The effect of different methods on entropy values ​​in cases wich depth of anesthesia is adjusted according to endtidal volatile anesthetic concentration

Aim: The primarily aim of this study is to observe the alveolar anesthetic agent concentrations with the aid of "entropy" which is a depth of anesthesia monitor in major abdominal surgeries, in cases where general anesthesia is combined with TEA or not. Materials and methods: Following the ethics committee approval and patient consent, the study was completed with a total of 44 patients. The patients were divided into 2 groups; patients with general anesthesia combined with TEA or not. Epidural anesthesia was applied to the patients combined with TEA, after the location of the catheter was confirmed, 7ml bupivacaine 0.25% + fentanyl 50 mcg bolus was administered through the epidural catheter, and the epidural block was expected to reach sufficient depth for 20 minutes. Patients in both groups were anesthetized with the same induction agents (0.05 mg / kg midazolam, 2mcg / kg fentanyl, propofol until the entropy value was below 60, and 0.6mg / kg rocuronium). After orotracheal intubation, maintenance inhalation anesthesia was provided with automatic gas control. During the operation, the patients in whom general anesthesia was combined with TEA was administered as an infusion of solution 7 ml / hour which is bolus applied. The dose of propofol used in induction, the endtidal sevoflurane concentration that keeps the entropy value within the target limits (between 40-60) after intubation, the time to reach the set concentration, the amount of inhalation anesthetic consumed during this period, the maximum fresh gas flow rate during this period, the total amount of inhalation anesthetic used during the operation. and at the end of the operation, after the inhalation anesthetic was closed, the time until the alveolar concentration was reset and the fresh gas flow rate exited during this period were recorded. Results: Between the groups (44 patients evaluated in two groups) in which general anesthesia was combined with TEA and TEA was not applied, the propofol dose used in induction, the end tidal alveolar concentration of the inhalation agent that keeps the entropy within the targeted normal limits, the amount of remifentanil used in the intraoperative process and the total amount of inhalation agent used during the operation were found statiscally difference. Propofol doses used during anesthesia induction between the groups were 141.9 ± 31.72 mg and 190.0 ± 16.79 mg in the group with and without TEA, respectively, and a significant statistical difference was found between the two groups p <0.001. The end tidal inhalation anesthetic concentration that keeps entropy values within the targeted limits during the operation was 1.68 ± 0.16 and 2.0 ± 0.2 in the groups with and without TEA, and a significant statistical difference was observed between the groups p <0.001. Although there was no significant difference in operation times between the groups, when the total inhalation anesthetic consumed during the operation was compared between the two groups, the result was 32.38 ± 11.28 ml and 40.83 ± 14.47 ml in the group with and without TEA and the statistical difference between the groups was determined p <0.033. Conclusion: In patients whom general anesthesia was combined with TEA, the required end tidal inhalation agent concentration to achieve the target entropy value, the amount of total inhalation anesthetic used intraoperatively, and the dose of propofol used in induction were significantly lower.