Effect of continuous intraoperative infusion of methoxamine on renal function in elderly patients undergoing gastrointestinal tumor surgery: a randomized controlled trial.

BACKGROUND: Acute renal injury (AKI) caused by hypotension often occurs in elderly patients after gastrointestinal tumor surgery. Although vasoactive drugs can increase effective filtration pressure, they may increase renal vascular resistance and reduce renal blood flow. The effect of methoxamine on renal function is not clear. METHODS: After obtaining written informed consent, 180 elderly patients undergoing elective gastrointestinal tumor surgery were randomly allocated into two groups: M group (continuous infusion of methoxamine at 2 µg/kg/min) and N group (continuous infusion of normal saline). The patients' mean arterial pressure was maintained within 20% of baseline by a continuous infusion of methoxamine or normal saline. Maintenance fluid was kept at 5 mL/kg/h. According to Kidney disease improve global outcome (KDIGO) guidelines, creatinine was measured at 1, 2 and 7 days after operation, and urine volume at 6, 12 and 24 h after operation was measured to evaluate the occurrence of AKI. 162 patients were included in the final data analysis. RESULTS: Significant differences in the incidence of postoperative Acute kidney injury (M group: 7.5%; N group: 18.3%; P < 0.05), the frequency of hypotension (M group: 1 [1-3]; N group: 3 [1-5]; P < 0.05), and the duration of intraoperative hypotension (M group: 2[0-10]; N group: 10 [5-16]; P < 0.05) were identified between the groups. Multivariate logistic regression analyses demonstrated that preoperative creatinine and the frequency of intraoperative hypotension were the common factors leading to the occurrence of postoperative AKI. The results of Cox multivariate analysis showed that age and AKI were independent risk factors for 30-day death. CONCLUSION: Compared with the intraoperative continuous infusion of placebo and methoxamine, continuous infusion of 2 µg/kg/min methoxamine reduced the incidence of postoperative AKI and other clinical complications in elderly patients undergoing gastrointestinal surgery by raising blood pressure and improved the prognosis of patients. TRIAL REGISTRATION: Trial registration: Chinese Clinical Trial Registry, ChiCTR1900020536, registered 7 January, 2019.