Placebo controls regional differences

Ketamine has also been studied as an adjuvant to lidocaine intravenous regional anesthesia for hand surgery in 40 patients who received ketamine 0.1 mg/kg either as an adjuvant to the lidocaine or as an intravenous injection [26 ]. There were no significant differences in tourniquet pain or opiate requirements, either intraoperatively or during the recovery period. There were no difference in the incidence of psychotomimetic effects and satisfaction was high in both groups. The authors felt that it would be unethical to include a control group, as ketamine has already been shown to be superior to placebo. However, this makes the conclusions hard to interpret. 

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