Awake intubation is, as its name suggest, passage of an endotracheal tube whilst the patient is still awake. The concept is that there is never a loss of airway control, with the airway control being transition immediately from patient to anaesthetist. It’s role is therefore primarily in cases where there is a high risk of the anaesthetist being unable to manage the patient’s airway after induction of anaesthesia.
There are several forms that it could take:
Fibreoptic intubation - the most well recognised approach
Blind nasal intubation
Conventional direct laryngoscopy
Awake tracheostomy may also be considered to be similar, as the indications mean that it will require consideration alongside awake intubation methods.
Suspected or known difficult airway
Cervical spine instability
The transition from a patient controlled airway to anaesthetist control can be a period of risk to the patient if the airway is difficult. Awake intubation is the prefered technique to minimise this risk. There is debate about the best approach in patients with airway due to airway obstruction, particularly periglottic tumours. In this scenario, awake intubation may lead to complete obstruction (‘cork in the bottle’ effect) and thus not be feasible.
Awake intubation (particularly AFOI) will minimise cervical movement that is a significant risk with direct laryngoscopy technique. It’s elective use in the patients can minimise the risk of neurological injury. In a similar way it can be employed to intubate patients who require difficult awake positioning for safety e.g. prone positioning with significant RA.
Patient refusal (despite careful discussion of risks and benefits)
Lack of compliance e.g. acute confusion, children
Airway bleeding (may include severe coagulopathy for nasal)
True local anaesthetic intolerance
High risk for aspiration (debatable)
Essentially, any lack of compliance from the patient will make the technique impossible to perform with the degree of safety that it is intended for. Other reasons are more based around the modification to the risk vs benefit ratio, and so will be varied depending on the clinical context.
Awake Fibreoptic Intubation (AFOI)
This is probably the most common form. Components to consider include:
The nasal approach is often prefered as it provides a better approach to the glottis and easier topicalisation
A clear expectation of what to expect will reduce patient anxiety with the procedure. This includes an awareness of what to expect with the topicalisation of the airway (horrible taste, coughing etc). This will involve an explanation of the need for this approach and the risks of an asleep approach. Consent should be obtained.
Some clinicians like to use an anti-sialogogue to reduce secretions and improve viability. Options include:
Glycopyrrolate 4mcg/kg IM one hour before
Glycopyrrolate IV - low dose to try and minimise tachycardia
Atropine - 0.3-0.6mg IM
Hyoscine 0.2mg IM
All the required equipment should be prepared beforehand, including:
Bronchoscope and stacker system
Appropriate tube - commonly size 6.0 ID reinforced tube (or nasal tube) - this should be of an appropriate length, lubricated and lightly taped to the scope (some anaesthetists like the conical shape of the iLMA tube as there is no bevel to catch on the laryngeal structures on insertion).
Surgeon - if high risk of needing surgical access to airway
Options to achieve airway anaesthesia include airway blocks and topical application.
Topical anaesthesia is probably the most common approach. Options include:
Nebulised lidocaine (2%/4%/10%)
Topical lidocaine (4%)
Spray as you go
Cocaine (4, 10, 25%)- max dose 1.5mg/kg
Nebulised lidocaine can be given via a tightly fitting facemask for 20-30 minutes beforehand. It will often need topical supplementation as the density of block can be variable. It has the advantage of being very easier to do.
Nasal application of LA will commonly include a vasoconstrictor e.g. co-phenylcaine which includes phenylephrine with lidocaine.
Initial topicalisation of the airway can be done prior to starting the technique. Gargling of lidocaine solution (e.g. 50ml of 4%) can be a good starting point. This is then spat out. Initial spraying of the pharynx can also be done prior to starting, though impaired mouth opening may make this difficult. Further topicalisation may need to be done under direct vision through the scope. Threading of an epidural catheter down the suction port of the scope can allow this, although direct injection down the port is also practiced. Asking to patient to start inhaling just prior to injecting can aid laryngeal spread (though will produce coughing and discomfort and so the patient should be warned).
The soaking of cotton wool swabs in local anaesthetic is another useful technique. Application of these, particularly in key locations, can provide a denser degree of anaesthesia that other techniques of topical application.
When considering the maximal safe dose, 9mg/kg is quoted when considered mucous membrane application.
Airway blocks are discussed elsewhere.
The goal of sedation here is to improve the patient tolerance of the procedure, and so properties such as anxiolysis and analgesia are favoured. Options include:
Remifentanil target controlled infusion (TCI) has many favourable properties for use in this context. It’s potent analgesic and antitussive effects mean that it has even been used to facilitate AFOI without airway anaesthesia, although the high doses required may mean a higher risk of the adverse effects e.g. bradycardia. The dose (in terms of effect site concentration) can be titrated to effect. Levels as low as 1-2ng/ml can be adequate in many people, though a higher level of 3-5ng/ml may be needed.
Midazolam has useful anxiolytic and amnesic effects. Low doses (0.5-1mg) can be useful for sedation, but the lack of any analgesic effect may mean that very effective airway anaesthesia or the addition of a short acting opioid e.g. fentanyl, is needed.
Propofol has primarily hypnotic effects so adequate sedation on its own is difficult to achieve. It is commonly used alongside remifentanil, but needs careful titration to avoid excessive sedation.
Extensive sedation may result in the problems that were trying to be avoided in the first place. As such, a specific sedationist may be required to focus on the patient whilst the operator is at risk of becoming fixated on the intubation. This is likely to be more a problem for specific agents e.g. propofol, and with certain patient population.
The patient should be appropriately positioned; the semirecumbent position is often best. Full AAGBI monitoring should be in place. IV access should be obtained. Supplemental oxygen should common be applied to provide an additional safety net against desaturation. A common position to perform the technique is facing the patient on their right hand side. The screen for the scope should be positioned appropriately to allow a good view.
After appropriate initial topical anaesthesia, and once all preparations are done, the scope can be careful inserted into the mouth/nose. A bite block may be used in oral intuations. Once the laryngeal anatomy is visualised through the scope, the final steps of topicalisation are usually undertaken under direct vision. Asking the patient to stick out their tongue or breath in may improve the anatomy e.g. a posterior epiglottis. After allowing time for the anaesthetic to act, the scope is passed through the vocal cords, aiming to keep it in the midline. Asking the patient to breath in whilst doing this can help abduct the cords. The tip of the scope is then positioned distal to the carina. The ETT is then railroaded over the scope - again asking the patient to breath in at this time can help to pass the cords.
Position of the ETT should be visualised confirmed as the bronchoscope is withdrawn. The ETT can then be attached to a breathing circuit and a capnograph trace confirmed. Induction of anaesthesia can now be performed, usually intravenously. The inflation of the cuff is often left until after anaesthesia - the cuff can be irritating and the sensation of trying to breath down a narrow ETT distressing.
Extubation remains a risky period, unless the cause for difficult intubation has be corrected. Options may include:
Delayed extubation - if short term difficulty like oedema
Exchange catheter left in the airway
The advent of the different forms of videolaryngoscopy have made this approach an increasingly considered option. Arguments in favour of its use note the increased familiarity with it (similarity to direct laryngoscopy technique, routine/semi-elective use). Disadvantages include the difficulty that impaired mouth opening will still impose (an important factor for difficult intubation.