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(Stroke. 2003;34:2404.)
© 2003 American Heart Association, Inc.

Original Contributions

Assessment of Cerebrovascular Autoregulation in Head-Injured Patients

A Validation Study

Luzius A. Steiner, MD; Jonathan P. Coles, FRCA; Andrew J. Johnston, FRCA; Doris A. Chatfield, BSc; Peter Smielewski, PhD; Tim D. Fryer, PhD; Franklin I. Aigbirhio, PhD; John C. Clark, PhD, DSc; John D. Pickard, MChir, FRCS, FMedSci; David K. Menon, MD, PhD, FRCA, FRCP, FMedSci Marek Czosnyka, PhD, DSc

From the Wolfson Brain Imaging Centre (L.A.S., J.P.C., A.J.J., D.A.C., P.S., T.D.F., F.I.A., J.C.C., J.D.P., D.K.M., M.C.), Academic Neurosurgery (L.A.S., J.D.P., M.C.), and University Department of Anaesthesia (L.A.S., J.P.C., A.J.J., D.A.C., D.K.M.), Addenbrooke’s Hospital, Cambridge, UK.

Reprint requests to Luzius A. Steiner, MD, Department of Anaesthesia, University of Basel, Kantonsspital, 4031 Basel, Switzerland. E-mail lsteiner{at}uhbs.ch

Background and Purpose— Cerebrovascular autoregulation is frequently measured in head-injured patients. We attempted to validate 4 bedside methods used for assessment of autoregulation.

Methods— PET was performed at a cerebral perfusion pressure (CPP) of 70 and 90 mm Hg in 20 patients. Cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO₂) were determined at each CPP level. Patients were sedated with propofol and fentanyl. Norepinephrine was used to control CPP. During PET scanning, transcranial Doppler (TCD) flow velocity in the middle cerebral artery was monitored, and the arterio-jugular oxygen content difference (AJDO₂) was measured at each CPP. Autoregulation was determined as the static rate of autoregulation based on PET (SROR_PET) and TCD (SROR_TCD) data, based on changes in AJDO₂, and with 2 indexes based on the relationship between slow waves of CPP and flow velocity (mean velocity index, Mx) and between arterial blood pressure and intracranial pressure (pressure reactivity index, PRx)

Results— We found significant correlations between SROR_PET and SROR_TCD (r²=0.32; P<0.01) and between SROR_PET and PRx (r²=0.31; P<0.05). There were no significant associations between PET data and autoregulation as assessed by changes in AJDO₂. Global CMRO₂ was significantly lower at the higher CPP (P<0.01).

Conclusions— Despite some variability, SROR_TCD and PRx may provide useful approximations of autoregulation in head-injured patients. At least with our methods, CMRO₂ changes with the increase in CPP; hence, flow-metabolism coupling may affect the results of autoregulation testing.

Key Words: autoregulation • brain injuries • monitoring, physiologic • tomography, emission computed

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