Inclusion Criteria:  Who were scheduled for bypass surgery at the Service of Anesthesiology and Bariatric Surgery of the Civil Hospital of Guadalajara "Dr. Juan I Menchaca", Jalisco, Mexico, were recruited.  Exclusion Criteria:  Patients with a history of ischemic heart disease, history of drug abuse, and with any known allergy to any of the drugs used during anesthesia. Elimination criteria were: patients who withdrew their consent or with insufficient and poor quality blood samples (coagulated) or other reasons that did not allow sample processing.