CEREBRAL BLOOD-FLOW VELOCITY IN PATIENTS WITH SUBCLINICAL PORTAL-SYSTEMIC ENCEPHALOPATHY

Alterations in cerebral blood flow (CBF) are implicated in the etiolog y of portal-systemic encephalopathy. We hypothesized that CO2 reactivi ty of the cerebral circulation may be impaired in subjects with chroni c liver disease (CLD) who also had subclinical portal-systemic encepha lopathy (SPSE). We compared the relationship between PETCO2 and cerebr al blood flow velocity in 10 patients with CLD with those of 10 health y control subjects. Middle cerebral artery mean blood flow velocity (M CAMFV) was measured using transcranial Doppler during rest, hyperventi lation, and hypoventilation. The degree of SPSE was quantified by usin g psychometric testing. Patients with CLD had poorer psychometric test scores compared with control subjects. Patients with CLD had lower PE TCO2, MCAMFV, and blood pressure Values and higher heart rates, differ ing from control subjects in all ventilation states. However, CO2 reac tivity, the rate of change in MCAMFV to changes in ventilation (expres sed as percent change in CBF velocity per mm Hg change in PETCO2) was similar for both groups (4.6% +/- 0.6% vs 4.2% +/- 0.5% for patients w ith CLD versus control subjects, P = 0.15). Implications: Psychometric test scores in patients with chronic liver disease revealed subclinic al impairment compared with control subjects. Transcranial Doppler mea surements of middle cerebral artery blood flow with varying PETCO2 wer e conducted, but the CO2 response of patients with liver disease was w ithin the range of control subjects.