Management of Acute Urea Poisoning in a 57-Year-Old Male
The next best step is to immediately initiate hemodialysis while simultaneously starting supportive care with intravenous glucose (8-10 mg/kg/min), stopping all protein intake, and administering nitrogen-scavenging agents (sodium benzoate and/or sodium phenylacetate). 1, 2
Immediate Priorities
Contact Poison Control and Stabilize
- Call the Poison Control Center (1-800-222-1222 in the US) immediately for specialized toxicological guidance, as board-certified toxicologists can provide expert treatment recommendations for this rare presentation 1, 3
- Establish airway management, provide 100% oxygen, and ensure hemodynamic support before the specific diagnosis is confirmed—supportive care takes precedence over everything else 1, 3
Assess Ammonia Level Urgently
- If ammonia level is >200 μmol/l (340 μg/dl), emergent hemodialysis is mandatory as the risk of fatal cerebral edema exceeds 55% at this threshold 4
- For ammonia levels 150-200 μmol/l, prepare for dialysis while initiating medical management 1
- Hemodialysis is the most effective modality for rapidly reducing blood ammonia levels in hyperammonemic encephalopathy 2, 5
Medical Management (Initiate Simultaneously)
Reduce Ammonia Production
- Stop all protein intake immediately 1, 5
- Administer intravenous glucose at 8-10 mg/kg/min to prevent catabolism 1
- Provide intravenous lipids 0.5 g/kg daily (up to 3 g/kg daily) to maintain caloric intake ≥100 kcal/kg daily 1
Nitrogen Scavenging Agents
- Administer intravenous sodium benzoate: For adults >20 kg, give 5.5 g/m² over 90 minutes as bolus, then as continuous maintenance over 24 hours (maximum 12 g daily—high doses can be toxic and lethal within 1 hour) 1
- Administer intravenous sodium phenylacetate: For adults >20 kg, give 5.5 g/m² over 90 minutes as bolus, then as maintenance over 24 hours 1
- Administer intravenous L-arginine hydrochloride: For adults >20 kg, give 4 g/m² over 90 minutes as bolus, then as maintenance over 24 hours 1
Alternative/Adjunctive Therapies
- Lactulose is NOT first-line for urea cycle disorders but may be considered as adjunctive therapy if hemodialysis is delayed 1, 6
- Intravenous L-ornithine-L-aspartate (LOLA) 30 g/day can lower plasma ammonia concentrations 1
Dialysis Strategy
Modality Selection
- Hemodialysis is superior to continuous renal replacement therapy (CRRT) and peritoneal dialysis for rapid ammonia removal 1, 2
- Intermittent hemodialysis and CKRT have proven more efficacious than peritoneal dialysis for hyperammonemia 1
- Continuous hemofiltration is also effective but slower than hemodialysis 2
Indications for Dialysis
- Ammonia level >200 μmol/l (340 μg/dl): Emergent hemodialysis mandatory 4
- Ammonia level 3-4 times upper limit of normal with encephalopathy: Initiate dialysis 2
- Severe encephalopathy (West-Haven grade 3-4) with seizures: Prepare for dialysis while starting scavenging agents 1
Monitoring and Complications
Neurological Monitoring
- Monitor for signs of cerebral edema: altered mental status, seizures, coma 7, 4, 5
- Persistent hyperammonemia causes irreversible neuronal damage if not treated rapidly 2
- Clinical status should be the primary determinant of treatment escalation, not just numerical ammonia values 1
Common Pitfalls to Avoid
- Do NOT delay hemodialysis if ammonia is >200 μmol/l—medical management alone is insufficient at this level 4
- Do NOT administer anything by mouth unless advised by poison control, as this may be harmful 1, 8
- Do NOT exceed maximum sodium benzoate dose of 12 g daily—high doses can be toxic and lethal within 1 hour 1
- Do NOT use neomycin or metronidazole for ammonia reduction due to nephrotoxicity, ototoxicity, and peripheral neuropathy risks 1