REHYDRATION OF DESICCATED BARALYME PREVENTS CARBON-MONOXIDE FORMATIONFROM DESFLURANE IN AN ANESTHESIA MACHINE

Background: Desiccated carbon dioxide absorbents degrade desflurane, e nflurane, and isoflurane to carbon monoxide (GO) in vitro and in anest hesia machines, which can result in significant clinical CO exposure. Carbon monoxide formation is highest from desflurane, and greater with BaraIyme than with soda lime. Degradation is inversely related to abs orbent water content, and thus the greatest CO concentrations occur wi th desflurane and fully desiccated Baralyme. This investigation tested the hypothesis that rehydrating desiccated absorbent can diminish CO formation. Methods: Baralyme was dried to constant weight. Carbon mono xide 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 monoxid e was measured by gas chromatography-mass spectrometry. Results: Carbo n monoxide formation from desflurane in vitro was decreased from 10,70 0 ppm with desiccated Baralyme to 715 ppm and less than 100 ppm, respe ctively, 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 produc ed 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 absorb ent. Conclusions Desflurane is degraded by desiccated Baralyme in an a nesthesia machine, resulting in CO formation. Adding water to dried Ba ralyme is an effective means of reducing CO formation and the risk of intraoperative CO poisoning. Although demonstrated specifically for de sflurane and Baralyme, rehydration is also applicable to enflurane and isoflurane, and to soda lime.