Effect of MGRNOX Index-Guided General Anesthesia on Opioid Consumption in Patients

After anesthesia induction, the remifentanil plasma target concentration was adjusted intraoperatively to maintain the MGRNOX index between 30 and 50,but MAP and HR also were considered .In case the MGRNOX index was below 30 for more than 1 minute, remifentanil target-controlled infusion levels were lowered in steps of 0.5 ng/ml , whereas in case of a value greater than 50 for more than 1 minute, remifentanil target-controlled infusion levels were increased in steps of 0.5 ng/ml.

After anesthesia induction, if hypertension (MAP \> 100 mmHg) or tachycardia (heart rate \> 90 bpm) persists for more than 2 minutes, remifentanil target-controlled infusion levels were increased in steps of 0.5 ng/ml.If there is no response to remifentanil or the MAP and HR exceed a certain threshold, then urapidil or esmolol will be administered.For hypotension (50 mmHg \< MAP ≤ 60 mmHg) persisting for more than 2 minutes, remifentanil target-controlled infusion levels were lowered in steps of 0.5 ng/ml (lowest target plasma concentration that was allowed is 1 ng/ml), and 4μg of norepinephrine were given. If MAP ≤ 50 mmHg, remifentanil target-controlled infusion levels were lowered in steps of 0.5 ng/ml(lowest target plasma concentration that was allowed is 1 ng/ml), and 8μg of norepinephrine were given.