Chemiluminescence underestimates nitric oxide concentration in the presence of potent inhalation anaesthetics

We investigated the effect of potent inhalation anaesthetics on nitric oxid e (NO) concentration measured by the chemiluminescence method. We found tha t the NO concentration was increasingly underestimated with increasing conc entrations of halothane, isoflurane, enflurane and sevoflurane (r(2)=0.918- 0.997, P<0.01). Statistical analysis showed that the four inhalation agents at the same concentration produced a similar error in the measured NO conc entration. In the presence of a fixed concentration of sevoflurane (5.0%), isoflurane (5.2%), enflurane (4.5%) or halothane (6.1%), the rate of reduct ion in the measured NO concentration increased in proportion to the NO conc entration (r(2)=0.909-0.982, P<0.01). No direct chemical interaction betwee n the potent inhalation agents and NO was detected by gas chromatography-ma ss spectrometry. We conclude that NO concentration can be underestimated wh en measured by the chemiluminescence method in the presence of potent inhal ation agents. This underestimation may result from emission absorption and/ or the quenching phenomenon, but is not attributable to a chemical reaction between the inhalation agent and NO.