Abstract
Patients undergoing ear nose and throat (ENT, otorhinolaryngeal) surgery probably present more airway management challenges than any other branch of surgery. ENT procedures encompass a range of operations varying in duration, severity and complexity from simple short cases such as myringotomy, through to complex resection and reconstructive surgeries for head and neck cancer. In all cases the surgical team operates close to the airway and in many within the airway, which is therefore shared with the anaesthetist. In this chapter, the authors discuss in some depth these challenges and how to address them, airway management and ventilation options and strategies including but not limited to awake intubation, different subtypes of jet ventilation, and high flow nasal oxygenation as well recent advances in the field. They further discuss extubation strategies and controversies as well as a plan to manage commonly encountered complications such as bleeding in the airway. For a successful outcome, these ‘shared airway’ procedures require close communication and cooperation between anaesthetist and surgeon, an understanding of each other’s challenges, knowledge of specialist equipment, and a thorough preoperative evaluation to identify potential risk factors for poor perioperative outcomes.
Patients undergoing ear nose and throat (ENT, otorhinolaryngeal) surgery probably present more airway management challenges than any other branch of surgery. ENT procedures encompass a range of operations varying in duration, severity and complexity from high-volume cases such as myringotomy, simple nasal procedures and tonsillectomy through to complex resection and reconstructive surgeries for head and neck cancer. In all cases the surgical team operates close to the airway and in many within the airway, which is therefore shared with the anaesthetist. For a successful outcome these ‘shared airway’ procedures require close communication and cooperation between anaesthetist and surgeon, an understanding of each other’s challenges, knowledge of specialist equipment, and a thorough preoperative evaluation to identify potential risk factors for poor perioperative outcomes.
Airway Safety and Maintenance
Factors affecting airway safety and maintenance during ENT surgery may be classified into eight groups.
Patient factors. Patients may present with distorted upper airway anatomy and/or airway obstruction. Airway reactivity is more prevalent than in other surgical groups.
Physical space factors. After surgery has begun the anaesthetist is remote from the airway, making adjustments more difficult and disruptive to the surgical procedure.
Surgical factors. Significant lateral rotation of the head may be required for ear procedures and head extension for neck procedures. During intra-oral procedures instruments to keep the mouth open may obstruct the airway.
Anatomical factors. Shared airway procedures involve surgery of the glottis, subglottis and trachea and require an understanding of the necessary special equipment, techniques and laser safety (when used).
Procedure-specific factors:
◦ Throat packs. Oropharyngeal and nasopharyngeal packs should be specifically recorded and accounted for at the end of the procedure. Failure to do this has led to fatal airway obstruction during or after emergence.
◦ Airway soiling. For nasal and intra-oral surgery, the airway requires protection from blood and debris.
◦ Coroner’s clot. Direct inspection and suction clearance of blood and debris from the oro- and nasopharynx as well as the tracheobronchial tree should be undertaken at the end of the procedure to avoid a potentially deadly (Coroner’s) clot in the airway.
Recovery factors. ENT operations, particularly intra-oral, laryngeal, subglottic and tracheal procedures, have a more challenging recovery profile compared with the general surgical population with a higher incidence of coughing, laryngospasm and desaturation following tracheal extubation.
Face Mask
Historically, face mask ventilation was used for simple, short ear procedures such as myringotomy and tube (grommet) insertion. The patient retained spontaneous ventilation but this required the anaesthetist to hold the face mask and the surgeon to work around the anaesthetist’s hands and the face mask. Most of these short duration procedures are now undertaken with a supraglottic airway (SGA). The quality of airway management with the SGA is superior to a face mask with better oxygenation, improved seal, less oropharyngeal air leak, better monitoring of tidal gases particularly at low flow, and with less operating room (OR) pollution. Surgical conditions are superior for ear surgery in children with an SGA compared with use of face mask because there is less movement of the surgical field.
Tracheal Tube
Tracheal tubes are commonly used in ENT surgery. Reinforced (flexible) tubes are useful for procedures where head and neck movements and positioning are anticipated for surgery. Caudad-facing oral tubes, such as the Ring–Adair–Elway (RAE) tube, are particularly suitable for surgery involving the pharynx where a gag is used. The advantages of using an oral tracheal tube are: (i) familiarity with its use, (ii) relative resistance to compression if using a wire-reinforced tube, (iii) the ability to secure and protect the lower airway – distal to tube cuff – from blood and debris in the oropharynx and regurgitated gastric contents, (iv) avoiding laryngospasm that may be encountered with mask or SGA ventilation, (v) allows for using higher-pressure ventilation when needed and (vi) less chance for losing the airway during surgery.
Extubation and Recovery
Tracheal extubation is usually undertaken with the patient awake; however, some anaesthetists consider ‘deep’ extubation as well and/or use of an SGA (often a flexible laryngeal mask airway, FLMA) as part of the extubation strategy (staged extubation).
For nasal surgery awake extubation involves removal of the tracheal tube when the patient responds to commands and makes purposeful attempts to remove the tracheal tube. The advantage of awake extubation for nasal surgery is the intrinsic airway control in an awake patient with better return of laryngeal reflexes and protection from further airway contamination by blood and secretions. The disadvantage is the higher incidence of laryngospasm, coughing, bucking, oxyhaemoglobin desaturation and increased risk of bleeding. That said, many anaesthetists who are specialised in ENT anaesthesia have developed different techniques to facilitate smooth awake extubation avoiding such complications. Some of those techniques include the incorporation of local or systemic (IV) lidocaine just before extubation, and/or a narcotic such as fentanyl, remifentanil, sufentanil, and/or alfentanil.
Deep extubation is used in an attempt to improve the recovery profile; however, for nasal surgery this leaves an unprotected airway. After surgery the nasal airway is often blocked with surgical packs and the patient is dependent on oropharyngeal airflow. In practice this may make it extremely difficult to maintain an airway in an obstructive sleep apnoea patient extubated deep lying on their side.
Considering the above considerations some anaesthetists prefer recovery with an SGA in place as they believe it provides protection of the lower airway from aspiration of blood and a superior recovery profile compared with awake or deep extubation.
Flexible Laryngeal Mask Airway (FLMA)
Amongst SGAs used for ENT surgery the FLMA has a special place and it is especially well suited to use for head and neck surgery including shared airway surgery. The ProSeal LMA has some benefits too but is not suited at all to shared airway surgery (see Chapter 13).
However, the use of any SGA including the FLMA seems to have a regional pattern; in the UK, and certain parts of the world, the FLMA is used in ear, nose and throat procedures including tonsillectomy. The cuff of the device is identical to a standard classic LMA but the flexible shaft is better suited and tolerant to head rotation, flexion and extension during surgery. The successful use of the FLMA requires the acquisition of new skills for the anaesthetist and surgeon. The FLMA requires training and experience for successful use and this is probably the main limitation. An understanding of the device, in particular sizing, insertion, placement and recognition of misplacement, is necessary.
The single greatest problem with the FLMA is placement. Unless a scrupulous technique is used (usually digital placement) that ensures that the mask portion is delivered deep into the hypopharynx and facing correctly there is risk of displacement and axial rotation. This will lead to poor device performance and poor airway protection.
During recovery the FLMA is tolerated better than a tracheal tube during emergence and can be left in place until return of protective reflexes. The improved recovery profile leads to a smoother recovery with a reduced incidence of respiratory complications including: coughing, bucking, straining, airway obstruction, laryngospasm and desaturation.
In other parts of the world, the tracheal tube is the preferred airway to use for the reasons mentioned above regarding airway protection, and the preference of some surgeons, as the tracheal tube has a lower profile in the oral cavity compared with an SGA.
FLMA: Nasal Surgery
Using an FLMA during nasal surgery requires care and attention to detail and if there is incorrect sizing or insertion, malposition, dislodgement or suboptimal recovery there is the potential for airway obstruction and blood contamination of the airway.
It seems intuitive that a tracheal tube would protect the airway more effectively than a FLMA because of the seal offered by contact of the tracheal tube cuff on the tracheal wall; however, this may not be completely true. The tracheal cuff is below the glottic and subglottic airway and blood can pass down from the nasopharynx, past a throat pack, along the outer surface of the tracheal tube to the level of the vocal cords, subglottis and upper trachea. In contrast, a correctly placed FLMA covers and protects the supraglottic and glottic airway and blood is diverted laterally to the pyriform sinus and post-cricoid region.
Direct comparisons of airway contamination by flexible optical bronchoscope (FOB) examination at the end of nasal surgery show patients managed with a FLMA are significantly less likely to have blood staining the airway (glottis and trachea) than patients managed with a tracheal tube. The FLMA effectively and satisfactorily protects the glottic and tracheobronchial airway from blood exposure during nasal and sinus surgery and may offer better protection of the tracheobronchial airway than a tracheal tube in many instances.
Those who are in favour of using FLMA believe that the emergence quality and overall airway protection following nasal surgery appear to be better for a FLMA than a tracheal tube – and it is certainly true that emergence with an SGA is better than with a tracheal tube in other settings. This must be balanced against the potential for misplacement and intraoperative problems that arise with the FLMA, especially when used by an inexperienced anaesthetist or with an inexperienced surgeon.
Whether the airway is managed by FLMA or tracheal tube, if there is considerable bleeding from nasal/sinus surgery an orogastric tube should be inserted to evacuate any blood that may have entered the stomach, before waking the patient up, to decrease the risks of post-operative nausea, vomiting and aspiration.
FLMA: Tonsillectomy
The use of a FLMA for tonsillectomy is an advanced technique and requires an experienced anaesthetist who is familiar with the insertion and maintenance of the device and a surgeon who is competent at working around a FLMA. In small children, the inexperienced should not use a FLMA for tonsillectomy.
The use of a FLMA for tonsillectomy requires close cooperation and meticulous attention to detail by both the anaesthetist and surgeon. Particularly, care is required by the surgeon on placement and opening of the mouth gag and intraoperative manipulation of the gag. Mechanical obstruction during the use of a tonsillar gag varies from 2% to 20% and for the majority of these cases the obstruction is correctable. Access to the inferior pole of the tonsil has been documented as being more difficult.
The FLMA is removed when patients open their eyes to command. The cuff should remain inflated enabling blood and secretions on the backplate to be suctioned out as the FLMA is removed from the mouth.
Potential advantages of using a FLMA for tonsillectomy are (i) the superior recovery profile with fewer episodes of bronchospasm, laryngospasm and desaturation, (ii) less aspiration of blood when compared with an uncuffed tracheal tube and (iii) better protection of the lower away from blood and secretions until awake.
The alternative to the FLMA for tonsillectomy is the use of a standard or oral RAE tracheal tube. A cuffed tracheal tube will also provide good protection of the lower airway at the end of surgery (Figures 26.1–26.3). The anaesthetist will need to make a clear decision about deep extubation or with the patient fully awake.
Figure 26.1 Uncuffed tube – note blood can pass tube.
Figure 26.2 Cuffed tube – note blood can pass down to cuff.
Figure 26.3 Correctly placed LMA protects laryngeal inlet from soiling.
Laryngeal Surgery
Operations on the airway are unique in that both anaesthetist and surgeon are working in the same anatomical field. The anaesthetist is concerned with oxygen delivery, removal of carbon dioxide (ventilation), maintenance of an adequate airway and the prevention of soiling of the tracheobronchial tree, while the surgeon requires an adequate view of a clear motionless operating field. Close cooperation and communication between anaesthetist and surgeon are essential for success. Patients presenting for laryngeal surgery vary from young healthy individuals, with voice changes secondary to benign vocal cord pathology (e.g. small nodules and polyps), to elderly, heavy smokers with chronic obstructive pulmonary disease and alcohol users/abusers with malnutrition and liver disease presenting with stridor caused by glottic carcinoma.
The Ideal Anaesthetic for Laryngeal Surgery
There is no ‘ideal anaesthetic technique’ (Table 26.1) for all laryngoscopy procedures. The technique chosen will be dependent on (i) the patient’s general condition, (ii) the size, mobility and location of the lesion and (iii) surgical requirements including the use of a laser.
Table 26.1 The ideal anaesthetic technique – goals
|
The presence of a standard polyvinyl chloride (PVC) cuffed tracheal tube, whilst providing control of the airway and preventing aspiration, may obscure a glottic lesion and is not ‘laser safe’. A cuffed laser tube provides some protection against laser-induced airway fires but has a greater external diameter to internal diameter ratio and may obscure laryngeal lesions. Jet ventilation techniques require special equipment and knowledge and understanding of their limitations and do not protect the airway from soiling.
Preoperative Assessment
Causes of laryngeal pathology are listed in Table 26.2.
At the end of the preoperative assessment, the anaesthetist should have some idea of the size, mobility, vascularity and location of the lesion. Standard airway assessments to predict the ease of ventilation, visualisation of the laryngeal inlet and tracheal intubation should be performed but should factor in the airway pathology and its impact on airway management (Table 26.3).
Table 26.3 Preoperative assessment of laryngeal lesions
| Assessment | Implication |
|---|---|
| History of endoscopic procedures | Previous difficulty, severity, vascularity and site of obstruction. Anaesthetic technique used |
| Hoarse voice | Non-specific symptom. Can occur without airway compromise |
| Voice changes | Non-specific symptom. Minor lesions can change the voice |
| Dysphagia | Significant and suggests supraglottic obstruction. If associated with carcinoma implies upper oesophageal extension |
| Altered breathing position | Significant. Patients with partially obstructing lesions will compensate by changing their body positioning to limit airway obstruction |
| Unable to lie flat | Significant. Suggests severe airway obstruction and patients may need to sleep upright, could also signify recurrent aspiration (e.g. after oesophagectomy with stomach pull through) |
| Breathing difficulty during sleep | Significant. Difficulty in breathing at night or waking up at night in a panic suggests severe airway obstruction |
| Inspiratory noise – stridor | Significant and indicates critical airway obstruction with over 50% reduction in airway diameter and in adults an airway diameter of less than 5 mm |
| Stridor on exertion | Significant. Suggests airway obstruction is becoming critical. Patients may have no stridor at rest |
| Stridor at rest | Significant. Critical airway obstruction is present |
| Inspiratory stridor | Significant. Suggests extrathoracic airway obstruction |
| Expiratory noise – wheeze | Significant. Suggests intrathoracic airway obstruction |
| Absence of stridor or wheeze | Generally reassuring BUT in exhausted adults and children there is limited chest movements and insufficient airflow to generate enough turbulent flow for stridor. These circumstances suggest life-threatening compromise. After chronic airway obstruction stridor may also decrease |
| Awake flexible optical laryngoscopy (‘nasendoscopy’) | All adult patients should have this to visualise the vocal cords. In patients with symptoms and signs of severe airway obstruction great care must be taken to avoid local anaesthetic and scope contact with the vocal cords precipitating total airway obstruction |
| CXR/CT/MRI scans | Can identify severity and depth of glottic, subglottic, tracheal and intrathoracic lesions |
The severity and size of lesions at the glottic level are assessed by direct or indirect laryngoscopy undertaken by ENT surgeons in an outpatient setting and a photograph of the findings is often recorded in the notes (Figures 26.4–26.7). The anaesthetist may perform their own assessment with nasendoscopy (also see Chapter 6). Information about subglottic and tracheal lesions is provided by chest radiography, CT and MRI.
Figure 26.4 Bilateral Reinke’s oedema on vocal cords.
Figure 26.5 Large vocal cord cyst occluding the majority of the airway.
Figure 26.6 Vocal cord polyp.
Figure 26.7 Extensive vocal cord papilloma.
Lesion size gives an indication of potential airflow obstruction. Stridor indicates a significantly narrowed airway. In the adult, stridor implies that the airway diameter is probably less than 5 mm, but the absence of stridor does not exclude a narrowed airway, especially if the lesion is chronic.
Very mobile lesions (e.g. multiple large vocal cord polyps or papillomas) may cause partial airway obstruction following induction of anaesthesia but total airway obstruction is extremely uncommon. Obstruction may change (worsen) after induction of anaesthesia because of the loss of supporting tone in the oropharynx and laryngo-hypopharynx collapsing the airway.
Supraglottic lesions, if mobile, can obstruct the airway or make visualisation of the laryngeal inlet difficult. Subglottic lesions may allow a good view of the laryngeal inlet but may cause difficulty during the passage of a tracheal tube.
Anaesthetic Techniques for Laryngoscopy
For the majority of benign vocal cord lesions and early malignant lesions, airway obstruction is not a feature. Where airway obstruction is anticipated, the anaesthetic plan will change but for non-obstructing lesions a number of anaesthetic techniques are suitable.
Anaesthetic techniques can be broadly classified into two groups: closed systems in which a cuffed tracheal tube is employed with protection of the lower airway and open systems in which no tube is used leaving the airway ‘open’. Open systems use spontaneous ventilation, jet ventilation or oxygen high flow techniques.
The decision to use a closed or open technique will be dependent upon the experience of the anaesthetist and surgeon, the equipment available, the requirements for surgical access, the size, mobility and location of the lesion and its vascularity. The technique chosen for any given procedure is not absolute and may have to change as surgical and anaesthetic requirements change. For example, an open system using jet ventilation on a lesion thought to be relatively avascular may change to a closed system employing a cuffed tracheal tube if the lesion is bleeding with the risk of soiling of the airway. Conversely a system employing a cuffed tracheal tube may have to change during surgery to an open system if the tracheal tube overlies a lesion making surgery very difficult or impossible.
Induction Technique for Laryngoscopy
An intravenous induction technique is suitable for the vast majority of benign and early malignant glottic lesions where airway obstruction is not anticipated. After intravenous induction of anaesthesia and administration of muscle relaxants appropriate to the length of surgery laryngoscopy is undertaken to visualise the larynx, establish laryngoscopy grade and local anaesthetic such as lidocaine may be administered topically. This improves cardiovascular stability, reduces airway reflexes and smooths recovery. Confirmation of pathology is important because the disease may have progressed since the last outpatient visit and the anaesthetic plan may have to change.
Related posts:
Chapter 4 – Structured Planning of Airway Management
Chapter 6 – Pre-anaesthetic Airway Endoscopy, Real and Virtual
Chapter 13 – Supraglottic Airways
Chapter 20 – Front of Neck Airway (FONA)
Chapter 29 – The Patient with a Tracheostomy
Chapter 38 – Airway Management in a Respiratory Epidemic or Pandemic
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