早产儿平稳气管拔管时七氟烷的最低肺泡有效浓度

Minimum alveolar concentration of sevoflurane for tracheal extubation in premature infants

摘要:

目的  确定矫正胎龄<37周早产儿全凭吸入麻醉时拔除气管导管无体动反应的七氟烷最低肺泡有效浓度（MAC）。方法  择期全凭吸入全身麻醉下行眼科手术的矫正胎龄<37周的早产儿31例，ASA分级Ⅱ级。吸入6%七氟烷进行全身麻醉诱导，手术过程中全凭吸入七氟烷维持麻醉。手术结束后，将呼气末七氟烷浓度调整至预定值，维持15 min不变，然后拔除气管导管。根据Dixon上下法进行试验，初始呼气末七氟烷浓度为1.6%，拔除气管导管时发生体动反应，下一例患儿升高1个浓度梯度，拔除气管导管时未发生体动反应，下一例患儿降低1个浓度梯度，相邻浓度梯度为0.2%。将无体动反应时呼气末七氟烷浓度至体动反应时呼气末七氟烷浓度的中点设为平衡点，计算所有平衡点七氟烷浓度的平均值即为MAC值。结果  矫正胎龄小于37周早产儿平稳拔除气管导管的七氟烷MAC为1.43%，95%有效量（ED95）是1.85%（95%CI：1.65%，3.17%）。结论矫正胎龄小于37周早产儿平稳拔除气管导管的七氟烷MAC为1.43%，低于足月儿童的参考值，这可能是归因于早产儿中枢神经系统发育尚不完善。

Abstract:

Objective To determine the minimum alveolar concentration (MAC) of sevoflurane for blunting the response to tracheal extubation in premature infants less than 37 weeks of corrected age. Methods Thirty-one ASA Ⅱ premature infants less than 37 weeks of corrected age were enrolled in this study. Anesthesia inductions were performed by inhaling 6% sevoflurane and the general anesthesia was maintained by totally inhaling sevoflurane. After the operation was finished, the end tidal sevoflurane concentration (ETsev) was adjusted to the target concentration and maintained stable for 15 min. After that, the endotracheal tube was extubated. The Dixon's up-and-down method was used to calculate the MAC. The initial ETsev was 1.6% and was increased or decreased by 0.2% in the next patient according to the endotracheal extubation response. If the extubation response was positive, then the ETsev was increased. If the extubation response was negative, then the ETsev was decreased. The midpoint from negative response to positive response was set as the balance point and the mean value of the concentrations of sevoflurane at all the balance points were calculated as MAC. Results The end tidal sevoflurane concentration for blunting the responses to tracheal extubation in 50% premature infants was 1.43%, and the ED95 was 1.85% (95% confidence interval 1.65%~3.17%). Conclusions The MAC of sevoflurane for blunting the responses to tracheal extubation in premature infants less than 37 weeks of corrected age is 1.43%, which is lower than that in the full-term infants. And this difference is probably because that the central nervous system has not been developed very well in premature infants less than 37 weeks of corrected age.