End Tidal Anesthetic Concentration in Different Anesthesia Techniques Where Depth of Anesthesia Adjusted With Entropy

The hypothesis of this study is that in general anesthesia cases which is combined with thoracic epidural anesthesia (TEA), lower alveolar concentration will be required to reach the same anesthesia depth. The main aim of the study is observing and comparing the alveolar concentrations of anesthetic agents with entropy monitoring which is an anesthesia depth monitor in major abdominal surgeries where general anesthesia is combined or not with TEA.

In cases where TEA is combined with general anesthesia or not, anesthesia depth will be effectively monitored by entropy monitoring, in this way the adequate depth of anesthesia will be provided with the use of minimal volatile anesthetics and we will be able to prevent the use of large amounts of volatile anesthetics., It will be determined how much reduction in alveolar concentration is required in cases combined with TEA.

Nowadays, with the development of reliable anesthesia machines, "low-flow anesthesia" (LFA) is becoming more widespread, and its benefits on patient health, economy and ecology have been demonstrated. In LFA, the depth of anesthesia should not be too superficial or too deep during the time the alveolar concentration of volatile agent reaches equilibrium. Therefore, alveolar concentrations of volatile anesthetics are monitored in modern anesthesia machines. Some machines may also adjust the depth of anesthesia according to the alveolar concentration of the agent.

Inclusion criteria

• undergoing major abdominal surgery
• Patients who will not undergoing operation for thoracic cavity
• Body Mass Index (BMI) between 20-30

Exclusion criteria

• denial of patients
• contraindications for thoracic epidural anesthesia
• patients who are FEV1/FVC < 60
• patients with thoracic and lomber vertebrae surgery