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03 November 2009

Pediatric Patient (EAM 4)

Pediatric Patient
The Pediatric patient- the principles of airway management in children are the same as in the adult. Confusion and error occur when we try to think about the pediatric airway as “different” than the adult airway. It is just not so! It is true that the dosages of medications are different, we just need to remember the doses in milligrams per kilogram or look them up. The anatomy is slightly different with larynx being somewhat anterior and superior to that of the adult and surgical airways are not recommended in children (The anatomy of the adult larynx is actually more variable than the child’s). With these two exceptions the pediatric airway should be approached in exactly the same way as the adult airway. Medications used for children to facilitate intubation and the need for alternative airway techniques in the case of a failed airway are no different than in the adult.

One concern in the pediatric airway is that the functional residual capacity is lower in the child and pre-oxygenation will not “buy” you as much time to intubate. With good pre-oxygenation in the adult, an adult can remain apneic for up to 5 minutes without significant oxygen desaturation. The child may desaturate in 1 minute or less. This is easily overcome by applying Sellick’s maneuver and briefly bagging the patient. During intubation, atropine is almost universally used in children during the pre-treatment phase (3 minutes before intubation) to blunt the bradycardia and hypotension that occurs when the larynx is manipulated. Also, a defasciculating dose of a nondepolorizer is almost never needed in children.
The Trauma Patient- The debate over which technique for intubation is safest in the cervical spine injured patient has been raging. Blind nasotracheal intubation was commonly used in the 1980’s but has fallen out of favor because of the high complication rate, high miss rate, stimulation of intracranial pressure and lack of protection of the C-spine. Recently, there is evidence indicating that with properly performed rapid sequence intubation and orotracheal intubation with in-line stabilization, there is little hazard to the patient. Since this affords the best opportunity to intubate with the least risk of a failed airway, RSI with in-line traction stabilization is now being recommended even in the presence of a cervical spine injury. Alternatively, if the patient has a proven C-spine injury and an incomplete neurologic deficit and does not need urgent intubation, then fiberoptic assisted orotracheal or nasotracheal intubation can be performed by those with experience in this technique in a more leisurely fashion. The choice of which neuromuscular blocking agent to use for RSI is also controversial. Most emergency physicians prefer succinylcholine over the longer acting nondepolarizing agents. This is ultimately safer in a failed airway or a “can’t intubate-can’t ventilate” situation as the neuromuscular blockade will last only a few minutes. The principal disadvantage of succinylcholine in trauma is its propensity to cause profound hyperkalemia in some situations. This occurs in burns, crush injuries and denervation processes like stroke or paralysis. However, the hyperkalemic effect does not occur for days to a week after injury and should not be a problem in the acutely injured patient.
Succinylcholine will also increase intracranial pressure, which is a concern in many traumatized patients. This can be mitigated by the use of a small dose of a competitive neuromuscular blocking agent in the pretreatment phase- for example 1 mg of Norcuron© 3 minutes before the succinylcholine. Lidocaine should also be used in head injured patients to protect from the rise in BP associated with tracheal stimulation. In the patient with a distorted airway either from facial fractures or a neck hematoma, the “wait and see” approach will only guarantee a more difficult airway in the future. Most authors now recommend an aggressive approach to the distorted airway with early intubation before the situation becomes more dangerous. Waiting for the nearly obstructed airway to become completely obstructed can be disastrous. The distorted airway always disquiets us, as it should. This is one case where the intubationist should plan ahead and have several options before beginning. Although RSI is not contraindicated, the optimal approach will probably be an awake intubation with the patient protecting his/her own airway as long as possible. A combined approach is sometimes also a good option. A little sedation can be used for a quick look for the glottis. If the glottis can be visualized, RSI can proceed. If the glottis can not be visualized, another approach must be entertained or a surgical airway anticipated.
The Patient with Increased Intracranial Pressure- Increased intracranial pressure presents a direct threat to the viability of the brain. Many of the techniques used in airway management may further increase pressure thus compounding the problem. The use of a laryngoscope to visualize the larynx causes a release of catecholamines causing increased BP and pulse- both of which are deleterious to the patient with increased ICP. There may also be a direct increase in ICP not related to tracheal stimulation of unknown etiology. The ICP will also be increased by the use of succinylcholine as a paralyzing agent. Although RSI remains the technique of choice in patients with increased ICP and succinylcholine remains the drug of choice, there are several special considerations. Several pharmacologic agents mitigate against this increased ICP. The administration of fentanyl, a synthetic opioid, can blunt the affect of the catecholamine release as will a beta blocker (not often used). Fentanyl could and should be used in almost all patients with an increased ICP but may cause transient hypotension and premature apnea in some patients at 3 micrograms/kg dose in the pretreatment phase. Lidocaine in a dose of 1.5 mg/kg will blunt the reflex response to intubation and should also be used in the patient with elevated ICP in the pretreatment phase. The increase in ICP related to succinylcholine is temporally related to the muscle fasciculations and can be avoided by use of a competitive neuromuscular blocking agent at 1/10th the paralyzing dose in the pretreatment phase. Since ketamine increases cerebral blood flow, this agent should be avoided in the patient with increased ICP.
The Patient with Asthma or COPD- Always remember that if the patient can’t breath secondary to reactive airway disease, you might not be able to breath for them either! These patients can be extremely difficult to ventilate and be hemodynamically unstable. First and foremost there should be aggressive therapy to “break” their asthma or COPD attack. Use of multiple standard agents as well as Heliox®, magnesium, anticholinergic agents, and BiPAP and less standard methods may be attempted before intubation. Asthma is a unique situation in which one MUST intubate the patient on the first try because often the patient can not be successfully bagged because of the high airway pressures. If the patient needs intubation, RSI is the best choice. However, the patient should be left in the sitting position until after the paralyzing medication, succinylcholine, is administered. Although succinylcholine is known to release histamine, this effect does not appear to be clinically significant. All patients with reactive airway disease should receive lidocaine in the pretreatment phase to attenuate the respiratory response to airway manipulation. Ketamine is the induction agent of choice as it has a direct effect on relaxation of bronchial smooth muscles and should be given just prior to succinylcholine.

Reference
Advanced Emergency Airway Management Walls RM, Luten RC, Murphy ME, Schneider RE. 1997

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