Effect Of Melatonin On Early Postoperative Cognitive Dysfunction In Elderly Patients Undergoing Gastrointestinal Tumor Surgery

Objective:To investigate the potential impact of perioperative administration of melatonin on the occurrence of early postoperative cognitive dysfunction(POCD)in elderly patients having gastrointestinal tumour surgery.Methods:Sixty-four elderly patients(age 60-80 years,American Society of Anesthesiologists(ASA)class II-III)undergoing elective gastrointestinal tract tumor surgery at the First Affiliated Hospital of Nanchang University between July 2022 and February 2023 were selected for random assignment to either the melatonin group(group M,n=32)or the control group(group C,n=32).Patients in group M received melatonin 5.6 mg orally half an hour before bedtime and half an hour before surgery one day before surgery.Patients in group C received a placebo(starch tablet)of similar appearance at the same time points as patients in group M.Patients’ cognitive function was assessed using the MMSE and Mo CA scales one day before surgery and 3 and 7 days after surgery,and pain scores were assessed using the VAS.Patients’ sleep quality was assessed using PSQI 1 day before and seven days after surgery.Serum levels of S-100β and TNF-α were measured by the Elisa method at four-time points: before anesthesia(Baseline),at the end of surgery(After surgery),24 hours after surgery(Day 1),and 72 hours after surgery(Day 3).The mean arterial pressure(MAP)and heart rate(HR)were recorded before induction of anesthesia(T0),after tracheal intubation(T1),30 min after surgery(T2),and at the end of surgery(T3)in both groups.Result:There were no significant differences between the two groups in preoperative baseline characteristics such as body mass index,gender,age,education,time of surgery,preoperative hemoglobin,ASA classification,hypertension,or diabetes(P >0.05).Moreover,there was also no difference in baseline cognitive function(P >0.05).At three days postoperatively,POCD occurred in 2 patients(6.3%)in group M and nine patients(28.1%)in group C(P < 0.05);at seven days postoperatively,POCD occurred in 2 patients(6.3%)in group M and five patients(15.6%)in group C(P > 0.05).At seven days postoperatively,the Pittsburgh Sleep Quality Index(PSQI)score was significantly lower in group M than in group C(P < 0.05).Compared with group C,patients in group M had lower serum TNF-α levels on postoperative days 1 and 3 and S-100β levels on postoperative day 1(P < 0.05).At the same time,there was no significant difference in S-100β levels between the two groups on postoperative day 3(P > 0.05).There was no significant difference in intraoperative MAP and HR between the two groups at each time point(P > 0.05).Conclusion:Perioperative melatonin may reduce the incidence of early postoperative cognitive dysfunction in patients undergoing gastrointestinal tumor surgery without affecting hemodynamics.The mechanism may be related to suppressing the inflammatory response,reducing perioperative blood-brain barrier dysfunction and neuronal cell damage,and improving sleep quality.