PEDIATRIC AIRWAY comparison between adults

Paediatric airway

1. PEDIATRIC AIRWAY AND ANAESTHETIC IMPLICATIONS PRESENTER: DR ABHISHEK MODERATOR:DR NAGESHA

2. AIRWAY ANATOMY: The pediatric patients have significant anatomical and physiological differences compared with adults, which impact on the techniques and tools that the anesthesiologist might choose to provide safe and effective control of the airway. The first anatomical difference between the pediatric and adult patient becomes important when positioning the child prior to or immediately after the induction of anesthesia. The head of a pediatric patient is larger relative to body size, with a prominent occiput. This predisposes to airway obstruction in asleep children.

3. The tongue is larger and the mandible shorter in the young child. In infancy, the child is an obligate nasal breather until 5 months of age. Prominent adenoids and tonsils are frequently found in preschool age children and are a frequent reason to present for elective ENT surgery. These factors all contribute to loss of upper airway space which can lead to difficulty with mask ventilation, obstruction during spontaneous ventilation, and can make laryngoscopy more difficult.

4. Relatively larger tongue Obstructs airway Obligate nasal breathers Difficult to visualize larynx Straight laryngoscope blade completely elevates the epiglottis, preferred for pediatric laryngoscopy Angled vocal cords: Infant’s vocal cords have more angled attachment to trachea, whereas adult vocal cords are more perpendicular Difficulty in nasal intubations where “blindly” placed ETT may easily lodge in anterior commissure rather than in trachea Differently shaped epiglottis: Adult epiglottis broader, axis parallel to trachea Infant epiglottis ohmega ( Ώ ) shaped and angled away from axis of trachea More difficult to lift an infant’s epiglottis with laryngoscope blade

5. Funneled shape larynx narrowest part of infant’s larynx is the undeveloped cricoid cartilage, whereas in the adult it is the glottis opening (vocal cord) Tight fitting ETT may cause edema and trouble upon extubation Uncuffed ETT preferred for patients < 8 years old Fully developed cricoid cartilage occurs at 10-12 years

6. Physiology: The pediatric patient has a number of physiological challenges which can predispose to hypoxemia. Oxygen consumption of an infant is relatively greater than an adult . This combined with a somewhat lower functional residual capacity can lead to rapid desaturation during apnea, such as during laryngoscopy or a rapid sequence induction, despite best efforts at preoxygenation. Oxygen consumption of infant (6 ml/kg/min) is twice that of an adult (3 ml/kg/min)

7. Greater oxygen consumption = increased respiratory rate The resistance to flow in the airway is governed by Poiseulle's law: R =8ƞL/πr 4 . The resistance to flow is inversely related to the radius of the airway raised to the fourth power, a small amount of narrowing (due to edema, inflammation, etc.,) in the already small pediatric airway could have severe consequences on respiratory function. A number of disease processes that could result in such narrowing of the airway include growths within the airway such as hemangiomas or papillomas , aberrant embryological development such as tracheomalacia, laryngomalacia, and laryngeal clefts, iatrogenic causes like vocal cord paralysis and subglottic stenosis, or compression of the airway structures by a mass located outside the airway

8. AIRWAY ASSESSMENT: The initial airway assessment starts with a good history. Questions are directed toward eliciting indications of a potentially difficult airway. This would include any complications of birth or delivery, any history of prior trauma or surgery to the airway or adjacent structures, or of prior anesthetics. Additionally, one should inquire about current or recent symptoms suggesting upper respiratory infection (URI), difficulty in speaking, difficulty breathing, difficulty feeding, hoarseness, and noisy breathing. Questions such as a history of snoring, day time drowsiness, or stopping breathing during sleep, may help to identify children with obstructive sleep apnea

9. BAG AND MASK VENTILATION: Clear, plastic mask with inflatable rim provides atraumatic seal Proper area for mask application-bridge of nose extend to chin Place fingers on mandible to avoid compressing pharyngeal space Hand on ventilating bag at all times to monitor effectiveness of spontaneous breaths Continous postitive pressure when needed to maintain airway patency NASOPHARYNGEAL AIRWAY : Distance from nares to angle of mandible approximates the proper length Nasopharyngeal airway available in 12F to 36F sizes Shortened endotracheal tube may be used in infants or small children Avoid placement in cases of hypertrophied adenoids - bleeding and trauma

10. Selection of laryngoscope blade: Miller vs. Macintosh: Miller blade is preferred for infants and younger children Facilitates lifting of the epiglottis and exposing the glottic opening Care must be taken to avoid using the blade as a fulcrum with pressure on the teeth and gums Macintosh blades are generally used in older children Blade size dependent on body mass of the patient and the preference of the anesthesiologist

11. Endotracheal Tube: Age Wt ETT(mm ID) Length(cm ) Preterm 1 kg 2.5 6 1-2.5 kg 3.0 7-9 Neonate-6mo 3.0-3.5 10 6 mo-1 3.5-4.0 11 1-2 yrs 4.0-5.0 12 New AHA Formulas: Uncuffed ETT: (age in years/4) + 4 Cuffed ETT: (age in years/4) +3 ETT depth (lip): ETT size x 3

12. Cuff vs Uncuffed Endotracheal Tube: Controversial issue Traditionally, uncuffed ETT recommended in children < 8 yrs old to avoid post- extubation stridor and subglottic stenosis Arguments against cuffed ETT: smaller size increases airway resistance, increase work of breathing, poorly designed for pediatric pts, need to keep cuff pressure < 25 cm H2O Arguments against uncuffed ETT: more tube changes for long-term intubation, leak of anesthetic agent into environment, require more fresh gas flow > 2L/min, higher risk for aspiration - Concluding Recommendations- For “short” cases when ETT size >4.0, choice of cuff vs uncuffed probably does not matter Cuffed ETT preferable in cases of: high risk of aspiration ( ie . Bowel obstruction), low lung compliance ( ie . ARDS, pneumoperitoneum, CO2 insufflation of the thorax, CABG), precise control of ventilation and pCO2 ( ie . increased intracranial pressure, single ventricle physiology)

13. Laryngeal Mask Airway: Supraglottic airway device developed by Dr. Archie Brain Flexible bronchoscopy, radiotherapy, radiologic procedures, urologic, orthopedic, ENT and ophthalmologic cases are most common pediatric indications for LMA Useful in difficult airway situations, and as a conduit of drug administration ( ie . Surfactant) Different types of LMAs: Classic LMA, Flexible LMA, ProSeal LMA, Intubating LMA Disadvantages: Laryngospasm, aspiration

14. Difficult Airway Management Techniques Rigid bronchoscopy Flexible bronchoscopy Direct laryngoscopy Intubating LMA Lighted stylet Bullardscope Fiberoptic intubation Surgical airway

15. CONCLUSION The airway of the pediatric patient has a number of significant differences when compared to the adult airway and presents some unique challenges. Awareness of anatomical and physiological differences, important pathological conditions affecting children, and a knowledge of the available airway techniques and tools will allow the anesthesiologist to formulate and execute safe and effective management of the pediatric airway.

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