Norepinephrine and Phenylephrine, Which Better for Elderly?

Comparison of the Effects of Norepinephrine and Phenylephrine on Tissue Oxygenation and Hemodynamic Stability During an Stroke Volume Variations(SVV) Fluid Guided Therapy in Elderly Undergoing Major Abdominal Surgery

this is a prospective, double-blinded and single-center study. this study is based on the Stroke volume variation fluid guided therapy, to compare the effects of norepinephrine and phenylephrine in treating perioperative hypotension, and to find the safest and most effective vasopressor for elderly.

Inclusion Criteria:

• radical resection of colorectal or gastric cancers,
• age over 65 years old,
• surgical time longer than 2hours,
• the American Society of Anesthesiologists(ASA) classification of II or III

Exclusion Criteria:

• history of severe cardiovascular diseases,
• history of severe liver and kidney diseases,
• evidence of arrhythmia on EKG,
• use of positive end-expiratory pressure (PEEP) during mechanical ventilation;
• conditions with relative contraindication for arterial catheterization