Introduction

Airway interventions are the procedures most commonly associated with mortality and serious morbidity in the intensive care unit (ICU). Approximately 6% of ICU patients have either a known difficult airway or features indicating anatomical difficulty. Physiological abnormalities such as pre-existing hypoxia and haemodynamic instability add to the degree of difficulty because they shorten the safe apnoea time and cognitively overload the operator. Added to this, ICU is rarely designed for airway management in the same way as the operating theatre is, creating logistical challenges to airway management. Thus, intubation in ICU will often include anatomical difficulty, physiological difficulty and logistical difficulty.

Anticipating difficult intubation is particularly important: complications are higher in difficult intubation than non-difficult intubation (51% vs. 36% for severe life-threatening complications such as hypoxaemia and cardiovascular collapse). De Jong reported that intubation-related cardiac arrest occurred in 2.7% of ICU patients (1000-fold higher than in elective surgery) and 28-day mortality was increased 3-fold when cardiac arrest occurred (hazard ratio 3.9 (95% CI 2.4–6.3), p < 0.0001, after adjustment for confounding variables). Five independent risk factors predictive of intubation-related cardiac arrest were hypoxaemia, haemodynamic failure, absence of pre-oxygenation (all modifiable before intubation), body mass index (BMI) > 25 kg m⁻² and age > 75 years.

Difficult intubation occurs in about 10% (range: 1–23%), but ICU intubation is still commonly managed in a relatively primitive manner. NAP4 reported that airway-related death and brain damage may be 50- to 60-fold more common than operating room practice. Jaber and colleagues demonstrated that using didactic ICU intubation bundles improves outcome. Elements of such a bundle are described in this chapter.

Reducing the Risks in the ICU by Using an Intubation Bundle Approach

In 2018, several UK organisations (the Difficult Airway Society (DAS), Intensive Care Society and the Faculty of Intensive Care with endorsement from the Royal College of Anaesthetists) created a UK national guideline for tracheal intubation in the critically ill adult. This establishes an intubation bundle, which retains the standard algorithmic structure of Plans A–D seen in the DAS guidelines, albeit with a unified Plan B/C, similar to the ‘Vortex’ approach.

Human Factors

More than individual technique or innovative devices, human factors may be the single most important modifiable element in ICU intubation: an average of 4.5 human factor elements per case were seen in reports of major airway complications reported to NAP4 (see also Chapter 36). The nature of modern critical care means that the team assembled to achieve intubation may never have performed this task together before. This can lead to rigidly vertical or chaotic communication, to poorly planned and executed actions and, when difficulty arises, to increasingly urgent and technically challenging cognitive tasks falling on a single team member, who receives limited support from others.

To avoid this, the intubation team leader must ensure the intubation plan is explained to all team members prior to induction and empower them to speak up or raise concerns. This is ‘sharing the mental model’: not only must the whole team know how the operator intends to secure the airway, but crucially, what will be needed should difficulty arise – the ‘plan for failure’. The team leader verbalising an appropriate intubation checklist in which the team prepares the patient, themselves, the equipment and also agrees on the plan for managing difficulty is an extremely powerful tool (Figure 28.1). This occurs concurrently with pre-oxygenation. Such proactive leadership engenders active followership in other team members.

Figure 28.1 ICU Intubation Checklist.

(Reprinted with permission of the Difficult Airway Society. Copyright © 2017 Difficult Airway Society. Higgs et al. (2018).)

Team performance is optimised using real-world simulation together in their own unit, following an agreed algorithm and using equipment with which they are trained. The intubation trolley should be identical to that used elsewhere in the hospital to avoid presenting operators with unfamiliar devices. The algorithm should be displayed clearly whenever intubation is performed (Figure 28.2). Shift handovers should detail potential airway difficulties and specific plans tailored to that resident team’s skill set should be made. Regular whole-team no-blame discussion of critical incidents and near misses is an efficient means of improving practice.

Figure 28.2 Algorithm for tracheal intubation in critically ill adults.

(Reprinted with permission of the Difficult Airway Society. Copyright © 2017 Difficult Airway Society. Higgs et al. (2018).)

Assessment

Predicting difficult intubation enables the team to prepare optimally. A tool predicting difficult intubation, the MACOCHA score, was developed and externally validated in a prospective multicentre French study and is shown in Table 28.1.

A cut-off of ≥ 3 predicts difficulty. This score has a negative predictive value of 98% and sensitivity of 73%. Importantly, Mallampati class can be assessed in a cooperative supine patient. Such prediction tools are only useful if they lead to a change in approach (see below) and none are wholly sensitive and specific, so preparing for unanticipated difficulty is crucial.

Use the ‘laryngeal handshake’ to identify the cricothyroid membrane (CTM). If this is impalpable but time permits, ultrasound should be used to locate the CTM, or as a minimum to mark the midline. This should be done with the head and neck extended in the position that would be used during an emergency front of neck airway (eFONA) procedure.

Haemodynamic assessment is also necessary; pre-intubation optimisation may prevent peri-intubation collapse.

Airway Plan A

This refers to the phase of preparation (including pre-oxygenation and haemodynamic optimisation), modified rapid sequence induction (RSI), peroxygenation (oxygenation throughout intubation attempts), laryngoscopy and intubation. Decide before induction whether awakening the patient is indicated if intubation fails; most ICU patients require intubation because of neurological, respiratory or cardiovascular failure and so attempting to awaken the patient is usually inappropriate.

Sit the patient 25–30° head-up (use reverse-Trendelenberg tilt if spinal instability is suspected). This maximises functional residual capacity (FRC) and may reduce passive regurgitation of gastric contents. Together with extending the head on the flexed neck, this permits optimal access to the airway. Ramp obese patients (see Chapter 24).

To help avoid cardiovascular collapse, administer a fluid load (500 mL balanced crystalloid) in the absence of cardiogenic pulmonary oedema and start vasopressors early if the blood pressure is low.

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 31 – Airway Management during CPR Chapter 26 – Ear, Nose and Throat Surgery: Airway Management

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