title: Noninvasive cerebrovascular autoregulation assessment in traumatic brain injury: validation and utility.
abstract: A moving correlation index (Mx-CPP) of cerebral perfusion pressure (CPP) and mean middle cerebral artery blood flow velocity (CBFV) allows continuous monitoring of dynamic cerebral autoregulation (CA) in patients with severe traumatic brain injury (TBI). In this study we validated Mx-CPP for TBI, examined its prognostic relevance, and assessed its relationship with arterial blood pressure (ABP), CPP, intracranial pressure (ICP), and CBFV. We tested whether using ABP instead of CPP for Mx calculation (Mx-ABP) produces similar results. Mx was calculated for each hemisphere in 37 TBI patients during the first 5 days of treatment. All patients received sedation and analgesia. CPP and bilateral CBFV were recorded, and GOS was estimated at discharge. Both Mx indices were calculated from 10,000 data points sampled at 57.4Hz. Mx-CPP > 0.3 indicates impaired CA; in these patients CPP had a significant positive correlation with CBFV, confirming failure of CA, while in those with Mx < 0.3, CPP was not correlated with CBFV, indicating intact CA. These findings were confirmed for Mx-ABP. We found a significant correlation between impaired CA, indicated by Mx-CPP and Mx-ABP, and poor outcome for TBI patients. ABP, CPP, ICP, and CBFV were not correlated with CA but it must be noted that our average CPP was considerably higher than in other studies. This study confirms the validity of this index to demonstrate CA preservation or failure in TBI. This index is also valid if ABP is used instead of CPP, which eliminates the need for invasive ICP measurements for CA assessment. An unfavorable outcome is associated with early CA failure. Further studies using the Mx-ABP will reveal whether CA improves along with patients' clinical improvement.
authors.affiliation: Department of Neurosurgery, University of Sydney, Westmead Hospital, Sydney, Australia. keeflang@optusnet.com.au
authors.forename: Erhard W
authors.initials: EW
authors.lastname: Lang
authors.forename: Jim
authors.initials: J
authors.lastname: Lagopoulos
authors.forename: Jane
authors.initials: J
authors.lastname: Griffith
authors.forename: Kwok
authors.initials: K
authors.lastname: Yip
authors.forename: Yugan
authors.initials: Y
authors.lastname: Mudaliar
authors.forename: H Maximilian
authors.initials: HM
authors.lastname: Mehdorn
authors.forename: Nicholas W C
authors.initials: NW
authors.lastname: Dorsch
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D001930:Brain Injuries / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000503:physiopathology; D011237:Predictive Value of Tests; D011379:Prognosis; D015203:Reproducibility of Results; D017585:Ultrasonography, Doppler, Transcranial / Q000592:standards*