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.
- 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