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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
60
patients will receive dexmedetomidine 0.2-0.7 mcg/kg/h infusion for 24h.
Patients will receive 10-70 mcg/kg/h propofol infusion for 24h.
Assiut university main hospital, Trauma ICU
Asyut, Assiut Governorate, Egypt
Middle cerebral artery flow velocity
1\. Right and left middle cerebral artery (MCA) will be measured via trans-temporal window and the depth of insinuation will be between 30-60 mm with the subject's head in neutral position. Mean values of simultaneously measured invasive blood pressure recordings and the outer envelope of time averaged MCA flow velocity (FV) recordings during ten consecutive cardiac cycles
Time frame: 24 hours
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