Cerebral function analyzing monitor and visual evoked potentials as a noninvasive method of detecting cerebral...

We monitored the effect of 7 intermittent machine hemofiltration treatments in 4 patients with fulminant hepatic failure who had progressed to grade IV coma and developed acute oliguric renal failure. Prior to treatment the processed EEG showed excess slow wave activity, and the latency of the later visual evoked potentials (N2 and P2) was delayed. Following treatment there was a further increase in both EEG slow wave activity and latency of the N1, N2, and P2 potentials. Intracranial pressure increased from a median of 8 mm Hg (2-12, range) to 14 (8-28) following treatment, p < 0.05. There was a correlation between intracranial pressure and all of the later visual evoked potentials, for N3 r = 0.71, for P1 r = 0.39, and P2 r = 0.74, all p < 0.05. Although there appeared to be a good correlation between intracranial pressure and the noninvasive electrophysiological recordings, there were major changes in intracranial pressure, cerebral perfusion pressure, and cerebrospinal fluid pH during the first hour of treatment, during which time there were no discernable changes in EEG or evoked potentials. In this study, non-invasive neurophysiological methods were not found to be reliable as invasive methods in assessing acute, minute-by-minute changes in cerebral metabolism but these methods may have a role in the longer term in assessing patient prognosis.