Transcranial Doppler CO2 Test as an Indicator of Cerebral Vasoreactivity and Prognosis in Patients with Regional CBF Alteration

Kim, Myung Hyun; Lee, Hoon Kap; Lee, Ki Chan; Chu, Jung Wha

Abstract

The assessment of cerebral vasoreactivity provides information on the reserve capacity of cerebral circulation in patients with cerevrovascular disease. It also allows for the diagnosis of impending ischemia and control of the effect of initiated corrective measures. The authors had performed transcranial doppler(TCD) studies to measure the CO2 reactivity of the entire basal cerebral arteries in 30 cases of age-adjusted control group and 42cases of disease group and 42 cases of disease group between the 3rd and 7th day after insult. The disease group involved 14 cases of head injury, 10 cases of intraventricular hemorrhage, 10 cases of subarachnoid hemorrhage and 8 cases of hydrocephalus. All patients were examined by single photon emission computed tomography(SPECT) and results of the 2 groups were compared with respect to their CO2 reactivities. In the patient group, the mean blood flow velocity(MBFV), pusatility index(PI) and MI index(middle cerebral artery MBFV/internal cerebral artery MBFV) had not changed but the CO2 index was significantly lower than that in the same age group of normal control. The regions showing abnormal ROI(region of interest) on SPECT well corresponded with the regions showing decreased CO2 reactivity on TCD. Both the increase of MBFV and the decrease of Pl were noted in the cerebral arteries with decreased CO2 reactivity. This indicates that the very arterial walls were dilated. As for the relationships between the investigated variables, ROI increased as the clinical status worsen(r=-0.05, p=0.0008). The acute prognosis(prognosis after 3month of insult) had positive correlation with CO2 index(r=0.32, p=0.04) of clinical status, while on the other hand, its correlation with ROI index was negative(r=0.40, p=0.0094). Transcranial doppler CO2 test provides useful information for the understanding of hemodynamic status, prognosis and beneficial effects of specific therapy. It is concluded that CO2 index measured during the subacute stage of insult correlates well with the acute prognosis.