From the Guidelines
In a patient with elevated ammonia and altered mental status (AMS) without known liver disease, immediate and comprehensive workup is crucial to identify the underlying cause and prevent further neurological damage. The next steps should include confirming the ammonia elevation with repeat testing, as ammonia levels can be variable and may not always correlate with the severity of the condition 1.
Key Considerations
- Simultaneously initiate treatment with lactulose (15-30 mL orally every 4-6 hours, titrated to 2-3 soft bowel movements daily) and rifaximin (550 mg twice daily) to reduce ammonia levels, even in the absence of known liver disease, as hyperammonemia can cause significant neurological damage 1.
- Urgent diagnostic evaluation should encompass a comprehensive metabolic panel, complete blood count, coagulation studies, and liver function tests to assess for previously undiagnosed liver disease or other metabolic derangements.
- Additional testing should include abdominal imaging (ultrasound or CT) to evaluate for structural abnormalities, toxicology screening to identify potential toxins or drugs contributing to AMS, and evaluation for infections that could cause both AMS and metabolic derangements.
- Consider less common causes such as urea cycle disorders, certain medications (valproic acid, carbamazepine), urinary tract infections with urease-producing bacteria, portosystemic shunts, or severe muscle catabolism, as these can also lead to elevated ammonia levels and AMS.
Supportive Care
- If the patient is critically ill, provide supportive care including airway protection if needed, as the neurotoxic effects of ammonia can lead to rapid deterioration.
- The urgency of the situation stems from ammonia's potential to cause cerebral edema and worsening encephalopathy if not promptly addressed, highlighting the need for rapid diagnosis and treatment 1. Given the potential for significant neurological damage from hyperammonemia, a thorough and expedited evaluation is essential, prioritizing the identification and management of the underlying cause to improve morbidity, mortality, and quality of life outcomes.
From the FDA Drug Label
For the prevention and treatment of portal-systemic encephalopathy, including the stages of hepatic pre-coma and coma. The FDA drug label does not answer the question.
From the Research
Evaluating Elevated Ammonia Levels in Altered Mental Status (AMS)
- In a patient with AMS and no history of liver disease, elevated ammonia levels can be caused by various factors, including hyperammonemic encephalopathy (HE) associated with multiple myeloma 2.
- The next steps in evaluating elevated ammonia levels in such a patient may include:
- Ruling out other potential causes of AMS, such as infection, and addressing them accordingly 2.
- Considering the possibility of HE, especially if the patient has a history of multiple myeloma or other conditions that may lead to hyperammonemia 2, 3.
- Initiating treatment with lactulose and rifaximin, although these medications may be ineffective if used solely 2.
- Evaluating the patient's medication history, as certain medications such as valproate can cause hyperammonemic encephalopathy 4.
- It is essential to note that hyperammonemia can occur without liver disease, and a thorough evaluation is necessary to rule out other etiologies of AMS 2, 3, 5.
- In some cases, patients with elevated ammonia levels may not require lactulose or rifaximin, and other treatments such as intravascular resuscitation may be beneficial 6.
- Amino acid analysis may be helpful in diagnosing underlying conditions such as urea cycle disorders, which can cause recurrent altered mental state associated with nonhepatic hyperammonemia 3.