INTRODUCTION

This is the first of a 2-part tutorial aiming to provide the anaesthetist with practical guidance and recommendations for airway management of patients with maxillofacial trauma. This first tutorial presents recommendations derived from the evaluation of challenges associated with airway and facial injuries, incorporating established airway protocols found in current academic literature. The second tutorial will focus on airway management techniques (see ATOTW number 542).

Airway management in patients with maxillofacial trauma often poses a significant challenge to the anaesthetist. The disruption of facial and airway anatomy, oedema, bleeding, and associated injuries contribute to the complexity of safely securing the airway. A nuanced comprehension of each scenario is essential for adequate preparation and successful airway management. A thorough understanding of the mechanism of injury is vital to enable the anaesthetist to anticipate potential adverse airway sequelae.

Figure 1. Incidences of common causes of maxillofacial trauma for different countries.^1-4

BACKGROUND: MAXILLOFACIAL TRAUMA AND THE AIRWAY

Aetiology and Incidence

The aetiology and incidence of maxillofacial trauma varies from country to country, often correlating with socioeconomic status (see Figure 1). Developed countries mainly attribute maxillofacial trauma to interpersonal violence, whereas developing countries have a higher incidence of road traffic accidents (RTAs).¹ Other causes include falls, sports injuries, industrial accidents, and warfare.

In South Africa, the predominant causative factor for maxillofacial trauma is interpersonal violence.² Historically, the major cause of maxillofacial trauma in the United Kingdom was RTAs.³ However, the decrease in such injuries due to the enforcement of basic road safety measures has led to a subsequent increase in the incidence of cases linked to interpersonal violence.³ India’s maxillofacial injuries are predominantly from RTAs, with fewer instances of interpersonal violence.⁴ Most maxillofacial fractures at an Iranian medical centre were caused by car and motorcycle accidents.¹ Moreover, a comparable proportion, constituting approximately 10% of cases, arose from both warfare-related injuries and interpersonal violence.¹

Relevant Anatomy and Considerations

Knowledge of facial and airway anatomy is imperative for a comprehensive understanding of the clinical presentation, pathophysiological mechanisms, and classification of maxillofacial injuries.

The facial skeleton comprises the frontal bone and 14 facial bones. It can be divided into upper, middle, and lower regions (see Table 1). The bones interlock at suture lines, which function as energy-absorbing zones, evenly dispersing the force transmitted to the face during trauma, thus reducing the risk of skull and brain injuries.⁵

Fractures typically manifest at structurally vulnerable sites, but high-energy trauma may impact regions of greater bone density.⁶ The face is exceptionally vascular, rendering it susceptible to substantial haemorrhage, particularly in the context of midface fractures.⁷

Table 1. Anatomical Classification of Important Maxillofacial Bones

Pathophysiology

The force and velocity of trauma impact the type and extent of injuries, originating from kinetic energy and dispersing into soft tissues and bone.⁸ Insight into the mechanism of injury is vital as this may determine the extent of damage and coexisting injuries (see Table 2).

Table 2. Mechanisms of Maxillofacial Injuries⁵; RTAs, road traffic accidents

Anaesthetic Considerations Related to Pathophysiology

Maxillofacial trauma often involves fractures of the facial bones with concurrent soft tissue damage. These fractures can cause misalignment and displacement of bone segments, resulting in deformities that may have a significant impact on airway management (see Table 2).⁵

Frontal Bone Fractures

Isolated fractures typically do not exert a direct impact on the airway. However, they can lead to complications like pneumocephalus and intracranial haemorrhage.⁹ Excessive pressure from bag-mask ventilation (BMV) can exacerbate the pneumocephalus.⁵ High-energy trauma increases the risk of concurrent anterior skull base fractures, posing a risk of intracranial penetration when inserting nasal tubes.⁵

Midface Fractures

The impact of these fractures on the airway varies with the fracture’s location and severity, potentially leading to airway obstruction, significant bleeding, and subcutaneous emphysema.⁵ Head and neck injuries are common in high-energy trauma.⁵

Maxillary Fractures

Maxillary fractures often result in dental injuries and malocclusion and are commonly associated with other facial fractures.⁵

Maxillary fractures are classified according to the Le Fort classification (see Figure 2). Classes II and III are particularly relevant to anaesthetists.

Class I manifests as a horizontal fracture isolating the tooth-bearing section of the maxilla that usually does not complicate airway management.

Class II manifests as a pyramidal-shaped fracture that separates the maxilla and nose from the upper lateral midface and zygoma, often associated with skull base fractures. The posteroinferior displacement of the fractured segment causes airway obstruction.

Class III fractures involve the zygomatic arch and present with midface separation from the skull base, often leading to airway issues. These fractures are associated with skull base and mandibular fractures.

Figure 2. Le Fort fracture patterns. Reproduced with permission from¹⁶.

Nasal Fractures

Nasal fractures often present with epistaxis; this can be substantial if the fracture is displaced. Difficult BMV is common.⁹

Naso-Orbital-Ethmoid Fractures

These fractures present in isolation or in combination with Le Fort or pan-facial fractures.⁵ The risk of intracranial penetration through the nasal passages is noteworthy.

Zygomatic Arch Fractures

Fractures of the zygomatic arch may be associated with restricted mouth opening that does not improve with general anaesthesia and neuromuscular blockade.⁹

Mandibular Fractures

The mandible typically fractures in at least 2 places due to its distinctive shape.⁵

Fractures are classified as simple (unilateral/bilateral) or comminuted.⁸ Bilateral (“bucket handle”) and comminuted fractures are regarded as unstable. The tongue is attached to the mandible’s symphysis and pulled forward by paired genioglossi muscles, consequently resulting in an unsupported state in instances of unstable fractures. Posterior displacement of the tongue may lead to acute airway obstruction. Dental injuries and malocclusion with restricted mouth opening are often encountered.⁵

Importantly, restricted mouth opening associated with pain and the directional pull from the muscles of mastication will improve with general anaesthesia and neuromuscular blockade, whereas in the presence of condylar neck fractures and temporomandibular joint involvement, mouth opening will remain restricted.

Laryngotracheal Trauma

Laryngotracheal injuries associated with maxillofacial trauma are of particular concern for the anaesthetist. Laryngotracheal trauma is often associated with cervical spine, oesophageal, and vascular injuries.⁵ This combination frequently leads to significant airway obstruction and challenges in achieving BMV, endotracheal intubation, and utilisation of a supraglottic airway device.^10,11

Due to the substantial impact that these injuries can have on the airway and airway management, the treating team must keep a high degree of suspicion for laryngotracheal trauma based on the mechanism of injury. This includes mechanisms that are associated with blunt trauma to the airway, for example, RTA, a significant fall, attempted hanging, accidental strangulation, a “clothesline” mechanism, assault, crush injuries to the chest, and pedestrian vehicle accidents.¹² Identifying the clinical features of laryngotracheal trauma (see Figure 3) and examining plain radiographs of the neck allows timely management and avoidance of serious morbidity and mortality. Furthermore, airway management may be time critical and dependent on the patient’s condition and cooperation.

Cervical Spine Injuries

Cervical spine injuries can occur with maxillofacial injuries, particularly with facial fractures associated with high-energy trauma. Many patients with maxillofacial injuries should be considered as having a potential for a C-spine injury.

Figure 3. Features suggestive of laryngotracheal injuries.⁵

Airway Compromise in Maxillofacial Injuries

Airway compromise is defined as impaired airway functioning and is often the result of obstruction in the airway.

Airway obstruction associated with maxillofacial trauma is usually multifactorial (see Table 3). It occurs because of occlusion due to oedema, blood, secretions, foreign bodies (teeth), or anatomical narrowing of the airway. Recumbent patients who are unable to swallow or who struggle with clearing the airway can experience a buildup of blood and secretions in the oropharynx. Causes of dysphagia include pain, oedema, an impaired level of consciousness, and intoxication. Damage to the jugular vein or carotid artery can result in the development of an enlarging haematoma. Conversely, a patient receiving anticoagulation therapy, even after minor trauma, may experience substantial bleeding and haematoma formation.

Table 3. Causes of Upper Airway Obstruction in Maxillofacial Trauma

In an awake patient, partial obstruction may present itself by the patient attempting to sit up and lean forward. This position facilitates passive drainage of blood and secretions and alleviates posterior tongue displacement. Signs of impending obstruction include stridor, voice changes, haemoptysis, and dyspnoea. A patient with complete obstruction will be unable to speak or breathe. Severe respiratory distress will rapidly deteriorate into respiratory failure. If the obstruction persists, hypoxia will lead to a loss of consciousness and death.

Hutchison et al¹⁰ described the following 5 situations that can lead to airway compromise in maxillofacial trauma:

1. Posteroinferior displacement of maxillary fractures
2. Posterior displacement of unstable mandibular fractures
3. Direct occlusion of the airway
4. Haemorrhage from open wounds in the airway and nasal fractures
5. Oedema and displacement of surrounding structures associated with laryngotracheal trauma

AIRWAY ASSESSMENT

Emergency Airway Assessment

In the emergency setting, assessment and management of a traumatised airway presents significant challenges. Trauma patients are initially assessed and treated systematically according to the Advanced Trauma Life Support protocol. The primary survey, also known as the ABCDE approach, starts with a fast but thorough airway assessment (see Table 4).

The primary objective is to promptly recognise and manage airway compromise and identify associated factors that will complicate airway management, such as cervical spine injuries. Details regarding the mechanism of injury are vital, and meticulous observation of any pre-existing facial abnormalities, dental appliances (bridges/crowns/implants/dentures), and missing and/or broken teeth should be done.

Table 4. Emergency Airway Examination

A complete review of the Advanced Trauma Life Support protocol is beyond the scope of this tutorial.

Common Constraints to Assessing the Airway in an Emergency

• • Limited time due to ensuing airway compromise, hypoxia, and other life-threatening conditions
  • Assessment must be performed in parallel to airway salvage manoeuvres
  • Significant anatomical distortion, oedema, and bleeding
  • C-spine immobilisation
  • Uncooperative and combative patients

In situations where an immediate airway intervention is not warranted, it is imperative to acknowledge the necessity for urgent airway management in the context of the secondary survey.

The secondary survey is a head-to-toe examination that is performed once the patient is stabilised. A less constrained airway examination is now possible, although it might be impossible to assess the Mallampati score or neck mobility due to C-spine immobilisation. Complete C-spine assessment requires a comprehensive clinical evaluation accompanied by radiographic investigations to rule out an injury, and this is not always feasible before urgent airway management.

Preoperative Airway Assessment

A comprehensive airway assessment is essential for maxillofacial trauma patients. Only after a complete history, physical examination, and consideration of coexisting medical conditions and injuries can a complete airway management strategy be formulated.

The aim is to predict the difficulty of the following:

1. BMV
2. Direct laryngoscopy
3. Endotracheal intubation
4. Use of a supraglottic airway device
5. Anatomical access for a surgical airway

A basic airway examination includes the following:

1. Inspection:
   • The external appearance of the face and neck
   • Oral cavity and nasal passages
   • Dentition
2. Evaluation:
   • Mouth opening and nasal patency
   • Interincisor, thyromental, and mento-hyoid distances
   • Neck circumference and range of movement (provided cervical spine injury has been ruled out)
3. Grading:
   • Mallampati classification
   • Jaw protrusion

Predicting Difficult Airway Management

Simple bedside airway assessments can aid in identifying predictors of difficult airway management (see Table 5). Mnemonics function as memory aids to easily recall predictors (see Figures 4, 5).

Table 5. Simple Bedside Airway Assessments Used to Predict Difficult Intubation¹⁴

Figure 4. Mnemonic for predictors of difficult bag-mask ventilation related to maxillofacial trauma.

The positive predictive value for detecting difficult intubation increases when more than 1 factor is not reassuring. Although individual assessments may have limited sensitivity, the absence of concerning findings generally predicts easier intubation. However, unforeseen challenging airways can still occur despite favourable assessments.

Figure 5. Mnemonic for predictors of difficult laryngoscopy and intubation related to maxillofacial trauma.

The El-Ganzouri Risk Index (EGRI) is a risk stratification tool that uses readily available and objective criteria in a multivariate model¹³ (see Table 6) to quantify the risk of difficult airway management. It has been validated in patients scheduled for elective surgery under general anaesthesia. It is believed that multivariate risk stratification tools provide better accuracy than individual assessments.

Table 6. El-Ganzouri Risk Index. A score of >3 predicts difficult intubation with conventional direct laryngoscopy

Cortelazzi et al evaluated the predictive values of the EGRI using Macintosh laryngoscopy and video laryngoscopy as reference standards (see Table 7). The results suggest that the EGRI is useful preoperatively to evaluate the risk for difficult intubation for direct laryngoscopy and video laryngoscopy.

Table 7. Results from the Comparative Study by Cortelazzi et al Evaluating the Predictive Values of the El-Ganzouri Risk Index (EGRI) for Conventional Macintosh Laryngoscopy and Videolaryngoscopy¹⁵

History of Previous Airway Management

If available, previous anaesthetic and patient records about past airway management should be reviewed. Records of the period following airway management may also contain relevant information.

Note the following:

• Airway management techniques
• Ability to bag-mask ventilate
• Best grading of the laryngeal view with direct laryngoscopy
• Airway equipment (types and sizes)
• Problems encountered
• Use of rescue devices
• Complications

Imaging Studies of the Airway

Point-of-care ultrasound is useful for both airway assessment and management.¹⁴ It is a rapid, noninvasive technique that can be performed at the bedside to reliably visualise upper airway structures. The anaesthetist can identify the trachea’s location, assess any tracheal deviation, and measure the tracheal width. Identifying the cricothyroid membrane enables preanaesthetic marking in preparation for potential cricothyroidotomy in a cannot intubate cannot oxygenate scenario. Notably, it provides real-time information that aids in decision-making. Following tracheal intubation, it can be used to confirm the correct depth of endotracheal tube placement.

Flexible fibreoptic nasolaryngoscopy can be used to examine the extent of oropharyngeal injuries.

Findings from plain radiographs, computerised tomography, and magnetic resonance imaging can assist in predicting airway difficulty, in finding missing teeth and dental appliances, and in developing an airway management strategy. The presence of a finalised radiologist’s report is not required if the management of the airway is an emergency.⁵