Extubation and Airway Exchange

EXTUBATION GUIDELINES

Securing the airway is only the beginning. At some point, the airway device will need to be removed or changed. This section of the course covers how we assess patients for extubation and device exchange, and how we perform these procedures safely.

In the 2011 National Audit Project 4 (NAP 4), about one third of anaesthesia incidents occurred around extubation and recovery.¹ The majority of these were due to airway obstruction, with a variety of causes including laryngospasm, occlusion of an airway device by patient biting, blood in the airway or airway swelling. The diagnosis of obstruction was often delayed, resulting in five cases of severe hypoxia and two deaths.

Extubation is hazardous for a variety of reasons. Airway reflexes can be affected by tracheal intubation, drugs and illness. They can be diminished, causing inadequate cough, poor clearance of secretions and a loss of muscle tone, resulting in collapse, obstruction, or regurgitation of stomach contents. Airway reflexes can also be exaggerated, resulting in coughing, laryngospasm and in severe cases, post-obstruction pulmonary oedema.²

The airway can be injured during surgery, tracheal intubation or by repetitive shearing forces caused by the tube, especially in agitated patients in the ICU. These can all cause airway swelling, which can be exacerbated by head-down positioning, fluid overload and any surgery or radiotherapy which alters lymphatic drainage. Nasogastric tubes, endoscopes and trans-oesophageal echocardiography probes can also cause damage which may not become evident until extubation is attempted.

The year after NAP4, the Difficult Airway Society (DAS) published guidelines for extubation.² They are based mainly on expert opinion, as there is very little trial evidence in this field, and of note, pertain to adult peri-operative care and not to critical care patients.

The basic approach involves planning and preparation, followed by risk assessment. There are then ‘low-risk’ and ‘at risk’ algorithms which should prompt the formation of an extubation strategy. Ideally this should all occur prior to intubation. The strategy should include a plan for the timing and technique of extubation, and the disposition and ongoing care of the patient. These guidelines are very much designed for anaesthetic practice, so the guidelines are not entirely applicable to the patients we encounter in the ED and ICU. However, the same basic principles of planning, preparation and post-extubation care still apply.

When planning to extubate an intensive care patient, there are many questions that need to be answered – see the CCAM Extubation Checklist below.³ Various test can be especially useful here including blood gas analysis, chest imaging, the bedside assessment of respiratory parameters and nasendosopy.

Extubation is a team decision and a team activity. It is important that the nursing and allied health staff are on board with the plan. It may be beneficial, for example, to arrange for an intensive physiotherapy regime after extubation of a patient who has a lot of secretions or a borderline cough.

Patients should be characterised as ‘low risk’ or ‘at risk’ as in the DAS extubation guideline. An example of an ‘at risk’ patient due to general factors might be a patient after surgery for ruptured aortic aneurysm, where haemodynamic instability, metabolic derangement, potential full stomach and distended abdomen would make early extubation challenging. An example of an ‘at risk’ patient due to airway factors would be a patient who has had neck surgery after awake fibre optic intubation for previous surgery and radiotherapy.²

Preparation for extubation should include gathering the right personnel and equipment in case of failure. Equipment should include resuscitation and difficult airway trolleys, wire cutters if the jaw has been wired, and clip removers if there is a risk of haematoma formation around the airway, for example, after thyroid surgery. Humidified oxygen is preferable is the airway is deemed to be at risk.

If airway oedema is suspected in an intensive care patient, either because of findings at nasendoscopy, or because of a poor or absent cuff leak, there is good evidence that steroids can decrease the incidence of post-extubation stridor and re-intubation. Multiple doses, equivalent to 100mg hydrocortisone four times daily, are preferable to single doses.⁴

If muscle relaxants have been administered, neuromuscular monitoring should be used to ensure that they have been completely reversed prior to extubation.

EXTUBATION PROCEDURE

• Head up position if possible
• Aspirate nasogastric tube (note that this does not reliably empty the stomach completely)
• Suction oropharynx, preferably under direct vision
• Administer 100% O2 via tracheal tube
• Apply positive pressure, deflate cuff and remove tube at end inspiration
• Administer oxygen by face mask

In ED and ICU, patients are extubated awake. In the operating theatre, patients may be extubated while asleep (‘deep extubation’). This is done if the airway is deemed to be low risk and there are perceived benefits to deep extubation, such as decreased coughing and haemodynamic stability. However, sedative or analgesic drugs might be of benefit in some patients, if there is agitation, or if emergence and extubation with haemodynamic stability is desired. Short acting agents are preferable, such as low-dose propofol, remifentanil, or dexmedetomidine.²

In high risk post-operative patients, other strategies may also be used, such as laryngeal mask exchange, trans-tracheal catheters and airway exchange catheters (see below).

It is important to remember that extubation can always be delayed. Admitting the patient to the ICU for further assessment is prudent if there is any doubt about the airway. The patient can also undergo elective tracheostomy if problems with the airway are thought to be insurmountable in the short term.

After extubation, patients must be cared for in the operating theatre, recovery area, ED resuscitation bay, high-dependency unit or intensive care unit. Patient monitoring should include ECG, blood pressure, oxygen saturations and continuous end-tidal CO2. Staff trained in airway management and monitoring of the patient post-extubation should care for these patients. Clinicians with advanced airway skills must be immediately available. Good communication and handover are essential.

Patients need to be monitored for signs of extubation failure, by staff trained to elicit these signs. Predictors of the requirement for re-intubation include hoarse voice, cough, difficulty swallowing, drooling, stridor and orthopnoea. Patients should also be closely watched for bleeding; into the airway, into drains or into an expanding haematoma.

Only one intervention has been found to be beneficial in the immediate treatment of the patient with post-extubation stridor. Nebulised adrenaline (3-5mls of 1:1000 solution, nebulised with oxygen at 6L/min) can relieve the situation, but its effect may only be temporary. This treatment should be administered while senior help is sought, so a thorough airway assessment can be performed and a decision made about re-intubation.²

AIRWAY EXCHANGE CATHETERS AND THE STAGED EXTUBATION KIT

Airway exchange catheters (AECs) are long catheters designed for changing one airway device (LMA or tube) for another. They include the Cook™ Airway Exchange Catheter (standard or extra-long version for use with double lumen tubes) and the Cook™ Aintree Intubating Catheter, which has a larger internal diameter to allow placement using a fibre-optic bronchoscope (see Plan B).

If a narrow gauge AEC is used, it can be combined with an Aintree Intubating Catheter (AIC) to ease passage of tube during re-intubation (the AIC acts as stiffener and also decreases step between catheter and tracheal tube which can impinge on the vocal cords or in the piriform fossae.⁵

AECs range in size from 8-19 Fr gauge and are between 45cm and 100cm in length. They usually have a hollow lumen for the delivery of oxygen, which is connected to the catheter by either a 15mm or Luer-lock Rapi-Fit™ connector.

Oxygen can then be delivered by insufflation (via a 15mm connector at constant flow), ventilation (via an anaesthetic circuit) or jet ventilation (with a jet injector). Pressures of 15-50 PSI have been described for jet ventilation (103-344kPa) the upper limit of which is approaching unrestricted wall oxygen (400kPa).⁶

In 2010, two deaths were reported in association with the use of airway AECs; one in Canada and one in Scotland. In the Scottish case, the AEC was used during a difficult intubation attempt, to facilitate changing an intubating LMA for a tracheal tube. During its use, oxygen was insufflated via the AEC at a flow rate of 15L/min. This caused the rupture of the right main bronchus, with migration of the catheter through the lung and out into the chest wall, resulting in massive surgical emphysema, barotrauma, cardiac arrest and death. In the Canadian case, a young man was discharged from the operating theatre to the recovery room with an AEC in situ, with oxygen being insufflated at 5L/min. He had undergone maxillofacial surgery with elastic band inter-maxillary fixation, which reduced his mouth opening and his ability to exhale gas. He rapidly developed chest pain due to a tension pneumothorax, and suffered a cardiac arrest. He died later with a hypoxic brain injury. Both coroner’s reports raised concerns over flow rate of oxygen used,^7,8 and pointed out prior guidance suggesting that the lowest driving pressure possible should be used, starting with insufflation at a rate of 1-2L/min.^6,9

These deaths were followed in 2011 by a review of the literature.¹⁰ The analysis revealed a worryingly high incidence of barotrauma associated with the delivery of oxygen via AECs. Of the 18 cases of barotrauma identified, jet ventilation was used in 16. In one case series included in the review, five out of 45 patients (11%) who received jet ventilation via an AEC developed barotrauma.⁶ Barotrauma also occurred in two cases where oxygen insufflation was used (different cases to those described above). The authors conclude that jet insufflation via an AEC is associated with significant risk. They also point out that there is no clear evidence that delivering oxygen via the AEC is superior to conventional delivery. Proponents of jet ventilation (and Cook™, the manufacturer) suggest that it can be made safer by starting with low pressures, ensuring that the distal tip of the catheter remains at least 2-3cm from the carina, and checking that the patient can exhale.^6,11 The authors of the review point out, however, that two cases of barotrauma occurred with correctly positioned catheters, and that it is often impossible to evaluate the adequacy of exhalation at the bedside. They caution against the delivery of oxygen via the AEC, and suggest that efforts should concentrate on tube delivery if the airway becomes threatened or inadequate.

In recent years, the use of AECs has been extended to ‘staged’ extubation. In this technique, the AEC is inserted through the tracheal tube, which is then removed. The AEC is left in situ to facilitate re-intubation if the patients should fail extubation. The AEC is left in place until the patient is deemed safe. The duration of use is highly variable, and the device may or may not be used to deliver oxygen during this time. It is important to note that Cook™ have stated that their AECs are designed for airway exchange only, and are not designed to be left in the airway for long periods.¹¹ However, this ‘off-label’ practice is relatively commonplace and seems to be well tolerated by patients, with only a small minority requiring the instillation of local anaestetic in one study.⁶

A large case series has retrospectively analysed the practice of staged extubation in 354 high-risk patients.¹² On initial examination, the study seems to suggest that the AEC is a useful adjunct. In 303/354 patients (86%), the airway was deemed to be safe and the AEC was removed. In 51 patients (14%), the airway was threatened and re-intubation was attempted. This was successful in 47 patient (92%), with no significant adverse effects, including barotrauma. Of note, the AEC was only used to deliver oxygen in 7 patients, by insufflation at a flow rate of 3-6L/min. Of the 303 patients who had their AEC removed, 36 patients (12%) required re-intubation. This was far more difficult overall than in the AEC patients: many attempts with several different devices were required, and in four patients, a surgical airway was performed. In only 14% of patients was the airway secured at the first attempt, with the first choice device.

Further analysis of this paper, however, calls into question the usefulness of the AEC for extubation.¹³ In this case series, 36 of 87 patients (41%) who went on to require re-intubation had their AEC removed. The assumption that these patients would tolerate extubation was therefore incorrect nearly half of the time. So were these AECs removed too soon? The average duration of use of AECs in this study was 3.9 hours, ranging from 5 minutes to 72 hours. It is difficult to know how long an AEC should be left in place until the airway is deemed safe, as laryngeal oedema can occur up to 8 hours post extubation.¹⁴

The effect of the AEC itself on the rate of re-intubation is unclear. It seems reasonable that AECs might actually increase the re-intubation rate, by narrowing the airway lumen, causing trauma and inflammation, and precipitating cough and stridor.

The Cook™ Staged Extubation Kit has been designed with these concerns in mind. In this technique, a soft-tipped wire is inserted through the tracheal tube, which is then removed. The wire is narrower and less irritating than an AEC, and can theoretically be left in for a long period. Should the patient require re-intubation, a catheter with a blunt, atraumatic tip is inserted over the guide-wire to stiffen the whole apparatus so that a tracheal tube can be introduced. The catheter comes with Rapi-Fit™ connectors to allow oxygen delivery during the re-intubation attempt.