A Randomized Clinical Trial Comparing the Effect of Phenylephrine and norepinephrine in Elderly Undergoing Major Abdominal Surgery

Interventions: Phenylephrine (PE):When hypotension occurred,Patients received PE infusion at a starting rate of 5 ml/h of 100µg/ml solution (prepared by diluting 10 mg of PE in 100 ml saline);Norepinephrine (NE):When hypotension occurred,Patients received NE infusion at a starting rate of 5 ml/h of 8 ug/ml solution (prepared by diluting 2 mg NE in 250 ml saline) Primary outcome(s): First flatus time after surgery;All complications, all-cause mortality, and readmission rates within 28 days after surgery Study Design: Parallel