Kapoor Mukul Chandra, Sashank Ayalasomayajula, Vats Ashok, Garg Shaloo, Puri Archana
Department of Anaesthesia, Max Smart Super-Specialty Hospital, Saket, Delhi, India.
J Anaesthesiol Clin Pharmacol. 2019 Oct-Dec;35(4):487-492. doi: 10.4103/joacp.JOACP_188_19.
More than 80% of delivered anesthetic gases get wasted at high fresh gas flows as they are vented out unused. Use of minimal flow anesthesia is associated with less waste anesthetic gas emission and environmental pollution. There is no approved or validated technique to initiate minimal flow anesthesia and simultaneously achieve denitrogenation of the breathing circuit. We studied the wash-in characteristics of desflurane, when delivered with 50% nitrous oxide, to reach a target end-tidal concentration at two different gas flow rates.
Patients were allocated randomly to two groups of 25 adults each. In Group A, with the vaporizer dial fixed at 4 vol %, after an initial fresh gas flow of 4 L/min was administered to wash-in of desflurane using the closed-circuit, with 50% NO in O, and in group B, 6 L/min was used. Minimal flow anesthesia, with 0.5 L/min, was initiated in both groups on attaining a target end-tidal desflurane concentration of 3.5 vol %. After initiation of desflurane delivery, the inspired/expired gas concentrations were noted every minute for 15 min.
In Group A, the target desflurane end-tidal concentration was reached in 499.2 ± 68.6 s±, and in the Group B ( < 0.001), it was reached significantly faster in 314.4 ± 69.89 s. Denitrogenation of the circuit was adequate in both groups.
Minimal flow anesthesia can be initiated, without any gas-volume deficit, in about 5 min with an initial fresh gas flow rate of 6 L/min and the vaporizer set at 4 vol%.
超过80%的呼出麻醉气体在高新鲜气流速时未被使用就被排出而浪费掉。使用最低流量麻醉可减少麻醉废气排放和环境污染。目前尚无获批或经过验证的技术来启动最低流量麻醉并同时实现呼吸回路的去氮。我们研究了在两种不同气流速下，与50%氧化亚氮一起输送时地氟烷的吸入特性，以达到目标呼气末浓度。
患者被随机分为两组，每组25名成年人。A组将蒸发器刻度盘固定在4%容积，初始新鲜气流速为4L/min，使用闭路系统，在氧气中加入50%氧化亚氮来吸入地氟烷；B组则使用6L/min。两组在达到目标呼气末地氟烷浓度3.5%容积时均启动0.5L/min的最低流量麻醉。开始输送地氟烷后，每分钟记录吸入/呼出气体浓度，持续15分钟。
A组在499.2±68.6秒达到目标呼气末地氟烷浓度，B组（P<0.001）显著更快，在314.4±69.89秒达到。两组回路的去氮情况均良好。
初始新鲜气流速为6L/min且蒸发器设置为4%容积时，大约5分钟即可启动最低流量麻醉，且无任何气体量不足的情况。
