Measurement of the expiratory ammonia concentration and its clinical significance
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Alghough gaseous ammonia (NH3) can freely enter cells through the plasma membrane where NH3 is cyto(neuro)toxic, NH3 and ionic ammonia (NH4 +) contents have not been studied in biological materials. We developed a new method for measurement of expiratory NH3 concentration, which may reflect blood NH3 concentrations. The method is a sensor tube type-gas assay system. Expiratory NH3 concentrations in patients with chronic liver diseases increased when their blood ammonia (NH4 ++NH3) concentrations increased above 90 μg/dl (normal range; 12–66 μg/dl). However, cirrhotic patients, who had relatively higher expiratory NH3 concentration compared to blood NH3 concentrations (calculated from Henderson-Hasselbalch formula), were found to have subclinical encephalopathy. Measurement of experatory NH3 concentration may be of clinical significance for the diagnosis of encephalopathy associated with hyperammonemia.
Key wordsAmmonia NH4+ gaseous ammonia expiratory air hepatic encephalopathy liver cirrhosis
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