Study 1: Inclusion Criteria:

Neuroscience patients in the NCCU who are:

1. 18-80 years of age;
2. Mechanically ventilated patients;
3. Requiring continuous sedation for a minimum of 9-11 hours (depending on whether or not pt is post-operative), yet frequent neurological examinations or Patients with a NICSS score > 0
4. Patient or family able to provide consent.
5. Considered to have guarded yet stable neurological state. Not fluctuating intracranial pressure (ICP), cerebral perfusion pressure (CPP), or ongoing known cerebral ischemia if ICP monitoring in place.

Study 1: Exclusion Criteria:

1. Pregnancy.
2. ICP> 30 mm Hg despite therapy if ICP monitored.
3. CPP <70 mm Hg if monitored.
4. Occurrence of: new cerebral stroke, hemorrhage, or change in edema by CT, increase in ICP if monitored.
5. Neuromuscular paralysis.
6. Non-functional cognitive exam - not following commands.
7. Renal insufficiency: Serum Creatinine >2.0 mg/dl or estimated Cr Clearance <40.0 ml/min.
8. Hepatic disease: AST, ALT > 300, or INR > 1.7 not on anticoagulants.
9. Severe COPD with baseline arterial pCO2>50.
10. Suspected alcohol or substance withdrawal.
11. Hypotension - requiring pressor therapy to maintain baseline adequate CPP or mean arterial pressure.
12. Cardiac arrhythmia - sinus bradycardia (HR <60), atrial fibrillation (>6 PVC's/min)
13. Bradycardia- heart rate less than 60 beats per minute.
14. Patient does not require mechanical ventilation.

Study 2: Inclusion Criteria:

Critically ill neuroscience patients who are:

1. 18-80 years of age;
2. Mechanically ventilated;
3. Require Intracranial Pressure (ICP) monitoring by either subarachnoid bolt (SA bolt), or by an Intra-Ventricular Catheter (IVC).
4. Amenable for placement of intra-cerebral oxygen sensor or jugular bulb catheter.
5. Have GCS score > 5 that requires sedation.
6. Requiring continuous sedation for minimum of 9-11 hours (depending on whether or not pt is post-operative) , yet frequent neurological examinations every 1-2 hours or Patients with a NICSS score > 0
7. Patient or family able to provide consent.

Study 2: Exclusion Criteria:

1. Pregnancy;
2. ICP> 30 mm Hg despite therapy;
3. CPP <70 mm Hg;
4. Occurrence of: new cerebral stroke, hemorrhage, or change in edema by CT, increase in ICP if monitored.
5. Continuous neuromuscular paralysis
6. Renal insufficiency: Serum Creatinine >2.0 mg/dl or estimated Cr <40.0 Clearance ml/min.
7. Hepatic disease: AST, ALT > 300, or INR > 1.7 not on anticoagulants.
8. Severe COPD with baseline arterial pCO2>50.
9. Suspected alcohol or substance withdrawal.

Study 3: Inclusion Criteria:

Critically ill neuroscience patients who are:

1. 18-80 years of age;
2. Requiring continuous sedation for minimum of 9-11 hrs (depending on whether or not pt is post-operative), yet frequent neurological examinations or Patients with a NICSS score >0
3. Patient or family able to provide consent.
4. Mechanically ventilated patients;
5. Considered to have guarded yet stable neurological state. Not fluctuating ICP, CPP, or ongoing known cerebral ischemia.
6. Presence of intra-operatively placed GRID electrode array or patients requiring continuous EEG monitoring.

Study 3: Exclusion Criteria:

1. Pregnancy
2. Occurrence of: new cerebral stroke, hemorrhage, or change in edema by CT, increase in ICP if monitored.
3. Continuous neuromuscular paralysis
4. Renal insufficiency: Serum Creatinine >2.0 or Cr Clearance <40.0
5. Hepatic insufficiency: AST, ALT> 300, or PT time > 1.7 not on anticoagulants.
6. Severe COPD with baseline arterial pCO2>50.
7. Suspected alcohol or substance withdrawal.