Many studies have explored the effects of inhalation anesthetics, intravenous anesthetics, and muscle relaxants on spectral entropy, but most did not monitor the degree of neuromuscular block. In addition, they do not explore the effects of different degrees of neuromuscular blockade on spectral entropy under different concentrations of isoflurane inhalation. Therefore, the present study will evaluate different levels of MAC to quantify the isoflurane concentration, as well as different degrees of neuromuscular blockade

The study will include 40 patients fulfilling the inclusion criteria. They will be randomized into 2 equal groups by a computer generated random numbers table, each consisting of 20 patients, namely group A and group R.

• Group A: Patients will receive Atracurium.
• Group R: Patients will receive rocuronium. No premedication will be given. After the patients enter the operating room, a venous cannula will be inserted into a large peripheral vein. Data from routine monitoring, including non-invasive arterial blood pressure, oxygen saturation, and end-tidal oxygen concentration (ETO2) and end-tidal carbon dioxide concentration (ETCO2) will be collected. Neuromuscular blockade will be continuously assessed by acceleromyography using the Train-of-Four-watch SX system (made in Ireland), starting when the patients will be unconscious. RE and SE will be monitored using a Datex Ohmeda Entropy Module (M-Entropy) and the Entropy Sensor system (made in finland).

Baseline RE and SE will be recorded. Anesthesia will be induced by propofol (dose 2-3 mg/kg) and fentanyl as analgesia (dose 1-2 mg/kg). Tracheal intubation will be facilitated with rocuronium (dose 0.6 mg/kg) /atracurium (dose 0.5 mg/kg) after an acceleromyography count of 0. Anesthesia will be maintained with isoflurane in an air-O2 mixture (FiO2 0.6, 2 L/min). Mechanical ventilation will be maintained at a tidal volume of 5-7 ml/kg. Ventilator frequency will be adjusted for maintenance of an ETCO2 of 35-40 mmHg. After equilibrium for 30 minutes SE, RE and the difference between them will be recorded at MAC 0.8 and MAC 1 at two levels of muscle relaxation assessed by TOF value of 50% and 100%. Rocuronium (dose 0.01-0.012 mg/kg/min ) /atracurium (dose 0.005-0.01 mg/kg/min) will be administered as a continuous IV infusion adjusted until 50% and 100% depression of T1 ( first twitch by acceleromyography) will be observed. The entire experiment ended before the start of surgery.

Inclusion Criteria:

1. Patients American Society of Anesthesiologists physical status (ASA) I to II.
2. Male patients (to avoid bias between gender).
3. Age between 20-50 years

Exclusion Criteria:

• a. Patients receiving any neuropsychiatric medications. b. Patients undergoing neurosurgical operation. c. Drug addiction. d. Body mass index (BMI) more than or equal to 40.

all collecting IPD will be shared

1 year

anesthesiologist