Preventative effects of ramelteon against postoperative delirium after elective liver resection.

Background: Postoperative delirium was reported to be associated with increased postoperative mortality after liver resection. Therefore, it is crucial to prevent postoperative delirium in such cases. Ramelteon, an agonist of melatonin receptor has been suggested to be useful for preventing delirium. The aim of this study was to examine whether ramelteon is effective at preventing delirium after elective liver resection. Methods: The cases of patients who underwent liver resection at Nara Medical University (Nara, Japan) between January 2014 and August 2018 were analyzed. During the period from January 2017 to August 2018, ramelteon was prospectively administered to patients who underwent liver resection [8 mg/day on the day before surgery and on postoperative days 1 to 3] (ramelteon group), whereas ramelteon was not administered during the period from January 2014 to December 2016 (control group). The perioperative outcomes of the two groups were compared. Results: There were 120 patients in the ramelteon group and 186 patients in the control group. No significant intergroup differences in background factors, including age, gender, and preoperative serological laboratory data, were detected. The incidence of postoperative delirium was significantly lower in the ramelteon group (5.8% vs. 15.1%, P = 0.035). Multivariate analysis revealed that being aged ≥75 (P = 0.002), being male (P = 0.020), cardiovascular disease (P = 0.023), blood loss ≥1000ml (P = 0.001) and the absence of ramelteon treatment (P = 0.046) were independent risk factors for postoperative delirium. Conclusion: The administration of ramelteon might reduce the risk of postoperative delirium after elective liver resection.