Use of Bispectral Index Monitoring to Detect Deep Sedation in Mechanically Ventilated Patients: Validity Study

Inclusion Criteria: * Adult patients are intubated and ventilated within the previous 24 hours, are administered with continuous or intermittent intravenous sedatives and/or analgesics, and are expected to receive mechanical ventilation and sedation for longer than 24 hours Exclusion Criteria: * Age under 18 or over 65 years; * Continuously infusion of muscle relaxants; * Diagnosed or suspected brain diseases, which including brain trauma, intracranial hemorrhage, stroke, brain tumors, hypoxic-ischemic encephalopathy, epilepsy and meningitis; * Diagnosed conditions that resulted in a decrease level of consciousness, which including hypoxemia with partial pressure of oxygen in arterial blood less than 60 mmHg, hypotension with systolic blood pressure less than 90 mmHg, hypoglycemia with blood glucose concentration less than 4.1 mmol/L, anemia with hemoglobin concentration less than 70 g/L, and body temperature below 36 °C.