Influence of dexmedetomidine upon sevoflurane end-expiratory concentration. Evaluation by bispectral index, suppression rate and electroencephalographic power spectral analysis.

Background And Objectives: Dexmedetomidine, an alpha2-adrenergic agonist, has been described as being able to decrease the demand for both venous and inhalational agents. This study aimed at evaluating the influence of Dexmedetomidine upon sevoflurane end-expiratory concentration (EC) with monitoring the depth of anesthesia.

Methods: Participated in this study 40 female adult patients, physical status ASA I, submitted to gynecological laparoscopy under general anesthesia maintained with sevoflurane, who were randomly divided in two groups: Group I (n=20), without dexmedetomidine; and Group II (n=20), with dexmedetomidine, in continuous infusion, as follows: Rapid phase (1 microg kg(-1) in 10 min(-1)) 10 minutes before anesthesia induction, followed by a maintenance phase (0.4 microg kg(-1) h(-1)) throughout the surgery. The following parameters were analyzed: BP, HR, BIS, SEF 95%, delta%, suppression rate (SR), rSO2, CE, SpO2 and P(ET)CO2, in the following moments: M1 - before dexmedetomidine or 0.9% saline infusion; M2 - prior to intubation; M3 - following intubation; M4 - before incision; M5 - following incision; M6 - before CO2 inflation; M7 - following CO2 inflation; M8 - 10 min after CO2 inflation; M9 - 10 min after M8; M10 - 20 min after M8; M11 - 30 min after M8; M12 - 40 min after M8; and M13 - at emergence. Time for emergence and hospital discharge were also recorded.

Results: Dexmedetomidine has decreased sevoflurane end-expiratory concentration from M4 to M13 (p<0.05) when comparing Group I and Group II. No clinically significant changes were observed in hemodynamic parameters. Time for emergence in Groups I and II was 11 +/- 0.91 min. and 6.35 +/- 0.93 min., respectively (p < 0.05). Time for hospital discharge was 7.45 +/- 0.69 h in Group I and 8.37 +/- 0.88 h in Group II (p < 0.05).

Conclusions: Dexmedetomidine was effective in decreasing sevoflurane end-expiratory concentration while maintaining hemodynamic stability without impairing time for hospital discharge, in addition to promoting an earlier emergence.