M. Schmidt et al., Transcranial doppler flow velocity vs. cerebral blood flow in pigs - A validation study using the radioactive microspheres method, APPL CARD P, 9(2), 2000, pp. 97-102
Introduction: Validity of determination of transcranial doppler flow veloci
ty in the middle cerebral artery as a measure for cerebral blood flow is di
scussed controversely. We have investigated the correlation between transcr
anial doppler flow velocity in the middle cerebral artery and the regional
cerebral blood flow measured with the radioactive microspheres method in pi
gs.
Materials and methods: The animals were randomly divided into xenon group (
n=5), which received anaesthesia with 70% xenon inhaled in 30% oxygen in ad
dition to buprenorphine 15 mu gkg(-1)h(-1). The TIVA group (n=5) was anaest
hetized with a continuous infusion of pentobarbital at a rate of 15 mgkg(-1
)h(-1) and buprenorphine at a rate of 15 mu gkg(-1)h(-1). Under normoventil
ation heart rate, mean arterial pressure, arterial oxygen saturation, arter
ial pH, arterial pCO(2) and temperature were determined. Then hyper- and hy
poventilation was carried out and controlled by measuring expiratory CO, le
vels and arterial blood gases. Transcranial doppler flow velocity was measu
red in normo-(target p(a)CO(2)=40 mmHg), hyper- (target p(a)CO(2)=30mmHg) a
nd hypoventilation (target p(a)CO(2)=50mmHg). Simultaneously radiolabelled
microspheres with three different radioactive markers (Niobium 95, Rutenium
103, Cereum 141) were injected into the left ventricle. Three tissue aliqu
ots were taken from several parts of the brain (cortex, brainstem, medulla
oblongata and cerbellum) to calculate the regional cerebral flow by measuri
ng radioactivity. A total number of 252 microsphere samples were studied.
Results: We found a good correlation between transcranial doppler flow velo
city and cerebral blood flow measured with the microspheres method in pigs.
The regional changes of CBF in cortex, brainstem, medulla and cerebellum w
ere parallel, revealing a nearly equal change on cerebral blood flow in the
different regions of the brain due to ventilatory manipulations under xeno
n or total intravenous anaesthesia.
Discussion: We conclude, that the transcranial doppler flow velocity measur
ement in the middle cerebral artery is a reliable and useful non-invasive m
ethod to estimate cerebral blood flow.