Norton J Russell, Ward Denham S, Karan Suzanne, Voter William A, Palmer Linda, Varlese Anna, Rackovsky Ori, Bailey Peter
Department of Anesthesiology, University of Rochester, New York, New York 14642, USA.
Anesthesiology. 2006 Jun;104(6):1155-64. doi: 10.1097/00000542-200606000-00009.
Upper airway obstruction (UAO) during sedation can often cause clinically significant adverse events. Direct comparison of different drugs' propensities for UAO may improve selection of appropriate sedating agents. The authors used the application of negative airway pressure to determine the pressure that causes UAO in healthy subjects sedated with midazolam or propofol infusions.
Twenty subjects (12 male and 8 female) completed the study. After achieving equivalent levels of sedation, the subjects' ventilation, end-tidal gases, respiratory inductance plethysmographic signals, and Bispectral Index values were monitored for 5 min. Negative airway pressure was then applied via a facemask in steps of 3 cm H(2)O from -3 to -18 cm H(2)O. UAO was assessed by cessation of inspiratory airflow and asynchrony between abdomen and chest respiratory inductance plethysmographic signals.
Equivalent levels of sedation were achieved with both drugs with average (+/- SD) Bispectral Index levels of 75 +/- 5. Resting ventilation was mildly reduced without any changes in end-tidal pressure of carbon dioxide. There was no difference between the drugs in the negative pressure resulting in UAO. Five female subjects and one male subject with midazolam and four female subjects and one male subject with propofol did not show any UAO even at -18 cm H(2)O. Compared with males, female subjects required more negative pressures to cause UAO with midazolam (P = 0.02) but not with propofol (P = 0.1).
At the mild to moderate level of sedation studied, midazolam and propofol sedation resulted in the same propensity for UAO. In this homogeneous group of healthy subjects, there was a considerable range of negative pressures required to cause UAO. The specific factors responsible for the maintenance of the upper airway during sedation remain to be elucidated.
镇静期间上呼吸道梗阻（UAO）常可导致具有临床意义的不良事件。直接比较不同药物导致UAO的倾向可能会改善合适镇静剂的选择。作者应用负压来确定在用咪达唑仑或丙泊酚输注镇静的健康受试者中导致UAO的压力。
20名受试者（12名男性和8名女性）完成了该研究。在达到等效镇静水平后，对受试者的通气、呼气末气体、呼吸感应体积描记信号和脑电双频指数值进行5分钟监测。然后通过面罩以3 cm H₂O的步长从-3至-18 cm H₂O施加负压。通过吸气气流停止以及腹部和胸部呼吸感应体积描记信号之间的不同步来评估UAO。
两种药物均达到了等效镇静水平，平均（±标准差）脑电双频指数水平为75±5。静息通气轻度降低，呼气末二氧化碳压力无任何变化。导致UAO的负压在两种药物之间无差异。5名使用咪达唑仑的女性受试者和1名男性受试者以及4名使用丙泊酚的女性受试者和1名男性受试者即使在-18 cm H₂O时也未显示任何UAO。与男性相比，女性受试者使用咪达唑仑导致UAO需要更大的负压（P = 0.02），但使用丙泊酚时则不然（P = 0.1）。
在所研究的轻至中度镇静水平下，咪达唑仑和丙泊酚镇静导致UAO的倾向相同。在这组同质的健康受试者中，导致UAO所需的负压范围相当大。镇静期间维持上呼吸道通畅的具体因素仍有待阐明。
