THE CLINICAL CHALLENGE

Airway management in the pediatric population presents many potential challenges, including age-related drug dosing and equipment sizing, anatomical variation that continuously evolves as development proceeds from infancy to adolescence, and the performance anxiety that invariably accompanies the resuscitation of a critically ill child. Clinical competence in managing the airway of a critically ill or injured child requires an appreciation of age- and size-related factors, and a degree of familiarity and comfort with the fundamental approach to pediatric airway emergencies.

The principles of airway management in children and adults are the same. Medications used to facilitate intubation, the need for alternative airway management techniques, and the basic approach to performing the procedure are similar whether the patient is 8 or 80 years of age. There are, however, a few important differences that must be considered. These differences are most exaggerated in the first 2 years of life, after which the pediatric airway gradually develops more adult-like features.

In adults, recognition and management of the difficult airway is the principal skill to be mastered. During training and in actual practice, there is ample opportunity to master and maintain these skills. In pediatrics, this is not the case. The paucity of sick children encountered in training and actual practice makes attaining the same level of comfort difficult to achieve. Although the incidence of difficult pediatric airways encountered by emergency physicians is negligible, the challenge for the emergency physician is developing comfort in managing small children who have predictable differences in anatomy and physiology compared with older children and adults. This chapter will review those difference with the aim of simplifying them and making the key skills more easily learned and maintained.

APPROACH TO THE PEDIATRIC PATIENT

General Issues

A review of pediatric resuscitation processes defined elements of the mental (cognitive) burden of providers, when dealing with the unique aspects of critically ill children compared with adults. Age- and size-related variables unique to children introduce the need for more complex, nonreflexive, or knowledge-based mental activities, such as calculating drug doses and selecting equipment. The concentration required to undertake these activities while under stress may subtract from other important mental activity such as assessment, evaluation, prioritization, and synthesis of information, referred to in the resuscitative process as critical thinking activities. The cumulative effect of these factors leads to inevitable time delays and a corresponding increase in the potential for decision-making errors in the pediatric resuscitative process. This is in sharp contrast to adult resuscitation, where drug doses, equipment sizing, and physiologic parameters are usually familiar to the provider, leading to more automatic decisions that free the adult provider’s attention for critical thinking. In children, drug doses are based on weight and may vary by an order of magnitude depending on age (i.e., 3-kg neonate vs. a 30-kg 8-year-old vs. a 100-kg adolescent). The use of resuscitation aids in pediatric resuscitation significantly reduces the cognitive load (and error) related to drug dosing calculations and equipment selection by relegating these activities to a lower order of mental function (referred to as “automatic” or “rule based”). The results are reduced error, attenuation of psychological stress, and an increase in critical thinking time. Table 24-1 is a length-based, color-coded equipment reference chart (based on the “resuscitation guide” of Broselow–Luten) for pediatric airway management that eliminates error-prone strategies based on age and weight. Both equipment and drug dosing information are included in the Broselow–Luten system and can be accessed by a single length measurement or patient weight. This system is also available as part of a robust online resource (www.ebroselow.com).

Specific Issues

Anatomical and Functional Issues

The approach to the child with airway obstruction (the most common form of a difficult pediatric airway) incorporates several unique features of the pediatric anatomy.

1. Children obstruct more readily than adults do, and the pediatric airway is especially susceptible to airway obstruction resulting from swelling. (See Table 26-4 [Chapter 26] that outlines the effect of 1-mm edema on airway resistance in the infant [4-mm airway diameter] vs. the adult [8-mm airway diameter].) Nebulized racemic epinephrine causes local vasoconstriction and can reduce mucosal swelling and edema to some extent. For diseases such as croup, where the anatomical site of swelling occurs at the level of the cricoid ring, functionally the narrowest part of the pediatric airway, racemic epinephrine can have dramatic results. Disorders located in areas with greater airway caliber, such as the supraglottic swelling of epiglottitis or the retropharyngeal swelling of an abscess, rarely produce findings as dramatic. In these latter examples, especially in the epiglottitis, efforts to force a nebulized medication on a child may agitate the child, leading to increased airflow velocity and dynamic upper airway obstruction.

2. Noxious interventions can lead to dynamic airway obstruction and precipitate respiratory arrest, leading to the admonition to “leave them alone.” The work of breathing in the crying child increases 32-fold, elevating the threat of dynamic airway obstruction and hence the principle of maintaining children in a quiet, comfortable environment during evaluation and management for upper airway obstruction (Fig. 24-1A–C).

3. Bag-mask ventilation (BMV) may be of particular value in the child with upper airway obstruction. Note in Figure 24-1C that efforts by the patient to alleviate the obstruction may actually exacerbate it, as increased inspiratory effort creates increased negative extrathoracic pressure, leading to collapse of the malleable extrathoracic trachea. The application of positive pressure through BMV causes the opposite effect by stenting the airway open and relieving the dynamic component of obstruction (Fig. 24-1C, D). This mechanism explains the recommendation to try BMV first as a temporizing measure, even if the patient arrests from obstruction. There have been numerous case reports of children with epiglottitis successfully being resuscitated utilizing BMV.

4. Apart from differences related to size, there are certain anatomical peculiarities of the pediatric airway. These differences are most pronounced in children <2 years of age, whereas children >8 years of age are similar to adults anatomically and the 2- to 8-year-old period is one of transition. The glottic opening is situated at the level of the first cervical vertebra (C-1) in infancy. This level transitions to the level of C-3 to C-4 by age 7 and to the level of C-5 to C-6 in the adult. Thus, the glottic opening tends to be higher and more anterior in children as opposed to adults. The size of the tongue with respect to the oral cavity is larger in children, particularly infants. The epiglottis is also proportionately larger in a child, making efforts to visualize the airway with a curved blade, by insertion of the blade tip into the vallecula and lifting the epiglottis out of the way more difficult. Thus a straight blade, which is used to get underneath and directly lift the epiglottis up, is recommended in children younger than 3 years (Table 24-2).

5. Blind nasotracheal intubation is relatively contraindicated in children younger than 10 years for at least two reasons: Children have large tonsils and adenoids that may bleed significantly when traumatized, and the angle between the epiglottis and the laryngeal opening is more acute than that in the adult, making successful cannulation of the trachea difficult.

Children possess a small cricothyroid membrane, and in children younger than 3 to 4 years, it is virtually nonexistent. For this reason, needle cricothyrotomy may be difficult, and surgical cricothyrotomy is virtually impossible and contraindicated in infants and small children up to 10 years of age.

Although younger children possess a relatively high, anterior airway with the attendant difficulties in visualization of the glottic aperture, this anatomical pattern is consistent in all children, so this difficulty can be anticipated. The adult airway is subject to more variation and age-related disorders leading to a difficult airway (e.g., rheumatoid arthritis, obesity). Children are predictably “different,” not “difficult.” Figure 24-2 demonstrates anatomical differences particular to children.

• FIGURE 24-1. Intra- and Extrathoracic Trachea and the Dynamic Changes That Occur in the Presence of Upper Airway Obstruction. A: Normal anatomy. B: The changes that occur with normal inspiration; that is, dynamic collapsing of the upper airway associated with the negative pressure of inspiration on the extrathoracic trachea. C: Exaggeration of the collapse secondary to superimposed obstruction at the subglottic area. D: Positive-pressure ventilation (PPV) stents the collapse/obstruction versus the patient’s own inspiratory efforts, which increase the obstruction. (Adapted from Cote CJ, Ryan JF, Todres ID, et al., eds. A Practice of Anesthesia for Infants and Children. 2nd ed. Philadelphia, PA: WB Saunders; 1993, with permission.)

• FIGURE 24-2. The anatomical differences particular to children are (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; and (7) larger relative size of the occiput in the infant.

There are two important physiologic differences between children and adults that impact airway management (Box 24-1). Children have a basal oxygen consumption that is approximately twice that of adults. Coupled with a proportionally smaller functional residual capacity (FRC) to body weight ratio, these factors result in more rapid desaturation in children compared with adults, given an equivalent duration of preoxygenation. Rapid desaturation is most pronounced in children less than 24 months old. The clinician must anticipate and communicate this possibility to the staff and be prepared to provide supplemental oxygen by BMV if the patient’s oxygen saturation drops below 90%.

In 1993, the U.S. Food and Drug Administration (FDA), in conjunction with pharmaceutical companies, revised the package labeling for SCh in the wake of reports of hyperkalemic cardiac arrest following the administration of SCh to patients with previously undiagnosed neuromuscular disease. Initially, it stated that SCh was contraindicated for elective anesthesia in pediatric patients because of this concern, although the wording was subsequently altered to embrace a risk–benefit analysis when deciding to use SCh in children. However, both the initial advisory warning and the revised warning continue to recommend SCh for emergency or full-stomach intubation in children. Pediatric drug doses are provided in Table 24-3.

Equipment Selection

Table 24-1 references length-based recommendations for emergency equipment in pediatric patients. Appropriately sized equipment can be chosen with a centimeter length measurement or with a Broselow tape.

A word of caution with respect to the storage of airway management equipment for children: Despite best efforts (e.g., equipment lists or periodic checks), it is not uncommon for newborn equipment to be mixed in with or placed in proximity to the smallest pediatric equipment. This practice may lead to newborn equipment being used in older children for whom it may not function properly or may, in fact, be dangerous. Examples include the no. 0 laryngoscope blade, which is too short to allow visualization of the airway; the 250-mL newborn BMV, which provides inadequate ventilation volumes; and various other equipments, such as oral airways that can cause airway obstruction if too small, or a curved laryngoscope blade that may not reach and pick up the relatively large epiglottis, or effectively remove the large tongue from the laryngoscopic view of the airway (see Table 24-4).

1. Endotracheal tubes

The correct endotracheal tube (ETT) size for the patient can be determined by a length measurement and by referring to the equipment selection chart. The formula (16 + age in years)/4 is also a reasonably accurate method of determining the correct tube size. However, the formula cannot be used in children younger than 1 year and is only useful if an accurate age is known, which cannot always be determined in an emergency. Either cuffed or uncuffed ETTs are acceptable in the younger pediatric age groups, and cuffed tubes are used for size 5.5 mm and up (Fig. 24-3). The admonition to avoid cuffed tubes in young infants is historical and in the past, there was an unacceptably high rate of subglottic stenosis resulting from failure to carefully monitor cuff pressures. Newer ETTs make it easier to monitor cuff pressures and can be safely used in infants and small children, provided clinicians recognize the following fact: A cuffed tube adds 0.5 mm to the internal diameter (ID), so a smaller than predicted (by 0.5 mm) tube may be required. The cuffed tube should be placed with the cuff deflated initially and inflated with the minimum volume of air needed to affect an adequate seal.

When intubating a young child, there is a tendency to insert the ETT too far, usually into the right mainstem bronchus. Various formulas can be used to determine the correct insertion distance (e.g., tube size times 3; age/2 + 10). For example, a 3.5-mm ID tube should be inserted 3.5 × 3 = 10.5 cm at the lip. Alternatively, a length-based chart can be used. We recommend placing a piece of tape on the tube at the appropriate lip-to-tip centimeter line, which serves as a constant reminder of the correct position of the tip of the ET tube in the intubated patient.

Note: Only appropriate size is functional. Frequently, very small sizes are placed in the pediatric area without attention to appropriateness of size. This can greatly contribute to a failed airway outcome.

• FIGURE 24-3. Airway Shape. Note the position of the narrowest portion of the pediatric airway, which is at the cricoid ring, creating a funnel shape, versus the cylindrical shape seen in the adult, where the vocal cords form the narrowest portion. This is the rationale for using the uncuffed tube in the child; it fits snugly, unlike the cuffed tube used in the adult, which is inflated once the tube passes the cords to produce a snug fit. (Modified with permission from Cote CJ, Todres ID. The pediatric airway. In: Cote CJ, Ryan JF, Todres ID, et al, eds. A Practice of Anesthesia for Infants and Children. 2nd ed. Philadelphia, PA: WB Saunders; 1993.)

An all too frequent complication following intubation is inadvertent extubation. ETTs must be secured at the mouth. Head and neck movement, particularly extension which translates into movement of the tube up and potentially out of the trachea, should be minimized. A cervical collar placed after intubation prevents flexion and extension and therefore can help prevent ETT dislodgement (Fig. 24-4). The ETT is traditionally secured by taping the tube to the cheek, although various commercial devices are also available.

3. Oxygen masks

The simple rebreather mask used for most patients provides a maximum of 35% to 60% oxygen and requires a flow rate of 6 to 10 L per minute. A non-rebreather mask can provide approximately 70% oxygen in children if a flow rate of 10 to 15 L per minute is used. For emergency airway management, and particularly for preoxygenation for rapid sequence intubation (RSI), the pediatric non-rebreather mask is preferable. Adult non-rebreather masks can be used for older children, but are too large to be used for infants and small children and will entrain significant amounts of “room” air. Apneic oxygenation (see Chapter 5) should be considered in children (at a rate of 1 L per min per year of age) as a low-risk maneuver to prolong safe apnea time. Recent evidence suggests that, in adults, turning the oxygen flow rate to the “flush” rate of 40 to 70 L per minute (varies depending on the wall spigot) increases FIO₂ (>90%) and end-tidal oxygen measurements. This has not been studied in children, but may be reasonable to try if preoxygenation is difficult. Additionally, properly configured bag-mask systems (i.e., those that function as one-way inspiratory and expiratory valves and small dead space) are capable of delivering oxygen concentrations >90%, if correctly used. The spontaneously breathing patient opens the duck-billed inspiratory valve on inspiration, and on expiration, the expired volume with carbon dioxide (CO₂) pinches the duckbill valve closed and is vented through the expiratory valve into the atmosphere. Adult-type units tend not to be used in infants and small children because of dead space considerations and size-related awkwardness, leading some to prefer pediatric non-rebreather masks.

• FIGURE 24-4. Securing the ET Tube. A: Unsecured tube sliding in/down. B: Unsecured tube sliding out/up. C: Tube secured to prevent in/out, up/down movement. D: Secured tube moving down and in as head flexes. E: Secured tube moving up/out as head extends. F: Neck movement prevented by cervical collar, thus preventing tube movement in the trachea.

4. Oral airways

Oral airways should only be used in children who are unconscious. In the conscious or semiconscious child, these airways can incite vomiting. Oral airways can be selected based on the Broselow tape measurement or can be approximated by selecting an oral airway that fits the distance from the angle of the mouth to the tragus of the ear.

5. Nasopharyngeal airways

Nasopharyngeal airways are helpful in the obtunded but responsive child. The correctly sized nasopharyngeal airway is the largest one that comfortably fits in the naris but does not produce blanching of the nasal skin. The correct length is from the tip of the nose to the tragus of the ear and usually corresponds to the nasopharyngeal airway with the correct diameter. Care must be taken to suction these airways regularly to avoid blockage.

6. Nasogastric tubes

BMV may lead to insufflation of the stomach, hindering full diaphragmatic excursion and preventing effective ventilation. A nasogastric (NG) tube should be placed soon after intubation to decompress the stomach in any patient who has undergone BMV and requires ongoing mechanical ventilation postintubation. Often in such patients, the abdomen is distended or tense, making the problem obvious, but other times it is difficult to identify the difference between this and the normally protuberant abdomen of the young child. Difficulty in ventilation that is felt to be related to reduced compliance should prompt the placement of an NG tube. Length-based systems identify the appropriate NG tube size.

7. BMV equipment

For emergency airway management, the self-inflating bag is preferred by most over the anesthesia ventilation bag. These bag-mask units should have an oxygen reservoir so that at 10 to 15 L of oxygen flow, one can provide a FIO₂ of 90% to 95%. The smallest bag that should be used is 450 mL. Neonatal bags that are smaller (250 mL) do not provide effective tidal volume even for small infants. Many of the pediatric BMV devices have a positive-pressure relief (pop-off) valve. The pop-off valve may be set by the manufacturer to open at anywhere between 20 and 45 cm of water pressure (CWP), depending on whether the bag unit is intended for infants or small children (respectively) and is used to prevent barotrauma. Emergency airway management often requires higher peak airway pressures, so the bag should be configured without a pop-off valve or with a pop-off valve that can be closed. Practically, it is a good practice to store the BMV device with the pop-off valve closed so that initial attempts to ventilate the patient can achieve sufficient peak airway pressure to achieve ventilation. Chapter 25 discusses this issue in more detail and offers suggestions to prevent its occurrence.

8. End-tidal CO₂ detectors

Colorimetric end-tidal CO₂ (ETCO₂) detectors are as useful in children as in adults. A pediatric size exists for children weighing <15 kg, while the adult model should be used for children weighing >15 kg. If an adult-sized ETCO₂ device is used inappropriately for a small child, there may be insufficient CO₂ volumes to cause the detector to change color, resulting in a false-negative reading and removal of a correctly placed tube. Conversely, the resistance in a pediatric ETCO₂ detector may be sufficiently high to make ventilation difficult in a larger child.

9. Airway alternatives (Table 24-5)

Orotracheal intubation is the procedure of choice for pediatric emergency airway management including those patients with potential cervical spine injury where RSI with in-line manual stabilization is preferred. Nasotracheal intubation is relatively contraindicated in children.

Cricothyrotomy is the preferred emergency surgical airway in adults. The cricothyroid space emerges as one ages and is really only accessible after the age of 10 years. “Needle cricothyrotomy” in children younger than 10 years is the term used when one accesses the airway in a percutaneous manner in young children, even though it is recognized that the point of entry into the airway is often the trachea as opposed to the cricothyroid space.

Other devices that may be of use in failed airway management in young children are laryngeal mask airways (LMAs) and the GlideScope. LMAs are made for even newborns and young infants and may be useful as a temporizing measure when direct laryngoscopy proves difficult. The GlideScope is supplied in sizes appropriate for pediatric patients, although currently the penetration of this technology to all clinical settings has not occurred. These and other adjuncts are discussed in Chapter 25.

INITIATION OF MECHANICAL VENTILATION

In emergency pediatrics, two modes of ventilation are used. Pressure-limited ventilation is the mode used for newborns and small infants, whereas volume-limited ventilation is used for older children and adults. One can arbitrarily set 10 kg as the weight below which pressure-limited ventilators should be used, although volume-limited ventilators have been used effectively in smaller children. Generally speaking, the younger the child is, the more rapid the ventilatory rate. The initial ventilatory rate in infants is typically set between 20 and 25 breaths per minute. Inspiratory:expiratory ratios are set at 1:2, and the typical peak inspiratory pressure at initiation of ventilation is between 15 and 20 CWP. These initial settings in a pressure-controlled ventilation mode will usually give a tidal volume of 8 to 12 mL per kg. These initial settings are adjusted according to subsequent clinical evaluation and chest rise. Positive end-expiratory pressure should also be set at 3 to 5 cm of water and FIO₂ at 1.0. The Broselow–Luten length-based system also provides guidance for approximate starting tidal volumes, ventilator rates, and inspiratory times.

Once initial settings have been established, it is critical that the patient be quickly reevaluated and adjustments made, particularly as pulmonary compliance, airways resistance, and leak volumes change with time, precluding adequate ventilation with the initial settings of pressure-controlled ventilation. Clinical evaluation of ventilatory adequacy is more important than formulae to ensure adequate ventilation. Once adjustments are made and the patient appears clinically to be ventilated and oxygenating, blood gas determinations, or continuous pulse oximetry and ETCO₂ monitoring, should be used for confirmation and to guide additional adjustments (Table 24-6 and Box 24-2).

RSI TECHNIQUES FOR CHILDREN

The procedure of RSI in children is essentially the same as in adults, with a few important differences outlined as follows:

1. Preparation

• Use resuscitation aids that address age- and size-related issues in drug dosing and equipment selection (e.g., Broselow–Luten tape).

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