Continuous neuromonitoring using transcranial Doppler reflects blood flow during carbon dioxide challenge in primates with global cerebral ischemia.
OBJECTIVE
At present, there is no consensus on the optimal monitoring method for cerebral blood flow (CBF) in neurointensive care patients. The aim of the present study was to investigate whether continuous transcranial Doppler (TCD) monitoring with modulation of partial pressure of CO2 reflects CBF changes. This hypothesis was tested in 2 pathological settings in which cerebral ischemia can be imminent: after an episode of cerebral ischemia and during vasospasm after subarachnoid hemorrhage.


METHODS
Sixteen cynomolgus monkeys were divided into 3 groups: 1) chemoregulation in control animals to assess the physiological range of CBF regulation, 2) chemoregulation during vasospasm after subarachnoid hemorrhage, and 3) chemoregulation after transient cerebral ischemia. We surgically placed a thermal CBF probe over the cortex perfused by the right middle cerebral artery. Corresponding TCD values were acquired simultaneously while partial pressure of CO2 was changed within a range of 25 to 65 mm Hg (chemoregulation). A correlation coefficient of CBF with TCD values of greater than r equals 0.8 was considered clinically relevant.


RESULTS
CBF and CBF velocity correlated strongly after cerebral ischemia (r = 0.83, P < 0.001). Correlations were poor in chemoregulation controls (r = 0.2) and in the vasospasm group (r = 0.55).


CONCLUSIONS
The present study provides experimental support that, in clearly defined conditions, continuous TCD monitoring combined with chemoregulation testing may provide an estimate of CBF in the early postischemic period.
Schatlo
Bawarjan
B
Surgical Neurology Branch, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
Gläsker
Sven
S
Zauner
Alois
A
Thompson
B Gregory
BG
Oldfield
Edward H
EH
Pluta
Ryszard M
RM
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D002545:Brain Ischemia / Q000175:diagnosis* / Q000503:physiopathology*; D002245:Carbon Dioxide; D002560:Cerebrovascular Circulation; D004195:Disease Models, Animal; D008252:Macaca fascicularis; D008991:Monitoring, Physiologic / Q000379:methods*; D012039:Regional Blood Flow / Q000502:physiology; D013223:Statistics as Topic; D013345:Subarachnoid Hemorrhage / Q000150:complications; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*; D020301:Vasospasm, Intracranial / Q000175:diagnosis / Q000209:etiology
D002245:Carbon Dioxide