Step 3 involves the actual performance of extubation.
General considerations. Any extubation technique used should ensure minimum interruption in oxygen delivery to the patient’s lungs. The following general considerations are relevant to extubation for both the ‘low-risk’ and the ‘at-risk’ groups:
Building oxygen stores (pre-oxygenation): the peri-operative anatomical and physiological changes described above compromise gas exchange, and make pre-oxygenation before extubation vital. As for induction of anaesthesia, the aim of pre-oxygenation before extubation is to maximise pulmonary oxygen stores by raising the FEO2 above 0.9, or as close to the FIO2 as possible . Although studies have shown that an FIO2 of 1.0 increases atelectasis, the clinical significance of this has yet to be determined [79, 80]. At extubation, the priority is to maximise oxygen stores to continue oxygen uptake during apnoea, and therefore pre-oxygenation with a FIO2 of 1.0 is recommended [81–85].
Patient position: there is no evidence to support a universal patient position for extubation. There is an increasing trend towards extubating in a head-up (reverse Trendelenburg) or semi-recumbent position. The head-up tilt is especially useful in the obese population as it confers a mechanical advantage to respiration and provides more familiar conditions in which to monitor and manage the airway. A left-lateral, head-down position has traditionally been used for the non-fasted patient [77, 86].
Suction: the soft tissues of the oropharynx are at risk of trauma if suction is not applied under direct vision [87, 88], ideally using a laryngoscope, particularly if there are concerns about oropharyngeal soiling from secretions, blood or surgical debris. Laryngoscopy should be carried out with the patient in an adequately deep plane of anaesthesia, but may need to be repeated. Special vigilance is necessary if there is blood in the airway, as NAP4 highlighted the danger of the ‘coroner’s clot’, where aspiration of blood can lead to airway obstruction and death . Suction of the lower airway using endobronchial catheters, together with aspiration of gastric tubes, may also be necessary.
Alveolar recruitment manoeuvres: patients undergoing anaesthesia develop atelectasis. Alveolar recruitment manoeuvres, such as sustained positive end-expiratory pressure (PEEP) and vital capacity breaths, may temporarily reverse atelectasis, but have not been shown to provide any benefit in the postoperative period [81, 90]. Simultaneous deflation of the tracheal tube cuff and removal of the tube at the peak of a sustained inflation generates a passive exhalation, and may be sensibly employed to expel secretions and possibly reduce the incidence of laryngospasm and breathholding.
Bite block: a bite block prevents occlusion of the tracheal tube should the patient bite down during emergence from anaesthesia [91–93]. Forced inspiratory efforts against an obstructed airway can rapidly lead to pulmonary oedema (see Appendix 2B) . Should biting occur, deflating the cuff of the tube or laryngeal mask airway (LMA) may prevent post-obstructive pulmonary oedema, as significant negative pressure cannot be generated if air can flow around the device. Various devices have been used as bite blocks, including the Guedel airway. When rolled gauze is used, it is important that it is tied or taped to the tracheal tube to prevent displacement or accidental airway obstruction.
Avoidance of the sequelae of airway stimulation: traditionally, extubation has been performed when the patient is either fully ‘awake’ or deeply anaesthetised.
Awake extubation is generally safer as the return of airway tone, reflexes and respiratory drive allows the patient to maintain their own airway.
Deep extubation reduces the incidence of coughing, bucking and the haemodynamic effects of tracheal tube movement, but these advantages are offset by an increased incidence of upper airway obstruction [95–97]. This is an advanced technique, which should be reserved for patients in whom airway management would be easy and who are not at increased risk of aspiration.
It is possible to reduce the risk of airway obstruction by exchanging the tracheal tube for a LMA before emergence (Bailey maneouvre; see below) .
Opioids such as alfentanil, fentanyl and morphine have been used to suppress any cough reflex. Currently, the ultrashort-acting opioid remifentanil, administered by infusion, is the drug of choice for this technique, but requires careful administration (see below). The benefits of cough suppression must be weighed against the increased risks of sedation and respiratory depression. Lidocaine has been used to reduce coughing; it may be administered topically at intubation, into the cuff of the tracheal tube or intravenously before extubation, with some benefit .
Other pharmacological agents have been used to attenuate the cardiovascular and respiratory changes associated with extubation, including opioids, calcium channel antagonists, magnesium, lidocaine, clonidine, ketamine and beta blockers [28, 99–103]. Doxapram has been used to prevent and/or treat laryngospasm, although it is associated with cardiovascular stimulation and robust evidence to support its use for this indication is lacking . The use of steroids to reduce inflammatory airway oedema is described below [105–107].
The performance of ‘at-risk’ extubation. An ‘at-risk’ extubation is one in which the risk stratification (steps 1 and 2 above) has identified general and/or airway risk factors that suggest that a patient may not be able to maintain his/her own airway after removal of the tracheal tube. ‘At-risk’ extubation is characterised by the concern that airway management may not be straightforward should reintubation be required.
An example of an ‘at-risk’ extubation might involve the patient having emergency surgery to repair a leaking aortic aneurysm for whom general factors such as a full stomach, unstable cardiovascular physiology, acid-base derangement or temperature control can make extubation more challenging.
An example of ‘at-risk’ extubation due to airway factors might involve the patient undergoing head and neck surgery after awake fibreoptic intubation before induction of general anaesthesia, because of previous head and neck radiotherapy.
Step 1 would stratify both these patients into the ‘at-risk’ extubation group. Step 2 would enable stabilisation of general factors and optimisation of logistical factors e.g. communication with the intensive care unit, assembling equipment, getting help.
The key decision to be made is whether it is safer to extubate, or preferable for the patient’s trachea to remain intubated. If it is considered safe to extubate, then an awake extubation or one the advanced techniques described below will overcome most of the challenges in the ‘at-risk’ patient. A broad range of equipment and advanced techniques are available, but no single technique covers all clinical scenarios. None of these techniques is without risk; training and experience in their use are vital before they are employed in a difficult airway situation. If it is considered unsafe to extubate, the options are to postpone extubation or perform a tracheostomy.
Awake extubation: the technique of awake extubation for the ‘at-risk’ patient is the same as that described above for the low-risk group, and is suitable for most patients in the ‘at-risk’ group (for example, those at risk of aspiration, the obese, and many patients with a difficult airway). However, in some situations, one or more of the following advanced techniques may be beneficial:
Laryngeal mask exchange (Bailey manoeuvre): this involves replacement of a tracheal tube with a LMA to maintain a patent, unstimulated airway with stable physiological observations and protection of the airway from soiling secondary to blood and secretions in the mouth. The emergence profile of this technique is superior to either awake or deep extubation [108–111], and is useful in cases where there is a risk of disruption of the surgical repair due to the cardiovascular stimulation resulting from the presence of a tracheal tube. It may also benefit smokers, asthmatics and other patients with irritable airways. It is inappropriate in patients in whom re-intubation would be difficult or if there is a risk of regurgitation. The technique was originally described using the Classic LMA [98, 112]. Data for use of other supraglottic airway devices are lacking. The technique requires practice and meticulous attention to detail; adequate depth of anaesthesia is critical to avoid laryngospasm (Table 4).
Table 4. Sequence for LMA exchange in ‘at-risk’ extubation.
| 1 Administer 100% oxygen|
| 2 Avoid airway stimulation: either deep anaesthesia or neuromuscular blockade is essential|
| 3 Perform laryngoscopy and suction under direct vision|
| 4 Insert deflated LMA behind the tracheal tube|
| 5 Ensure LMA placement with the tip in its correct position|
| 6 Inflate cuff of LMA|
| 7 Deflate tracheal tube cuff and remove tube whilst maintaining positive pressure|
| 8 Continue oxygen delivery via LMA|
| 9 Insert a bite block|
|10 Sit the patient upright|
|11 Allow undisturbed emergence from anaesthesia|
This method favours correct positioning of the LMA as the tracheal tube splints the epiglottis as it is inserted, preventing downfolding of the epiglottis. Similar techniques to the Bailey manoeuvre include:
- 1 Removal of the tracheal tube before LMA insertion, following laryngoscopy and pharyngeal suction;
- 2 Insertion of a flexible fibreoptic bronchoscope through the stem of the LMA, to confirm its correct position, and to observe vocal cord motion. This technique is useful for patients who have had thyroid/parathyroid surgery and other situations in which airway integrity may have been impaired;
- 3 Laryngeal mask airway exchange for a nasotracheal tube, using one of two methods: the LMA may be inserted from the side of the nasotracheal tube so that the former slides behind the latter; or the nasotracheal tube can be removed before inserting the LMA.
Remifentanil extubation technique: the presence of a tracheal tube may trigger coughing, agitation and haemodynamic disturbances during emergence from anaesthesia. In certain groups of patients (for example, neurosurgical, maxillofacial, plastics and those with significant cardiac or cerebrovascular disease), these responses are undesirable. Although possible, both awake and deep extubation are far from ideal in these situations. The cough suppressant effects of opioid drugs and their ability to attenuate the cardiovascular changes with extubation have been known for many years [113, 114]. Infusion of the ultrashort-acting opioid remifentanil attenuates these undesirable responses and may be used to provide the beneficial combination of a tube-tolerant patient who is fully awake and obeys commands.
Remifentanil infusions have been extensively described as a method of providing conscious sedation for awake fibreoptic intubation in the spontaneously breathing patient [115–119] and evidence is emerging to support a similar strategy during emergence and extubation [120–125]. Several factors influence the dose of remifentanil necessary to prevent coughing at extubation, and relate to patient characteristics, surgical procedure and the anaesthetic technique. A remifentanil infusion can be used in two ways: infusion may be continued after intra-operative use; or it can be administered specifically for extubation. The success of these approaches lies in removing the hypnotic component of anaesthesia (inhalational agent or propofol) well in advance of extubation, allowing appropriate titration of remifentanil. A broad range of doses have been described in the literature, but generally titration aims to avoid either coughing (too low a dose) or delayed emergence and apnoea (too high a dose) (Table 5).
Table 5. Sequence for use of a remifentanil infusion for ‘at-risk’ extubation.
| 1 Consider postoperative analgesia. If appropriate, administer intravenous morphine before the end of the operation |
| 2 Before the end of the procedure, set the remifentanil infusion at the desired rate|
| 3 Antagonise neuromuscular blockade at an appropriate phase of surgery and emergence|
| 4 Discontinue anaesthetic agent (inhalational agent or propofol)|
| 5 If using inhalational agent, use high-flow oxygen-enriched gas mixture to aid full elimination and monitor its end tidal concentration|
| 6 Continue ventilation|
| 7 Laryngoscopy and suction should be performed under direct vision if appropriate|
| 8 Sit the patient upright|
| 9 Do not rush, do not stimulate, wait until the patient opens their eyes to command|
|10 Discontinue positive pressure ventilation|
|11 If spontaneous respiration is adequate, remove the tracheal tube and stop the infusion|
|12 If spontaneous respiration is inadequate, encourage the patient to take deep breaths and reduce the infusion rate|
|13 When respiration is adequate, remove the tracheal tube and discontinue the remifentanil infusion, taking care to flush residual drug from the cannula|
|14 After extubation, there is a risk of respiratory depression and it is essential that the patient is closely monitored until fully recovered|
|15 Remember that remifentanil has no long-term analgesic effects|
|16 Remember that remifentanil can be antagonised by naloxone|
Airway exchange catheter-assisted extubation: patients for whom reintubation is likely to be difficult may benefit from continuous airway access, which can be achieved with an airway exchange catheter (AEC) [127, 128]. This device is inserted into the trachea through the tracheal tube before extubation. The concept of managing extubation with specially designed long, hollow tracheal ventilation catheters in patients with difficult airways was developed by Bedger and Chang and later used by Cooper in a series of 202 patients [129–131]. Other similar devices have been described, but the only device that is commercially available in the UK for this purpose is the Cook Airway Exchange Catheters (William Cook Europe, Bjaeverskov, Denmark). The use of suction catheters, nasogastric tubes, bougies and the Aintree Intubation Catheter (William Cook Europe) have been described, but these have limitations .
Airway exchange catheters are long, thin hollow tubes made from semi-rigid thermostable polyurethane. They are blunt-ended, have distal terminal and side holes, are radiopaque and have length markings on the exterior surface. They are supplied with removable 15-mm connectors that are compatible with anaesthetic circuits and/or Luer lock connectors for use with high-pressure source (jet) ventilation or oxygen tubing. They are available in a range of sizes, the most appropriate for extubation being the 83-cm long 11- and 14-FG catheters; these have internal diameters of 2.3 and 3 mm respectively, with external diameters of 3.7 and 4.7 mm that are compatible with tracheal tubes of internal diameters more than 4 and 5 mm, respectively.
Airway exchange catheters can be used as a guide over which a tracheal tube can be passed should reintubation become necessary, and can be used to oxygenate the patient’s lungs. They have a high success rate when used as a guide for reintubation. Most of the morbidity attributed to their use is associated with oxygenation and inappropriate positioning. Meticulous care must be taken to ensure that the distal tip is positioned in the mid trachea at all times. Oxygen insufflation and high-pressure source (jet) ventilation should only be undertaken with extreme caution as barotrauma and death have been reported [133–136]. Anaesthetists should be familiar with these devices: training, practice and rehearsal can be achieved using manikin-based scenarios.
A prospective study of 354 patients with difficult airways over a nine-year period confirmed the safety and efficacy of AECs . There was a high degree of successful first attempts at reintubation. Complications, including low oxygen saturation, bradycardia, hypotension, oesophageal intubation and use of accessory airway adjuncts were less common when reintubation was performed using an AEC. Other studies in patients with difficult airways have also reported successful outcomes [128, 138]. Observation of the larynx, either by direct or videolaryngoscopy, increases the success of reintubation using an AEC and reduces complications . Attention to detail and due care must be exercised in the use of an AEC, as the complications of their use may be severe.
Four techniques involving AEC-assisted extubation require consideration:
- 1 Inserting the AEC before extubation (Table 6).
- 2 Respiratory deterioration: maintaining oxygenation. Identify the cause of the respiratory deterioration and institute appropriate measures. If the deterioration is associated with upper airway obstruction, high-flow oxygen should be given by facemask only (not via the AEC), standard airway manoeuvres or adjuncts should be used, mask-delivered continuous positive airway pressure (CPAP) can be applied if the AEC is moved to the corner of the mouth to provide an adequate facemask seal, and adrenaline should be nebulised via the facemask. Helium-oxygen (Heliox) can be given as a temporising measure to reduce the impact of airway swelling [140, 141].
Oxygen should only be insufflated through the AEC in extremis because of the risk of barotrauma. It is essential to ensure that the tip of the catheter is above the carina and that there is a route for exhaled gas. Flows should not exceed 1–2 l.min−1. In this situation, reintubation will usually be required.
- 3 Reintubation using an AEC. This is a complex procedure. Full monitoring, skilled assistance and essential equipment should be available (Table 7).
- 4 High-pressure source (jet) ventilation via an AEC during airway rescue. Jet ventilation via an AEC aims to avoid life-threatening hypoxia, rather than achieve full ventilation. Familiarity with the equipment and technique is essential. Barotrauma, resulting from AEC migration and subcarinal jet ventilation, is a potentially serious complication, so this technique should only be considered as a last resort and only used when there is a leak around the AEC enabling expiratory flow [134, 137]. The patency of the upper airway, using airway manoeuvres and/or adjuncts to allow expiration, further assists the avoidance of barotrauma. Many high-pressure source ventilation devices are available, but the safest incorporate a pressure sensor that stops gas flow above a pause pressure of 10–20 cmH2O. The risk of barotrauma can be reduced by using a minimal effective inflation pressure, ensuring that the chest falls to the neutral position before further inflation, and a short inspiratory time.
In addition to barotrauma, the risks associated with AECs include direct perforation of the tracheal mucosa, interstitial pulmonary emphysema [133–136, 142, 143] and dislodgement (due to poor patient compliance, poor supervision, inadequate fixation of the AEC or airway manipulation).
Table 6. Sequence for use of an airway exchange catheter for ‘at-risk’ extubation.
| 1 Decide how far to insert the AEC. It is essential that the distal tip remains above the carina. If there is any un certainty about the position of the tracheal tube tip, its position relative to the carina should be checked with a fibreoptic bronchoscope before AEC insertion. An AEC should never be inserted beyond 25 cm in an adult patient|
| 2 When the patient is ready for extubation, insert the lubricated AEC through the tracheal tube to the predetermined depth. Never advance an AEC against resistance|
| 3 Employ pharyngeal suction before removal of the tracheal tube|
| 4 Remove the tracheal tube over the AEC, while maintaining the AEC position (do not advance the AEC)|
| 5 Secure AEC to the cheek or forehead with tape|
| 6 Record the depth at the teeth/lips/nose in the patient’s notes|
| 7 Check that there is a leak around AEC using an anaesthetic circuit|
| 8 Clearly label the AEC to prevent confusion with a nasogastric tube|
| 9 The patient should be nursed in a high dependency or critical care unit|
|10 Supplemental oxygen can be given via a facemask, nasal cannula or CPAP mask|
|11 The patient should remain nil by mouth until the AEC is removed|
|12 If the presence of the AEC causes coughing, check that the tip is above the carina and inject lidocaine via the AEC|
|13 Most patients remain able to cough and vocalise|
|14 Remove the AEC when the airway is no longer at risk. They can be tolerated for up to 72 hours |
Table 7. Sequence for use of an airway exchange catheter for reintubation.
|1 Position the patient appropriately|
|2 Apply 100% oxygen with CPAP via a facemask|
|3 Select a small tracheal tube with a soft, blunt bevelled tip (for example, the tube developed for use with an intubating LMA (Intavent Direct Ltd, Maidenhed UK). |
|4 Administer anaesthetic or topical agents as indicated|
|5 Use direct or indirect laryngoscopy to retract the tongue and railroad the tracheal tube (with the bevel facing anteriorly) over the AEC|
|6 After reintubation, confirm the position of the tracheal tube with capnography|
Postpone extubation: extubation is an entirely elective process. At times, the threat of airway compromise is so severe that extubation should not take place. Postponing extubation for a few hours, or in some cases for a few days, may be the most appropriate course of action. A delay may allow airway oedema to resolve and increase the chances of successful extubation. It is a sensible choice if there is a potential need to return to theatre within 24 hours. It may be the best option to match the availability of skilled, experienced personnel with the period of greatest risk; for example, it may be safer not to extubate the trachea of a patient with a very difficult airway in the late evening.
If the patient is transferred to a critical care area, there should be a written emergency reintubation plan, as recommended by NAP4 .
Elective surgical tracheostomy: tracheostomy should be considered when airway patency may be compromised for a considerable period due to pre-existing airway problems, the nature of surgery (for example, free flap reconstruction) or the extent of tumour, swelling, oedema or bleeding. The anaesthetist and surgeon should discuss these concerns during the planning or preparation steps and a decision made to place a tracheostomy electively.
The decision to perform tracheostomy is informed by: (1) the extent of airway compromise at the end of surgery; (2) the likelihood of postoperative airway deterioration (usually due to swelling); (3) the ability to rescue the airway; and (4) the expected duration of significant airway compromise.
Tracheostomy reduces the risk of glottic damage compared with a long-term use of a tracheal tube, and is particularly important if the patient has laryngeal oedema, or if slow resolution of a problem airway is anticipated. In addition, rapid postoperative emergence is possible without fear of unplanned extubation or failure to reintubate. Postoperative nursing in a high dependency care unit can be followed by specialist ward care.
Prophylactic (rescue) subglottic cannula: transtracheal cannulae do not provide a definitive airway, but in situations where they have been inserted at induction for an anticipated difficult airway, they can be left in situ . The ‘insurance’ of having a transtracheal catheter in place and being able to insufflate oxygen or ventilate with a high-pressure source can be life-saving, but must be balanced against potential complications, including barotrauma, displacement, obstruction or kinking, trauma, haemorrhage, and infection. The same level of postoperative care and monitoring is required as for a tracheostomy. They can be left in place for up to 72 hours.