Measuring Partial Pressure of Ammonia in Arterial or Venous Blood VS total Ammonia Levels in Hepatic Encephalopathy

Abstract

AIM: To find out the correlation between clinical grade of hepatic encephalopathy and different serum ammonia levels, namely, serum arterial ammonia, serum venous ammonia, partial pressure of ammonia in arterial plasma and partial pressure of ammonia in venous plasma. METHODS: After informed consent from patients or their relatives, 100 patients in hepatic encephalopathy due to advanced liver disease, were examined for their clinical grade of hepatic encephalopathy within 24 hours of admission. Fasting arterial and venous blood samples were collected and sent to lab within 30 minutes. ection. Blood pH was measured in both samples for each patient. Ammonia levels were measured directly by an enzymatic UV-Method. Partial pressure in a given sample was calculated by the recommended formula, using total ammonia and blood pH of the respective sample. RESULTS: Maximum number of patients (53%) in this study was in clinical grade I of hepatic encephalopathy, 30% were in grade II, and 12% were in Grade III. Only 5% were in grade IV. While comparing means of serum arterial ammonia (0.26049), serum venous ammonia (0.264), partial pressure of ammonia in arterial blood (4.520) and partial pressure of ammonia (4.357) in venous blood with clinical grades of hepatic encephalopathy, they increased with increasing clinical grade of hepatic encephalopathy with p-values of 0.001, 0.01, 0.002, and 0.003 respectively. Partial pressure of ammonia in venous blood was most strongly associated with hepatic encephalopathy (p-value 0.001) followed by serum venous ammonia (p-value 0.002). CONCLUSIONS: Total arterial ammonia, total venous ammonia, partial pressure of arterial ammonia, & partial pressure of venous ammonia, all are positively and significantly correlated with worsening clinical grades of hepatic encephalopathy. Partial pressure of ammonia in venous blood followed by that in serum venous ammonia were most strongly associated with grade of hepatic encephalopathy.