Source

PET Centre & Department of Nuclear Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Medicine V, Aarhus University Hospital, Aarhus, Denmark. dam@pet.auh.dk.

Abstract

Studies have shown decreased cerebral oxygen metabolism (CMRO(2) ) and blood flow (CBF) in cirrhotic patients with hepatic encephalopathy (HE). It remains unclear, however, whether these disturbances are associated with HE or with cirrhosis itself and how they may relate to arterial blood ammonia concentration and cerebral metabolic rate of blood ammonia (CMRA). We addressed these questions in a paired study design by investigating cirrhotic patients during and after recovery from an acute episode of HE type C. CMRO(2) , CBF, and CMRA were measured by dynamic PET/CT. Ten cirrhotic patients were studied during an acute episode of HE; nine were reexamined after recovery. Nine cirrhotic patients with no history of HE served as controls. Mean CMRO(2) increased from 0.73 μmol oxygen/mL brain tissue/min during HE to 0.91 μmol oxygen/mL brain tissue/min after recovery (paired t-test; P < 0.05). Mean CBF increased from 0.28 mL blood/mL brain tissue/min during HE to 0.38 mL blood/mL brain tissue/min after recovery (P < 0.05). After recovery from HE, CMRO(2) and CBF were not significantly different from values in the control patients. Arterial blood ammonia concentration decreased 20% after recovery (P < 0.05) and CMRA was unchanged (P > 0.30); both values were higher than in the control patients (both P < 0.05). CONCLUSIONS: The low values of CMRO(2) and CBF observed during HE increased after recovery from HE and were thus associated with HE rather than the liver disease as such. The changes in CMRO(2) and CBF could not be linked to blood ammonia concentration or CMRA.