Restoration of cerebral blood flow autoregulation and reactivity to carbondioxide in acute liver failure by moderate hypothermia

In patients with acute liver failure (ALF) and uncontrolled intracranial hy pertension, moderate hypothermia (32 degreesC) reduces intracranial pressur e (ICP) and cerebral blood flow (CBF), and can be used as a bridge to liver transplantation. The purpose of this study was to test the hypothesis that moderate hypothermia reduced ICP by restoring CBF autoregulation. Nine pat ients with uncontrolled intracranial hypertension and ALF who fulfilled the criteria for poor prognosis were studied. CBF autoregulation and reactivit y to carbon dioxide were evaluated before and 4 hours after cooling (32 deg reesC). Significant reductions were observed in the ICP (median, 46 [range, 27-54] mm Hg to 19 [15-22] mm Hg; P < .01) and CBF (median, 111 [69-134] t o 56 [38-67] mL/100 g/min; P < .05). The defective CBF autoregulation and t he absence of reactivity to carbon dioxide that was observed in all patient s was restored with cooling. The results of our study suggest that the impr ovement in ICP observed with hypothermia may be the result of its effects o n CBF autoregulation and provides a tool to explore the mechanisms associat ed with the deranged CBF autoregulation in ALF.