Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden; Department of Anesthesiology and Intensive Care Medicine, Otto von Guericke University, Magdeburg, Germany.
Oscillogy LLC, Pittsburgh, Pennsylvania; Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
Anesthesiology. 2021 Dec 1;135(6):1027-1041. doi: 10.1097/ALN.0000000000004007.
Previous studies have established the role of various tissue compartments in the kinetics of inhaled anesthetic uptake and elimination. The role of normal lungs in inhaled anesthetic kinetics is less understood. In juvenile pigs with normal lungs, the authors measured desflurane and sevoflurane washin and washout kinetics at three different ratios of alveolar minute ventilation to cardiac output value. The main hypothesis was that the ventilation/perfusion ratio (VA/Q) of normal lungs influences the kinetics of inhaled anesthetics.
Seven healthy pigs were anesthetized with intravenous anesthetics and mechanically ventilated. Each animal was studied under three different VA/Q conditions: normal, low, and high. For each VA/Q condition, desflurane and sevoflurane were administered at a constant, subanesthetic inspired partial pressure (0.15 volume% for sevoflurane and 0.5 volume% for desflurane) for 45 min. Pulmonary arterial and systemic arterial blood samples were collected at eight time points during uptake, and then at these same times during elimination, for measurement of desflurane and sevoflurane partial pressures. The authors also assessed the effect of VA/Q on paired differences in arterial and mixed venous partial pressures.
For desflurane washin, the scaled arterial partial pressure differences between 5 and 0 min were 0.70 ± 0.10, 0.93 ± 0.08, and 0.82 ± 0.07 for the low, normal, and high VA/Q conditions (means, 95% CI). Equivalent measurements for sevoflurane were 0.55 ± 0.06, 0.77 ± 0.04, and 0.75 ± 0.08. For desflurane washout, the scaled arterial partial pressure differences between 0 and 5 min were 0.76 ± 0.04, 0.88 ± 0.02, and 0.92 ± 0.01 for the low, normal, and high VA/Q conditions. Equivalent measurements for sevoflurane were 0.79 ± 0.05, 0.85 ± 0.03, and 0.90 ± 0.03.
Kinetics of inhaled anesthetic washin and washout are substantially altered by changes in the global VA/Q ratio for normal lungs.
先前的研究已经确定了各种组织隔室在吸入麻醉药摄取和消除动力学中的作用。正常肺在吸入麻醉药动力学中的作用还不太清楚。在正常肺的幼年猪中，作者测量了肺泡分钟通气量与心输出量比值为三个不同值时的地氟烷和七氟烷的洗入和洗出动力学。主要假设是正常肺的通气/灌注比（VA/Q）影响吸入麻醉药的动力学。
七只健康猪接受静脉麻醉并机械通气。每只动物在三种不同的 VA/Q 条件下进行研究：正常、低和高。对于每种 VA/Q 条件，以亚麻醉吸入的恒定部分压力（七氟烷为 0.15 体积%，地氟烷为 0.5 体积%）给猪输注地氟烷和七氟烷 45 分钟。在摄取期间的八个时间点和消除期间的相同时间点采集肺动脉和体动脉血样，以测量地氟烷和七氟烷的部分压力。作者还评估了 VA/Q 对动脉和混合静脉部分压力差的影响。
对于地氟烷的洗入，低、正常和高 VA/Q 条件下 5 分钟至 0 分钟的标化动脉分压差值分别为 0.70 ± 0.10、0.93 ± 0.08 和 0.82 ± 0.07（平均值，95%CI）。七氟烷的等效测量值分别为 0.55 ± 0.06、0.77 ± 0.04 和 0.75 ± 0.08。对于地氟烷的洗出，0 分钟至 5 分钟的标化动脉分压差值分别为低、正常和高 VA/Q 条件下的 0.76 ± 0.04、0.88 ± 0.02 和 0.92 ± 0.01。七氟烷的等效测量值分别为 0.79 ± 0.05、0.85 ± 0.03 和 0.90 ± 0.03。
正常肺的整体 VA/Q 比值变化会显著改变吸入麻醉药的洗入和洗出动力学。
