儿童手术前口服咪达唑仑对呼吸功能的影响

背景为了缓解焦虑、提高患儿配合度，临床上常在麻醉前给患儿服用咪达唑仑。然而咪达唑仑的肌肉松弛作用具有影响患儿呼吸功能的潜在风险。我们分别评估患儿清醒时以及手术前口服咪达唑仑（0．3mg／kg）20分钟后的功能残气量（functionalresidualcapacity，FRC）、通气协调性和呼吸力学特征，其中通气协调性以肺清除率指数（1ungclearanceindex，LCI）加以评价。方法18例3—8岁患儿口服咪达唑仑前后，采用六氰化硫（SF6）多次呼吸洗脱技术测定FRC和LCI，通过振荡技术获得输入阻抗，测定呼吸系统阻力与肺弹性阻力。结果麻醉前给予咪达唑仑导致患儿FRC均值降低6．5％，从25．0ml／kg降低至23．4ml／垤，该差异虽小但具有显著统计学意义，同时LCI由6．4增加至6．9，提高7．8％，这些都显示患儿的通气不协调性增加。此外，咪达唑仑导致患儿呼吸系统阻力增加了7．4％（从3．38±0．6到3．62±0．6cmH，0S／L，P〈0．001）．呼吸弹性阻力增加9．2％（48．8到52．9cmH2OS／L，P〈0．001）。FRC、LCI、肺阻力和弹性阻力等指标的变化具有显著相关性（P〈0．001）。结论手术前，给肺功能正常的患儿小剂量的咪达唑仑，短时间内呼吸参数改变较小。然而，麻醉医生应该意识到，对于存在呼吸系统并发症的高危患儿，咪达唑仑可能会明显抑制其呼吸功能。

BACKGROUND： Premedication with midazolam is commonly used in children to reduce anxiety and im- prove cooperation before anesthesia. However, it has the potential to alter respiratory function because of its musde relaxant properties. We assessed functional residual capacity （FRC）, ventilation homogeneity, using a lung clearance index （LCI）, and respiratory mechanics in children awake and 20 min after oral premedication with midazolam （0.3 mg/kg）. METHODS： FRC and LCI were measured using a SF6 multibreath washout technique while respiratory resistance and elastance were extracted from the input impedance obtained by forced oscillation technique in 18 children （3 -8 yr） before and after oral premedica- don with midazolam. RESULTS： Premedication led to a small （6.5%） but statistically significant decrease in group mean FRC from 25.0 （sd 1.4） to 23.4 （1.9） ml/kg and an associated increase in LCI by 7.8% from 6.4 （0.4） to 6.9 （0. 4）, indica- ting increased ventilation inhomogeneities. Furthermore, midazolam resulted in a statistically significant increase in respirato- ry resistance by 7.4% from 3.38 （0. 6） to 3.62 （0. 6） cm H2O s/L （P 〈 0. 001 ） and in respiratory elastance by 9.2% from 48.8 to 52.9 cm H20 s/L （P 〈 0. 001 ）. The changes in FRC, LCI, resistance and elastance were significantly correlated （P 〈 0. 001 ）. CONCLUSIONS： In children with normal lungs, premedication with a relatively small-dose of midazolam led to mild changes in respiratory variables shortly after its administration. However, the anesthesiologist should be aware that using mi- dazolam in children at high risk of respiratory complications under anesthesia might lead to a greater decrease in respiratory function.