THE RESPONSE OF ANESTHETIC AGENT MONITORS TO TRIFLUOROMETHANE WARNS OF THE PRESENCE OF CARBON-MONOXIDE FROM ANESTHETIC BREAKDOWN

Objective. Trifluoromethane and CO are produced simultaneously during the breakdown of isoflurane and desflurane by dry CO2 absorbents. Trif luoromethane interferes with anesthetic agent monitoring, and the inte rference can be used as a marker to indicate anesthetic breakdown with CO production. This study tests representative types of gas monitors to determine their ability to provide a clinically useful warning of C O production in circle breathing systems. Methods, Isoflurane and desf lurane were reacted with dry Baralyme(R) at 45 degrees C. Standardized samples of breakdown products were created from mixtures of reacted a nd unreacted gases to simulate the partial degrees of reaction which m ight result during clinical episodes of anesthetic breakdown using 1% or 2% isoflurane and 6% or 12% desflurane. These mixtures were measure d by the monitors tested, and the indication of the wrong agent or a m ixture of agents due to the presence of trifluoromethane was recorded and related to the CO concentration in the gas mixtures. Results. When presented with trifluoromethane from anesthetic breakdown, monochroma tic infrared monitors displayed inappropriately large amounts of isofl urane or desflurane. Agent identifying infrared and Raman scattering m onitors varied in their sensitivity to trifluoromethane. Mass spectrom eters measuring enflurane at mass to charge = 69 were most sensitive t o trifluoromethane. Conclusions, Monochromatic infrared monitors were unable to indicate anesthetic breakdown via interference by trifluorom ethane, but did indicate falsely elevated anesthetic concentrations. A gent identifying infrared and Raman monitors provided warning of desfl urane breakdown via the interference of trifluoromethane by displaying the wrong agent or mixed agents, but may not be sensitive enough to w arn of isoflurane breakdown. Some mass spectrometers provided the most sensitive warnings to anesthetic breakdown via trifluoromethane, bur additional data processing by some patient monitor units reduced their overall effectiveness.