Pediatric Anesthetic Techniques: Inhalational Induction

Inhalational Induction

Many children do not arrive in the operating room with an intravenous line in place and nearly all dread the prospect of being stuck with a needle. Fortunately, sevoflurane can render small children unconscious within minutes. We find this easier in children who have been sedated (most often with oral midazolam) prior to entering the operating room and who are sleepy enough to be anesthetized without ever knowing what has happened (“steal” induction). One can also insufflate the anesthetic gases over the face, place a drop of food flavoring on the inside of the mask (eg, oil of orange), and allow the child to sit during the early stages of induction. Specially contoured masks minimize dead space (see Figure 19–8).

There are many differences between adult and pediatric anatomy that influence mask ventilation and intubation. Equipment appropriate for age and size should be selected (Table 42–6). Neonates and most young infants are obligate nasal breathers and obstruct easily. Oral airways will help displace an oversized tongue; nasal airways, so useful in adults, can traumatize small nares or prominent adenoids in small children. Compression of submandibular soft tissues should be avoided during mask ventila-tion to prevent upper airway obstruction.

Typically, the child can be coaxed into breath-ing an odorless mixture of nitrous oxide (70%) and oxygen (30%). Sevoflurane (or halothane) can be added to the gas mixture in 0.5% increments every few breaths. As previously discussed, we favor sevo-flurane in most situations. Desflurane and isoflu-rane are avoided for inhalation induction because they are pungent and associated with more cough-ing, breath-holding, and laryngospasm. We use a single (sometimes two) breath induction technique with sevoflurane (7–8% sevoflurane in 60% nitrous oxide) to speed the induction. After an adequate depth of anesthesia has been achieved, an intrave-nous line can be started and propofol and an opi-oid (or a muscle relaxant) administered to facilitate intubation. Patients typically pass through an excite-ment stage during which any stimulation can induce

laryngospasm. Breath-holding must be distin-guished from laryngospasm. Steady application of 10 cm of positive end-expiratory pressure will usu-ally overcome laryngospasm.

Alternatively, the anesthesiologist can deepen the level of anesthesia by increasing the concen-tration of volatile anesthetic, and place an LMA or intubate the patient under “deep” sevoflurane anesthesia. Because of the greater anesthetic depth required for tracheal intubation with the latter tech-nique, the risk of cardiac depression, bradycardia, or laryngospasm occurring without intravenous access detracts from this technique. Intramuscular succinylcholine (4–6 mg/kg, not to exceed 150 mg) and atropine (0.02 mg/kg, not to exceed 0.4 mg) should be available if laryngospasm or bradycar-dia occurs before an intravenous line is established; intralingual succinylcholine may be an alterative route (see above).

Positive-pressure ventilation during mask induc-tion and prior to intubation sometimes causes gastric distention, resulting in impairment of lung expansion. Suctioning with an orogastric or nasogastric tube will decompress the stomach, but it must be done without traumatizing fragile mucous membranes.