Abstract
Conventional airway management, including intubation and the various modes of lung ventilation, is usually successful. When it fails (cannot intubate, cannot ventilate/oxygenate) it is a life-threatening emergency and will lead to hypoxic brain damage in a few minutes, followed by death, if not resolved. The common final pathway for securing the airway and oxygenation is an emergency front of neck airway (eFONA). Immediate action with a clear plan, appropriate equipment and skills is essential. The ability to efficiently perform an eFONA is a fundamental requirement for any practitioner engaged in advanced airway management. Many techniques are described and it is a difficult area to study, so the evidence of superiority of one technique over others is hard to establish. Preparation, in terms of equipment availability, procedural practice, team familiarity and prompt transitioning through the algorithm when other techniques fail, is important for patient safety. These human factors aspects of eFONA management are at least as important as the procedural technique chosen. This chapter considers the risk factors for airway failure and management of the cannot intubate, cannot oxygenate situation and eFONA procedure in adults and children.
Introduction
The clinical situation where a patient’s trachea cannot be intubated and other methods to ventilate the lungs fail is traditionally termed the ‘cannot intubate, cannot ventilate’ (CICV) situation. However, to emphasise the importance of oxygenation in this setting, the term ‘cannot intubate, cannot oxygenate’ (CICO) is now preferred. It poses a rare, life-threatening event. CICO requires an emergency front of neck airway (eFONA) to avoid hypoxic brain damage or death. Immediate action with a clear plan, appropriate equipment and skills is essential. The ability to efficiently perform eFONA is a fundamental requirement for any practitioner engaged in advanced airway management. This chapter will consider the risk factors and management of CICO and the eFONA procedure.
Incidence
Some anaesthetists may never be required to perform an eFONA procedure. In a Danish airway audit, eFONA occurred in 1:17,000 anaesthetics. In the United Kingdom NAP4 audit, eFONA was performed in 1:50,000 anaesthetics. Of the six patients who died during NAP4, three died after failed emergency airway access. The incidence of eFONA is much higher in the emergency department and community retrieval medicine and may be as high as 1:200 attempted intubations.
Predictors
Percutaneous palpation of the cricothyroid membrane (CTM) can be difficult when performed under stressful conditions, particularly in obese patients and women (pregnant and non-pregnant), where success rates are consistently less than 50%. This is a concern when using any technique that relies on palpation of neck landmarks as a first step. Palpation difficulty is also more likely in patients with a fixed cervical flexion, thick immobile neck, deviated airway, previous radiotherapy and inflammation or induration of the neck.
Indications and Contraindications for eFONA
The most common indication for eFONA is CICO. This may occur acutely where the need for an eFONA is immediately apparent. Conversely, it might evolve insidiously after multiple upper airway manoeuvres; a presentation often difficult to recognise, leading to delayed management. Team training in situation awareness and communication aims to address this delay.
Contraindications for eFONA include total distal airway obstruction or transection and the use of cricothyroidotomy in infants (≤ 12 months old) due to CTM size and fragility.
Pre-eFONA Management
Due to the invasive nature, technical difficulty and potential for failure, avoidance of eFONA is perhaps the most important safety message, and steps should be taken to safely avoid the need for it (acknowledging that when it is indicated it must be undertaken without delay). For example, careful assessment and planning might lead to the decision to perform an awake intubation. Other alternatives could include deferring the case, inserting an elective cricothyroid cannula or calling for help to establish an awake eFONA.
Attempts at supraglottic airway (SGA) management should be optimised and limited. Muscle relaxants can improve airway management for many patients with functional airway obstruction including laryngospasm and opioid-induced muscle rigidity. Conversely, patients with distal airway obstruction, including tracheomalacia and mediastinal masses, should not be paralysed. In these cases, paralysis can lead to extrinsic large airway compression, elimination of diaphragmatic movement and decreased expiratory flow.
Avoiding hypoxia, although intuitively obvious, may not be prioritised and hypoxia may even go unnoticed as the team struggles with tracheal intubation. Hypoxia risk can be mitigated by attention to pre-oxygenation and oxygenation during intubation attempts. Options include pre-oxygenation by face mask and low flow nasal oxygen (< 15 L min−1) or heated humidified high flow nasal oxygen (up to 70 L min−1 in adults) (see Chapter 8). During an eFONA procedure, efforts to oxygenate via the upper airway should continue.
eFONA Management
Practice guidelines clearly describe recommended steps required to manage a CICO situation and eFONA. Recognition is the most important step. Delays in managing CICO events lead to a poor outcome in over 60% of cases. Delays have been attributed to human factors including fixation error with multiple intubation attempts, poor situation awareness (losing track of time and/or failure to recognise urgency or seriousness), lack of available functioning equipment and lack of eFONA skills. Cognitive aids, checklists, cohesive practised teamwork and time checks can help to mitigate these problems.
Time can be saved by preoperatively extending the patient’s neck and identifying the trachea and CTM with the aid of ultrasound. Marking the CTM is a visual indicator that eFONA is an anticipated potential outcome and part of the predetermined team-reviewed plan. When the possible need for eFONA is anticipated a ‘double set-up’ may also be useful: one team managing the airway conventionally with a second team prepared and ready to perform eFONA if required.
The most expert airway practitioner available should perform eFONA. Ideally, that clinician will be a skilled airway surgeon. In their absence, other appropriately skilled surgeons may be called to establish eFONA, but anaesthetists must also be prepared to act. Precious time should not be wasted waiting for a surgeon.
eFONA Techniques
The ideal eFONA technique should have the following features:
a high success rate
a low complication rate
easy to learn
involves only a few steps
provides protection against aspiration
enables adequate ventilation regardless of upper airway obstruction
Three main techniques have evolved for eFONA using various ventilation devices, both ‘home-made’ and commercial. These are:
Needle cricothyroidotomy (i.e. small-bore cannula (2–3 mm inner diameter (ID)). This requires a high-pressure gas source (wall or cylinder pressure, e.g. up to 4 bar = 58 psi = 400 kPa) to overcome cannula flow resistance. A sufficiently patent upper airway is important to allow passive expiration and avoid barotrauma.
Large-bore cannula (> 4 mm ID). This technique is used in various commercial kits. Some use a Seldinger (wire-guided) technique. A cuffed cannula facilitates positive pressure ventilation. The cannula may allow for adequate passive expiration in the presence of upper airway obstruction.
Needle Cricothyroidotomy and Corresponding Equipment
Needle cricothyroidotomy requires identification of the CTM. If right-handed the operator stands on the patient’s left side and if left-handed on the right side). Using the laryngeal handshake technique with an optimally extended neck, the fingers and thumb of the non-dominant hand then move down the lateral borders of the thyroid cartilage to the cricoid cartilage, the index finger then moves to the midline in an attempt to palpate the CTM (Figure 20.1).
