Lafreniere G, Milne B, Brunet D G, Adams M A, Parlow J L
Department of Anesthesiology, Queen's University, Kingston, Ontario, Canada.
Can J Anaesth. 2000 May;47(5):441-8. doi: 10.1007/BF03018974.
To describe the relative effects of graded central nervous system (CNS) depression, using increasing propofol infusion rates, on neurovegetative brainstem-mediated circulatory control mechanisms and higher cortical activity in healthy humans.
Propofol was administered using an infusion scheme designed to achieve three target blood concentrations in ten healthy volunteers. Blood propofol concentrations and sedation scores were determined at baseline, during the three propofol infusion levels, and 30 min into the recovery period. Electroencephalographic (EEG) power was measured in three frequency bands to quantify cortical activity, and autonomic heart rate control was quantified using spontaneous baroreflex assessment and power spectral analysis of pulse interval.
Sedation scores closely paralleled propofol blood concentrations (0, 0.53 +/- 0.34, 1.24 +/- 0.21, 3.11 +/- 0.80, and 0.96 +/- 0.42 microg x mL(-1) at baseline, three infusion levels and recovery respectively), and all subjects were unconscious at the deepest level. Indices of autonomic heart rate control were decreased only at the deepest levels of CNS depression, while EEG effects were apparent at all propofol infusion rates. These EEG effects were frequency specific, with power in the beta band being affected at light levels of sedation, and alpha and delta power altered at deeper levels.
The results of this study support a relative preservation of neurovegetative circulatory control mechanisms during the early stages of CNS depression using gradually increasing rates of infusion of propofol. Indices of circulatory control did not reliably reflect depth of sedation.
描述在健康人体中，使用递增的丙泊酚输注速率导致的分级中枢神经系统（CNS）抑制对神经植物性脑干介导的循环控制机制和高级皮层活动的相对影响。
采用一种输注方案对十名健康志愿者给予丙泊酚，以达到三个目标血药浓度。在基线、三个丙泊酚输注水平期间以及恢复期30分钟时测定血丙泊酚浓度和镇静评分。在三个频段测量脑电图（EEG）功率以量化皮层活动，并使用自发压力反射评估和脉搏间期功率谱分析来量化自主心率控制。
镇静评分与丙泊酚血药浓度密切平行（基线、三个输注水平和恢复期时分别为0、0.53±0.34、1.24±0.21、3.11±0.80和0.96±0.42μg·mL⁻¹），并且所有受试者在最深水平时均无意识。自主心率控制指标仅在CNS抑制的最深水平时降低，而EEG效应在所有丙泊酚输注速率下均明显。这些EEG效应具有频率特异性，在轻度镇静水平时β频段功率受到影响，而在较深水平时α和δ功率发生改变。
本研究结果支持在使用逐渐递增速率输注丙泊酚导致CNS抑制的早期阶段，神经植物性循环控制机制相对保留。循环控制指标不能可靠地反映镇静深度。
