过度通气对异丙酚麻醉作用的影响

Effects of hyperventilation on propofol anesthesia

目的:通过观察异丙酚-瑞芬太尼静脉麻醉下过度通气时脑电双频谱指数(BIS)的变化,了解过度通气对异丙酚麻醉作用的影响。方法:20例ASAⅠ～Ⅱ级择期下肢手术患者,靶控输注异丙酚和瑞芬太尼行麻醉维持,效应室靶浓度分别为2～5μg/mL和2～6ng/mL。术中通过调节通气量使呼气末二氧化碳分压(PetCO2)依次降低至35、30、25mmHg(1mmHg=0.133kPa),各个阶段稳定30min后观察BIS值;并在各时段终期快速静注异丙酚1mg/kg后,再次观察BIS值的变化及变化所需时间。结果:术中靶控输注异丙酚和瑞芬太尼进行麻醉维持,随着PetCO2依次降低至35、30、25mmHg,患者BIS值无显著性变化;在各时段快速静注异丙酚1mg/kg后,BIS值均显著降低,但随着PetCO2的下降,BIS值降低幅度逐渐减小且从用药到BIS发生变化所需时间逐渐延长(P<0.05)。结论:随着PetCO2的降低,异丙酚的麻醉作用有所减弱且起效时间逐渐延长,这种影响可能与过度通气降低脑血流量有关。

AIM： To study the effects of hyperventilation on propofol anesthesia by measuring Bispectral index （BIS）. METHODS.. Twenty patients （ASA Ⅰ-Ⅱ ） undergoing lower limbs surgeries were enrolled in this study. Anesthesia was maintained with target controlled infusion （TCI） propofol and remifentanyl intravenously. The target concentration of propofol and remifentanyl were 2 - 5 μg/mL and 2 - 6 ng/mL, respectively. During the period of anesthesia, BIS values were recorded when the end-tidal pressure of CO2 （PetCO2） was kept to 35 mm Hg, 30 nun Hg and 25 nan Hg respectively for 30 rain by changing the ventilation rate and the tidal volume. Also, the BIS values and the time required were recorded following bolus intravenous injection of pmpofol at 1 mg/kg at above three PetCO2 levels. RESULTS： The BIS values kept stable when ventilation was adjusted to PetCO2 at 35nun Hg, 30 nun Hg and 25 nun Hg for 30 min respectively. Propofol injected at 1 mg/kg intravenously made the BIS values a significant decrease at the three PetCO2 levels. However, the decreasing extent of the BIS and the time when BIS began reducing were different between groups. The BIS values showed a less decrease and slower reacting time at the deep hyperventilation with PetCO2 descending （ P 〈 0.05 ）. CONCLUSION： Hyperventila- tion or low PaCO2 can affect the anesthesia effects of propofol and slower action time when propofol injected at bolus. This effect may be related to the physiological reaction of CBF to CO2.