The most important difference between children and adults when it comes to airway management is exactly what you'd expect: size. Smaller nasal passages are more likely to become obstructed with blood or secretions, and tracheal edema is more likely to increase airway resistance.
But there are other factors, too. For example, in infants, the back of the skull is larger in relation to the body, which flexes the neck in the supine position, causing them to assume a "sniffing" position. Children also have a relatively narrow and short epiglottis that's angled into the lumen of the airway and is often difficult to displace during laryngoscopy. Understanding the challenges and your options can help you breathe easier when small patients depend on your skills and expertise. Let's review our options.
These days, I only use mask ventilation for short cases, such as when ENT docs put in ear tubes, and only because the procedure is so short. It's usually easy in children 4 years and older who have normal facial anatomy. Hold the mask over the mouth and nose with the thumb and forefinger, with the middle finger on the bony portion of the mandible. The middle finger lifts the chin to extend the head without compressing the neck. One caution: Be sure to rest the upper part of the mask on the bridge of the nose. Inexperienced practitioners often mistakenly hold the mask too low, which obstructs the nasal passages.
On the rare occasions that it's difficult, it's usually due to intrinsic airway obstruction for neonates and infants, large tongues or soft tissue collapse around the area of the epiglottis; for older children, large tongues, tonsils or adenoids. As I'll discuss below, a sequential series of corrective maneuvers can usually eliminate the obstruction. But one relatively easy approach is to use an oral airway, which sits behind the tongue and isn't as invasive as an LMA. It can establish airflow by bypassing soft tissue obstruction, enlarged tonsils or adenoids.
After induction of general anesthesia, but before airway instrumentation, check for loose or chipped teeth and remove primary teeth that are very loose. Grasp the tooth firmly with gauze and rock it back and forth while pulling or twisting. You can stop minor bleeding with firm pressure. And all personnel in attendance should be required to contribute to the tooth fairy fund.
Laryngeal mask airways (LMAs) have revolutionized airway management and saved countless lives. I use them for almost all elective cases that don't involve surgery around the airway or neck.
There are many ways to place them in children. One is to push the flattened LMA cuff against the hard palate and simultaneously guide the LMA into position. You can also insert them with the cuff partially or fully deflated, or with the aperture facing posterior, and then turned 180 degrees after passing behind the tongue. Putting water-based lubricant on the posterior surface decreases resistance. There may be some pharyngeal bleeding with LMAs, and some children may end up with sore throats, but those are less common than they are after endotracheal intubation.
Laryngoscopy is also relatively straightforward and technically easy in most children 2 or older, because the glottis is usually easy to see in children. But in neonates and small infants, laryngoscopy can be challenging, because the anesthesiologist's optimal position differs from that of adults. The line of sight should be nearly directly over the child's airway, and to gain the easiest view of the glottis, insert the blade more perpendicular to the OR table than with older children or adults.
Unless I have to, I try not to intubate or use a laryngoscope. But when necessary, tracheal intubation is straightforward, unless the child has altered facial or airway anatomy. If you anticipate a difficult intubation, I advise against attempting direct laryngoscopy. Each unsuccessful direct attempt increases the severity of airway edema and bleeding, and decreases the chance of success, even with more specialized methods.
The most reliable predictor of a difficult intubation is the patient's history. If a previous anesthetic record is available, review it. Focus physical exams on anatomic anomalies involving the head, face or neck. Check the size and mobility of the mandible. A small, malformed or immobile mandible is the most reliable physical predictor of a difficult intubation. Look for anatomic features that cause distortion of the airway. Ask about symptoms of obstructed airways, like snoring. Be sure to have all necessary airway equipment in the OR, including anything that might be needed for 2nd, 3rd and even 4th options. Different-sized laryngoscope blades and endotracheal tubes (cuffed and uncuffed) should be within easy reach. If you know a child is likely to be difficult to intubate, it's a good idea to secure IV access while the child is still awake, if possible.
Indirect techniques include video laryngoscopy, intubating LMA, optical stylet, lighted stylet and the flexible fiberoptic bronchoscope. The choice largely depends on your experience and preference, but it may also be influenced by the patient's anatomy.
Flexible fiberoptic bronchoscopy is usually considered the gold standard for managing difficult tracheal intubation in both adults and children, and pediatric anesthesiologists have become better at manipulating the ultrathin scope. But bronchoscopy is still more challenging in children, for several reasons, including the unique anatomical variance of infants and children. Ultrathin bronchoscopes, required for smaller patients, can't be manufactured with effective suction ports, so secretions and blood are more likely to obscure the view. It's important to use an antisialagogue (glycopyrrolate, for example) and to briefly and gently suction the oropharynx before the procedure.
Apneic oxygenation is usually ineffective in small children because they desaturate faster and require alternate means of oxygenation during intubation. And flexible bronchoscopy performed through a supraglottic airway (SGA) is more difficult because SGAs are more likely to be wrongly positioned in children, which leads to an obscured view of the glottic opening. Many types of video laryngoscopes are designed for pediatric patients. Comfort and familiarity are the keys. I'm most familiar with a laryngoscope that has an angled camera at its end. It provides a better view of the vocal cords and the glottis than you can get with your own eyes.
Unanticipated airway obstruction is alarming, especially in small infants, because they desaturate so quickly. The most serious complication you'll likely see in outpatient centers is laryngospasm. Untreated, it usually resolves by itself, but it can be catastrophic if it doesn't resolve right away. Certain risk factors are associated with increased likelihood of laryngospasm, including active or recent upper respiratory infection and chronic exposure to second-hand smoke. The distinction between partial and complete upper airway obstruction is important, because the best way to treat laryngospasm differs between the two.
- Partial upper airway obstruction. In a partial obstruction, recognizable by the presence of high-pitched inspiratory stridor, a small amount of air can enter with the administration of positive-pressure ventilation. Often, this prevents hypoxemia and lets anesthetic gases pass, deepening the level of unconsciousness and alleviating the laryngospasm.
- Complete upper airway obstruction. This usually rapidly results in hypoxemia. Avoid positive airway pressure, which may exacerbate the problem. Instead, administer succinylcholine, intravenously if you can, but intramuscularly, if necessary.
Unanticipated difficult ventilation
When difficulties arise with ventilation, a sequential series of corrective maneuvers can usually eliminate any obstruction. First, reposition the head and neck while simultaneously checking for appropriate facemask placement. Chin lift, which stretches and tightens the soft tissue structures along the length of the upper airway, may alleviate the obstruction. If that fails, jaw thrust (with fingers under the mandible, pull the chin up, jutting the jaw out), can alleviate obstruction caused by the epiglottis protruding into the airway. A third maneuver, usually done along with the first two, is to use continuous positive airway pressure (CPAP), which distends all the soft tissues of the pharynx and larynx. If these maneuvers are ineffective, oral airway insertion will likely relieve the obstruction, especially in children with large tonsil or adenoid tissue. Deliver rapid ventilations at a high inspiratory pressure until the child's chest rises and adequate ventilation is confirmed.
Nasotracheal intubation preferable when an oral tube would interfere with an intraoral surgical procedure is safe in children of all ages and isn't technically different than that for adults, with one exception. The angling of the child's oropharynx usually requires a Magill forceps to feed the tracheal tube in an anterior direction toward the glottic inlet. Use a half-size smaller tube than you'd use for the oral route. Decrease bleeding in the nasal passages by pre-soaking the tube in hot water to soften it. I also administer a few drops of 0.05% oxymetazoline into each nasal passage.
If these basic maneuvers fail, and the oxyhemoglobin saturation is still decreasing, the situation becomes dire and 1 of 3 possible actions is appropriate:
- Insert an LMA. Appropriately sized LMAs should be immediately available in every anesthetizing location. The LMA will establish adequate ventilation unless it's wrongly positioned (which is more common with children) or the obstruction is caused by laryngospasm. So you need to be very confident that the obstruction isn't being caused by laryngospasm.
- Tracheal intubation. But only by adept practitioners and only if there's some doubt about the cause of the obstruction. If laryngospasm has occurred, it's usually possible to introduce a styletted endotracheal tube through the glottic opening.
- Administer succinylcholine. Since laryngospasm is a common cause of unrelenting upper airway obstruction in children, this may be needed if conventional methods fail to reverse hypoxemia.
In the rare instance that none of these measures succeed, and the child is becoming dangerously hypoxic, perform desperate last-chance measures immediately:
- Reposition the patient. If an anterior mediastinal mass is suspected and conventional measures have failed, reposition the child to the lateral or prone position. This may alleviate obstruction of the lower trachea or great vessels surrounding the heart.
- Cricothyrotomy. Once you've placed a 14- or 16-gauge angiocatheter into the cricothyroid membrane, there are several ways to provide oxygenation. Every anesthesiologist should have a plan for oxygenation through a cricothyrotomy for every case, every day.
- Tracheotomy. If a qualified surgeon is present, this option may be better than cricothyrotomy. However, it's extremely difficult in small children and should be considered a last resort.