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Airway Management

The accurate assessment and safe management of the airway is fundamental to the care of critically ill or injured children.

The Anatomy of the Airway

The larynx consists of nine cartilages, including the thyroid, cricoid, epiglottis, corniculate, cuneiform, and arytenoid cartilages. These cartilages are covered by folds of mucosa, connective tissue, and muscle; laryngeal tissue folds define the glottis. The superior, inferior, and recurrent laryngeal nerves innervate the larynx. Supraglottic sensation is mediated by the superior laryngeal nerve, and infraglottic sensation is mediated by the inferior laryngeal nerve. The recurrent laryngeal nerve provides most laryngeal motor innervation. Only the cricothyroid muscle is innervated by the superior laryngeal nerve. The airway is lined with ciliated and squamous epithelium that is highly vascular and overlies a rich network of lymphatic vessels.

Developmental Airway Considerations

The anatomy of the pediatric airway differs from the adult airway until it reaches mature position at approximately 8 to 14 years of age.

The major differences between the pediatric and the adult airway are size, shape, and position in the neck.

Because the diameter of the pediatric trachea is small, relatively small compromise in trachael radius can significantly increase resistance to airflow and work of breathing. Resistance to airflow is inversely related to the fourth power of the radius during quiet breathing, when airflow is laminar, but is inversely related to the fifth power of the radius when airflow is turbulent.

When respiratory distress is present, providers should attempt to keep the child as quiet as possible, minimizing agitation to reduce turbulent flow, airway resistance, and work of breathing.

The anatomic differences particular to children are these:

 1. Higher, more anterior position of the glottic opening. (Note the relationship of the vocal cords to the chin/neck junction.)

2. Relatively larger tongue in the infant, which lies between the mouth and glottic opening.

3. Relatively larger and more floppy epiglottis in the child.

4. The cricoid ring is the narrowest portion of the pediatric airway versus the vocal cords in the adult.

5. Position and size of the cricothyroid membrane in the infant.

6. Sharper, more difficult angle for blind nasotracheal intubation.

7. Larger relative size of the occiput in the infant.

Anatomic differences between adult and pediatric airways

Anatomy

Clinical significance

Tongue occupies relatively large portion of the oral cavity. High anterior airway position of the glottic opening compared with that in adults
High tracheal opening (relative to cervical vertebrae):
C1 in infancy
C3 to C4 at 7 years of age
C4 to C5 in the adult
Straight blade preferred over curved blade to push distensible anatomy out of the way to visualize the larynx
Large occiput may cause flexion of the airway, and large tongue can fall against the posterior pharynx when child is supine. Sniffing position opens the airway. The larger occiput actually elevates the head toward the sniffing position in most infants and children (neck must be extended). A towel may be required under shoulders to elevate torso relative to head in small infants.
Cricoid ring is the narrowest portion of the child's trachea (vocal cords are the narrowest portion in the adult). Uncuffed tubes may provide adequate seal, as they can fit snugly at the level of the cricoid ring.
Selection of correct tube size is essential because use of excessively large tube may cause mucosal injury.
Consistent anatomic variations with age, with fewer anatomic abnormal variations related to body habitus, arthritis, and chronic disease. Age-related variations:
<2 years: High anterior airway
2-8 years: Transition
>8 years: Small adult
Large tonsils and adenoids may bleed. More acute angle between epiglottis and laryngeal opening makes endotracheal intubation difficult. Blind nasotracheal intubation not indicated in children.
May cause failure of attempted nasotracheal intubation.
Small cricothyroid membrane. Needle cricothyrotomy difficult; surgical cricothyrotomy is impossible in infants and small children.

Basic Airway Assessment

Before performing any invasive airway procedure, the provider must assess the child to identify the potentially difficult airway. The three basic components of this assessment are the oropharyngeal examination, evaluation of atlanto-occipital joint extension, and measurement of the potential mandibular displacement area.

Basic Airway Management

Initial Maneuvers to Clear Airway

If the child is awake, with mild-to-moderate airway obstruction and no suspected cervical spine injury, she should be allowed to assume a position of comfort. The airway is suctioned as needed, and oxygen is administered. If the child is obtunded, the airway can become obstructed by a combination of neck flexion, jaw relaxation, displacement of the tongue against the posterior pharyngeal wall, and collapse of the hypopharynx. A simple jaw-thrust maneuver is the most effective method of opening the airway, although a head tilt-chin lift may also be successful. Providers should use the jaw thrust to open the airway if cervical spine injury is suspected, and they must perform the jaw thrust to provide effective bag-mask ventilation. If no cervical spine injury is suspected, or if the airway cannot be opened using the jaw thrust, the provider should open the airway using a head tilt-chin lift maneuver.

Oropharyngeal Airway

The oropharyngeal airway (OPA) consists of a flange, a short bite-block segment, and a curved plastic body that provides an airway and suction channel through the mouth to the pharynx. It is designed to relieve airway obstruction by fitting over the tongue to hold it and the soft hypopharyngeal structures away from the posterior wall of the pharynx. An OPA may be used in the unconscious child if manual attempts to open the airway (e.g., head tilt-chin lift or jaw thrust) fail to provide and maintain a clear, unobstructed airway. Use of an OPA in patients with intact cough or gag reflexes may stimulate gagging and vomiting; therefore; it is not recommended.

Nasopharyngeal Airways

A nasopharyngeal airway (NPA) is a soft rubber or plastic tube (a shortened endotracheal tube can be used) that provides an airway and channel for suctioning between the nares and the pharynx. NPAs may be used in patients with or without an intact cough and gag reflex.

NPAs are available in sizes 12 to 36 French. A 12-French NPA (approximately the size of a 3-mm ETT) will generally fit the nasopharynx of a full-term infant. The NPA should be smaller than the inner aperture of the nares, and its proper length is approximately equal to the distance from the tip of the nose to the tragus of the ear. If the NPA is too long, it may cause vagal stimulation and bradycardia, or it may injure the epiglottis or vocal cords.

Bag-Mask Ventilation

Bag-mask ventilation is an essential skill that requires adequate training and frequent use or periodic retraining.

The most common technique for single-rescuer bag-mask ventilation involves the β€œE-C clamp” technique. The rescuer tilts the child's head and uses the last three fingers of one hand (forming a capital letter β€œE”) to lift the jaw while pressing the mask against the face with the thumb and forefinger of the same hand (creating a β€œC”). The second hand squeezes the bag to deliver each breath over 1 sec to produce visible chest rise. It is important that the jaw is lifted to open the airway and the mask is simultaneously held tightly against the face. The rescuer should not simply press the mask down on the face, because this can close the airway and prevent effective ventilation.

Choice of Advanced Airway

The ETT has long been considered the optimal advanced airway. However, evidence in a prehospital setting documented that endotracheal intubation may offer no survival benefit over bag-mask ventilation when the transport interval is short. In addition, when personnel assigned to intubate the patient lack adequate training and experience, the incidence of complications, such as unrecognized esophageal intubation, is unacceptably high . Alternatives to the ETT that have been studied in children include the bag-and-mask and the laryngeal mask airway (LMA).

Equipment for endotracheal intubation

Monitoring Equipment (apply before intubation if at all possible)
Cardiorespiratory monitor (including monitoring of blood pressure, if possible)
Pulse oximeter

Length-based Tape to Estimate Tube and Equipment Sizes
Suction Equipment
Tonsil-tipped suction device or large-bore suction to suction pharynx
Suction catheter of appropriate size to suction endotracheal tube
Suction canister and device capable of generating suction of “80 to “120 mm Hg (a wall-suction device capable of generating “300 mm Hg is preferred)

Bag and Mask
Check size and oxygen connections
Connected to high-flow oxygen source with reservoir (capable of providing ~100% oxygen)

Medications
Anticholinergics (atropine)
Sedatives
Paralytics
Appropriate IV equipment and syringes for administration of medications.

Intubation Equipment
Stylet
Cuffed and uncuffed tubes of estimated size and cuffed and uncuffed tubes that are 0.5 mm larger and smaller than estimated sizes
Laryngoscope blades (curved and straight) and handle with working light (keep extra batteries and bulb ready)
Water-soluble lubricant
Syringe to inflate tube cuff (if appropriate)
Towel or pad to place under patient (if appropriate)

Confirmation Device(s)
Exhaled CO2 detector (pediatric size for patients <15 kg and adult size for patients >15 kg)
Esophageal detector device may be used for children who are >20 kg with a perfusing rhythm

Tape/device to Secure Tube
Tape and tincture of benzoin or
Commercial device

Rapid-sequence Intubation

General Principles

Rapid-sequence intubation (RSI) is a technique used to secure the airway in the patient who presents with a full (or presumed full) stomach, where even moderate preintubation gastric insufflation by bag-mask ventilation may cause gastric regurgitation and pulmonary aspiration. The steps of the classic RSI include (18):

A basic airway assessment, including relevant patient history using the SAMPLE mnemonic (signs and symptoms, allergies, medications, past history, last meal, events leading to intubation) to assess the risk/suitability for the use of anesthetics or paralytics.

Preparation of personnel and equipment and establishment of monitoring.

Preoxygenation (or more accurately, denitrogenation) for 2 to 3 mins with 100% O2, delivered via a tight-fitting mask, which helps to maintain oxygenation during the period of apnea that follows.

Administration of an IV anesthetic/sedative/analgesic and almost simultaneous delivery muscle relaxant.

Application of cricoid pressure (once patient is deeply sedated).

A period of apnea until the patient has full muscle relaxation.

Tracheal intubation.

Removal of cricoid pressure only after tube position is confirmed and the tube cuff (if present) is inflated.

RSI in children is particularly challenging for several reasons. As discussed earlier, the normal child can rapidly develop arterial oxygen desaturation after relatively short periods of apnea. The desaturation will be more rapid if the child is hypoxic prior to the procedure. Some patients who require emergent intubation (e.g., those with intracranial or pulmonary hypertension) will be intolerant of even brief periods of hypercapnia associated with apnea.

For these reasons, a modified RSI techniqueis often used in the intubation of critically ill children. After establishment of monitoring, some degree of bag-mask ventilation is provided while cricoid pressure is applied to minimize gastric distention. This technique should prevent or delay the onset of hypoxia and hypercarbia and their sequelae.

Before initiating RSI, the provider must determine if the patient will tolerate the procedure. Some patients have tenuous airways that allow for some oxygenation during spontaneous ventilation. Administration of sedatives and paralytics will remove spontaneous respiratory effort. If the provider is unable to maintain the patient's airway (with or without intubation), hypoxia and hypercarbia can develop rapidly. Examples of scenarios in which RSI may lead to losing the airway include patients with significant airway obstruction, facial trauma, or congenital craniofacial anomalies.

Rapid-sequence intubation drugs and doses

Drug

Dose/Route

Duration

Comments

Cardiovascular adjuncts      
Atropine IV: 0.01-0.02 mg/kg (min: 0.1 mg max: 1 mg) 30 min

Inhibits bradycardic response to hypoxia; may cause tachycardia

May cause pupil dilation

Glycopyrrolate IV: 0.005-0.01 mg/kg (max: 0.2 mg) 30 min

Inhibits bradycardic response to hypoxia; may cause tachycardia

Sedative hypnotic agents/analgesics      
Diazepam Lorazepam IV: 0.1-0.2 mg/kg (max: 4 mg)
IV: 0.05-0.1 mg/kg (max: 4 mg)
30-90 min 4-6 hr

May cause respiratory depression or potentiate depressant effects of narcotics and barbiturates

Midazolam IV: 0.1-0.3 mg/kg (max: 4 mg) 1-2 hr

May cause hypotension

Minimal cardiac depression

Occasional respiratory depression

No analgesic properties

Fentanyl citrate IV, IM: 2-4 mcg/kg IV: 30-60 min
IM: 1-2 hrs

May cause respiratory depression, hypotension, chest wall rigidity with high-dose (>5 mg/kg) infusions

May elevate ICP

Anesthetic agents (in doses indicated)      
Thiopental IV: 2-5 mg/kg 5-10 min

Negative inotropic effects and often causes hypotension

Decreases cerebral metabolic rate and ICP

Potentiates respiratory depressive effects of narcotics and benzodiazepines

No analgesic properties

Etomidate IV: 0.2-0.4 mg/kg 5-15 min

Decreases cerebral metabolic rate and ICP

May cause respiratory depression

Minimal cardiovascular effects

Causes myoclonic activity; may lower seizure threshold

Causes cortisol suppression; contraindicated in patients dependent on endogenous cortisol response

No analgesic properties

Lidocaine IV: 1-2 mg/kg ~30 min

Causes myocardial and CNS depression with high doses

May decrease ICP during RSI

Hypotension occurs infrequently

Ketamine IV: 1-2 mg/kg
IM: 3-5 mg/kg
30-60 min

May increase blood pressure, heart rate, cardiac output

May cause increased secretions, laryngospasm

Causes limited respiratory depression

Bronchodilator

May cause hallucinations, emergence reactions

Propofol IV: 2 mg/kg (up to 3 mg/kg in young children) 3-5 min

May cause hypotension, especially in hypovolemic patients

May cause pain on injection

Highly lipid soluble

Causes less airway reactivity than barbiturates

Neuromuscular blocking agents      
Succinylcholine Infant IV: 2 mg/kg
Child IV: 1-1.5 mg/kg
IM: Double the IV dose
3-5 min

Depolarizing muscle relaxant; causes muscle fasciculation

May cause rise in ICP and intraocular and intragastric pressures

May cause rise in serum potassium

May cause hypertension

Avoid in renal failure, burns, crush injuries, or hyperkalemia

Atracurium IV: 0.5 mg/kg 30-40 min

Metabolized by plasma hydrolysis

May cause mild histamine release

cis-Atracurium IV: 0.1 mg/kg, then 1-5 mg/kg/min 20-35 min

Metabolized by plasma hydrolysis

May cause mild histamine release

Rocuronium IV: 0.6-1.2 mg/kg 30-60 min

Few cardiovascular effects

Vecuronium IV: 0.1-0.2 mg/kg 30-60 min

Few cardiovascular effects

Laryngeal Mask Airway

The LMA consists of a small mask with an inflatable cuff that is connected to a plastic tube with a universal adaptor. It is designed to be placed in the oropharynx with its tip in the hypopharynx and the base of the mask at the epiglottis. When the cuff of the mask is inflated, it creates a seal with the supraglottic area, allowing air flow between the tube and the trachea.

The LMA can be used with spontaneously breathing patients to deliver PPV or as a guide for insertion of another airway device, such as an ETT, airway-exchange catheter, lighted stylet, or flexible fiberoptic bronchoscope. The maximum seal pressure possible is ~25 cm H2O, which may limit effective PPV in critically ill children. Use in conscious patients requires sedation to minimize airway protective reflexes, including laryngospasm and bronchospasm.

The ease of insertion and relatively low complication rate have made the LMA an important component of the management of patients with difficult airways. However, because it is a supraglottic device, it is less effective in patients with glottic or subglottic pathology. Complications due to malpositioning of the device (resulting in airway obstruction) or increased difficulty of insertion are more common in younger children , but the complication rate decreases with increased operator experience.