into account both for the well-planned scheduled procedure and for the urgent procedure with a threatened airway. Surgical complications such as bleeding and infection challenge the skills of the anaesthetist making the airway handling difficult. Awake flexible optical bronchoscope-guided intubation is a safe option and a plan for extubation must be made. A structured approach to handle the patient with maxillofacial trauma is given both in the emergency case and later for final surgery. Priority and timing of surgery is crucial in the patient with multiple injuries, and especially the neurotrauma patient with respect to control of intracranial pressure.
Maxillofacial and dental surgery presents novel challenges to the skill of the anaesthetist, due to sharing the anatomical space with the surgeon and because of the particular conditions required for surgical success. The anaesthetist should have knowledge of the surgical terms and techniques peculiar to this field. Although elective surgery is largely routine and predictable, emergency surgery may challenge the skills of even very experienced anaesthetists. Of note, surgical procedures that start out as routine and predictable have the potential to deteriorate into life-threatening situations. To avoid poor outcomes, a knowledge of the techniques and challenges of the subject, supplemented by development of skills in the workplace, is essential. This chapter provides a brief introduction to anaesthesia for maxillofacial and dental surgery.
Dental Surgery
Dental surgery refers to minor surgery to the gums and teeth, whether dealing with extraction of teeth (exodontia), preservative treatments (fillings) or replacement (implants).
Patient Population
Patients presenting for dental surgery under general anaesthesia typically either require extensive procedures or are unable to comply safely with dental treatment under local anaesthesia. The latter patients tend to be younger children, adults with learning difficulties or patients with severe dental phobia. Extensive dental infection may also prevent local anaesthesia from working adequately and thus may require general anaesthesia.
Because of the potential complications of general anaesthesia, it is useful to discuss whether the planned procedure could be managed with sedation or other techniques. In adults, sedation using benzodiazepines or nitrous oxide administered via a nasal mask is useful, but in children, friendly staff and surroundings and the use of distractors such as tablet computers may be enough to avoid general anaesthesia.
Recommended standards for fasting, monitoring, resuscitation equipment and personnel for general anaesthesia are applicable for dental surgery, wherever it is carried out. Historically, there have been reports of a number of deaths in otherwise healthy children and adults from airway complications, often contributed to by substandard practice.
Patients with learning difficulties often present for dental surgery, and they may pose significant challenges for the anaesthetist because of difficulties with communication, compliance and associated co-morbidities. Down syndrome patients have the potential for airway problems (see Chapter 5), but also may have congenital cardiac defects that increase the risks of general anaesthesia and also endocarditis (from poor dental hygiene). It is not unusual for patients to present for dental extraction under general anaesthesia whilst awaiting cardiac transplantation.
Anaesthesia
Post-operative nausea and vomiting is a common problem in this patient population: total intravenous anaesthesia supplemented with antiemetics is an effective way to minimise this risk. Airway management should aim to provide optimal conditions for the surgeon. Sedation in a spontaneously breathing patient without an airway device is possible, but is a compromise between providing adequate surgical conditions whilst maintaining an open and free airway. Blood, debris, saliva and foreign bodies pose a threat during the whole procedure, and the avoidance of soiling of the airway depends to a large extent on the skill, diligence and speed of the surgeons. With all but the briefest procedures, general anaesthesia with tracheal intubation or airway management with a supraglottic airway device (SGA) is strongly recommended.
The choice of airway device is often dictated by the flexibility of the dental surgeon and the procedure to be carried out. Many dental surgeons prefer complete oral access, not limited by a tracheal tube or SGA, and for some procedures they have to test occlusion, which precludes the use of an oral tracheal tube. However, for simple dental extractions an SGA gives adequate oral access, although risk of displacement and airway soiling is always present and more likely with prolonged and bloody procedures. An SGA with reinforced tubing (although more difficult to insert) is more flexible and mobile, enabling repositioning of the connecting tube without compromising the laryngeal seal.
If surgery allows, an oral tracheal tube is less traumatic than a nasotracheal tube. This may be either a preformed south-facing type fixed in the midline, or a straight standard oral tube moved from side to side at the request of the dental surgeon. Nasal tubes provide ideal oral access for the operator, but at the risk of trauma to the nasal mucosa and post-operative haemorrhage.
Nasal Intubation
Nasal intubation remains the gold-standard airway management technique for dental surgery, providing the best conditions for the dental work by providing excellent surgical access and enabling the bacterial/heat and moisture exchanger filter to be placed away from the surgical field. Ideally it should be performed with a soft PVC nasal tube to reduce the incidence of nasal trauma and complications, such as epistaxis and the abruption of conchae. Use of a small tube – e.g. 6.0–6.5 mm ID – will reduce trauma. Some precautions and techniques are useful to help avoid trauma to the nasal mucosa.
Preoperative history and examination can determine the occurrence of complications during previous surgical procedures, and also identify the best nasal airway by asking the patient to occlude one nostril followed by the other. Vasoconstrictors can be administered nasally prior to intubation to reduce the risk of bleeding and to shrink the nasal mucosa.
Laryngoscopy prior to introduction of the nasal tube will help to assess intubation difficulty and the presence of potential problems (such as large tonsils) before committing to a procedure that could cause haemorrhage and threaten the airway. The nasal tube may be railroaded over a lubricated suction catheter or bougie before introduction into the nasal cavity to help guide the larger tube past the conchae. Nasotracheal intubation is usually easy to achieve by gentle rotation of the tube and flexion/extension of the head, but often progress of the tube tip through the larynx is held up by impaction against the tracheal rings. In these circumstances, the tube can be gently rotated anticlockwise to achieve passage of the whole cuff past the laryngeal inlet. External pressure on the cricoid cartilage by an assistant or flexion of the neck to reduce the angle between the tube and the tracheal wall may also facilitate passage of the tracheal tube. If these manoeuvres fail, a Magill forceps may be used to change the angle of tube insertion into the trachea, but this risks damage to the cuff and so is only appropriate if other measures fail.
Throat Packs
It is usual to place throat packs before surgery to prevent surgical debris such as blood, surgical drill bits, fragments of bone and soft tissue from entering the oesophagus or the airway during the procedure and upon extubation. Because of the potential complications associated with the use of a throat pack, the practice of routine insertion is currently being reviewed. If a throat pack is inserted it is essential to remove it at the end of surgery, and if overlooked this can cause airway obstruction immediately following extubation or in the recovery area. Pack removal may usefully be included in the surgical checklist at the end of the procedure, but it is the responsibility of the anaesthetist to ensure that the pharynx is clear before extubation.
Emergency Dental Surgery
Infection originating from dental caries is a common condition that in most cases can be dealt with by dental extraction under local anaesthesia. However, if left unresolved it can produce severe anatomical distortion due to oedema, collection of pus and may progress to systemic infection which may be life-threatening. In these circumstances, surgical intervention under general anaesthesia is required.
Poor oral hygiene provides optimal conditions for acid-producing bacteria to dissolve dental enamel, leading to odontogenic infection. Most commonly, the infection starts in a mandibular molar from where it can spread to the alveolar bone, giving rise to a periapical abscess protruding into the oral cavity or spreading through the submandibular tissue. There can be swelling of the soft tissue in the oral cavity and the tongue. Posteriorly and inferiorly the tongue, pharynx and glottis can become inflamed with oedema, eventually resulting in an obstructed airway. Infection may also spread along the great vessels of the neck to the mediastinum, which is a serious complication with high mortality. CT imaging may reveal mediastinal gas formation with pleural and epicardial effusions. From the maxillary teeth, infection can spread superiorly to the maxillary sinuses and the infraorbital cavity. Infection can also expand intracranially and give rise to cavernous sinus thrombosis.
Ludwig’s angina can arise from either a peritonsillar abscess or dental infection, with hardening and swelling (cellulitis) of the floor of the mouth and the masseter muscles, giving rise to trismus and making conventional laryngoscopy impossible. The patient may be unable to lie supine and/or may be unable to swallow saliva, which are indications of the severity of the condition. Dysphonia is a late sign that precedes complete airway obstruction. Awake flexible optical bronchoscope (FOB)-guided intubation is usually the preferred approach, but may also be complicated by poor patient cooperation and difficulty with obtaining good local anaesthesia (due to changes in tissue pH secondary to infection).
Following surgical drainage, safe extubation may not be possible until resolution of airway oedema. Ventilation in the intensive care unit for a prolonged period may be required, as may repeated surgical drainage of the infected tissues. Establishing a tracheostomy prior to transfer to intensive care may be extremely difficult in the presence of submandibular oedema, but is often a safer option than relying on a precarious oral or nasal tracheal tube which may be pulled out by increasing oral and pharyngeal oedema. Broad-spectrum antibiotics are used to control infection and steroids are often used in an attempt to reduce airway oedema. Occasionally, severe sepsis, septic shock and multi-organ failure is a complication of dental infection.
Maxillofacial Surgery
Orthognathic Surgery
Orthognathic is a word of Greek derivation that means to straighten or correct the jaws. Osteotomies of the maxilla and mandible change the shape of the facial skeleton in order to treat malocclusion and deformities of the face. The purpose is both aesthetic and functional, enabling patients to chew, masticate, and breathe freely through the nose and to speak clearly.
Most patients are in late adolescence, and typically present for surgery after 12–18 months of orthodontic presurgical treatment with braces and appliances to correct malocclusion. The orthodontic treatment is continued post-operatively. All permanent teeth have erupted and the bone structures of the face have finished growing, but orthognathic surgery is required for definitive treatment of the underlying skeletal deformity causing malocclusion. The patients are generally healthy without co-morbidities. Surgery is elective and well planned by a multidisciplinary team of surgeons and orthodontists. Dental models are worked out after virtual planning on the basis of three-dimensional CT or cone-beam CT (CBCT) imaging (Figure 25.1).
