Safety Study of Dexmedetomidine in Elderly Under General Anesthesia

All patients will be screened to determine eligibility for study entry, and the patients who meet the eligibility requirements will be informed about the study and potential risks. After giving written informed consent, the patients will be randomized into different doses of dexmedetomidine groups and the comparative groups in a same ratio.

Inclusion criteria

• age ≥65yr, American Society of Anesthesiologists (ASA) physical status scale grade I-III, ready for HP; body weight between 45 and 75kg, body mass index (BMI) between 18 and 24kg/m2;
• the health conditions generally well according to medical history, physical examination, and laboratory tests;
• no signs of difficult intubation;
• no history of dementia and mental problems;
• normal cognitive function, ability to understand and comply with study procedures.

Exclusion criteria

• Age <65 yr or >90 yr; BMI greater than 24 kg/m2; ASA grade higher than III;
• Heart failure, severe arrhythmias, severe bradycardia (heart rate less than 40 beats/min), atrioventricular block of degree 2 or above, sick sinus syndrome, systolic blood pressure (SBP) ≥180 or <90 mmHg, diastolic blood pressure (DBP) ≥110 or <60 mmHg;
• Severe liver or kidney dysfunction, severe infection, and other pathological conditions that interfere with study results.
• Dementia, cerebrovascular accidents within 3 months, mental illness, epilepsy, and other adverse events that interfere with study results.
• Patients with the conditions that block communication and preoperative assessment, such as serious hearing or visual impairment;
• History of chronic analgesic use, long-term psychotropic medication use, alcohol or drug addiction.