title: Correlation of end-tidal CO2 with transcranial Doppler flow velocity is decreased during chemoregulation in delayed cerebral vasospasm after subarachnoid haemorrhage--results of a pilot study.
abstract: BACKGROUND
  Cerebrovascular responses to variations in blood pressure and CO2 are attenuated during delayed vasospasm after subarachnoid hemorrhage (SAH). Transcranial Doppler sonography (TCD) is routinely used to assess the presence of vasospasm, but cerebral blood flow velocities (CBF-V) measured by TCD do not necessarily reflect cerebral blood flow (CBF) or the severity of vasospasm. We hypothesized that the correlation of end-tidal pCO2 levels with CBF-V and CBF is equally decreased in subjects with cerebral vasospasm during variations in pCO2.
  
  
  METHODS
  Four cynomolgus monkeys were assigned to the vasospasm group and eight animals to the control group. The animals in the vasospasm group underwent placement of an autologous subarachnoid blood clot and vasospasm was confirmed by angiography on day 7. In both groups, CBF and CBF-V were measured simultaneously while end-tidal pCO2 was altered. CBF was measured using a thermal probe placed on the cortical surface and CBF-V was measured using a commercial TCD device.
  
  
  RESULTS
  Pearson's correlation coefficient between CBF-V values and pCO2 levels in the control group was strong (r = 0.94, p < 0.001) while it was moderate in the vasospasm group (r = 0.54, p = 0.04). The correlation of CBF values with pCO2 in healthy controls was equally strong (r = 0.87, p = 0.005), while there was no correlation in the vasospasm group (r = -0.09, p = 0.83).
  
  
  CONCLUSIONS
  In this pilot study, correlations of CBF-V with pCO2 values during chemoregulation testing were lower in animals with vasospasm than in healthy ones. This correlation coefficient based on modifications in pCO2 may potentially facilitate the non-invasive assessment of vasospasm.
authors.affiliation: Surgical Neurology Branch, National Institute of Health, National Institutes of Neurological Disorders and Stroke, Bethesda, MD, USA.
authors.forename: B
authors.initials: B
authors.lastname: Schatlo
authors.forename: S
authors.initials: S
authors.lastname: Gläsker
authors.forename: A
authors.initials: A
authors.lastname: Zauner
authors.forename: G B
authors.initials: GB
authors.lastname: Thompson
authors.forename: E H
authors.initials: EH
authors.lastname: Oldfield
authors.forename: R M
authors.initials: RM
authors.lastname: Pluta
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D004195:Disease Models, Animal; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008252:Macaca fascicularis; D010865:Pilot Projects; D013345:Subarachnoid Hemorrhage / Q000150:complications* / Q000503:physiopathology*; D020301:Vasospasm, Intracranial / Q000209:etiology / Q000503:physiopathology*
chemical_list: D002245:Carbon Dioxide