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Background: The pharmacodynamics of propofol are closely linked to gender. Dexmedetomidine can decrease propofol needs during propofol anesthesia. The aim of this study was to compare the gender differences on the calculated effect site median effective concentration (EC50) of propofol for loss of consciousness (LOC) after pretreatment with different concentrations of dexmedetomidine.Methods: In this study 60 male and 60 female patients were randomly allocated to receive dexmedetomidine at target plasma concentrations of 0.0 ng/ml (0.0 group), 0.4 ng/ml (0.4 group), 0.6 ng/ml (0.6 group) and 0.8 ng/ml (0.8 group). Propofol was administered after dexmedetomidine had been intravenously infused for 15 min. The propofol infusion was targeted to provide an initial effect-site concentration of 1.0 μg/ml, followed by increments by 0.2 μg/ml when the effect-site concentration and target concentration of propofol were in equilibrium until LOC was established, where LOC was defined by the observer's assessment of alertness/sedation scale (OAA/S) score < 2.Results: The calculated effect-site EC50 of propofol LOC was higher in males than in females in the 0.0, 0.4, 0.6, and 0.8 groups (2.43 vs. 2.17, 1.99 vs. 1.82, 1.72 vs. 1.56 and 1.50 vs. 1.32 μg/ml, respectively, all p < 0.05). The hypnotic interaction between dexmedetomidine and propofol could be described with an additive model of pharmacodynamic interaction.Conclusion: Gender significantly influenced the calculated effect-site EC50 of propofol for LOC after pretreatment with different concentrations of intravenous dexmedetomidine. It was concluded that an additive interaction could describe the results seen. Thus, gender has to be considered when these drugs are co-administered. [ABSTRACT FROM AUTHOR]

Regarding the question of an adequate depth of anesthesia, over the past decade anesthesiologists have focused on the prevention of intraoperative consciousness in combination with explicit memory. Recent studies approached the topic from a different way postulating that deep anesthesia, quantified as time with a bispectral index (BIS)< 45, is associated with increased postoperative mortality and four out of the five published studies revealed such a correlation. However, the finding is limited by a suboptimal study design, e.g. none of the studies presented randomized data. Furthermore, it is ambiguous whether the correlation is causal as the administration of deep anesthesia determines higher postoperative mortality or the study results reveal an epiphenomenon. An epiphenomenon implies e.g. that patients with cancer respond to general anesthesia with deeper cortical depression. In summary, as long as there is a lack of adequately performed randomized trials, there is no reason why anesthesiologists should change the current practice. [ABSTRACT FROM AUTHOR]