Why are blood ammonia levels typically measured?

Blood ammonia levels are typically measured primarily to assess liver function, particularly in cases of hepatic coma or hepatic failure. When the liver is functioning properly, it converts ammonia, a toxic byproduct of protein metabolism, into urea, which is then excreted by the kidneys. In situations where the liver is compromised, such as in severe liver disease or liver failure, this process is impaired, leading to an accumulation of ammonia in the bloodstream. Elevated ammonia levels can indicate that the liver is not performing its detoxification role adequately, which can contribute to the development of hepatic encephalopathy—a serious condition that affects brain function due to liver failure. Therefore, measuring blood ammonia levels serves as an important diagnostic tool in evaluating the severity of liver dysfunction and the potential for encephalopathy in patients with liver disease.

The other options relate to different physiological functions and disorders. For instance, while kidney function and metabolic acidosis can involve other metabolic byproducts, blood ammonia specifically is not a primary marker for these conditions. Monitoring blood glucose levels pertains to diabetes management rather than ammonia levels, and while respiratory failure can lead to various metabolic disturbances, it does not directly involve measuring blood ammonia for assessment purposes.