Conference Lectures
It is partly true that the same importance given to the intubation was not given, at least in the early period, to extubation. We assumed that all that starts well and proceeds well would end well. Only when the causes of faults in anaesthetic techniques responsible for frequent claims by the affected individuals were analysed, the importance of extubation and the number of adverse incidents occurring during and after extubation were to be realised. Ease of intubation or LMA insertion during induction of anaesthesia does not guarantee the same after the surgery and reintubation in the same patient, may become difficult, when the extubation fails for some reason.
Statistics
American Society of Anesthetists (ASA) formed a Task Force for the Difficult Airway (DA), which published its report in 1993. The same was revised in 2003. The propagation of the protocol recommended for DA led to progressive decrease in the incidence of complications related to intubation. 1 Death or brain damage following intubation has decreased from 62% during the period of 1985-92 to 35% during the period of 1993-99 probably due to the observance of DA guidelines recommended by ASA. But the incidence of adverse events following extubation did not decrease during the same period. 2,3,4,5 During the period mentioned above, the incidence of mortality and morbidity during the peri-extubation period remained the same.
ASA Closed Claims Database indicates that there were 16 claims due to failed extubation since 2000. Death or permanent brain damage had occurred in 15 out of the 16 patients. All the eight claims due to difficult airway management in the post extubation period ended up in either death or permanent brain damage.1
The Fourth National Audit Project of Royal College of Anaesthetists and the Difficult Airway Society (DAS) have highlighted the serious airway complications in the perioperative period occurring either in the OT, Recovery room, Emergency or ICU over a period of one year. One third of these airway complications occurred in the post-extubation period.6, 7
Both the ASA Closed Claims Database and the Fourth National Audit Project point out that the poor outcomes from the adverse events occurring in the post extubation period are either due to “less than appropriate care and/or judgement”, inadequate communications and lack of adequate monitoring in the postoperative period.
The original assessment of the airway done for intubation becomes more important during extubation since situations can arise when the patient may need reintubation in the postoperative period. Reintubation, in the same patient, in the post extubation period, may become more difficult than the previous intubation, due to additional factors like airway obstruction of various reasons, bronchospasm, and respiratory insufficiency due to the side effects of inhalational anaesthetic agents, opioids and neuromuscular blocking agents. The incidence of reintubation in the OT or in the PACU ranges from 0.1 to 0.45%.
In January 2012, DAS in U.K. released a set of guidelines for tracheal extubation. 8 ASA Practice Guidelines for management of DA 2003, also contains “a strategy for extubation of the DA”.
Definition of Terminologies
Difficult Airway: “The clinical situation in which conventionally trained anaesthesiologists experiences difficulty with face mask ventilation of the upper airway, difficulty with tracheal intubation or both” – as per 2003 ASA Practice Guidelines for management of DA.
Extubation Failure: “Inability to tolerate the removal of translaryngeal tube”. The reasons for the extubation failure may be various causes of upper airway obstruction or the effects of inhalational anaesthetics, opioids or the muscle relaxants.
Weaning Failure is ‘the inability to tolerate spontaneous breathing without ventilator support’ and this is commonly seen in ICU patients and should not be confused with the difficult extubation or extubation failure.
When the ability of the patient to maintain airway patency and/or oxygenation after tracheal extubation is uncertain that patient falls to the category of At-Risk Extubation.
Situation may arise when the patient who is extubated may not tolerate extubation and may require reintubation to maintain the airway. If the reintubation is done within minutes and up to 6 hours after extubation it is called ‘early reintubation’. If it is done between 6hrs to 72hrs after extubation (which is seen commonly in ICUs), it is called ‘late reintubation’.
Physiological responses due to extubation
The following minor complications are so frequently seen immediately after extubation, I quote them as ‘physiological’ responses due to extubation
Stress response to extubation: Though much importance is given to the stress response to intubation and various drugs and techniques are used to attenuate the response, attenuation of extubation response is not given that much of priority. Extubation is associated with 10 to 30% increase in the blood pressure and the heart rate lasting for 5 to 15 mins. 9 This can decrease the ejection fraction of the heart by 40 to 50% in patients with coronary artery disease. This can be attenuated by drugs like esmolol, glyceryl trinitrate, magnesium, propofol, remifentanyl, alfentanyl, or lignocaine given 2 to 5 mins before extubation or by extubating at a deeper plane of anaesthesia and inserting a supraglottic device like LMA.
Respiratory complications like sore throat and coughing after extubation are very common, seen in 38 to 96% of the patients. The incidence of these side effects can be minimized by
a) Filling the tracheal cuff with water instead of air: Water does not overinflate due to heat and the volume does not increase due to the diffusion of N2O.
b) Filling the cuff with 2% lignocaine with NaHCO3: It has good diffusion across the PVC cuff, 45 to 65% in 6hrs. It is safe and less irritant even when the cuff ruptures. It reduces sore throat, coughing, bucking, restlessness and hoarseness during emergence after extubation without suppressing the swallowing reflex. 8
c) Laryngotracheal instillation of topical anaesthetic: It reduces coughing during extubation and decreases the requirement of postoperative sedation.
Complications following extubation
In spite of managing the patient well during induction and maintenance, occasionally the anaesthesiologists face complications, after extubation of the patients, many a times minor ones, and a few times, of serious nature. The incidence is more common in patients with preoperative co-morbid conditions related to the airway and the respiratory system.
Postoperative hypoxemia was seen in 0.9% of 24000 patients who underwent general anaesthesia.10 The incidence is more among smokers, children with upper respiratory infections (URI) and in patients with COPD (Chronic Obstructive Pulmonary Disease). A study conducted in the PACU (Post anaesthesia Care Unit or recovery room) shows that 50% of patients have SPO2 of less than 95% on arrival to the PACU and 20% of the patients have SPO2 less than 92% in spite of being administered 40% O2.10 It is highly recommended that 100% oxygen should be given to all the patients who are being transferred from OT to the recovery room. But in UK, only 63% of the anaesthesiologists recommend 100% oxygen routinely during transfer of the patients from OT to the recovery room.11 Many factors contribute for this high incidence of hypoxemia in the immediate postoperative period including the duration of surgery, posture of the patient during surgery, starvation status of the individual, presence of diseases like GERD (Gastro Esophageal Reflux Disease), COPD, respiratory allergy, URI etc., adequacy of the reversal from neuromuscular blockade, adequacy of pain relief and many other co-morbid diseases.
Pulmonary aspiration immediately after extubation is another common complication encountered, many a times managed with simple maneuvers, occasionally needing reintubation and postoperative ventilation. The incidence of postoperative pulmonary aspiration remains between 2.9 and 10.2 per 10,000 anaesthetics over the past few decades even in well prepared patients.11 In a multicentric study of 2,00,000 operations in France from 1978 to 1982, it was found that 14 of the 27 significant aspirations occurred after extubation.1 Though in general left lateral head down position is recommended in the immediate post extubation period, in a few situations like OSA (obstructive sleep apnea) and obesity, semi upright position may ease the function of the lungs.
Post extubation stridor (PES), apart from being a sign of upper airway obstruction, can be noticed frequently in children with URI, upper airway surgeries and patients with mild residual neuromuscular paralysis. Continued observation and administration of oxygen will avert major problems. PES should never be taken lightly, since it may be the first sign of serious upper airway obstruction.
More serious complications that may be encountered in the post extubation period are upper airway obstruction (UAO) and postoperative pulmonary oedema and very rarely, inability to remove the tracheal tube.
UAO may be due to laryngospasm, laryngeal oedema, tracheal obstruction due to external pressure, laryngomalacia and vocal cord paralysis.
Laryngospasm is the most common cause of UAO in the post extubation period. This is more common in children with URI undergoing airway surgery like tonsillectomy. Blood clot or drops of saliva aspirated in to the tracheal may trigger the laryngospasm. Smoking and obesity are contributing factors. The Australian Incident Monitoring Study (of 4000 cases) revealed 5% incidence of post extubation laryngospasm. Laryngospasm in young healthy adults may lead to negative pressure pulmonary oedema. Intravenous lignocaine or magnesium can be used to prevent this in patients susceptible to develop laryngospasm.
Laryngeal oedema is a serious cause of UAO in the post extubation period, more commonly seen in neonates and infants especially when they have URI. Tight fitting tracheal tubes, trauma during intubation due to multiple attempts, prolonged intubation for more than one hour, coughing and bucking on the tracheal tube and frequent change of position of the head and neck during surgery may contribute to the incidence of laryngeal oedema. Upper airway trauma and burns, prone or Trendelenberg posture during surgery, fluid overload and radiation of the neck are contributing factors for increased incidence of laryngeal oedema. Oedema can occur in the supraglottic area, causing posterior displacement of epiglottis thus causing UAO. Oedema can occur in the retro arytenoid level causing limitation of the vocal cord abduction. If the oedema occurs in the infra glottic area, the tracheal lumen may be narrowed even up to 35 to 40%. Laryngeal oedema can be evident immediately after extubation or it can develop even 6 hrs after extubation. It is usually managed with warm, humidified oxygen/air mixture, nebulized epinephrine 1in 1000 (0.5ml /Kg, up to 5 ml) and dexamethasone iv (0.25 mg / Kg followed by 0.1 mg/Kg 6 hrly for 24 hrs). Patient may need reintubation with smaller tracheal tube if the saturation could not be maintained with above therapy.
Tracheal obstruction due to external compression is seen following head and neck surgeries and upper thoracic surgeries. Haematoma following thyroid surgery and anterior cervical spine surgery are the common scenario leading to this type of airway obstruction. Patients who have received anticoagulants are more likely to develop this.
Another rare cause of UAO is arytenoid cartilage dislocation, which can cause dysphonia, dysphagia and respiratory stridor. This can be treated by gentle reduction of the dislocation and if not effective, by intubation for a short period or, rarely for a prolonged period.
Vocal cord paralysis is another cause of UAO. This is seen in cases of intra operative injury to the vagus or recurrent laryngeal nerve in head and neck surgeries and upper thoracic surgeries. Recurrent nerve damage is seen 10.6% of surgeries for malignant thyroid. Unilateral injury does not cause respiratory insufficiency, but bilateral palsy can lead to UAO necessitating reintubation or tracheostomy.
Tracheomalacia is a rare, though often described in literature, cause of UAO following extubation. Long standing huge tumors from thyroid or from upper thoracic region pressing on the trachea may lead on to tracheomalacia which will become evident only after extubation.
Postoperative pulmonary oedema is another common complication seen in 1in 1000 patients, immediately after extubation. This is said to be due to the negative pressure in the pleural space, seen in cases of UAO, assisted by other underlying factors like increased cardiac filling and rupture of the pulmonary vessels. Majority of the patients will recover following artificial ventilation and diuretics. A few progress to acute lung injury and death. Mortality due to negative pressure pulmonary oedema is 2% to 40%. Negative pressure pulmonary oedema should be distinguished from neurogenic pulmonary oedema which is seen some patients with head injury.
Preparation and Criteria for safe extubation in OT
Apart from the position of the patient during extubation to avoid aspiration and the various methods of cuff inflation mentioned above, the following criteria should be checked before extubating a patient following surgeries.
The patient must have fully recovered from the effect of neuromuscular blocking agents as evidenced by good respiratory movements as shown by the tidal volume, ability to lift the limbs, and good cough reflex following oral or endotracheal suction. This can be supplemented by the NM monitoring, whenever the facility is available.
The patient should have recovered adequately from the effects of the inhalational anaesthetic agents as well as opioids, as evidenced by the prompt eye opening on request and obeying the commands.
Abnormally high blood pressure and a few basal rales in the chest and the inability to sustain the saturation at 100% in spite of oxygen supplementation should caution the possibility of postoperative pulmonary oedema.
Cuff-leak test is commonly done whenever UAO obstruction after extubation is a possibility as in thyroid, upper cervical and other upper thoracic surgeries. This is useful whenever the UAO is due to laryngeal oedema, tracheomalacia or due to external compression due to haematoma and not useful in diagnosing laryngospasm and obstruction due to vocal cord paralysis, which will become evident only after extubation. As soon as the cuff of the endotracheal tube is deflated there will be audible leak after each inspiration when the patient is manually or artificially ventilated. There will be a sudden fall of the expiratory tidal volume from that of the inspiratory tidal volume. If there is no such fall, it shows that the tracheal wall is already closer to the endotracheal tube as in the case of laryngeal oedema, laryngomalacia or external compression of the trachea. If the fall of the expiratory tidal volume, averaged over six breaths, is less than 10to12% of the inspiratory tidal volume, the cuff-leak test is said to be positive and indicative of post extubation UAO.1 Of late, ultrasound is being tried to find out the amount of laryngeal oedema or laryngomalacia.
A rare cause of difficult extubation is due to the inability to remove the tracheal tube either due to difficulty in deflating the cuff, cuff herniation, cuff being adherent to the tracheal mucosa and rarely due to a surgical suture through the tube preventing extubation.
Extubation Protocol
The complications following extubation mentioned above are in addition to the already existing intubation problems found in the patient. The various types of intubation difficulties the patient can have, from burns scars, maxillofacial injuries, large tumors of the head and neck, Pierre Robin syndrome, morbid obesity, OSA (Obstructive Sleep Apnea), radiation to the neck, pregnancy, cervical spine surgery, and rheumatoid arthritis of temperomandibular and cervical spinous joints are beyond the scope of this article. The following recommended protocols for extubation have to be modified according the amount and type of the intubation difficulty, the patient already had. Each extubation is a trial extubation since there is no guarantee that the patient will not need reintubation. Accordingly, extubation can be planned either in the OT, or in the recovery room and sometimes in the ICU, at a later stage. The basic requisite is that the patient should be able to maintain the airway and ventilation on his own in the postoperative period and the anaesthesiologist must be prepared, at any time after extubation, to reintubate and ventilate the patient. Slackness, callousness and injudicious judgement may cause the patient his life. Though tracheostomy is the last resort for management of difficult or failed extubation, it should be kept in mind to save the patient.
Direct laryngoscopy and suctioning of the posterior pharynx, ventilation with 100% oxygen to wash out inhalational anaesthetic agents and nitrous oxide and positive pressure breath at the end of expiration are routine maneuvers to be adopted just before extubation. Extubation should be done during maximum inspiratory effort since the glottis is wide open at this phase of respiration. Guedel airway may be used to prevent the patient biting the tracheal tube. If, by chance, the patient is biting the tube strongly, the cuff should be released so that he can breathe through the space around the tube.
The three recommended methods adopted during anticipated extubation failure are extubation in a deeper plane of anaesthesia, extubating using Fibre Optic Bronchoscope (FOB) and using airway exchange catheters (AEC).
In cases of preexisting mild intubation difficulty it is better to avoid coughing and straining during extubation, which may precipitate laryngo and bronchospasm, especially in children with mild URI. After extubating the patient in a deeper plane, LMA is introduced and then the neuromuscular block is reversed and the inhalational agents are switched off. The LMA is removed after the patient has become awake and starts obeying commands.
In suspected cases of laryngeal oedema and laryngomalacia, patient is extubated and the LMA is introduced. Then FOB is passed through the LMA and the amount of laryngeal oedema or laryngomalacia is assessed and then the FOB is removed. In case of necessity reintubation can be done over the FOB.
Originally described by Bedger and Chang, AEC (Airway Exchange Catheter) is a hollow tube with 15 mm adapter at the proximal end, for jet or manual ventilation, with distal and side holes, and radio opaque markers. It is usually 65 cms long and has inner diameter of 3.7 to 4mm (11 F) for average patients or 4.7 mm (14F) for tall patients. After all criteria for extubation are fulfilled, the AEC is introduced to just above the carina and tracheal tube is extubated. This catheter is well tolerated by the patients and is usually kept for 30 to 60 minutes; but can be kept for a longer time (even up to 72 hrs) in ICU patients. Patients can talk with catheter in situ. If required patient can be ventilated through this catheter, for a short time, either manually or through jet ventilator, bearing in mind that the latter can cause barotrauma.
Risk stratification for extubation in OT
The following method can be used to predict and prepare for the extubation of the patient in the OT or in the recovery room, especially when the patient had prior intubation difficulty.
Risk 1. Patient with no prior intubation difficulty and who had no intraoperative factors worsening the airway (as in head and neck surgery, upper thoracic surgery, tracheomalacia, laryngeal oedema etc.)
Risk 2. a) Patient with mild intubation difficulty, with a laryngeal view of
2 or 3 and who did not develop intraoperative worsening of
the airway, as mentioned above.
b) Patient with no preoperative intubation difficulty and who
have developed suspected airway narrowing during surgery,
like laryngeal oedema, laryngomalacia or vocal cord palsy.
Risk 3. a) Patient with severe intubation difficulty prior to induction,
with a laryngeal view of 4 or worse, who needed FOB,
intubating LMA or like procedures
b) Patient with mild intubation difficulty prior to induction and
who has developed established (As per the cuff-leak test,
ultrasound examination or FOB examination) airway
narrowing during surgery, like laryngeal oedema,
laryngomalacia or vocal cord palsy.
Patients with risk 1 extubation will need routine precautions before extubation, as in normal persons.
Patients with risk 2 extubation may need extubation in a deeper plane of anaesthesia with supraglottic device insertion till full recovery.
Patient with risk 3 extubation will require AEC before extubation or continuation of ventilation in ICU till the airway obstruction is optimized.
To summarise:
Minor and major complications that can follow extubation, in otherwise normal patient, were discussed. These are due to the effects of the residual anaesthetic agents, faulty intubation techniques, abnormal posture of the patient during surgery and nature of the surgery itself. Cuff leak test may be useful in the anticipation of difficulty in extubation. FOB and portable ultra sonogram may assist in the airway assessment before extubation. Only three options are available to the anaesthesiologist who is challenged with ‘high-risk’ extubation, namely, extubation in a deeper plane of anaesthesia, extubation using FOB and extubating with AEC in situ. When any of these extubation problems is encountered in a patient who had intubation difficulty (anticipated or un anticipated), timing and the method of extubation are to be decided considering both the nature of preoperative intubation difficulty and the nature of intraoperative extubation problems. Though a general protocol has been drawn for extubation, the experience of the anaesthesiologist goes a long way in the decision-making, timing and method of extubation and the outcome. With the exception of AEC, no other specific tool or procedure has gained acceptance for safety extubation.
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