title: Cerebral vascular effects of loading dose of dexmedetomidine: A Transcranial Color Doppler study.
abstract: BACKGROUND
  Dexmedetomidine has been widely used in critical care settings because of its property of maintaining stable hemodynamics and inducing conscious sedation. The use of dexmedetomidine is in increasing trend particularly in patients with neurological disorders. Very few studies have focused on the cerebral hemodynamic effects of dexmedetomidine. This study is aimed to address this issue.
  
  
  METHODS
  Thirty patients without any intracranial pathology were included in this study. Middle cerebral artery flow velocity obtained from transcranial color Doppler was used to assess the cerebral hemodynamic indices. Mean flow velocity (mFV), pulsatility index (PI), cerebral vascular resistant index (CVRi), estimated cerebral perfusion pressure (eCPP), and zero flow pressure (ZFP) were calculated bilaterally at baseline and after infusion of injection Dexmedetomidine 1 mcg/Kg over 10 min.
  
  
  RESULTS
  Twenty-six patients completed the study protocol. After administration of loading dose of dexmedetomidine, mFV and eCPP values were significantly decreased in both hemispheres (P < 0.05); PI, CVRi, and ZFP values showed significant increase (P < 0.05) after dexmedetomidine infusion.
  
  
  CONCLUSIONS
  Increase in PI, CVRi, and ZFP suggests that there is a possibility of an increase in distal cerebral vascular resistance (CVR) with loading dose of dexmedetomidine. Decrease in mFV and eCPP along with an increase in CVR may lead to a decrease in cerebral perfusion. This effect can be exaggerated in patients with preexisting neurological illness. Further studies are needed to evaluate the effect of dexmedetomidine on various other pathological conditions involving brain like traumatic brain injury and vascular malformations.
authors.affiliation: Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India.
authors.forename: Appavoo
authors.initials: A
authors.lastname: Arulvelan
authors.affiliation: Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India.
authors.forename: Sethuraman
authors.initials: S
authors.lastname: Manikandan
authors.affiliation: Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India.
authors.forename: Hari Venkat
authors.initials: HV
authors.lastname: Easwer
authors.affiliation: Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Ulloor, Trivandrum, Kerala, India.
authors.forename: Kesavapisharady
authors.initials: K
authors.lastname: Krishnakumar
keywords: Cerebral vascular resistance; dexmedetomidine; transcranial color Doppler