Management of a difficult airway and failed intubation

Introduction

• Probably the most important job of an anaesthetist is to maintain a safe airway of an anaesthetised patient
• Difficulty in airway management is the single most important cause of anaesthesia related morbidity and mortality     
• If a difficult airway is detected and appropriate measures are taken to face it before anaesthetising a patient, morbidity and mortality associated with airway related problems can be minimised
• Hence the importance of assessing the airway during the pre-operative visit

What is a Difficult Airway?

• An airway which is difficult to be maintained or intubated or unable to be intubated in an anaesthetised or unconscious patient

Assessment of Airway

 

• History (positive features of a difficult airway)
• Difficult mouth opening, difficulty in breathing, snoring, sleeping upright on a chair, symptoms related to obstructive sleep apnoea (OSA)
• Past anaesthetic and surgical history
• Airway related problems (?transient/persistent)
• Head and neck surgery, tracheostomy etc 
• Medical history
• Illnesses associated with airway problems
• Rheumatoid arthritis
• Cervical arthropathy (ankylosing spondylitis, cervical spondylosis, rheumatoid arthritis, Down’s syndrome, Klippel-Feil abnormality etc.)
• Diabetes mellitus
• Dermatomyositis, sub mucus fibrosis of oral cavity
• Acromegaly
• OSA, morbid obesit 
• Syndromes associated with airway problems
• Down’s
• Pierre Robin, Treacher Collins, Goldenhar etc 
• Radiotherapy to head and neck
• Surgical history
• Head and neck tumours
• Trauma
• Facial
• Laryngeal
• Tracheal
• Infection
• Head and neck
• Especially with oedema and abscess formation

• Examination(positive features of a difficult airway)
• General
• Morbid obesity / short neck/large breasts
• ? Dysmorphic facies / syndromi 
• Head and neck - masses/surgical scars/burns/evidence of radiotherapy/infection  
• Airway
• Facial or oropharyngeal trauma/tumours/infection
• Signs of upper airway obstruction
• Stridor, tracheal tug, intercostal recession
• Limited mouth opening (inter incisor gap <2 finger breadths/3 cm)
• Small mouth/large tongue/high arched palate
• Dentition
• buck teeth, absent / loose teeth, edentulous
• Mallampati class (III and IV)
• Inability to protrude the lower incisors anterior to the upper incisors
• Receding chin (thyromental distance < 3 finger breadths/6.5 cm)
• Inability to sufficiently extend head (flexion extension range at the cranio-cervical junction < 90°)
• Laryngeal/tracheal deviation
• Beards may hide adverse anatomical features

• Investigations (positive features of a difficult airway)
• Laryngoscopy
• Indirect
• Fibre optic  

(evidence of airway obstruction/narrowing, usually due to malignancy/infection)

 

• X rays  
• Neck – antero posterior, lateral, root of the neck, flexion /extension
• Chest

(evidence of airway obstruction/narrowing/disruption or unstable cervical spine/cervical spine with a limited mobility)

 

• CT scans
• Head and neck, chest  

(Evidence and details of airway obstruction/ narrowing /disruption or unstable cervical spine)

• Identification of a difficult airway
• If a patient is having any of the positive features of a difficult airway described above, the anaesthetist should prepare in advance to manage such an airway with the necessary airway equipment and expertise at hand
• Combination of several tests will increase the positive predictive value of a predicted difficult intubation
• The degree of anticipated difficulty may vary with the experience of the anaesthetist
• If there is a high likelihood that mask ventilation /direct laryngoscopy will be difficult, consideration should be given to securing the airway with the patient awake

• Equipment necessary to manage a difficult airway
• Tiltable table/trolley
• Checked anaesthetic machine with an adequate oxygen supply, ambu bag
• Standard masks, breathing systems, laryngoscopes, laryngoscope blades, endotracheal tubes, laryngeal mask airways (LMA) and oral and nasal airways
• Suction apparatus
• Basic monitoring facilities – blood pressure, electrocardiogram, pulse oxymetry, end tidal carbon dioxide and Wee’s detector
• McCoy and polio blades, short laryngoscope handle
• Gum elastic bougie, airway exchange catheter
• Combitube, intubating LMA
• Fibre optic bronchoscope/intubating fibreoscope/rigid bronchoscope
• Cricothyroidotomy set
• Facility to perform an emergency tracheostomy

(the level of preparation should match the degree of anticipated difficulty in managing the airway)

·    Management of the difficult airway

·    Preparation

• Be ready with necessary equipment/personnel (depending on the availability and requirement) as described above
• Inform the patient about the procedure and get consent for special procedures (awake fibre optic intubation etc.)
• Check fasting status and whether antacid prophylaxis has been given if indicated
• Prepare anaesthetic and resuscitation (atropine, ephedrine, metaraminol etc.) drugs
• Start monitoring (see above)
• Gain reliable intra venous access

·    Positioning

• Sniffing position
• head extended
• neck flexed (head on a single pillow 
• Procedure
• Pre oxygenate the patient (give 100% oxygen until the airway is secured)

·  If no risk of aspiration

·  If you are confident that you can ventilate the patient with the mask and there is no evidence of  airway obstruction

• Give an intravenous anaesthetic agent
• Try to gently ventilate the patient (with head tilt, chin lift and jaw thrust [triple manoeuvre)

·  If the patient can be ventilated easily with the mask

• Paralyse the patient with your choice of muscle relaxant if the intubation is likely to be successful. Otherwise deepen with a volatile agent
• Try to intubate the patient
• If successful, proceed with the surgery

·  If the attempt at intubation is unsuccessful

• Oxygenate with mask (do not persist with attempts to intubate at the expense of oxygenation)
• Correct correctable causes (adjust position of head, change the lryngoscope/blade, backward upward and rightward pressure on larynx, breasts out of the way, wait till relaxant act etc.) and try to intubate again
• Try using a gum elastic bougie (GEB) 

·  If still unsuccessful

• Oxygenate with mask

·  If the surgery can be performed with a Laryngeal Mask Airway (LMA)/face mask+/- airway

• Insert a LMA/apply a face mask+/- airway and if ventilation is satisfactory proceed with the surgery with artificial/spontaneous ventilation 

·  If the surgery needs intubation (for patients not at risk of aspiration)

• Try - blind nasal intubation/intubation through an intubating LMA or by passing a GEB or a fibre optic scope through a LMA/fibre optic intubation
• If successful, confirm the tube position. If in doubt pull the tube out and continue bag and mask ventilation 
• If unsuccessful and the surgery needs to be carried out urgently, consider trcheostomy. Otherwise recover the patient and think of another strategy (transferring to an institution with more facilities and expertise etc.)

·  After inducing if the patient cannot be ventilated with the mask

• Call for help
• Do not give a muscle relaxant
• Correct correctable causes (adjust the position of head, correct application of triple manoeuvre, changing to two hands mask holding technique with an assistant squeezing the anaesthetic bag etc.)
• An oral/nasal airway may help
• If laryngospasm
• give positive pressure (CPAP) with the mask and deepen the anaesthesia with an intravenous agent or give a small dose of suxamethonium

·  If successful go back to the step “If the patient can be ventilated easily with the mask

·  If still unsuccessful

• Try ventilation with a LMA
• If successful and the surgery needs to be carried out, proceed with spontaneous ventilation with an inhalational agent
• Otherwise recover the patient and consider a regional technique/awake fibre optic intubation

·  If the patient cannot be ventilated with an LMA

• Do not relax the patient
• Apply a CPAP with 100° oxygen with the face mask
• Recover the patient if spontaneous breathing reappears and the patient does not desaturate
• Otherwise do a cricothyroidotomy followed by a formal tracheostomy
• Proceed with the surgery if a secure airway is achieved only if it is in the patient’s best interests

·  If the patient is at risk of aspiration

• If you are fairly certain that you can intubate the patient, go for a rapid sequence induction (RSI)
• Otherwise consider a regional technique/go for an awake fibre optic intubatio

·  If intubation is failed, call for help and  go back to the step “If the attempt at intubation is unsuccessful”, while applying the cricoid pressure

·  If the intubation is still not possible and the surgery is in the best interests of the patient only

• Proceed with it if the airway can be maintained with a mask +/- airway/LMA while the patient breathing spontaneously.
• Otherwise recover the patient and think about another strategy (awake fibre optic intubation in a more controlled environment, employing a regional technique, transferring to an institute with more facilities and expertise etc.)

·  You may relax the cricoid pressure if ventilation is impaired

·  If ventilation is also not possible (after correcting correctable causes) go back to the step “if the patient cannot be ventilated with an LMA”

A failed intubation drill for a patient with the risk of aspiration

 

 Other situations of concern:

·  If you are uncertain whether the airway can be maintained under anaesthesia (e.g.. morbidly obese)

• Go for elective awake fibre optic intubation

·  If intubation is thought impossible due to anatomical reasons (e.g. markedly reduced mouth opening) but with no evidence of airway obstruction

• Go for elective awake fibre optic intubation or tracheostomy under local anaesthesia if facilities or expertise for former is not available  

·   If there is a significant threat to an unstable cervical spine

• You may perform an elective awake/asleep fibre optic intubatio

·   If there is upper airway obstruction but intubation is likely to be straightforward

• Facilities for an emergency tracheostomy/cricothyroidotomy should be available before anaesthetising the patient
• Be ready with a rigid ventilating bronchoscope
• Do an inhalational induction
• Do not give a relaxant until the airway is secured with a tube
• If the patient cannot be intubated
• Do a tracheostomy on the anaesthetised spontaneously breathing patient

·   If intubation is expected to be difficult/impossible

• go for a tracheostomy under local anaesthesia or a cricothyroidotomy if the patient’s oxygenation is severely compromised 

·   In patients with significant tracheal compression /stenosis (e.g. mediastinal masses)

• Do inhalational induction
• Intubate with a small ETT without relaxing and relax the patient only after the obstruction is negotiated (if a suitable small ETT is not available, use a catheter airway exchanger and secure the airway by railroading an ETT)
• May perform an awake fibre optic intubation if expertise is available  
• A rigid bronchoscope may have to be passed to get below the obstruction if airway can not be secured with the ETT