Hyperventilation restores cerebral blood flow autoregulation in patients with acute liver failure

G Strauss, B A Hansen, G M Knudsen, F S Larsen

Abstract

BACKGROUND/AIMS: In patients with acute liver failure loss of cerebral blood flow autoregulation may result from cerebral vasodilatation. Since arterial hypocapnia induces cerebral vasoconstriction, we investigated whether cerebral blood flow autoregulation could be reestablished by mechanical hyperventilation.

METHODS: Seven consecutive patients (median age 45, range 30-50 years) with acute liver failure and hepatic encephalopathy stage IV entered the study. They were all maintained on mechanical ventilation. Cerebral blood flow autoregulation was evaluated by using transcranial Doppler sonography to assess mean flow velocity (Vmean) in the middle cerebral artery, during a rise in mean arterial pressure by norepinephrine infusion (0.5-10 microg/h). The patients were subsequently hyperventilated for 15 min before cerebral blood flow autoregulation was re-evaluated in the same mean arterial pressure range.

RESULTS: At baseline PaCO2 (4.0 (3.5-4.9)kPa), all patients had impaired cerebral blood flow autoregulation as Vmean increased from 47 (30-78) to 68 (49-107) cm x s(-1) (p<0.05), as MAP was raised from 82 (60-88) to 106 (89-123) mmHg. During hyperventilation, five of seven patients restored cerebral autoregulation as Vmean remained unchanged at 51 (45-70) cm x s(-1) during a rise in MAP from 84 (65-94) to 110 (89-130) mmHg. Cerebral blood flow autoregulation was not restored in two patients, but hyperventilation reduced the slope of the mean arterial pressure-Vmean correlation. These two patients had renal failure and were treated with intermittent hemodialysis.

CONCLUSIONS: Cerebral blood flow autoregulation was restored by hyperventilation in five of seven patients with acute liver failure, indicating that cerebral vasodilatation is of pathophysiological importance in dysregulation of cerebral circulation in acute liver failure.

Original languageEnglish
JournalJournal of Hepatology
Volume28
Issue number2
Pages (from-to)199-203
Number of pages5
ISSN0168-8278
DOIs
Publication statusPublished - Feb 1998
Externally publishedYes

Keywords

  • Adult
  • Cerebrovascular Circulation/physiology
  • Female
  • Hepatic Encephalopathy/diagnostic imaging
  • Homeostasis/physiology
  • Humans
  • Hyperventilation
  • Liver Failure, Acute/physiopathology
  • Male
  • Middle Aged
  • Respiration, Artificial
  • Treatment Outcome
  • Ultrasonography, Doppler, Transcranial

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