EMERGENCE FROM ISOFLURANE N2O OR ISOFLURANE ANESTHESIA/

Background: The first goal of anaesthetic recovery is return of the pa tient's ability to independently maintain respiratory and circulatory functions. Nitrous oxide remains popular due to minor effects on the c ardiovascular and respiratory systems. However, diffusion hypoxaemia c an occur during recovery and there is a potential advantage of providi ng the patient with only a potent vaporised agent. Methods: This rando mised study of 20 gynaecological patients evaluated respiratory and ci rculatory variables during emergence after anaesthesia with equipotent mixtures of isoflurane/nitrous oxide or isoflurane. Inspired, end-tid al and mixed expired gas concentrations, expired minute volume, pulse oximetry saturation and arterial blood,eases were registered. Monitori ng of cardiac output was performed by transthoracic bioimpedance. Resu lts: Patients anaesthetised with isoflurane/N2O resumed their spontane ous breathing 16 min earlier and were extubated 22 min earlier than th ose anaesthetised with only isoflurane. At extubation, total MAC and e nd-tidal CO2 were similar in both groups, 0.22-0.26 and 5.5-5.9 vol%, respectively. The isoflurane/N2O group had greater minute ventilation and CO2 excretion rates than the isoflurane group throughout the emerg ence period. There were no significant differences between the groups in blood gas variables or in heart rate, mean arterial blood pressure or cardiac index. Cardiac index was between 3.4 and 3.3 1 m(-2) min(-1 ) throughout the emergence period in both groups. Conclusion: Patients anaesthetised with only isoflurane had a longer delay until resumptio n of spontaneous breathing and extubation in the emergence period. Min ute ventilation and carbon dioxide elimination were also significantly more suppressed throughout emergence after anaesthesia with isofluran e as compared with isoflurane/N2O.