1987 Volume 9 Issue 5 Pages 397-402
As an index implying the severity of damages in cerebral circulations in patients with cerebrovascular diseases (CVD), CO2-reactivity (CO2-R) is important. However, in the past, measuring the CO2-R has sometimes needed invasive procedures and real-time recording of the cerebral circulation fluctuating with CO2 has been difficult. We employed the transcranial Doppler flowmetry as a casual tool to measure the CO2-R and investigated the reliability of this method in comparison with cerebral blood flow studies by the Argon inhalation method.
Fifteen patients thirteen with cerebral infarctions, one with aortitis syndrome, one with orthostatic hypotension were monitored middle cerebral artery blood velocity (MCAV), cerebral blood flow (CBF), and arterial gases in the condition of hyperventilation, normoventilation, and 3%, 5%, 7% CO2 load. MCAV was measured by the use of a transcranial pulsed Doppler blood velocimeter (Aaslid et al., 1982). Basal CBF was directly measured by the Argon inhalation method based on the Fick's principle using the mass spectrometry of Argon at an artery and an internal jugular vein and CBF changes were calculated from the changes in arterio-venous oxygen differences. CO2-R was calculated as k value in the formula of LnCBF=kpCO2 + A presented by Olesen et al.
The mean value of MCAV was 34.5, 54.4, 62.4, 80.1, 96.8 cm/sec and the mean value of CBF was 27.3, 44.1, 49.8, 65.8, 86.2 ml/100 g/min in the condition of hyperventilation, normoventilation, and 3%, 5%, 7% CO2 load, respectively. The CO2-R in MCAV was 0.0391 ± 0.0062 (mean ± S.D.) and the CO2-R in CBF was 0.0406 ± 0.0060 (mean ± S.D.). The association of the CO2-R in MCAV with that in CBF was significant with a coefficient of correlation r=0.89 (p<0.001).
These data suggested that the transcranial Doppler flowmetry on the middle cerebral artery provided reliable information about the vasomotor reactivity of the cerebrovascular system and could be utilized in monitoring patients with CVD or metabolic crises and in the evaluation of the efficacy of the therapeutic regimens.
