Phenylephrine Vs. Norepinephrine on the Renin-Angiotensin-Aldosterone System and Postoperative Complications in Acute Abdomen Emergency Surgery: A Randomized Controlled Trial.

Objectives: This study aimed to explore how phenylephrine (PE) and norepinephrine (NE) affect renin-angiotensin-aldosterone system (RAAS) components and postoperative complications in patients undergoing acute abdomen emergency surgery.

Design: A randomized controlled trial.

Setting: The Anesthesiology Department at the Affiliated Hospital of Xuzhou Medical University.

Patients: We enrolled 156 patients 18 years older who were undergoing emergency acute abdominal surgery under general anesthesia.

Interventions: Patients were randomized to receive PE (PE group) or NE (NE group) to maintain their mean arterial pressure at 70-80 mm Hg during operation.

Measurements and main results: The plasma renin level increased in the immediate postoperative period in the NE group (median difference [MD]: 21 μIU/mL (interquartile range [IQR]: 5-51], p = 0.020), but not in the PE group (MD: 7 μIU/mL [IQR: -1 to 33], p = 0.336). However, the plasma renin levels were significantly decreased in both groups at 24 hours postoperation. Furthermore, in both groups, the levels of angiotensin II and aldosterone were reduced at 24 hours postoperation. The upper quartile of the plasma renin level before surgery was associated with higher vasopressor requirements and higher acute kidney injury (AKI) incidence. Furthermore, the groups showed no significant difference in AKI incidence (relative risk [RR]: 1.50 [95% CI, 0.65-3.47], p = 0.569), myocardial injury (RR: 1.11 [95% CI, 0.64-1.93], p = 0.497), and 30-day mortality rate (RR: 1.00 [95% CI, 0.44-2.27], p = 1.000).

Conclusions: PE and NE exert similar effects on RAAS components and postoperative complications. A higher plasma renin level before surgery is associated with greater vasopressor requirement and a higher incidence of postoperative complications.