Pj. Baxter et Ed. Kharasch, REHYDRATION OF DESICCATED BARALYME PREVENTS CARBON-MONOXIDE FORMATIONFROM DESFLURANE IN AN ANESTHESIA MACHINE, Anesthesiology, 86(5), 1997, pp. 1061-1065
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.