Blood ammonia
- The liver normally removes ammonia during urea synthesis
- Substantial liver failure must be present for blood ammonia to rise
- The test is primarily used to evaluate patients with mental status changes; elevated blood ammonia supports a diagnosis of hepatic encephalopathy
- Disrupted hepatic blood flow patterns in cirrhotic patients cause blood ammonia to elevate after milder degrees of liver failure in that group
- Arterial plasma is the best specimen; smoking should be avoided prior to the test (it raises blood ammonia)
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Last modified:
1/31/97; Author:
J. Harrison