The aim of the study is to investigate whether dexmedetomidine could suppress catecholamine release into peripheral blood to prevent PSH attacks and to achieve neuroprotection.

Paroxysmal sympathetic hyperactivity (PSH) is a syndrome typically recognized in patients suffering from traumatic brain injury, characterized by paroxysmal increases in sympathetic activity such as elevated heart rate, increased blood pressure and respiratory rate, high temperature, excessive sweating and abnormal motor (posturing) activity.

This prospective study will include patients with traumatic brain injury,who will be divided into two groups, evaluated by the Paroxysmal Sympathetic Hyperactivity-Assessment Measure (PSH-AM). Patients will also be evaluated with head CT.

The aim of the study is to investigate whether dexmedetomidine could suppress catecholamine release into peripheral blood to prevent PSH attacks and to achieve neuroprotection.

Inclusion Criteria:

1. Age: 18-70 years
2. Moderate or severe traumatic brain injury
3. GCS≤12
4. Diagnosed by CT
5. No catecholamines (such as dopamine, adrenaline, norepinephrine) have been used before admission
6. Have a clear history of head trauma
7. Non-open traumatic brain injury

Exclusion Criteria:

1. Severe liver dysfunction (Child-Pugh B or C)
2. Severe renal dysfunction (serum creatinine > 445 mmol / L or blood urea nitrogen > 20 mmol / L)
3. Hemodynamic instability when entering the ICU (heart rate <50 beats / min or hypotension, SBP <90mmHg or MAP <65mmHg)
4. Deaths within 72 hours after entering the ICU
5. Severe multiple injuries (ISS≥25 points)
6. Have central nervous system diseases (such as hypoxic ischemic encephalopathy, stroke, brain tumors, etc.)
7. Allergic to dexmedetomidine or midazolam
8. Observed with the results of disease interference test (such as pheochromocytoma, etc.)
9. In pregnancy or lactation
10. Receiving hypothermia treatment
11. Are participating in other drug research or clinical trials