Inclusion Criteria:  Aged 18 -60 years american society of anesthesiologists status I-II Scheduled for elective laparoscopic cholecystectomy  Exclusion Criteria:  Patients with chronic renal dysfunction. Patients with hypo/hyper-thyroidism. Patients with diseases of the autonomic and central nervous systems. Patients with cardiopulmonary dysfunction. Patients with history of treatment with long-term oral tranquilizers.