Enlund M, Kietzmann D, Bouillon T, Züchner K, Meineke I
Department of Anesthesia & Intensive Care, Central Hospital, Västerås, Sweden.
Acta Anaesthesiol Scand. 2008 Apr;52(4):553-60. doi: 10.1111/j.1399-6576.2008.01579.x.
The Anesthetic Conserving Device (AnaConDa) uncouples delivery of a volatile anesthetic (VA) from fresh gas flow (FGF) using a continuous infusion of liquid volatile into a modified heat-moisture exchanger capable of adsorbing VA during expiration and releasing adsorbed VA during inspiration. It combines the simplicity and responsiveness of high FGF with low agent expenditures. We performed in vitro characterization of the device before developing a population pharmacokinetic model for sevoflurane administration with the AnaConDa, and retrospectively testing its performance (internal validation).
Eighteen females and 20 males, aged 31-87, BMI 20-38, were included. The end-tidal concentrations were varied and recorded together with the VA infusion rates into the device, ventilation and demographic data. The concentration-time course of sevoflurane was described using linear differential equations, and the most suitable structural model and typical parameter values were identified. The individual pharmacokinetic parameters were obtained and tested for covariate relationships. Prediction errors were calculated.
In vitro studies assessed the contribution of the device to the pharmacokinetic model. In vivo, the sevoflurane concentration-time courses on the patient side of the AnaConDa were adequately described with a two-compartment model. The population median absolute prediction error was 27% (interquartile range 13-45%).
The predictive performance of the two-compartment model was similar to that of models accepted for TCI administration of intravenous anesthetics, supporting open-loop administration of sevoflurane with the AnaConDa. Further studies will focus on prospective testing and external validation of the model implemented in a target-controlled infusion device.
麻醉保存装置（AnaConDa）通过将液体挥发剂持续输注到一个经过改良的热湿交换器中，使挥发性麻醉剂（VA）的输送与新鲜气体流量（FGF）解耦，该热湿交换器能够在呼气时吸附VA，并在吸气时释放吸附的VA。它结合了高FGF的简单性和响应性以及低药物消耗。在开发用于使用AnaConDa进行七氟醚给药的群体药代动力学模型之前，我们对该装置进行了体外特性分析，并回顾性测试了其性能（内部验证）。
纳入18名女性和20名男性，年龄31 - 87岁，体重指数20 - 38。呼气末浓度变化，并记录进入装置的VA输注速率、通气情况和人口统计学数据。使用线性微分方程描述七氟醚的浓度 - 时间过程，并确定最合适的结构模型和典型参数值。获得个体药代动力学参数并测试协变量关系。计算预测误差。
体外研究评估了该装置对药代动力学模型的贡献。在体内，用二室模型充分描述了AnaConDa患者端的七氟醚浓度 - 时间过程。群体中位数绝对预测误差为27%（四分位间距13 - 45%）。
二室模型的预测性能与静脉麻醉药靶控输注给药所接受的模型相似，支持使用AnaConDa进行七氟醚的开环给药。进一步的研究将集中于在靶控输注装置中实施的模型的前瞻性测试和外部验证。
