Gastroenterology · Liver Disease
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Hepatic encephalopathy is primarily caused by the accumulation of ammonia due to impaired hepatic clearance and portosystemic shunting.
The classic physical exam finding is asterixis, a coarse, flapping tremor elicited by extending the wrists.
Precipitating factors for acute episodes include gastrointestinal bleeding, constipation, infection (specifically spontaneous bacterial peritonitis), and hypokalemia.
First-line pharmacologic treatment is lactulose, which works by acidifying the gut lumen to convert ammonia to non-absorbable ammonium.
Rifaximin is the preferred add-on therapy for patients who have recurrent episodes despite adequate lactulose treatment.
The diagnosis of hepatic encephalopathy is clinical, and serum ammonia levels do not correlate well with the severity of symptoms.
Dietary protein restriction is not recommended; target 1.2-1.5 g/kg/day of protein, with branched-chain amino acid supplementation if intake is inadequate.
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A 58-year-old male with a history of cirrhosis secondary to alcohol use disorder is brought to the emergency department by his daughter due to increased confusion. She reports he has been sleeping during the day and awake at night for the past 48 hours. On physical examination, the patient is disoriented to time and place, and demonstrates asterixis when asked to extend his wrists. His abdomen is distended with a positive fluid wave. Laboratory studies show no fever or leukocytosis.
What is the most appropriate initial pharmacologic treatment for this patient's condition?
Lactulose
The patient presents with classic signs of hepatic encephalopathy, and lactulose is the first-line treatment to reduce ammonia absorption by promoting its excretion in the stool.
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Etiology / Epidemiology
Occurs in patients with cirrhosis or portosystemic shunting; triggered by GI bleed, constipation, or infection.
Clinical Manifestations
Characterized by asterixis, altered mental status, and fetor hepaticus.
Diagnosis
Clinical diagnosis; serum ammonia is often elevated but does not correlate with severity.
Treatment
Lactulose is first-line; avoid sedatives that worsen mental status.
Prognosis
Recurrence is common; 5-year survival is poor once overt episodes occur.
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Epidemiology & Etiology
Precipitated by factors increasing nitrogenous load, most notably GI hemorrhage (blood protein breakdown). Other common triggers include hypokalemia, metabolic alkalosis, and diuretic overuse. Patients with transjugular intrahepatic portosystemic shunt (TIPS) are at high risk; start rifaximin 14 days before elective TIPS and continue at least 6 months to reduce post-TIPS overt HE.
Pertinent Anatomy
The portal venous system normally delivers gut-derived toxins to the liver for metabolism. In cirrhosis, collateral circulation allows neurotoxins to bypass the liver and enter systemic circulation, directly affecting the blood-brain barrier.
Pathophysiology
The liver fails to convert ammonia (a byproduct of protein metabolism) into urea. Elevated systemic ammonia crosses the blood-brain barrier, causing astrocyte swelling and cerebral edema. This leads to impaired neurotransmission, specifically involving GABAergic tone and glutamine accumulation.
Clinical Manifestations
Patients present with a spectrum from sleep-wake cycle reversal to coma. The hallmark physical finding is asterixis (flapping tremor). Look for fetor hepaticus (musty breath odor) and seizures, which are rare and suggest an alternative diagnosis.
Diagnosis
Diagnosis is clinical based on history and physical exam. Serum ammonia levels are supportive but not diagnostic; do not rely on them to grade severity. Mental status examination and the West Haven Criteria are used to stage the disease.
Treatment
Initiate Lactulose, titrated to 2-3 soft bowel movements daily, to acidify the gut lumen and convert ammonia to non-absorbable ammonium; PEG 3350 is an alternative if lactulose is not tolerated. Titrate lactulose to 2-3 soft bowel movements daily; rifaximin is added to lactulose in acute overt HE and is recommended as add-on therapy for breakthrough episodes on lactulose maintenance. Avoid benzodiazepines and other CNS depressants, as they precipitate or worsen the condition.
Prognosis
Development of overt encephalopathy indicates advanced decompensated cirrhosis. Patients should be evaluated for liver transplantation. Monitor for spontaneous bacterial peritonitis as a common concurrent trigger.
Differential Diagnosis
Subdural hematoma: focal neurological deficits present
Wernicke encephalopathy: classic triad of ataxia, ophthalmoplegia, and confusion
Alcohol withdrawal: autonomic hyperactivity and tremors
Hypoglycemia: rapid resolution with glucose administration
Uremic encephalopathy: markedly elevated BUN/creatinine with asterixis and myoclonus