Cerebral microdialysis in patients with fulminant hepatic failure

Fulminant hepatic failure (FHF) is often complicated by high intracranial pressure (ICP) and fatal brain damage. In this study, we determined if a rise in [glutamate]ec and [lactate]ec preceded surges of high ICP in patients with FHF (median age, 42; range, 20-55 years; 7 women; 3 men) by inserting a microdialysis catheter into the brain-cortex together with an ICP catheter. The microdialysis catheter was perfused with artificial cerebrospinal-fluid at a rate of 0.3 microL/min. Dialysate was collected approximately every 30 minutes or when ICP increased. A total of 352 microdialysis samples were collected during a median of 3 days and allowed for approximately 1,760 bedside analyses of the collected dialysate. In 5 patients that later developed surges of high ICP, the initial values of [glutamate]ec and [lactate]ec were 2 to 5 times higher compared with patients with normal ICP. [Glutamate]ec then tended to vanish with time in both groups of patients. An increase in [glutamate]ec did not precede high ICP in any of the cases. In contrast, [lactate]ec was high throughout the study in the high ICP group and increased further before surges of high ICP. We conclude that in patients with FHF, cerebral [glutamate]ec and [lactate]ec are elevated. However, the elevated [glutamate]ec is not correlated to high ICP. In contrast, elevations in [lactate]ec preceded surges of high ICP. In conclusion, accelerated glycolysis with lactate accumulation is implicated in vasodilatation and high ICP in patients with FHF. The data suggest that bedside cerebral microdialysis is a valuable tool in monitoring patients with FHF and severe hyperammonemia.