Effect Of Different MAC Of Sevoflurane Combined With Remifentanyl On Anesthesia Index And Bispectral Index During Laparoscopy Cholecystectomy

Objectives:The main objective of this study was to explore the effect of different MAC(minimum alveolar concentration)of sevoflurane combined with remifentanil on electroencephalography(EEG)based brain monitoring anesthesia index(Ai)and bispectral index(BIS)during laparoscopy cholecystectomy.Methods:This is a clinical prospective study conducted in a single center "Second Affiliated Hospital of Kunming Medical University".After ethics committee approval and informed consent,63 patients aged 18 to 65 years,American Society of Anesthesiologists physical status I and ? were enrolled in the study.All eligible patient of our study was selected randomly and divided into 3 groups equally.All the selected patients undergo laparoscopic cholecystectomy under inhalational anesthesia.In all the patients,the depth of anesthesia was monitored by using EEG based brain monitoring Anesthesia Index(Ai)and Bispectral Index(BIS).63 patients were randomly divided into 3 groups according to MAC of inhaled sevoflurane:MAC 0.7 group(n=21),MAC 1.0 group(n=21),and MAC 1.3 group(n=21).Sevoflurane was delivered in a tidal breathing technique in all groups.During induction of anesthesia,5%sevoflurane and 6 liters of oxygen per minute were delivered by using mask till intubation.Remifentanil was administered via the Agilia TCI syringe pump in Minto mode with Cpt(plasma concentration)concentration 4 ng/ml to all patients from initiation of induction to the closure of skin.Rocuronium was administered at the rate of 0.6 mg/kg intravenously when the patient has a loss of consciousness with verbal command and loss of eyelash reflex.During this study,the researcher waited two minutes for intubation after administration of rocuronium.At the time of intubation,if BIS and Ai range dropped to less than 60,then endotracheal intubation was done.After the intubation concentration of sevoflurane was managed as MAC required accordingly in the defined set group.The patient kept in mechanical ventilation with a set tidal volume of 6-8 mL/kg with respiration ratio 1:2,respiratory rate 12,target to maintain ETCO2 in-between range of 35-45 mmHg with PEEP 5 cmH2O,and peak pressure<25 cmH2O.Data of HR(heart rate),MAP(mean arterial pressure),MAC level,the value of Ai(anesthesia index),BIS(bispectral index),EMG(electromyogram)and BSR(burst suppression ratio)were recorded as mentioned in different time points:before induction of anesthesia(T1).loss of consciousness(T2).immediately before intubation(T3).immediately after intubation(T4).separation of the gallbladder(T5).MAC 0.4(T6).awake/eye open in verbal command(T7)and extubation(T8).For postoperative analgesia,given sufentanil 0.2 mcg/kg and for antiemetic prophylaxis given ramosetron hydrochloride 0.3 mg intravenously to all patients after stopping the administration of sevoflurane and remifentanil.Intraoperative muscle relaxant was given only 30 minutes before finishing surgery if surgery prolonged in some cases.Reversal drugs(neostigmine with atropine)were administered after spontaneous breathing appeared or 40 minutes after administration of rocuronium.All the patient was extubated in the operating table to monitor the vital signs,any immediate complication after extubation.Ai.and BIS value during a recovery period.The patient was shifted to PACU for postoperative observation and later transferred to the respective department.All patients were followed on the 1st postoperative day.During follow up.the patient was interviewed for assessing intraoperative awareness.Results1.Comparing the change in HR between groups at any time point,there was no significant difference(P>0.05).2.During this study,the MAP at T5,the MAC 1.3 group was lower than the MAC 0.7 group(P<0.01)and the MAC 1.0 group(P<0.05).3.The BIS score in the MAC 1.3 group was lower than those in the MAC 0.7 group(P<0.01)at T5.4.The Anesthesia Index(Ai)score in the MAC 1.3 group was lower than those in the MAC 0.7 group at T5(P<0.01).5.There was found agreement between BIS and Ai for measuring the depth of anesthesia.6.After follow up on the 1st postoperative day,there was no incidence of intraoperative awareness.Conclusions1.Using the MAC 0.7 and the MAC 1.0 of sevoflurane combined with remifentanil in laparoscopic cholecystectomy has more stable hemodynamic as compare to MAC 1.3 group.2.Both MAC value 0.7 and 1.0 was adequate for the maintenance of anesthesia in laparoscopic cholecystectomy in combination with remifentanil via TCI Minto Model.But MAC 1.3 with remifentanil may produce deep anesthesia,most of the patient's BIS and Ai score dropped less than 40 and hemodynamic instability observed.3.Between Ai and BIS have a better agreement in terms of evaluating the depth of anesthesia during general anesthesia.Thus,anesthesia index,Con View monitor can be used for monitoring depth of anesthesia4.Even though many studies including RCTs are available,preventing unintentional intraoperative awareness by measuring the depth of anesthesia in the perioperative period still has challenges and further studies need to be carried out.