A diseased liver cannot detoxify protein metabolites, such as ammonia, leading to increased levels in the blood. Liver damage prevents use of metabolites in your body because the liver is unable to filter, convert or utilize end-products. Ammonia, produced by bacterial activity on protein in the intestine, is absorbed and transported to the liver. The liver degrades ammonia into end products and waste products. Ammonia can circumvent a diseased liver and collect in the blood.
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High blood ammonia levels can affect your brain, which is permeable to ammonia and highly sensitive to the toxic effects. Symptoms of toxicity might include confusion, lethargy, altered attention span and poor coordination. Increased ammonia levels in the brain can lead to swelling, edema, increased intracranial pressure and possible brain herniation. A clinical diagnosis, based on complaints, signs, symptoms and lab values, requires further research to exclude other significant causes of mental status changes.
Plasma ammonia level is the test to determine ammonia content in your blood. But elevated levels might not reflect liver disease since increases also occur with congestive heart failure, gastrointestinal hemorrhage, certain medications and consuming protein before the test. Testing can indicate worsening liver disease, monitor treatment, and aid in the diagnosis of approaching hepatic coma. Remember that toxic levels can be higher in the brain than might be reflected in the blood.
Laxative use is crucial to lowering ammonia levels in your gastrointestinal tract. The primary laxative used is lactulose, which alters your bacterial flora and makes fewer organisms available to produce ammonia. Lactulose dosages are regulated until 3 to 4 soft bowel movements occur daily. Another is magnesium citrate, frequently used to remove bloody stool after intestinal bleeding and administered via nasogastric tube to expedite blood removal.
Administering an antibiotic by the oral route, rather than intravenously, restricts the antibacterial action to only the gastrointestinal tract where it's needed. The primary goal is to reduce ammonia-producing bacteria from the intestine. Three of those antibiotics are neomycin, vancomycin and rifaximin. Occasionally, both an antibiotic and lactulose are given to reduce bacteria and improve clearance in the intestine. Administering at separate intervals prevents lactulose from removing the antibiotic too quickly.
Another method used to decrease ammonia production might include a temporary reduction in protein intake through diet. It can also include reducing or eliminating medications broken down by the liver, lowering the liver's workload. Avoiding medications that contain ammonium, such as antacids, are included in restrictions.
- Drugs.com: Rifaximin
- Lab Tests Online: Ammonia
- "The Hospitalist"; What Is the Best Therapy for Acute Hepatic Encephalopathy?; Marwa Shoeb, M.D., and Jennifer Best, M.D.; April 2010
- MedlinePlus: Lactulose
- "Cleveland Clinic Journal of Medicine"; What is the utility of measuring the serum ammonia level in patients with altered mental status?; Hesham M. Elgouhari, M.D.; April 2009