Correlation between ammonia levels and the severity of hepatic encephalopathy.
OBJECTIVE
Because the correlation between ammonia levels and the severity of hepatic encephalopathy remains controversial, we prospectively evaluated the correlation in 121 consecutive patients with cirrhosis.


METHODS
The diagnosis of hepatic encephalopathy was based on clinical criteria, and the severity of hepatic encephalopathy was based on the West Haven Criteria for grading of mental status. Arterial and venous blood samples were obtained from each patient. Four types of ammonia measurements were analyzed: arterial and venous total ammonia, and arterial and venous partial pressure of ammonia. Spearman rank correlations (r(s)) were calculated.


RESULTS
Of the 121 patients, 30 (25%) had grade 0 encephalopathy (no signs or symptoms), 27 (22%) had grade 1, 23 (19%) had grade 2, 28 (23%) had grade 3, and 13 (11%) had grade 4 (the most severe signs and symptoms). Each of the four measures of ammonia increased with the severity of hepatic encephalopathy: arterial total ammonia (r(s) = 0.61, P < or = 0.001), venous total ammonia (r(s) = 0.56, P < or = 0.001), arterial partial pressure of ammonia (r(s) = 0.55, P < or = 0.001), and venous partial pressure of ammonia (r(s) = 0.52, P < or = 0.001).


CONCLUSIONS
Ammonia levels correlate with the severity of hepatic encephalopathy. Venous sampling is adequate for ammonia measurement. There appears to be no additional advantage of measuring the partial pressure of ammonia compared with total ammonia levels.
Ong
Janus P
JP
Department of Gastroenterology, Cleveland Clinic Foundation, Cleveland, Ohio, USA.
Aggarwal
Anjana
A
Krieger
Derk
D
Easley
Kirk A
KA
Karafa
Matthew T
MT
Van Lente
Frederick
F
Arroliga
Alejandro C
AC
Mullen
Kevin D
KD
D000328:Adult; D000368:Aged; D000641:Ammonia / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis / Q000379:methods; D001795:Blood Pressure Determination / Q000379:methods; D005260:Female; D006501:Hepatic Encephalopathy / Q000097:blood* / Q000145:classification* / Q000453:epidemiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009820:Ohio / Q000453:epidemiology; D010313:Partial Pressure; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012720:Severity of Illness Index; D013223:Statistics as Topic / Q000379:methods
D015415:Biomarkers; D000641:Ammonia