Cerebral Vascular Effects of Dexmedetomidine Versus Propofol Sedation in Intubated Mechanically Ventilated ICU Patients

Cerebral Vascular Effects of Dexmedetomidine Versus Propofol Sedation in Intubated Mechanically Ventilated ICU Patients With and Without Traumatic Brain Injury.

Serial transcranial Doppler (TCD) exams in healthy volunteers and in animal models showed a strong linear relationship between middle cerebral artery (MCA) flow velocity (FV) and dexmedetomidine infusion. The concomitant elevation of pulsatility index (PI) indicates vasoconstriction of the cerebral vasculature as the most profound underlying mechanism.

Available clinical evidence on the use of dexmedetomidine sedation in neurosurgical and neurocritical care is limited and no definite conclusion can be drawn. There is a need for The use of dexmedetomidine might be a useful adjunct in clinical situations when the increase in CBF could be detrimental such as vasogenic cerebral edema (i.e., TBI, large brain tumors). However, dexmedetomidine sedation is questionable in patients with subarachnoid hemorrhage and acute stroke, since the associate drop in arterial pressure could worsen the coexisting increase in circulating catecholamines and massive sympathetic outflow. Further high-quality RCTs to evaluate the use of dexmedetomidine as a sedative agent both in general ICU patients and in patients with TBI.

Transcranial Doppler (TCD) is a simple noninvasive bedside tool to assess the cerebral blood flow pattern. The new development of transcranial color Doppler with angle correction option helps to improve the sensitivity of test results. TCD can assess the evolution of CBF alterations and possibly cerebral autoregulation performance and ICP estimation in patients presenting with cerebral pathology.

Inclusion Criteria:

• Adult trauma patients (18-50 years old, ASA I-II).
• With and without mild TBI.
• Mild traumatic brain injury will include; brain edema, brain contusion, fracture base, fissure fracture and depressed fracture.
• The severity of traumatic brain injury will be defined as mild based on basal Glasgow Coma Scale and basal Computerized tomography scanning.
• Requirements of endotracheal intubation, mechanical ventilation and light to moderate sedation because of associated abdominal or chest traumatic injuries.
• The sedation needed should of an estimated duration not less than 24h.
• Baseline hemodynamic parameters within the normal range.
• Baseline middle cerebral artery flow velocity within the normal range.

Exclusion Criteria:

• Severe traumatic brain injury, subarachnoid hemorrhage and Intra-cerebral hemorrhage.
• Spinal cord injury.
• Hemodynamically unstable patients and patients on inotropes.
• Patients who have a cardiac pacemaker or automatic implantable cardioverter defibrillator.
• Patients with hepatic or renal impairment.
• Pregnant females.
• Patients who are incarcerated.