Gunter Joel B, Ball John, Than-Win Sean
Department of Anesthesia, Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA.
Anesth Analg. 2008 Dec;107(6):1936-45. doi: 10.1213/ane.0b013e31818874d3.
Anesthesia machines must be flushed of halogenated anesthetics before use in patients susceptible to malignant hyperthermia. We studied the kinetics of sevoflurane clearance in the Dräger Fabius anesthesia machine and compared them to a conventional anesthesia machine (Dräger Narkomed GS).
Before each trial, the anesthesia machine was contaminated for 2 h with 3% sevoflurane and then prepared by changing the CO(2) absorbent, removing the vaporizer(s), and mounting a clean circuit and artificial lung. The basic flush procedure consisted of oxygen 10 L/min with the ventilator set to a tidal volume of 600 mL at a rate of 10/min. Residual sevoflurane in the inspiratory limb of the circuit was measured using an ambient air analyzer capable of measuring sevoflurane to < 1 ppm. Results were analyzed using log-linear regression of residual concentration as a function of time. This model was used to estimate the time required to achieve a desired residual anesthetic concentration.
Times to achieve 10 and 5 ppm in the Dräger Narkomed GS were 11 and 18 min, respectively. For the Dräger Fabius anesthesia machine, times to 10 and 5 ppm were 75 and 104 min, respectively. Several maneuvers to accelerate clearance of residual sevoflurane from the Dräger Fabius resulted in only modest reductions in these times (10 and 5 ppm times 40-50 min and 60-80 min, respectively). Insertion of an activated charcoal filter (QED, Anecare Laboratories, Salt Lake City, UT) into the inspiratory limb of the Dräger Fabius circuit reduced the residual anesthetic concentration to <5 ppm within 10 min; this concentration was maintained for > 6 h despite a fresh gas flow of only 2 L/min after the first 15 min.
Preparation of the Dräger Fabius anesthesia machine using conventional flushing techniques required almost 10 times as long as an older, conventional anesthesia machine. If a prolonged flush is impractical or impossible, we describe a procedure using an activated charcoal filter inserted on the inspiratory limb of the breathing circuit which can effectively scrub residual sevoflurane to a concentration < 5 ppm within 10 min. This procedure includes an initial 5 min flush without the activated charcoal filter followed by a 5 min flush with the charcoal filter, after which the machine is ready for use in the malignant hyperthermia-susceptible patient. The charcoal filter must remain on the machine for the remainder of the anesthetic, and the fresh gas flow should be maintained > or = 10 L/min for the first 5 min, and > or = 2 L/min thereafter.
在用于易患恶性高热的患者之前，麻醉机必须清除卤化麻醉剂。我们研究了德尔格法比乌斯麻醉机中七氟醚清除的动力学，并将其与传统麻醉机（德尔格纳科美GS）进行了比较。
在每次试验前，用3%的七氟醚将麻醉机污染2小时，然后通过更换二氧化碳吸收剂、移除蒸发器并安装清洁回路和人工肺来进行准备。基本冲洗程序包括以10L/min的氧气流量，将呼吸机设置为潮气量6OOmL，频率为10次/分钟。使用能够测量低至<1ppm七氟醚的环境空气分析仪测量回路吸气支中的残余七氟醚。使用残余浓度作为时间函数的对数线性回归分析结果。该模型用于估计达到所需残余麻醉剂浓度所需的时间。
在德尔格纳科美GS中达到10ppm和5ppm的时间分别为11分钟和18分钟。对于德尔格法比乌斯麻醉机，达到10ppm和5ppm的时间分别为75分钟和104分钟。为加速德尔格法比乌斯麻醉机中残余七氟醚的清除而采取的几种操作仅使这些时间略有缩短（达到10ppm和5ppm的时间分别为40 - 50分钟和60 - 80分钟）。在德尔格法比乌斯回路的吸气支中插入一个活性炭过滤器（QED，Anecare实验室，犹他州盐湖城）可在10分钟内将残余麻醉剂浓度降至<5ppm；尽管在前15分钟后新鲜气流仅为2L/min，但该浓度在>6小时内保持不变。
使用传统冲洗技术准备德尔格法比乌斯麻醉机所需的时间几乎是一台较旧的传统麻醉机的10倍。如果长时间冲洗不切实际或不可能，我们描述了一种在呼吸回路吸气支上插入活性炭过滤器的程序，该程序可在10分钟内有效地将残余七氟醚清除至浓度<5ppm。该程序包括在不使用活性炭过滤器的情况下初始冲洗5分钟，然后使用活性炭过滤器冲洗5分钟，之后该机器即可用于易患恶性高热的患者。在麻醉的剩余时间内活性炭过滤器必须保留在机器上，并且在最初5分钟新鲜气流应保持>或 = 10L/min，此后>或 = 2L/min。
