Evaluation of Equivalent Minimum Alveolar Concentration (eMAC) During Propofol/Remifentanil Anesthesia

Detection of Nociceptive Stimulation and Anesthesia State by Equivalent Minimum Alveolar Concentration (eMAC) During Anesthesia With Varying Propofol and Remifentanil Concentrations

The aim of this study is to verify the accuracy of eMAC compared to Bispectral Index (BIS) for depth and nociceptive stimulation monitoring of anesthesia during general anesthesia.

eMAC is a new index based on response surface model for evaluating anesthesia state and anti-nociceptive stimulation levels. To valid it's clinical accuracy, a protocol was designed.

Patients will be allocated to receive a specific effect-site concentration of remifentanil and propofol during tonic electrical stimulation (5s, 50mA) and intubation. The concentration combinations include the electrical stimulation combination (effector chamber concentration random: remifentanil 0-3 ng/ml, propofol 3-5 ug/ml) and the intubation combination (effector chamber concentration random: remifentanil 3-5 ng/ml, propofol 3-5 ug/ml). All combinations were decided before operation. Every combination had a 5 min equilibration period, and the vital signs (Heart Rate, Blood pressure, any body movement) and BIS, eMAC will be recorded before and after the electrical stimulation and intubation. After this period, patients will be randomly allocated to receive an intravenous anesthesia or intravenous combined anesthesia, and regular anesthesia is executed. This study only records vital signs and BIS, eMAC during maintenance period of perioperative.

Inclusion Criteria:

1. Patients undergoing elective surgery under general anesthesia;
2. Patients with ASA rating I~III;
3. The age of the patient is more than 18 years old;
4. The informed consent has been signed;

Exclusion Criteria:

1. Patients who are participating in other trials;
2. Patients with cognitive impairment, mental illness or taking psychotropic drugs within three months;
3. Patients with a history of stroke;
4. Patients with a history of alcoholism (long-term drinking more than 5 years, daily white wine consumption ≥ 50ml);
5. Pregnant women;
6. Patients with BMI>30;
7. Patients and family members who are unwilling to participate after understanding the research content;
8. According to the evaluation of the researcher, the actual condition is not suitable for the patients participating in this trial.