Extubation is the process of removal of the endotracheal tube representing transition from a well-protected to an unprotected airway, performed with the anticipation that the airway will be protected by protective reflexes. Extubation in a patient with difficult airway, anticipated or unanticipated, could be as challenging as, if not more challenging than, intubation. Difficulty is compounded by several factors, most important being surgical factors. As a result of surgery, a previously normal or mildly difficult airway can be converted into difficult airway during extubation. The various aspects associated with extubation are discussed in this article.
In a normal airway, extubation is relatively straightforward, more so if patient is ASA I and II category. It involves ensuring adequate recovery from anaesthetics, 100% oxygen, reversal of neuromuscular blockade, clearing airway of secretions and blood, deflating the cuff and removing the tube. Even though apparently normal airway in an apparently normal patient is also not immune from extubation related complications, in this article only extubation related to difficult airway is discussed.
- Severity of the problem
- Literature review
- Risk stratification
- Objectives/goals of extubation
- Management of extubation
- Complications of extubation
- Re intubation after extubation
- Extubation of difficult airway in special situation
Severity of the problem
Extubation is in a difficult airway is a potentially life threatening event, if not planned and performed with care and skill. In an anticipated difficult airway, intubation is always a planned procedure with adequate preparation and personnel. There are multiple devices and techniques to assist in ventilation and intubation. Many a times, a supraglottic airway device can be used if there is a difficulty. Also, there are established and widely accepted algorithms for different clinical scenarios of airway management during induction. Moreover, the airway is anatomically and physiologically “intact” and most of the time there is a possibility in most of the situations for the patient to be woken up in case of difficulty. Lastly, very important, intubation leads to establishment of protection of airway with an artificial airway.
In contrast, extubation is a process without so much of “luxury”. It is to be done as a single step procedure in patient whose airway could have been altered due to so many factors. Also, the post extubation situation is influenced by co morbid conditions. Even ASA I and II patients are prone for complications of extubation, which is unique to the specialty of anaesthesia. To imagine a normal patient walking in to hospital for a day care surgery under general anaesthesia ending up with irreversible brain damage or death or admission to ICU following extubation is very difficult to accept, both for the surgical team and patient family. Extubation done in a patient with difficult airway or where the airway was normal previously but made difficult due to intra operative factors or events is a recipe for disaster. Till recently, extubation was almost a neglected part of airway teaching and training and was assumed to be a simple natural end to the process of airway management.
Changes in the airway following surgical procedures
Factors contributing to changes
- Head and neck surgery
- Maxillofacial, oral and airway surgery
- Prone and steep Trendelenburg positions
- Excessive cuff pressures
- Difficult intubation with multiple attempts
- Trauma during intubation
- Prolonged compression form thyroid or other growths in different parts of the airway
These factors induce airway oedema, difficulty in maintaining patency post extubation and bleeding.
In addition, alteration in the anatomy of the airway can lead to significant difficulty in mask ventilation as well as laryngoscopy and intubation, should it be required after initial extubation. Finally, the integrity of surgical procedure may be threatened by the need for active airway interventions.
There is sufficient literature to support the need for a careful planned procedure.
- 17% of brain injuries and deaths occurred after extubation in the OT or in post anaesthesia recovery units according the findings of ASA Closed Claims Project analysis of adverse respiratory events.
- Need for re intubation was 0.09 to 0.19% in a retrospective analysis of a quality data base of more than 15000 patients (J Clin Anesth 2003).
- Reintubation attempts could up to 3% in selected subpopulation of surgical patients, where airway is more likely to be involved in surgical or endoscopic procedures.
- Respiratory events formed 58% of aetiology for reintubation in an analysis from University of Michigan of 107,317 general anaesthetics between 1994 and 1999.The respiratory causes included hypercapnia, hypoxia, respiratory obstruction, laryngospasm and bronchospasm.
- 27 patients per 10,000 patients required reintubation within 24 hours in a prospective study from Thailand
- Patients who underwent laryngeal biopsy had 5% incidence of re intubation
- One third of the airway complications in National Audi Project (NAP4) of UK were reported during recovery and emergence.
- Poor judgement was one of the etiological factors for airway related complications, thus underscoring the importance of non-technical factors.
Risk stratification of patients for extubation
Patients requiring extubation are classified as low risk and at risk as proposed by difficult airway society. Identifying the latter group of patients is crucial as it is these patients who are prone for more severe life threatening complications and consequently need more planning.
- Normal airway, not altered during or due to surgery
- No risk of aspiration
- Mask ventilation and re intubation, if required are not difficult
- No significant co morbid conditions
- Patient fully awake and reversed before extubation
Low risk extubation does not require much additional preparation in terms of equipment or strategies. It is usually performed in the operation theatre itself immediately after surgery, similar to extubation in a patient with normal airway.
- Patient factors: Comorbid conditions, particularly morbid obesity, obstructive sleep apnoea, difficult airway or difficult intubation, ankylosing spondylosis, rheumatoid arthritis etc where airway could be directly or indirectly involved.
- Surgical factors: Maxillofacial, orthognathic, neurosurgical and airway procedures, prolonged surgery, prone or Trendelenburg positions, large quantity of fluids, intraoperative complications, hypothermia, angioedema etc
- Delayed recovery
- Recurrent laryngeal nerve injury
More details are available in the guidelines, included at the end of the article.
Goals of extubation
- To ensure a patent airway post extubation, without need for re intubation or positive pressure ventilation
- To avoid significant hemodynamic changes during extubation
- Prevention of aspiration
- To avoid any potential disruption or damage to surgical repair
Management of extubation
The strategies for safe extubation can be described under the 4 Ps, as proposed in Difficult Airway Society (DAS) guidelines. They are planning, Preparation, Performing and Postoperative care. Various algorithms have been developed for the smooth and safe management of extubation
Planning includes developing a strategy in terms of the
- risk for extubation- low or at risk
- timing of extubation: immediate or delayed
- drugs: for reversal and to attenuate hemodynamic response
- location – OT, High dependency unit or intensive care unit
- identifying the impact of co morbid conditions and
- anticipation of complications
Preparation includes working out the details of the plan so that it can be executed well.
- Stop anaesthetics and administer 100% oxygen
- Suction of the airway and endotracheal tube (if required, keep in mind effects on hemodynamic and oxygenation)
- Reverse neuromuscular blockage (confirm the adequacy of reversal with clinical and neuromuscular blockade monitor based criteria)
- Optimise the physiology: hemodynamic status, temperature etc
- Keep the required equipment ready (see the table)
- Adjust the table height, level
- Keep appropriate size face mask, endotracheal tube and working laryngoscope or other additional equipment as required
- Keep ready intubation aids for extubation or for reintubation. They include boogie, airway exchange catheter, optical stylet etc
- Video laryngoscope, if available can be kept ready
- Deflate the cuff: Gradual deflation minimises the occurrence of coughing or bucking over the tube.
Performing extubation means execution of the chosen technique.
- Patient is extubated in supine position (most common) or lateral. A head down tilt can be given.
- Suctioning of airway is done prior to actual process of extubation. Suctioning during removal of tube can stimulate laryngospasm.
- Unless clearly contraindicated, patients are extubated in completely awake state. At any cost, extubation in light plane of anaesthesia is contraindicated and can precipitate laryngospasm.
- Extubation is delayed in presence of
- Facial swelling, as in case of maxillofacial and orthographic surgery
- Tongue oedema
- Delayed recovery
- Distortion of airway anatomy
- Cranial nerve palsy
- Major perioperative complications
- Retropharyngeal and hypo pharyngeal swelling
- Anterior cervical spine surgery where the blood loss is > 500 ml, more than 5h duration, surgery involving more than three levels, previously difficult airway and comorbid conditions like obesity, obstructive sleep apnoea etc
Essentially, most of the patients in whom the extubation is delayed are “at risk” category, except those who have only delayed recovery as the risk factor.
Delayed extubation is performed in the recovery area or High Dependency Unit(HDU) if the patient has no co morbid condition, is breathing spontaneously, has not had any major intraoperative complications and the endotracheal tube is kept only to ensure complete recovery or due to presence of facial swelling.
In other conditions, extubation is performed in intensive care unit or in the operation theatre (patient is brought to OT only for extubation).
Deep extubation: In modern anaesthesia practice incidence of deep extubation is significantly less. The primary considerations for extubation in deep planes are avoidance of hemodynamic and cough response and to prevent damage to surgical repair. Pre requisites for deep extubation are complete reversal of neuromuscular blockade, adequate spontaneous ventilation and absence of risk of aspiration.
A modification of deep extubation is Bailey’s technique where in a supraglottic airway device, classic LMA or channelled device, replaces the endotracheal tube in deep planes of anaesthesia. Here after a thorough suctioning of the airway a SGAD is placed behind the endotracheal tube near the laryngeal inlet and then the tube is removed after cuff deflation followed by inflation of the SGAD in proper position. The neuromuscular blockage is reversed after the removal of the tube. Patient is allowed to recover over the SGAD. Risk of aspiration and distortion of airway including reduced mouth opening are contraindications to this technique.
Available techniques are
- Direct extubation
- Extubation over intubation fiberscope
- Extubation over airway exchange catheter
- Extubation using jet stylets
- Extubation with a gum elastic bougie or Mizus endotracheal tube replacement obturator
- Baileys technique: Use of Supraglottic airway device to assist extubation
Mizus Endotracheal tube replacement Obturator (METRO) is a product of Cook Critical care developed for replacement of endotracheal or tracheostomy tubes.
How to choose the best technique?
The factors which help one to decide the optimal technique for a given patient are
- Perioperative course of airway management and perioperative complications
- Expected ease of extubation
- Easy/ difficult mask ventilation after extubation
- Risk of aspiration after extubation
- Ease of laryngoscopy or visualization of glottis opening, should reintubation likely
- Potential for damage to surgical repairs
- Influence on co morbid conditions
- Experience and preferences of the anaesthesiologist performing extubation
In low risk category of patient’s tracheal tube can be removed after fulfilling the recovery and reversal criteria. A check laryngoscopy can be done if required, before extubation.
Extubation over intubation aids
These techniques, where extubation is performed over any of the intubation aids, are chosen in at risk category of difficult airway patients where there is a) anticipated difficulty in mask ventilation b) restricted mouth opening or gross distortion of anatomy resulting in difficult laryngoscopy or intubation and c) potential reintubation. In these situations, having a guide to the trachea over which extubation is performed helps in reintubation over the same guide, without laryngoscopy.
- Chooses the device (guide) to be used as a guide
- Prepare the patient: see above
- Pass the intubation guide after cuff deflation
- Gradually pull out the tube over the guide. Continue to administer oxygen through the tube from the breathing circuit using a swivel connector
- Connect to oxygen, if the device is a hollow catheter like airway exchange catheter
- Observe the patient for potential airway obstruction, hypoventilation etc
- Remove the guide after 30 min or one hour., or as per the institutional protocol. If the device is a bougie, it should be removed immediately as oxygen cannot be administered through it.
Extubation over intubation fiberscope
Using an intubation fiberscope, also called fiberoptic bronchoscope, can make the extubation safer in a difficult airway situation by a) providing a conduit and guidance to the trachea like the other intubation assist devices and b) directly visualizing the trachea and the vocal cords as the tube is gradually withdrawn. With this, the anaesthesiologist is detect the pathologies like tracheomalacia, airway collapse, oedema and vocal cord palsy. This helps in immediate re intubation with minimal risk of hypoxia.
Pharmacology of extubation
Various drugs have been used to reduce the physiological responses to and complications of extubation which include coughing and hemodynamic response, mostly tachycardia, hypertension and arrhythmia.
Various drugs used towards this goal include propofol (0.5mg/kg), Dexmedetomedine, beta blockers like esmolol and intravenous lignocaine. Inflating the cuff with lignocaine is also supposed to be reduce the airway stimulation during extubation. Lastly, the cuff should be deflated slowly, may be in deep plane itself if there is no risk of aspiration and the tube should always be withdrawn gradually.
Complications/adverse consequences related to extubation and management
- Extubation failure
- Airway obstruction
- Post extubation stridor
- Post obstructive pulmonary oedema
- Hypertension, tachycardia
- Rare complications like inability to deflate the cuff, suturing or anchoring the cuff to the trachea, disruption of or injury to arytenoid cartilage etc
The keys to prevention or risk of complications are
- Atraumatic intubation
- Cuff pressure monitoring and maintaining a minimal leak
- Reversal and recovery, extubation in a fully awake state
- Clearing of airway
- Check laryngoscopy and inspection for oedema
- Administration of 100% oxygen before and if required, during extubation
Complications of extubation could have both direct and indirect effect on the recovery and surgical process. Inadequate reversal of neuromuscular blockade is an important predisposing factor for airway obstruction. Other contributory factors are residual sedation, bleeding, anaphylaxis etc.
Important aspects of management of complications of extubation are as follows
- Monitor for oxygenation, level of consciousness, airway patency. Normal SpO2 on the monitor doesn’t always mean that there is no airway problem as it takes longer period of time for SpO2 to fall.
- Supplemental oxygen. This again, is no substitute for careful monitoring
- Monitor for bleeding
- Keep Ambu bag with a reservoir bag and equipment for re intubation always available near the patient
- A supraglottic airway device is useful to manage the airway obstruction and ventilation following extubation, if there is no risk of aspiration, bleeding, if the obstruction is only supraglottic and if the re intubation is required only for short period of time.
For detailed management and guidelines, the readers are expected to consult text books. The outline of management of laryngospasm are:
- Prevention is better. Laryngospasm is much easier to prevent than to treat once it develops. Prevention is by a) clearing of airway of blood and secretions b) Extubation in complete awake state and c) use of pharmacological adjuncts like lignocaine and propofol
- Early detection. Absence of or decreased gas exchange or air movement across the mouth, either felt by palm of the hand held near the mouth and nose or by applying a face mask, indicates the possibility of laryngospasm. This is accompanied by reduced or absence of breath sounds and subsequently drop in SpO2.Laryngospasm can be total or partial. In partial stridor can be present.
- Aggressive management. Early and aggressive management depending on complete or partial is essential. The key points are a) Positive pressure ventilation with mask and CPAP with 100% oxygen (it is difficult and requires skill and careful mask holding, as the ventilation is against a partially or closed glottis) b) deepening of anaesthesia with propofol c) Scoline, 10-20mg IV in adults, if laryngospasm is total and not responding to other measures d) Pressure over laryngospasm notch (Larson’s manoeuvre) and e) Intubation and positive pressure ventilation
Post obstructive pulmonary oedema (POPE)
Also called negative pressure pulmonary oedema, POPE, follows sudden relief (by endotracheal intubation) of persistent airway obstruction of any cause. Management is similar to pulmonary oedema of other causes and include positive pressure ventilation, increased FiO2, diuretics and inj morphine intravenous. Usually it resolves spontaneously.
Re intubation following extubation of a difficult airway
Re intubation may be required for various reasons which include
- Persistent airway obstruction, not relieved by mask ventilation
- Respiratory complications
- To provide tracheal toilet
- Inadequate recovery
- Inability to ventilate with face mask
- Failure to wean in ICU
Re intubation can be difficult because of the changes in the airway, agitated patient, airway obstruction with actual or impending hypoxia, difficulty with mask ventilation, blood in the airway, difficulty with laryngoscopy and impact of comorbid conditions.
Anticipation and being prepared with appropriate equipment and personnel is the best safeguard against failure. Video laryngoscopes, McCoy’s blade, bougie, airway exchange catheter, are all useful in reintubation. Fiberoptic guided technique can be very difficult to perform because of presence of blood and secretions.
Reintubation is always attempted with smaller size endotracheal tube and extubation following re intubation is performed only after the indication for re intubation is completely resolved.
Difficult Airway Society (DAS) has developed guidelines for extubation of a difficult airway. Recently, All India Difficult Airway Association (AIDAA) has also published guidelines for extubation. Both are provided at the end of the article.
In several clinical situations, the difficulty of extubating a difficult airway is made more difficult non airway factors. Some of those scenarios and their implications are mentioned below:
Paediatric difficult airway
Children are most prone for laryngospasm and utmost caution should be exercised during extubation. Extubation when fully awake is the key to prevention of complications. Among the children at high risk are neonates, syndromic children, obstructive sleep apnoea and procedures like adenotonsillectomy, cleft repairs etc.
Here the extubation may have to be delayed for management of head injury, for re exploration, protection of airway, management of shock or pulmonary injuries. Patients with cervical spine injury represent a higher risk and all efforts should be made to avoid re intubation.
Extubating a parturient with a difficult airway should consider the additional effects of pregnancy on airway “environment” and also continued risk of aspiration. Extubation over a tube exchanger or bougie is safer. Patient should be fully awake.
Intensive care unit
In ICU, extubation usually takes place after few days of ventilation and it’s the weaning difficulty or failure which compounds the problems and can lead to re intubation. Usually by the time extubation is planned, patient is expected to be reasonably stable and hence the same principles for post extubation described above applies to them.
- Extubation in a difficult airway is challenging due to various factors, which are patient or surgery related.
- Alterations in anatomy and threat to integrity of surgical repair are important considerations
- Extubation should be well planned, as in case of intubation in a difficult airway
- Planning, Preparation, Performing and Post extubation care are the four Ps of extubation
- Categorizing the patients into high or at risk and low risk helps in deciding the plan
- Different techniques are available, choose the one which is best suitable for the situation.
- Clearing the airway, reversal of relaxants, recovery from anaesthetics are common prerequisites for all
- Extubation is to be done in fully awake state and rarely in deep plane. Never in light plane of anaesthesia
- Complications of extubation should be anticipated, diagnosed early and aggressively managed
- Laryngospasm is more common in children
- Re intubation is a potential possibility in all patients with difficult airway following extubation
- DAS and AIDAA guidelines are available on extubation of a difficult airway