 The selection of patients will be done during the pre-anesthetic assessment the day before surgery. After obtaining informed consent, eligible patients will be randomly allocated to one of the following regimes: nabiximols high dose 21.6 mg THC 20 mg CBD, nabiximols low dose 10.8 mg THC 10 mg CBD, active placebo prefilled syringe with 1 mg midazolam 1 g acetaminophen I.V., placebo control no premedication drugs. 