Intubation

Prior to intubation, the ability to mask ventilate is of utmost importance in all patients. In patients who may be potentially difficult to intubate, this is especially crucial since adequate mask ventilation ensures adequate oxygenation and ventilation while the intubation technique is modified (i.e., a different blade, better positioning or a more experienced anesthesiologist). In the worst case scenario, the child can be woken up and the procedure terminated. In children and infants the ability to effectively preoxygenate, by filling the lungs with 100% oxygen for 5 minutes prior to induction, is sometimes limited by the in ability of the patient to cooperate. Infants may be irritable and children may be too anxious to cooperate with the anesthesiologist.

Equipment

Intubation in the pediatric neurosurgical patient is fraught with potential pitfalls. A very large head relative to the body size, as seen in congenital hydrocephalus, will greatly increase the difficulty of laryngoscopy and tracheal intubation. Facial anomalies seen in patients with craniosynostosis syndromes and abnormalities such as cleft lip/palate, Pierre Robin syndrome, Treacher-Collins syndrome and others, may result in problematic airway management.

The selection of an age-appropriate endotracheal tube (ETT) and laryngoscopy blade is critical (Table 4). The age-appropriate ETT size can be approximated by a formula: (age / 4) + 4. For infants less than 1 year old, the size is determined by their age: 3.5 ETT for a full term infant, smaller for a premature infant. Each ETT must be checked for fit when it is placed. An ETT that is too tight can cause tracheal edema, leading to airway problems in the postoperative period. A loose ETT with a large leak will interfere with the ability to appropriately ventilate the patient, particularly when hyperventilation with regard to ICP may be important.

In trained hands, the use of a Macintosh (MAC) or curved blade can help keep a child or infant's relatively large tongue out of the way and allow for an unobstructed view of the vocal cords. The positioning for a curved blade may not require a shoulder roll and this may decrease the chances of obtaining a good view of the vocal cords. A fiberoptic intubation is an option for a skilled pediatric anesthetist familiar with this technique.

Table 4. Choice of laryngoscopy blade

in children of various ages

Age of Child

Laryngoscopy Blade

Premature infant to neonate

Miller 0

Infant to age 1 1/2 yrs old

Miller 1

1 1/2 yrs—4 yrs old

Whishipple 1 1/2

4-5 yrs old

MAC 2

5-12 yrs old

Miller 2

>12 yrs old

Proper positioning of the patient is essential. Normal infants have a relatively large occiput with respect to their body and may require a towel roll placed under the shoulders to facillitate a view of the vocal cords with a straight blade, e.g., a Miller 1. In a child with a particularly large head, the entire torso may need to be elevated with a support in order to allow a view of the larynx on laryngoscopy. The head may be placed inside a soft foam donut to maintain its position. Good extension of the head will also improve the view. In the patient with a meningomyelocele, the neural sack may be placed in a soft, foam donut; a blanket under the torso, and placing the head within a foam donut prevent movement. This more elaborate positioning results in a similar position to a normal supine infant.

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