title: Autoregulation after ischaemic stroke.
abstract: OBJECTIVE
  Absent outcome data from randomized clinical trials, management of hypertension in acute ischaemic stroke remains controversial. Data from human participants have failed to resolve the question whether cerebral blood flow (CBF) in the peri-infarct region will decrease due to impaired autoregulation when systemic mean arterial pressure (MAP) is rapidly reduced.
  
  
  METHODS
  Nine participants, 1-11 days after hemispheric ischaemic stroke, with systolic blood pressure more than 145 mmHg, underwent baseline PET measurements of regional CBF. Intravenous nicardipine infusion was then used to rapidly reduce mean arterial pressure 16 +/- 7 mmHg and CBF measurement was repeated.
  
  
  RESULTS
  Compared with the contralateral hemisphere, there were no significant differences in the percent change in CBF in the infarct (P = 0.43), peri-infarct region (P = 1.00) or remainder of the ipsilateral hemisphere (P = 0.50). Two participants showed CBF reductions of greater than 19% in both hemispheres.
  
  
  CONCLUSIONS
  In this study, selective regional impairment of CBF autoregulation in the infarcted hemisphere to reduced systemic blood pressure was not a characteristic of acute cerebral infarction. Reductions in CBF did occur in some individuals, but it was bihemispheric phenomenon that likely was due to an upward shift of the autoregulatory curve as a consequence of chronic hypertension. These results indicate individual monitoring of changes in global CBF, such as with bedside transcranial Doppler, may be useful to determine individual safe limits when MAP is lowered in the setting of acute ischaemic stroke. The benefit of such an approach can only be demonstrated by clinical trials demonstrating improved patient outcome.
authors: Department of Neurology, University of North Carolina School of Medicine, North Carolina 27599-7025, USA. powersw@neurology.unc.edu
authors: William J
authors: WJ
authors: Powers
authors: Tom O
authors: TO
authors: Videen
authors: Michael N
authors: MN
authors: Diringer
authors: Venkatesh
authors: V
authors: Aiyagari
authors: Allyson R
authors: AR
authors: Zazulia
mesh_terms: D000368:Aged; D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009529:Nicardipine / Q000008:administration & dosage; D049268:Positron-Emission Tomography; D020521:Stroke / Q000000981:diagnostic imaging / Q000503:physiopathology*
chemical_list: D009529:Nicardipine