Effects Of Low-dose Nocturnal Dexmedetomidine On Early Postoperative Immune Function In Elderly Patients Undergoing Gastrointestinal Tumors

Objective:To evaluate the effects of nocturnal intravenous infusion of dexmetomidine on early immune function in elderly patients undergoing laparoscopic radical resection of gastrointestinal tumors.Methods:Ninety-six Elderly patients（ASA statusⅡorⅢ,regardless of gender,age 65-78 years,BMI 18-26 kg/m²）who were scheduled to undergo elective laparoscopic radical resection of gastrointestinal tumors were screened for inclusion.Those who met any of the following criteria would be excluded:preoperative heart rate（HR）less than 50 beats/min,severe psychiatric or mental disorder,severe system disease,severe sleep disorder and cognitive impairment,sleep apnea.Patients were divided into three groups（n=32）by random number table:control group（group C）,dexmedetomidine0.2μg·kg^-1·h^-1（group D1）,and dexmedetomidine 0.3μg·kg^-1·h^-1（group D2）.The Pittsburgh Sleep Quality Index（PSQI）was used to evaluate the sleep quality of the patients for nearly one month and the cognitive function of the patients was evaluated by Mini-Mental State Examination（MMSE）when the preoperative anesthesia visited on the day before surgery.2 ml peripheral venous blood samples were collected at T₁（8:00 a.m.on the morning of operation）.The percentage of T lymphocytes,CD4⁺and CD8⁺cells,NK cells and CD4⁺/CD8⁺ratio were detected by flow cytometric analysis using Epics-XLⅡflow cytometry made by Beckman Coulter company in America.Intraoperative monitoring included electrocardiogram（ECG）,heart rate（HR）,percutaneous oxygen saturation（Sp O2）,body temperature and bispectral index（BIS）,arterial blood pressure（BP）,and central venous pressure（CVP）.Anaesthesia was induced with intravenous etomidate 0.2 mg/kg,cis-atracurium 0.15 mg/kg and sufentanil 0.3μg/kg,A spiral-flex reinforced tracheal tube was inserted under laryngoscope and patients would be received volume-controlled mechanical ventilation after the endotracheal tube depth determined.Intravenous inhalation combined anesthesia was used with intravenous infusion of remifentanil and inhaled sevoflurane and intermittent intravenous injection of cisatracurium to maintain the BIS of 40-60.According to the progress of the operation,the depth of anesthesia should be adjusted in time.After the operation,transversus abdominis plane block（TAPB）was performed,followed by ultrasound-guided injection of 0.375%ropivacaine 15 ml on each side using the in-plane technique.Postoperative analgesia was performed with PCIA,including dizoxin 0.4 mg/kg and ketorolac tromethamine 1.5 mg/kg,diluted to 100ml with normal saline,setting up a rate of 2 ml/h with a bolus dose of 2 ml and a lockout time of 30min to maintain postoperative VAS score≤4.When VAS>4,flurbiprofen axetil 50mg was injected intravenously for analgesia.Group D1 and group D2received intravenous infusion of dexmetomidine 0.2 and 0.3μg·kg^-1·h^-1from9:00 on the evening of the operation day and on the first day after operation until 6:00 the next morning,respectively.Group C received intravenous infusion of normal saline for 3 ml/h at the same time.Sleep quality was evaluated by Leeds Sleep Evaluation Questionnaire（LSEQ）and sleep time was monitored by Jiule bracelet at 8 a.m.on the first day（T₂）and 8 a.m.on the second day（T₃）respectively.At the time point T₃,2 m L peripheral venous blood samples were collected under the fasting state for detection as at T₁.The application of vasoactive drugs during operation,the occurrence of postoperative complications and remediation of analgesicson the first and second day after operation were recorded in each group.Results:Among the 96 patients,five ones were admitted to the ICU postoperatively（two ones were transferred out of ICU before 9 PM on the day of operation,three ones got worse）,and four ones refused postoperative intravenous dexmedetomidine,and 89 patients were actually enrolled in the group,including group C（n=30）,group D1（n=28）and group D2（n=31）.1.There were no significant differences in the general conditions（sex ratio,age,BMI,type of operation）among the three groups（P>0.05）.2.There were no significant differences in preoperative indexes（PSQI score,MMSE score and preoperative body temperature）among the three groups（P>0.05）.3.There were no significant differences in intraoperative remifentanil dosage,infusion volume,blood loss,urine volume and operation time among the three groups（P>0.05）.4.T lymphocyte percentage,CD4⁺/CD8⁺ratio and NK cell percentage at T₃ in group C were lower than T₁ in group C（P<0.05）,while T lymphocyte percentage,CD4⁺/CD8⁺ratio and NK cell percentage at T₃ in D1 and D2groups were higher than those in group C（P<0.05）,but there was no significant difference between D1 and D2 groups（P>0.05）.5.Compared with group C,the sleep time of group D1 and group D2 was longer at different time points（P<0.05）,there was no significant difference in sleep time between group D1 and group D2 at different time points（P>0.05）.And there was no significant difference in LSEQ score among the three groups（P>0.05）.There was no significant difference in the rate of remedial analgesia in different periods（P>0.05）.6.There were no significant differences in intraoperative vasoactive drug application and postoperative complications among the three groups（P>0.05）.Conclusions:1.Ncturnal intravenous infusion of dexmetomidine(0.2,0.3μg·kg^-1·h^-1)can improve the sleep quality of elderly patients after laparoscopic radical resection of gastrointestinal tumors.2.Sleep disturbance may be the cause of immune decline in elderly patients undergoing laparoscopic radical resection of gastrointestinal tumors.3.Nocturnal intravenous infusion of dexmetomidine can improve the early immune function of elderly patients after laparoscopic radical resection of gastrointestinal tumors,which may be related to the improvement of postoperative sleep quality.