Calculating the venous blood concentration of inhalation anesthetics with a clinical gas analyzer.

Objective To set up a method to measure blood concentration of inhalation anesthetics using a "headspace equilibration" method with a clinical gas analyzer during surgeries.Methods Enflurane,isoflurane,and sevoflurane of six different concentrations were respectively prepared.Voltage peak value of each sample was determined in the mode "GAS SERVICE" of the gas analyzer.Then we got linearity between gas concentration and voltage.The standard blood samples were prepared using the "headspace equilibration" method,and retrieval rate of inhalation anesthetics in blood samples was measured using the clinical gas analyzer and the "headspace equilibration" method.Each sample was repeated six times.Precision of this method,namely relative standard deviations(RSD) was observed.Results The results were well correlated with the actual concentrations of enflurane,isoflurane,and sevoflurane(r=0.999 8,0.999 9,0.999 9).The average retrieval rate of enflurane,isoflurane,and sevoflurane was 96.53%,97.27%,and 97.74%,and their RSD was 1.63%,1.82%,and 1.24%,respectively.Conclusion A clinical gas analyzer can be used to exactly measure concentrations of inhalation anesthetics and not increase the error of inhalation anesthetic retrieving rate in the blood.