Step 6: Assess/Treat Cerebral Edema 

Cerebral edema resulting from rapid accumulation of ammonia in the brain is the most common cause of death in patients with HE.⁹ While ammonia levels generally do not help diagnose or prognosticate hepatic encephalopathy (a fact many are surprised to learn), a Danish study suggests that arterial ammonia levels >150 µmol/L, measured within 24 hours of reaching grade III hepatic encephalopathy, were associated with a higher likelihood of developing cerebral edema.¹⁰ Cerebral edema in these patients may be clinically subtle, so maintain suspicion in comatose patients with HE. If signs of raised intracranial pressure are present, keep the head of the bed elevated at 45 degrees and consider hypertonic saline (20 mL of 30 percent sodium chloride targeting a serum sodium level of 145–150 mmol/L). Mannitol is not recommended for treating cerebral edema in this setting.¹¹ 

Step 7: Consider Rifaximin for Antimicrobial Coverage 

Rifaximin 400–550 mg orally is the antibiotic of choice for long-term maintenance in patients with recurrent HE because it is poorly absorbed in the gut and therefore both reaches and covers ammonia–producing E. coli. Initiating this drug in the emergency department is reasonable. Rifaximin in combination with lactulose is effective for the prevention of HE recurrence.¹² 

Summary 

Next time you are faced with an altered LOA patient who is flapping their wrists as soon as you extend them, remember that HE is a clinical diagnosis and that serum ammonia levels are unreliable. Assume high central nervous system ammonia levels and treat with lactulose and/or polyethylene glycol and rifaximin. Intravenous albumin must be considered in the patient with HE, especially if they are in acute liver failure and have a low threshold to treat for HE on speculation because it is a diagnosis of exclusion. 

A special thanks to Dr. Walter Himmel and Dr. Brian Steinhart, the guest experts on the EM Cases podcast that inspired this article.

References

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