Baxter P J, Kharasch E D
Department of Anesthesiology, University of Washington, Seattle 98195-6540, USA.
Anesthesiology. 1997 May;86(5):1061-5. doi: 10.1097/00000542-199705000-00009.
Desiccated carbon dioxide absorbents degrade desflurane, enflurane, and isoflurane to carbon monoxide (CO) in vitro and in anesthesia machines, which can result in significant clinical CO exposure. Carbon monoxide formation is highest from desflurane, and greater with Baralyme than with soda lime. Degradation is inversely related to absorbent water content, and thus the greatest CO concentrations occur with desflurane and fully desiccated Baralyme. This investigation tested the hypothesis that rehydrating desiccated absorbent can diminish CO formation.
Baralyme was dried to constant weight. Carbon monoxide formation from desflurane and desiccated Baralyme was determined in sealed 20.7-ml vials without adding water, after adding 10% of the normal water content (1.3% water), and after adding 100% of the normal water content (13% water) to the dry absorbent. Similar measurements were made using an anesthesia machine and circle system. Carbon monoxide was measured by gas chromatography-mass spectrometry.
Carbon monoxide formation from desflurane in vitro was decreased from 10,700 ppm with desiccated Baralyme to 715 ppm and less than 100 ppm, respectively, when 1.3% and 13% water were added. Complete rehydration also decreased CO formation from enflurane and isoflurane to undetectable concentrations. Desflurane degradation in an anesthesia machine produced 2,500 ppm CO in the circuit, which was reduced to less than 180 ppm when the full complement of water (13%) was added to the dried absorbent.
Desflurane is degraded by desiccated Baralyme in an anesthesia machine, resulting in CO formation. Adding water to dried Baralyme is an effective means of reducing CO formation and the risk of intraoperative CO poisoning. Although demonstrated specifically for desflurane and Baralyme, rehydration is also applicable to enflurane and isoflurane, and to soda lime.
干燥的二氧化碳吸收剂在体外及麻醉机中可将地氟烷、恩氟烷和异氟烷降解为一氧化碳（CO），这可能导致临床上显著的CO暴露。地氟烷产生的一氧化碳最多，且碱石灰比钠石灰产生的更多。降解与吸收剂含水量呈负相关，因此地氟烷与完全干燥的碱石灰一起使用时会出现最高的CO浓度。本研究检验了给干燥的吸收剂补水可减少CO生成这一假设。
将碱石灰干燥至恒重。在不加水、加入正常含水量的10%（1.3%水）以及向干燥的吸收剂中加入正常含水量的100%（13%水）后，在密封的20.7毫升小瓶中测定地氟烷与干燥碱石灰产生的一氧化碳。使用麻醉机和环路系统进行类似测量。通过气相色谱 - 质谱法测量一氧化碳。
体外实验中，当加入1.3%和13%的水时，地氟烷与干燥碱石灰反应产生的一氧化碳分别从10700 ppm降至715 ppm和低于100 ppm。完全补水还将恩氟烷和异氟烷产生的CO降至无法检测的浓度。麻醉机中地氟烷降解在回路中产生2500 ppm的CO，当向干燥的吸收剂中加入全部水分（13%）时，该浓度降至低于180 ppm。
麻醉机中干燥的碱石灰可使地氟烷降解，导致CO生成。向干燥的碱石灰中加水是减少CO生成及术中CO中毒风险的有效方法。尽管本研究专门针对地氟烷和碱石灰进行了验证，但补水也适用于恩氟烷、异氟烷以及钠石灰。
