De Medts Robrecht, Carette Rik, De Wolf Andre M, Hendrickx Jan F A
Department of Anesthesiology, Intensive Care and Pain Therapy, OLV Hospital, Moorselbaan 164, 9300, Aalst, Belgium.
Department of Anesthesiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
J Clin Monit Comput. 2018 Aug;32(4):763-769. doi: 10.1007/s10877-017-0031-1. Epub 2017 Jun 9.
AGC (Automatic Gas Control) is the FLOW-i's automated low flow tool (Maquet, Solna, Sweden) that target controls the inspired O (FO) and end-expired desflurane concentration (Fdes) while (by design) exponentially decreasing fresh gas flow (FGF) during wash-in to a maintenance default FGF of 300 mL min. It also offers a choice of wash-in speeds for the inhaled agents. We examined AGC performance and hypothesized that the use of lower wash-in speeds and NO both reduce desflurane usage (Vdes). After obtaining IRB approval and patient consent, 78 ASA I-II patients undergoing abdominal surgery were randomly assigned to 1 of 6 groups (n = 13 each), depending on carrier gas (O/air or O/NO) and wash-in speed (AGC speed 2, 4, or 6) of desflurane, resulting in groups air/2, air/4, air/6, NO/2, NO/4, and NO/6. The target for FO was set at 35%, while the Fdes target was selected so that the AGC displayed 1.3 MAC (corrected for the additive affect of NO if used). AGC was activated upon starting mechanical ventilation. Varvel's criteria were used to describe performance of achieving the targets. Patient demographics, end-expired NO concentration, MAC, FGF, and Vdes were compared using ANOVA. Data are presented as mean ± standard deviation, except for Varvel's criteria (median ± quartiles). Patient demographics did not differ among the groups. Median performance error was -2-0% for FO and -3-1% for Fdes; median absolute performance error was 1-2% for FO and 0-3% for Fdes. MAC increased faster in NO groups, but total MAC decreased 0.1-0.25 MAC below that in the O/air groups after 60 min. The effect of wash-in speed on Vdes faded over time. NO decreased Vdes by 62%. AGC performance for O and desflurane targeting is excellent. After 1 h, the wash-in speeds tested are unlikely to affect desflurane usage. NO usage decreases Vdes proportionally with its reduction in Ftdes.
AGC（自动气体控制）是FLOW-i的自动低流量工具（瑞典索尔纳的迈柯唯公司），它可目标控制吸入氧浓度（FO）和呼气末地氟烷浓度（Fdes），同时在洗入过程中按指数方式降低新鲜气体流量（FGF），直至维持在300 mL/min的默认FGF。它还提供了多种吸入麻醉药的洗入速度选择。我们研究了AGC的性能，并假设使用较低的洗入速度和一氧化氮（NO）均可减少地氟烷用量（Vdes）。在获得机构审查委员会（IRB）批准并征得患者同意后，78例接受腹部手术的美国麻醉医师协会（ASA）I-II级患者根据载气（氧气/空气或氧气/一氧化氮）和地氟烷的洗入速度（AGC速度2、4或6）被随机分为6组（每组n = 13），形成空气/2组、空气/4组、空气/6组、一氧化氮/2组、一氧化氮/4组和一氧化氮/6组。FO的目标设定为35%，同时选择Fdes目标，以便AGC显示1.3最低肺泡有效浓度（MAC）（若使用一氧化氮，则针对其相加效应进行校正）。机械通气开始时启动AGC。采用Varvel标准描述实现目标的性能。使用方差分析比较患者人口统计学数据、呼气末一氧化氮浓度、MAC、FGF和Vdes。数据以均数±标准差表示，但Varvel标准除外（中位数±四分位数）。各组患者人口统计学数据无差异。FO的中位性能误差为-2%至0%，Fdes为-3%至1%；FO的中位绝对性能误差为1%至2%，Fdes为0%至3%。一氧化氮组的MAC升高更快，但60分钟后总MAC比氧气/空气组低0.1至0.25 MAC。洗入速度对Vdes的影响随时间逐渐减弱。一氧化氮使Vdes降低了62%。AGC对氧气和地氟烷的目标控制性能优异。1小时后，所测试的洗入速度不太可能影响地氟烷用量。一氧化氮用量随其在Ftdes中的减少而使Vdes成比例降低。
