An Assessment of Dynamic Autoregulation from Spontaneous Fluctuations of Cerebral Blood Flow Velocity: A Comparison of Two Models, Index of Autoregulation and Mean Flow Index

BackgroundCerebral autoregulation can be impaired after ischemic stroke, with potential adverse effects on cerebral blood flow during early rehabilitation.ObjectiveThe objective of this study was to assess changes in cerebral blood flow velocity with orthostatic variation at 24 hours after stroke.DesignThis investigation was an observational study comparing mean flow velocities (MFVs) at 30, 15, and 0 degrees of elevation of the head of the bed (HOB).MethodsEight participants underwent bilateral middle cerebral artery (MCA) transcranial Doppler monitoring during orthostatic variation at 24 hours after ischemic stroke. Computed tomography angiography separated participants into recanalized (artery completely reopened) and incompletely recanalized groups. Friedman tests were used to determine MFVs at the various HOB angles. Mann-Whitney U tests were used to compare the change in MFV (from 30° to 0°) between groups and between hemispheres within groups.ResultsFor stroke-affected MCAs in the incompletely recanalized group, MFVs differed at the various HOB angles (30°: median MFV=51.5 cm/s, interquartile range [IQR]=33.0 to 103.8; 15°: median MFV=55.5 cm/s, IQR=34.0 to 117.5; 0°: median MFV=85.0 cm/s, IQR=58.8 to 127.0); there were no significant differences for other MCAs. For stroke-affected MCAs in the incompletely recanalized group, MFVs increased with a change in the HOB angle from 30 degrees to 0 degrees by a median of 26.0 cm/s (IQR=21.3 to 35.3); there were no significant changes in the recanalized group (−3.5 cm/s, IQR=−12.3 to 0.8). The changes in MFV with a change in the HOB angle from 30 degrees to 0 degrees differed between hemispheres in the incompletely recanalized group but not in the recanalized group.LimitationsGeneralizability was limited by sample size.ConclusionsThe incompletely recanalized group showed changes in MFVs at various HOB angles, suggesting that cerebral blood flow in this group may be sensitive to orthostatic variation, whereas the recanalized group maintained stable blood flow velocities.

Download Full-text

Cerebral Blood Flow Velocity Changes in Preterm Infants After a Single Dose of Indomethacin: Duration of Its Effect

PEDIATRICS ◽

10.1542/peds.84.5.802 ◽

1989 ◽

Vol 84 (5) ◽

pp. 802-807

Author(s):

Frank Van Bel ◽

Margot Van de Bor ◽

Theo Stijnen ◽

Jan Baan ◽

Jan H. Ruys

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Preterm Infant ◽

Flow Velocity ◽

Preterm Infants ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Cerebral Arteries ◽

Mean Flow ◽

Mean Flow Velocity

Indomethacin decreases cerebral blood flow velocity and blood flow in the preterm infant. The duration of this negative effect has not been established. Cerebral blood flow velocity was evaluated in 24 preterm infants with symptomatic patent ductus arteriosus before and during the first 12 hours after a single intravenous dose of indomethacin, 0.1 mg/kg. Cerebral blood flow velocity was estimated by serial Doppler investigations of the anterior cerebral arteries. Indomethacin administration led to an instantaneous decrease of peak systolic flow velocity, temporal mean flow velocity, and end-diastolic flow velocity of the anterior cerebral arteries in all infants, which was maximal between 2 and 40 minutes after indomethacin administration and was followed by a more sustained recovery of all velocities to baseline values. Temporal mean flow velocity was not different from pre-indomethacin values at 3 hours after the administration. It is concluded that indomethacin can impact the cerebral circulation of the preterm infant for at least 2 hours. This may have consequences in preterm infants with unstable hemodynarnics and pulmonary function.

Download Full-text