摘要：

Clinically-used ketamine is a racemic mixture of two isomers, S-(+)- and R-()-ketamine. Previous investigations showed theanaesthetic potency of S-(+)-ketamine to be three times higher than that of R-()-ketamine. It was the aim of this study tocompare the effects of S-(+)-ketamine and racemic ketamine on endocrine and cardiovascular parameters, recovery, and sideeffects in geriatric patients during total intravenous anaesthesia (TIVA) for orthopaedic surgery. Methods. Forty patients over 60 years of age scheduled for elective hip or knee replacement were investigated in a double-blind, randomiseddesign. For induction of TIVA, patients received 0.1mg midazolam, 0.5mg atropine, 1mg/kg S(+)-ketamine or 2mg/kg racemicketamine, respectively, 2mg vecuronium, and 5mg/kg suxamethonium. After intubation and relaxation with a total dose of0.1mg/kg vecuronium, a continuous infusion of 2mg/kg per hour S-(+)- or 4mg/kg per ho

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