 At the arrival to the operating room, blood samples for baseline levels of cannabinoids will be drawn at the moment of placing the intravenous line, and the first anxiety assessment should be done by the examineranesthetist. The study drugs will be administered at the entrance to the O.R. or at the induction room 15 minutes before the induction of anesthesia i.e.:. Premedication dose should be calculated to be the equivalent of 10 mg and 20 mg oral THC for the low and high dose groups, respectively 4, 8 puffs. At the same time, the prefilled syringe containing either 1 mg midazolam 1 g acetaminophen or sodium chloride 0.9 will be administered as intravenous bolus. The patients will be immediately connected to the standard O.R. monitoring. 