Prof. Dr Raveendra Ubaradka S
Jerudong Park Medical Centre
Objective of this write up
It is aimed at providing outline or framework for the study and preparation of the above topic for the residents preparing for the examination. It is primarily directional, providing the key information, guidance for further information on the topic, possible questions and scenarios and also references for the topic.
CPAP Continuous positive airway pressure, CICV Cannot Intubate Cannot Ventilate, CICVCO Cannot Intubate Cannot Ventilate and Cannot Oxygenate, DA Difficult airway, DMV Difficult Mask Ventilation, DL Direct Laryngoscopy, DI Difficult Intubation, ETT Endotracheal tube, ICU Intensive care unit, LMA Laryngeal mask airway, PEEP Positive end expiratory pressure POPE Post obstructive pulmonary edema, SGAD Supraglottic airway device USG Ultrasound guidance.
Definitions of difficult airway, Contexts of airway management in children : emergency and elective surgery, ICU, emergency department, Airway devices, Available guidelines including All India Difficult Airway Association (AIDAA) Guidelines and Difficult Airway Society of UK guidelines, Strategies and options for difficult airway management, difficult airway cart for children, recent advances in assessment and management of pediatric difficult airway.
From exam point of view, airway management can be discussed either during case presentation of any pediatric patient or a child with anticipated difficult airway. The topic is also important for theory papers, basic sciences, clinical anaesthesia and recent advances.
Expected to know
- Definition of difficult airway, difficult mask ventilation, intubation and tracheostomy
- Difference between difficult airway, compromised airway and obstructed airway
- Brief embryology of the airway. The branchial arches and structures developing from them. Especially for the cases related cleft lip and palate cases.
- How pediatric airway differs from adult? What are the implications of these changes on airway management?
- What are the differences in assessment of a pediatric difficult airway compared to adults?
- Differences between a pediatric and neonatal airway. How it impacts your anesthetic management?
- Predictors of difficult airway in a child
- Name some syndromes and associated airway anomalies
- Pediatric airway equipment
- How to choose a plan for airway management in a child
- How do you plan for oxygenation during difficult airway management
- Inhalational vs Intravenous induction
- Intubation with and without muscle relaxant
- Role of supraglottic airway devices
- Different techniques of airway management: endotracheal intubation, video laryngoscopy, fiberoptic etc
- Extubation of a child
- Laryngospasm, Post obstructive pulmonary edema(POPE)
- Microcuff tube
- Monitoring during airway management
Following descriptions cover the details of answers to the above questions, but not completely. References are included at the end of write up where you can find more information.
- How assessment differs in children compared to adults?
- Lack of cooperation. Mouth opening may be difficult to assess. Information from mother is important
- Difficult to assess Mallampati in small children and neonates.
- No specific values for measurements for most of the parameters which are used in adults.
- Differences in structure and physiology also makes assessment different. Anatomical and physiological differences become more important and distinct as the age of the child decreases.
Assessment of a pediatric airway
History : birth history, prematurity and intubation for any reason (if yes, duration and details. A child intubated in neonatal period, and prolonged ICU stay can have asymptomatic tracheal stenosis)
Inspection and examination : front and side view for gross anomalies : you can make out micrognathia, auricular abnormalities, low set years, cleft deformity, congenital temporomandibular ankylosis, swellings, hemifacial anomalies, etc
Thyromental distance is considered to be normal if it is at least equal to the size of 3 middle fingers of the child joined together.
Temporomandibular joint can be palpated for restriction of the movement.
Cleft Lip and Palate are among the common cases for exams and during assessment you should identify whether the defect is :
a)unilateral (complete or incomplete) or bilateral which is usually complete b) Cleft lip with cleft palate as well c) Isolated cleft palate ( complete or incomplete).
In terms of difficulty of airway management,
- Repair of bilateral complete cleft lip, especially when associated with palatal defect, is most challenging due to the difficulty in laryngoscopy, intubation, small age of the child and potential difficult extubation.
- Complete cleft palate is more challenging mainly due to longer duration, risk of blood loss and risk of tongue edema.
- Airway management in cleft surgery is complicated by presence of syndromes and associated anomalies in the face or vertebra or tongue and other organs.
Ultrasound based assessment of the airway
In adults use of ultrasound(USG) in airway assessment has become almost a standard of care. Once you have experience with adult airway using ultrasound it can be extended to pediatric use as well.
USG can be used to
- Measure size of the tongue
- Collapsibility of submandibular tissue, important for laryngoscopy
- Evaluate size, shape and pathology of epiglottis
- Evaluate vocal cord position and movement
- Subglottic diameter measurement
- Diameter of trachea and identification of tracheal pathology. Helps in prediction of endotracheal tube size
For best results, size and type of probe, position of the patient, plane of assessment and experience and knowledge of the anaesthesiologist in USG are important.
USG use is not limited to assessment but extends to the complete range of airway management like confirming endotracheal intubation and assessing the risk of post extubation complications.
Predictors of difficult airway in children
a) Stridor and snoring
b) Precious difficult airway management
c) Prolonged ICU care with intubation and ventilation
1) Small mouth, with high arched palate
2) TMJ ankylosis
4) Cleft defects
5) Syndromic children
6) Large tongue
7) Short neck or web neck
8) Auricular defects
10) Submandibular space infections
11) Laryngeal web
12) Lingual tonsil
13) Adenotonsillar hypertrophy
14) Burns and post burns neck contracture
15) Foreign body aspiration
16) Mediastinal mass
17) Connective tissue disorders Eg : Hurlers and Hunters syndrome
1)X Ray neck and thorax : a) deviation and narrowing of trachea b) Mediastinal widening
CT scan and MRI to confirm the findings with more accurate information
Diagnostic endoscopy of the airway, mediastinoscopy and biopsy for suspected mediastinal mass
Virtual Endoscopy where using a special software the CT images are converted into a continuous imaging
Trauma, bleeding, loose milk teeth, full stomach, hyperreactive airway, poor physical status contribute to increased risk
Remember: History of previous difficulty (presence or absence) does not necessarily confirm or rule out difficult airway in the next general anesthetic due to the dynamic nature of clinical scenario.
Predictors of difficulty in individual technique of airway management
Predictors of difficulty
Micro or retrognathia, connective tissue disorders, syndromes like Trecher Colin and Pierre Robin Syndrome, adenotonsillar enlargement, obstructive sleep apnea, Obesity
Laryngoscopy and Intubation
TMJ ankylosis, high arched palate and microstomia, Syndromic children, Large tongue, Trauma, Cleft lip and palate associated with other anomalies, Obesity
Supraglottic Airway Device Insertion
Restricted mouth opening, large tongue, intraoral lesions, infraglottic pathology as a cause of difficult airway or compromised airway
Tracheostomy and Cricothyrotomy
Difficulty in identification of cricothyroid membrane, difficulty in positioning, contractures, submandibular space infections, small children
Negative leak test, Altered airway anatomy at the end of the procedure, tongue edema, implants placed in and around the airway (mandibular external fixator for eg)
A new scoring system, Colorado Pediatric Airway Score (COPUR) has been introduced and has the following components : Chin, Opening (mouth), Previous intubation difficulty and OSA, Uvula, Range(of movements) and modifying factors which include buck tooth, macroglossia, extreme obesity and mucopolysaccharidosis.
It is a scoring system with scores from 1 to 25 and a score of 16plus implies immediate need for artificial airway. All the residents are advised to read the details of COPUS in the original article(1). The same article also gives detailed information about the non-airway abnormalities in syndromic children which will affect airway management and the detailed airway implications of the common syndromes.
Pediatric difficult airway registry (PeDI) defined 4 criteria for difficult airway (2,3)
- Failure to visualize vocal cords on direct laryngoscopy by an experience observer
- Failed DL because of abnormal airway anatomy
- Failed Dl in the last 6 months
- DL felt to be harmful in a child with difficult airway
The main findings of the PeDI include
- Higher incidence of DI with decreasing age, especially less than one year
- No correlation between DMV and DI
- Incidence of DI 0.06 to 3%
- Incidence of unanticipated DI 0.03%
- In a series of 1018 children , 2% had failed intubations and 20% of children with DA had complications related to airway problem. Most important, 2% of those had complications suffered cardiac arrest.
3 Column assessment : This is one of the recent approaches to assessment of a difficult airway where airway is viewed as a 3 column structure, anterior, middle and posterior(6). This approach helps to identify the problems of airway better and in a more structured way and helps in planning investigation and strategizing airway management.
Pediatric Airway Equipment
Choosing age and size specific airway equipment leads to higher chances of success and reduces complications.
- A) Laryngoscopes with straight blades : Magill blade is one example.
- B) Paediatric oropharyngeal and nasopharyngeal airway
- C) Supraglottic airway deices : Almost all the SGADs, both in disposable and re-usable options, come in all sizes starting from neonates to older children. Sizes usually start from 1 and go as 1.5, 2,2.5, 3,4, etc. Sizes are selected based on weight. SGADs have multiple roles in airway management.
- D) Endotracheal Tubes
- Traditionally, uncuffed tubes were used for children less than 12 years old because of the belief that the subglottic region and cricoid ring are the narrowest region of pediatric airway and a cuffed tube would cause damage to this part. This perceived difference in the airway was based on cadaveric study based models, and is being contested now.
- Even among the conventional cuffed tubes the problems were related to a) material of the cuff b) lack of uniformity in the shape of the cuff and the distance from the distal end of the cuff to the tip of the tube, even when the same size tubes are compared.
- The result of the efforts to overcome the above disadvantages was the introduction of microcuff endotracheal tubes, designed by Markus Weiss and Andreas Gerber, Zurich, Switzerland.
- Cuffed endotracheal tubes (Microcuff) are available for conventional and oral RAE tubes as well
- Cuffed ETT prevent gas leak, provide better seal and thereby more effective ventilation and reduced need for the change of the ET
How to choose an airway plan?
A plan includes
1. Strategy : Awake vs after General anaesthesia, relaxant vs spontaneous ventilation
2. Plan for continuous oxygenation in high risk patients or those with difficult airway. This includes apneic oxygenation
3. Method of induction : intravenous vs inhalational vs intramuscular (rarely used)
4. Device : primary, back up and adjunct
5. Drugs : Premedication, induction, muscle relaxation
6. Technique for intubation (if decided to intubate) and extubation
7. Back up plan if primary plan can not be implemented or fails
8. Rescue plan in case of difficulty
9. Team work and roles in case of difficult airway
Airway plan depends on :
- Patient factors : Age, presence of difficult airway, ability to cooperate, full stomach, other complicating factors such as bronchial asthma, recent respiratory infections, contraindication to any muscle relaxants.
- Procedure related : Need for definitive airway device (endotracheal tube), duration, position, surgical site and procedure, special needs of the surgeon, access to airway after the procedure starts, need for intraoperative airway interventions, changes in airway as a result of surgery and plan for end of procedure airway plan (extubation, ventilation)
- Anesthesiologist related : expertise, experience, personal preference, local and national guidelines
Based on the above factors choose the best one to provide safe and secure airway
Choices in airway management are between :
- Awake technique (only in older children) or after induction
- Intravenous and inhalation agents for induction
- Routine and rapid sequence intubation
- Intubation, SGAD and mask ventilation
- Relaxant or without relaxant, if intubation is chosen
- Succinylcholine and nondepolarizing muscle relaxant, if decided to intubate with relaxation
- Oral and nasal intubation
- Uncuffed and microcuff endotracheal tube: conventional or special tubes like RAE
- Direct laryngoscopy, video laryngoscopy and fiberoptic guided intubation
- Direct intubation and intubation through SGAD
- With and without using intubating aids like boogie, Frova Introducer etc
- Channeled and non-channeled SGAD, if intubation not required
- Deep, awake and delayed extubation
Also consider a) optimal external laryngeal manipulation b) use of bougie c) Sellcik maneuver in emergency d) 2 person intubation where the person performing laryngoscopy himself/herself provides external laryngeal manipulation and another person intubates standing by the side e)use of Capnogram to confirm position of the tube as a mandatory practice.
Some foundation facts regarding difficult airway management in children
1. Smaller size of the airway precludes multiple attempts and demands delicate performance of techniques
3. Rapid onset of hypoxia with multiple attempts
4. Rapid onset of obstruction due to mucosal edema
5. Awake techniques are more difficult, if not impossible
6. Appropriate equipment may not always be available
7. Endotracheal intubation is THE safest and surest way of maintaining and protecting the airway, especially when in doubt
Differences between anticipated and unanticipated difficult airway management
DA could be anticipated or unanticipated. Irrespective of anticipated or unanticipated, factors contributory factors include a) very young age, less than 1 year, neonates b) prematurity c)ASA 3 and more status d) emergency surgery e)full stomach f)bleeding tendencies g)preexisting airway obstruction.
Anticipated difficult airway
- Could be difficult mask ventilation, difficult intubation, difficult supraglottic airway device insertion, difficult extubation or a combination of any of the above factors.
- Understand the nature of difficulty and develop a primary, backup plan and rescue plan
- Have proper help ready
- Check your equipment well before procedure
- Maintaining and monitoring oxygenation continuously, by incorporating strategy for oxygenation as a part of airway plan
- Priority for oxygenation rather than “somehow intubate” attitude
- Consider SGAD as a backup or rescue device early during airway management
- If intubation is required, consider carefully the need for relaxant. Difficult Airway does not necessarily mean need to avoid muscle relaxant.
- If intubation is not mandatory, keep it as a back up and use appropriate type and size of SGAD. Choice is between a channeled and non- channeled device. If appropriate and you are familiar, you can choose a SGAD through which you can directly intubate, if necessary (Intubating LMA, Air Q mask, Ambu Aura i etc)
- Keep waking up of the patient as one of the options when you fail to intubate, but still can ventilate, even if it means rescheduling of surgery as an option.
- Tracheostomy should rarely be required in anticipated difficult airway unless it is a back up or primary plan rather than a rescue plan.
______________________________________________________________________________Unanticipated difficult airway
Planning to manage failures prevents real failure in airway management
- Unanticipated difficult mask ventilation is much less common in children compared to adults, often it is due to lack of experience rather than real difficulty.
- Unanticated difficult intubation could be due to difficulty in laryngoscopy or intubation or both.
- First step is always to call for help and keep a close watch on oxygenation
- Management depends on what stage the difficulty was encountered and nature of difficulty
- Consider administering relaxant if not given and if difficulty is due to residual muscle tone or laryngospasm etc. Always muscle paralysis should be accompanied by adequate depth of anaesthesia.
- If already paralyzed and then encountered difficult intubation, consider the options of SGAD, Mask ventilation, waking up or surgical option.
- Reversal with sugammadex may be possible
Strategies for management of Difficult Mask Ventilation
- Use 2 hand ventilation with ventilation being carried out by 2nd person
- Insert an oral airway or rarely nasal airway (in restricted mouth opening ,obese children etc.)
- Increase the depth of anesthesia and consider paralysis if child is stable and no contraindication
- Consider using CPAP/PEEP by partially closing the APL valve
- Place the child in lateral position
- Use a supraglottic airway device, if ventilation difficulty persists
Inhalation vs Induction and intubation without relaxants
- Inhalational induction is preferred when there is no venous access, child is uncooperative and as a matter of preference by many anaesthesiologist. It is not mandatory that every child with difficult airway should be induced with inhalation agent
- If decided choices are a) Inhalation induction with Oxygen and Air (or nitrous oxide) and sevoflurane followed by venous access followed by intravenous analgesia and propofol and muscle relaxant (if decided as per plan) or b) Continue inhalational anaesthetic and achieve adequate depth and intubate without intravenous drugs(or only analgesic is given intravenously). The second option is not often practiced.
- Intubation under deep sevoflurane anaesthesia is possible and is done at a stage when the baby is flaccid and apneic. Due to rapid elimination of sevoflurane, time available for intubation is short and always there is a risk of laryngospasm if depth is not adequate. A dose of propofol will prevent laryngospasm and also help in providing better intubating condition without relaxant.
- Among the intravenous induction agents only propofol suppresses the airway reflexes adequately and provides satisfactory conditions for intubation in children, without relaxants. Analgesia with fentanyl or other drugs is required.
- Any difficulty in intubation in the first technique should lead to change in the position, equipment, or person or approach in the second attempt. Not more than 2 attempts recommended.
- If relaxant is needed rocuronium and atracurium or vecuronium are among the options, Succinylcholine reserved for selected cases. Only sugammadex can reverse effects of rocuronium and to a lesser extent vecuronium, immediately after administering intubating dose.
Role of SGAD in difficult pediatric airway management
- Elective ventilation as a primary airway device
- Temporary ventilation device as alternate to mask ventilation
- Elective intubation assist device in anticipated difficult intubation, as a conduit for intubation
- Rescue ventilation after the 2nd failed intubation attempt or when ventilation is becoming difficult
- Rescue device for management of CICV or CICVCO
- Temporary ventilation device during establishment of a surgical access
- If the first SGAD cannot be placed properly one more attempt can be made with a different size or type of device. Usually change is for the bigger size.
In addition to the above roles, SGAD also is an accepted device for airway management during cardiopulmonary resuscitation and used for surfactant administration in premature babies.
Extubation following a difficult airway
4Ps are the key words
1)Planning(a part of overall airway management plan. Should decide 1) deep or awake 2) immediate vs delayed. If delayed, decide about location, in recovery or in ICU
2) Preparation : Suctioning, cutting of anaesthetics, 100% oxygen, necessary devices like airway exchange catheter if needed, reversal, positioning the patient
3) Perform : Actual act of extubation
4) Post extubation care : recognition and management of complications, plan for reintubation after extubation if required.
Deep extubation is rarely performed. If decided one of the options is to replace the ETT with a SGAD when the child is deep, before reversal. Other option is to remove the tube gently after reversal and suctioning but maintain deep plane of anaesthesia with spontaneous breathing,
Important complications are laryngospasm and post obstructive pulmonary edema.
Laryngospasm is a dreaded complications and manifests immediately after extubation. Can be partial or complete, the latter being potentially fatal. Presence of secretion or blood during extubation and extubation in light plane of anaesthesia are precipitating factors. Treatment depends on whether it is partial or complete and whether there is already hypoxia.
Treatment of laryngospasm include
- Forcible jaw thrust and positive pressure breaths with 100% oxygen
- Pressure over “laryngospasm notch”, called Larson maneuver.
- Propofol if laryngospasm not completely relieved
- Inj succinyl choline, 10% of intubation dose, to relieve severe spasm
Prevention is better than treatment, by adequate clearing of airway and extubating when child is fully awake.
“Laryngospasm notch” is located immediately beneath the pinna of the ear bounded on the superior, anterior and posterior aspects by the base of the skull, the mandibular condyle and the mastoid process respectively.
POPE: This is another severe but rare complication , if there is a prolonged airway obstruction after extubation. Treatment is similar to other causes of pulmonary edema.
Other complications like airway obstruction, post extubation stridor, risk of aspiration and need for reintubation should be watched for.
- Pediatric airway is different and can be difficult too.
- Younger the age, more likely to be the possibility of difficulty
- Difficult airway includes difficulty in different components of airway management such as mask ventilation, intubation and surgical airway
- Age and size specific equipment are available for difficult airway management in children
- Clear plan of action with backup plan should be followed for airway management
- Plan for oxygenation, avoiding repeated attempts at intubation, early recognition of problems, waking up of patients when feasible are some of the options
- Neonatal airway management is not discussed in any detail here. Residents are required to prepare for the topic as well
- Extubation is one of the important aspects of difficult airway management, more so in children.
- Managing the difficult airway in the syndromic child Diana Raj and Igor Luginbuehl, Continuing Education in Anaesthesia, Critical Care & Pain Vol 15, Number 1, 2015
- Focused review on the management of difficult pediatric airway. Andre S Huang et al Indian J Anaesth 2019 Jun: 63 (6) ; 428-436
- Airway management in children with difficult tracheal intubation from the pediatric difficult intubation (PeDI) registry : A prospective cohort analysis Lancet Respir Med 2016 Jan;4(1)
- AIDAA 2016 guidelines for the management of unanticipated difficult tracheal intubation in Children. Indian J Anaesth 2016 Volume 60(12);906-914 :37-48
- Pediatric difficult airway management: what every anaesthetist should know! N. Jagannathan, L.Sohn, J.E. Fiadjoe British Journal of Anaesthesia, Volume 117, Issue suppl_1, September 2016, Pages i3-i5
- Airway assessment based on a three column model of direct laryngoscopy K B Greenland Anaesth Intensive Care 2010 Jan;(38):14-9
- The Vortex: a universal ‘high-acuity implementation tool’ for emergency airway management British Journal of Anaesthesia, Volume 117, Issue suppl-1, September 2016