高浓度七氟醚麻醉对儿童喉刺激反射的影响
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Impact of high concentrations of sevoflurane on laryngeal reflex responses
背景与目的
儿童极易发生强烈的气道防御性反射，如咳嗽，屏气，喉痉挛等，这可避免误吸，但同时也会造成低氧血症等损害。已有临床经验表明浅麻醉下更容易发生喉刺激反射。然而，当儿童保留自主呼吸，使用七氟醚麻醉时，喉反射与麻醉深度和七氟醚的呼末浓度的关系不明确。因此，本研究探讨高浓度的七氟醚麻醉对小儿气道防御反射的作用：即保留儿童自主呼吸条件下，比较4.7%七氟醚和2.5%七氟醚对气道刺激反射的抑制效果的作用。
方 法
本研究为前瞻性观察试验，经伦理委员会批准，共纳入40名择期外科手术儿童（3-7岁）。所有儿童随机接受4.7%或2.5%七氟醚进行麻醉，分别于两种麻醉状态下，经支气管镜将蒸馏水喷入喉部，通过视频图像记录喉刺激反射与呼吸模式恢复稳定的时间间隔，以评估喉刺激反射的持续时间。
结 果
完成所有试验的儿童共38名，2.5%七氟醚麻醉组喉刺激反射发生率为32%，然而4.7%七氟醚麻醉组发生率为18%（95%CI：0.72～16.84，P=0.18）；其余刺激反射反应在两种浓度七氟醚状态下几乎无差别。
结 论
即便在高浓度七氟醚麻醉下，喉痉挛的发生率仅部分降低，仍可为18%，这表明在七氟醚麻醉下下，保留自主呼吸的儿童在喉部受到刺激后都可能发生喉痉挛，从而导致低氧血症。
原始文献摘要
Erb T O, von UngernSternberg B S, Moll J, et al. Impact of high concentrations of sevoflurane on laryngeal reflex responses.[J]. Paediatric Anaesthesia, 2017, 139(41-42):2S-2S.
Background: Exaggerated defensive upper airway reflexes, particularly laryngospasm, may cause hypoxemic damage, especially in children. General clinical experience suggests that laryngeal reflex responses are more common under light levels of anesthesia, and previous clinical studies have shown an inverse correlation between laryngeal responsiveness and depth of hypnosis. However, this seems to be less obvious in children anesthetized with sevoflurane. The aim of this study was to assess the impact of high concentrations of sevoflurane on laryngeal and respiratory reflex responses in spontaneously breathing children. Accordingly, we tested the hypothesis that laryngeal and respiratory reflex responses were completely suppressed in spontaneously breathing children when anesthetized with sevoflurane 4.7% (=MACED95Intubation) as compared with sevoflurane 2.5%(=1 MAC).
Methods: In this prospective observational study, we tested the hypothesis that the incidence of laryngospasm evoked by laryngeal stimulation is diminished under high concentrations of sevoflurane. Following Ethics approval,trial registration, and informed consent, 40 children (3–7 years) scheduled for elective surgery participated in the trial. All children received sevoflurane 2.5% (1 MAC) and 4.7% (ED95Intubation) in random order with 5-min equilibration between the states. Under both conditions, distilled water was sprayed under bronchoscopic view onto the larynx. Potential laryngeal and respiratory reflex responses were assessed offline by a blinded reviewer.
Results: Laryngospasm (episodes lasting >10 s) occurred in 12/38(32%) of the patients anesthetized with sevoflurane 2.5%, vs 7/38 (18%) in those anesthetized with sevoflurane 4.7% (difference: OR 3.5; 95% CI [0.72–16.84], P = 0.18). All other reflex responses (coughing, expiration reflexes, and spasmodic panting) were infrequent and were similar among the examined concentrations.
Conclusion: Against our hypothesis,laryngospasm could still be observed in 18% of children under the higher concentration of sevoflurane (4.7%,ED95Intubation).
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