Regional cerebral blood flow during mechanical hyperventilation in patients with fulminant hepatic failure

Hyperventilation is frequently used to prevent or postpone the development of cerebral edema and intracranial hypertension in patients with fulminant hepatic failure (FHF). The influence of such therapy on regional cerebral b lood flow (rCBF) remains, however, unknown, In this study the CBF-distribut ion pattern was determined within the first 12 hours after development of h epatic encephalopathy (HE) stage 4 before and during hyperventilation. Ten consecutive patients (median age 48 [range 33-57] years) with FHF and 9 hea lthy controls (median age 54 [24-58] years) had rCBF determined by single p hoton emission computed tomography (SPECT) using intravenous injection of 1 33Xenon. For determination of high resolution CBF pattern, the patients wer e also studied with 99mTc-hexa-methylpropyleneamine oxime (HMPAO) in the hy perventilation condition. There was no significant difference in the rCBF d istribution pattern during normoventilation as compared with hyperventilati on, The anterior to posterior (AP) ratio was significantly lower in patient s as compared,vith healthy controls. After hepatic recovery and disappearan ce of HE, 3 patients had restored normal rCBF distribution pattern as compa red with healthy controls. We conclude that in sedated patients with FHF, a relatively lower rCBF is found in the frontal regions and in the basal gan glia as compared with posterior regions. This rCBF-distribution pattern was not aggravated during hyperventilation. It is speculated that this change of rCBF in patients with FHF may render the frontal brain regions more susc eptible to hypoxia. The relative frontal rCBF decrease was shown to be reve rsible with hepatic recovery and alleviation of HE.