• Reinhard Kitzberger, Georg Christian Funk, Ulrike Holzinger, Wolfgang Miehsler, Ludwig Kramer, Alexandra Kaider, Peter Ferenci, and Christian Madl.
• Department of Gastroenterology, Hepatology and Medical Intensive Care Medicine, Medical University Hospital Vienna, Vienna, Austria. reinhard.kitzberger@meduniwien.ac.at
• Clin. Gastroenterol. Hepatol. 2009 Sep 1;7(9):1000-6.

Background & AimsIonized ammonia (NH(3)) and partial pressure of the gaseous ammonia (pNH(3)) are associated with hepatic encephalopathy and intracranial hypertension in patients with acute liver failure; NH(3) is also believed to contribute to extrahepatic organ failure. We investigated whether the severity of organ failure was associated with intracranial hypertension and evaluated the correlation between NH(3) and pNH(3) and grade of hepatic encephalopathy.MethodsIn 87 patients with acute liver failure admitted to the intensive care unit, we simultaneously evaluated arterial ammonia, pNH(3), clinical grade of hepatic encephalopathy, the sequential organ failure assessment score (SOFA score), and evidence of intracranial hypertension.ResultsIn comparing patients with intracranial hypertension (n = 37) with patients without intracranial hypertension (n = 50), the highest NH(3) and pNH(3) levels and SOFA scores before onset of intracranial hypertension were independent predictors of intracranial hypertension (P < .001). Among patients with NH(3) levels less than 146 mumol/L, those with intracranial hypertension had a higher SOFA score than those without intracranial hypertension (median, 10 vs 5.5; P = .004), despite the patients' similar levels of NH(3). NH(3) (r = 0.68, P < .0001) and pNH(3) (r = 0.78, P < .0001) both correlated with grade of hepatic encephalopathy. However, in multiple regression analysis, only pNH(3) (P < .0001) was shown to be a significant independent parameter for predicting grade of hepatic encephalopathy (P = .27).ConclusionsSOFA score and ammonia levels are independent predictors of intracranial hypertension. In patients with acute liver failure admitted to the intensive care unit, pNH(3) level is a better predictor of clinical grade of hepatic encephalopathy than arterial NH(3) level.

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