Reduction of Cerebral Blood Flow in Subclinical Hepatic Encephalopathy and its Correlation with Plasma-Free Tryptophan

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Abstract
Cerebral blood flow (CBF), measured by the noninvasive xenon-133 inhalation method, EEG, and plasma levels of ammonia (NH3) and free tryptophan were determined in 18 hospitalized cirrhotic patients affected with subclinical hepatic encephalopathy, as diagnosed by the Kurtz test. CBF results were significantly lower (p < 0.001) in the patients' group as compared with a sex- and age-matched normal control population, although seven patients had values in the normal range. NH3 was increased only in six, while free tryptophan was increased in all but two patients. A significant negative correlation (p = 0.02) between CBF and free tryptophan was found, even though it appears to be difficult to interpret. We suggest that CBF impairment in some cirrhotic patients with subclinical hepatic encephalopathy may be related to the systemic metabolic derangement caused by the liver disease; free tryptophan could have some implication in producing CBF reduction.