How to manage elevated ammonia levels in cases of bowel obstruction?

From the Guidelines

Management of elevated ammonia levels in bowel obstruction requires addressing both the underlying obstruction and the hyperammonemia, with initial treatment focusing on resolving the obstruction and administering lactulose at 20-30g (30-45mL) orally or via nasogastric tube every 1-2 hours until bowel movements occur. To directly reduce ammonia levels, the dose of lactulose should be adjusted to 15-30mL 2-3 times daily to maintain 2-3 soft bowel movements daily 1. Rifaximin 550mg twice daily can be added as it reduces ammonia-producing gut bacteria without systemic absorption 1. For severe cases, consider intravenous L-ornithine L-aspartate (LOLA) at 20-40g/day if available, as it can lower plasma ammonia concentrations and produce improvements in hepatic encephalopathy (HE) 1. Protein restriction to 0.5-1.2g/kg/day may be temporarily necessary while addressing the obstruction. Ammonia elevation occurs because bowel obstruction increases bacterial overgrowth and protein breakdown, while impairing ammonia clearance through the enterohepatic circulation. Regular monitoring of ammonia levels, mental status, and electrolytes is essential, as treatment can cause electrolyte imbalances, particularly hypokalemia. Once the obstruction resolves, gradually normalize protein intake and taper medications while monitoring ammonia levels. Key considerations include:

• Resolving the underlying bowel obstruction through nasogastric decompression, fluid resuscitation, and possible surgical intervention
• Administering lactulose and adjusting the dose to maintain 2-3 soft bowel movements daily
• Adding rifaximin for its ability to reduce ammonia-producing gut bacteria
• Considering intravenous LOLA for severe cases
• Temporarily restricting protein intake
• Monitoring ammonia levels, mental status, and electrolytes closely.

From the FDA Drug Label

Lactulose causes a decrease in blood ammonia concentration and reduces the degree of portal-systemic encephalopathy. Controlled studies have shown that lactulose solution therapy reduces the blood ammonia levels by 25 to 50%; The acid colonic contents converts NH3 to the ammonium ion (NH4)+, trapping it and preventing its absorption.

The management of elevated ammonia levels in cases of bowel obstruction may involve the use of lactulose.

• Lactulose has been shown to decrease blood ammonia concentration by 25 to 50% in controlled studies 2.
• It works by acidifying the colonic contents, which traps ammonia in the colon and prevents its absorption into the blood 2.
• The use of lactulose may help reduce the degree of portal-systemic encephalopathy associated with elevated ammonia levels.

From the Research

Management of Elevated Ammonia Levels in Bowel Obstruction

• The management of elevated ammonia levels in cases of bowel obstruction is crucial to prevent further complications, such as hepatic encephalopathy (HE) 3.
• Current treatments for hyperammonemia target the organs and metabolic processes involved in ammonia detoxification, with lactulose and rifaximin being the mainstay of therapy 3.
• Rifaximin has been shown to be effective in reducing the recurrence of overt HE and hospitalizations in patients with cirrhosis, and its use may be beneficial in managing ammonia levels in bowel obstruction cases 4.
• The use of rifaximin with or without lactulose has been found to improve minimal HE, with a lasting effect on microbiota metabolic function even after the end of treatment 5.

Diagnosis and Treatment of Bowel Obstruction

• Bowel obstruction is a common condition that requires prompt diagnosis and treatment to prevent complications, such as strangulation and ischemia of the obstructed bowel loop 6, 7.
• Multidetector computed tomography (MDCT) is the preferred diagnostic tool for suspected bowel obstruction, and reports should focus on confirming the obstruction, determining the cause, and seeking signs of complications 7.
• Treatment of bowel obstruction typically involves intravenous fluid resuscitation, analgesia, and determining the need for operative vs. nonoperative therapy, with surgery being necessary for strangulation and cases that fail nonoperative therapy 6.

Ammonia Levels and Bowel Obstruction

• Elevated ammonia levels can occur in cases of bowel obstruction, particularly if the obstruction is complete and complicated, leading to mucosal ischemia and necrosis 6.
• The management of ammonia levels in bowel obstruction cases should be tailored to the individual patient, taking into account the underlying cause of the obstruction and the presence of any complications, such as HE 3, 4.