BACKGROUNDA sufficiently high blood pressure (BP) is essential for flap perfusion after microsurgical breast reconstruction. However, postoperative hypotension is common after these procedures. Perioperative volume overload may increase flap-related complications, and postoperative vasopressor use may be limited depending on institutions. Red Bull has been shown to increase BP in several studies. We aimed to evaluate the effect of Red Bull on perfusion-related variables after microsurgical breast reconstruction.METHODSWe conducted a multicenter, prospective, randomized controlled trial. Female patients undergoing unilateral microsurgical breast reconstruction from June 2020 to October 2022 were randomly assigned to the intervention or control groups. The intervention group received 250 ml of Red Bull 2 h after surgery and twice on postoperative day (POD) 1. The control group received 250 ml still water at the respective intervals. BP was measured using a 24-hour monitoring device. Vasopressor use, fluid balance, and flap outcomes were compared.RESULTSOne hundred patients were included in the study. Both groups were comparable concerning age, body mass index, and caffeine consumption. Mean arterial and diastolic BP were significantly higher in the Red Bull group after the second drink in the morning of POD1 (p-value = 0.03 and 0.03, respectively). Vasopressor use was similar, with a tendency for less postoperative etilefrine in the Red Bull group (p-value = 0.08). No flap loss was observed.CONCLUSIONSWe observed increased mean arterial and diastolic BP in the Red Bull group after the second drink. Red Bull may be a useful adjunct after microsurgical breast reconstruction.LEVEL OF EVIDENCEI, therapeutic.