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Other Factors Affect the Occurrence of Perioperative Respiratory Adverse Events.

To the Editor: With great interest, we read the article by Ramgolam et al., which reports inhalational versus IV induction of anesthesia in children with a high risk of perioperative respiratory adverse events. In addition to the limitations described in the discussion, we noticed other questions that may have influenced their findings. First, it may be not in the interest of patients because preoxygenation was not routinely used, but preoxygenation should and could be used. It is well known that preoxygenation can delay the onset of apnea-induced arterial oxyhemoglobin desaturation. Because the “cannot intubate, cannot ventilate” situation is unpredictable, the need for preoxygenation is desirable in all patients. Preoxygenation should be performed, especially in high-risk patients. Although all children in this study were high-risk patients, only children with at least two clinically relevant risk factors for perioperative respiratory adverse events could be recruited. Also, the children were given up to 66% N 2 O in oxygen for 20 s to 30 s before sevoflurane; the time was nearly adequate for deep breathing preoxygenation. Maximal preoxygenation (ETo 2 = 90%) can be accomplished in children faster than in adults; with tidal volume breathing, an ETo 2 of 90% can be reached within 100 s in almost all children, which could be shortened to 30 s with deep breathing. Second, the data shortage of patient response to laryngeal mask airway (LMA) insertion reduced the reliability of the results. As we know, if LMA was inserted at different anesthesia depths between two groups, the result might be quite different. Though LMA was performed for all children who did not react to a bimanual jaw thrust maneuver, it did not mean the intubation responses were the same. Only with complete data can we judge the anesthesia depths of two groups. Third, it would be more beneficial to clarify the results if the infants age 1 yr or younger were separated from the 0.0 to 3.0 yr age group because the incidence of perioperative respiratory adverse events in infants was doubled from the 15% in a general pediatric population. As per protocol, difference already existed in the 0.0 to 3.0 yr age group, given that it was 17% and 26% in IV group and inhalation group, respectively. The incidence of perioperative respiratory adverse events would be higher in the inhalation group if the difference mainly came from the infants. We believe that addressing the above issues could further increase the value of this study.