This is a prospective double-blinded randomized controlled trial (RCT) where patients will be assigned randomly by the investigational pharmacist. Patients will be assigned to one of three groups: (1) A control group that receives 0.9 mcg/kg sodium chloride (NaCL), (2) a fentanyl group that receives 1 mcg/kg fentanyl, or (3) a fentanyl group that receives 2 mcg/kg fentanyl.
The definition of intraoperative hypotension in this study is defined as a mean blood pressure (MAP) less than 25% compared to the baseline value (i.e., the participants' first blood pressure reading after entering the operating room). All study drug agents will be dispensed by the pharmacy in five milliliter syringes labeled as "study medication". The volume of any of the three study medication will be adjusted by the pharmacist to reflect an equal volume.
