Document Detail

Incorporating a parenchymal thermal diffusion cerebral blood flow probe in bedside assessment of cerebral autoregulation and vasoreactivity in patients with severe traumatic brain injury.
MedLine Citation:
PMID:  20707619     Owner:  NLM     Status:  MEDLINE    
OBJECT: Cerebral autoregulation may be altered after traumatic brain injury (TBI). Recent evidence suggests that patients' autoregulatory status following severe TBI may influence cerebral perfusion pressure management. The authors evaluated the utility of incorporating a recently upgraded parenchymal thermal diffusion probe for the measurement of cerebral blood flow (CBF) in the neurointensive care unit for assessing cerebral autoregulation and vasoreactivity at bedside.
METHODS: The authors evaluated 20 patients with severe TBI admitted to San Francisco General Hospital who underwent advanced neuromonitoring. Patients had a parenchymal thermal diffusion probe placed for continuous bedside monitoring of local CBF ((loc)CBF) in addition to the standard intracranial pressure and brain tissue oxygen tension (P(bt)O(2)) monitoring. The CBF probes were placed in the white matter using a separate cranial bolt. A pressure challenge, whereby mean arterial pressure (MAP) was increased by about 10 mm Hg, was performed in all patients to assess autoregulation. Cerebral CO(2) vasoreactivity was assessed with a hyperventilation challenge. Local cerebral vascular resistance ((loc)CVR) was calculated by dividing cerebral perfusion pressure by (loc)CBF. Local cerebral vascular resistance normalized to baseline ((loc)CVR(normalized)) was also calculated for the MAP and hyperventilation challenges.
RESULTS: In all cases, bedside measurement of (loc)CBF using a cranial bolt in patients with severe TBI resulted in correct placement in the white matter with a low rate of complications. Mean (loc)CBF decreased substantially with hyperventilation challenge (-7 ± 8 ml/100 g/min, p = 0.0002) and increased slightly with MAP challenge (1 ± 7 ml/100 g/min, p = 0.17). Measurements of (loc)CBF following MAP and hyperventilation challenges can be used to calculate (loc)CVR. In 83% of cases, (loc)CVR increased during a hyperventilation challenge (mean change +3.5 ± 3.8 mm Hg/ml/100 g/min, p = 0.0002), indicating preserved cerebral CO(2) vasoreactivity. In contrast, we observed a more variable response of (loc)CVR to MAP challenge, with increased (loc)CVR in only 53% of cases during a MAP challenge (mean change -0.17 ± 3.9 mm Hg/ml/100 g/min, p = 0.64) indicating that in many cases autoregulation was impaired following severe TBI.
CONCLUSIONS: Use of the Hemedex thermal diffusion probe appears to be a safe and feasible method that enables continuous monitoring of CBF at the bedside. Cerebral autoregulation and CO(2) vasoreactivity can be assessed in patients with severe TBI using the CBF probe by calculating (loc)CVR in response to MAP and hyperventilation challenges. Determining whether CVR increases or decreases with a MAP challenge ((loc)CVR(normalized)) may be a simple provocative test to determine patients' autoregulatory status following severe TBI and helping to optimize CPP management.
Guy Rosenthal; Rene O Sanchez-Mejia; Nicolas Phan; J Claude Hemphill; Christine Martin; Geoffrey T Manley
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Publication Detail:
Type:  Evaluation Studies; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2010-08-13
Journal Detail:
Title:  Journal of neurosurgery     Volume:  114     ISSN:  1933-0693     ISO Abbreviation:  J. Neurosurg.     Publication Date:  2011 Jan 
Date Detail:
Created Date:  2011-01-03     Completed Date:  2011-02-01     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0253357     Medline TA:  J Neurosurg     Country:  United States    
Other Details:
Languages:  eng     Pagination:  62-70     Citation Subset:  AIM; IM    
Department of Neurosurgery, University of California, San Francisco, California, USA.
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MeSH Terms
Blood Pressure / physiology
Brain / blood supply*,  physiology*
Carbon Dioxide / metabolism
Hyperventilation / physiopathology
Intracranial Pressure / physiology
Monitoring, Physiologic / instrumentation*,  methods
Oxygen / metabolism
Point-of-Care Systems / trends*
Regional Blood Flow / physiology*
Thermal Diffusion / physiology*
Vascular Resistance / physiology
Grant Support
Reg. No./Substance:
124-38-9/Carbon Dioxide; 7782-44-7/Oxygen

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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