A51-56 When the Urea Cycle Fails: Catabolic Crisis Leading to Cerebral Edema and Status Epilepticus

Introduction Ornithine transcarbamylase deficiency is the most common urea cycle disorder causing accumulation of ammonia and glutamine. Though typically a pediatric disease, increasingly this patient population is surviving into adulthood. Adults with OTC deficiency often present with acute hyperammonemic encephalopathy, cerebral edema or other neurologic emergencies often triggered by catabolic stress, high-protein intake, or illness. Prompt recognition and treatment are critical to prevent irreversible neurologic injury and death. Case A 23-year-old woman with OTC deficiency, developmental delay, epilepsy, and schizophrenia was admitted for acute encephalopathy following a psychiatric crisis. She presented with suicidal ideation and rising ammonia levels, peaking at 499µmol/L. Quickly in her course she became obtunded, developed cerebral edema and developed refractory status epilepticus. Her case was managed by a multidisciplinary team including intensivists, neurologists, clinical pharmacists, pediatric geneticists and dietician. She was started on a regimen of glycerol and sodium phenylbutyrate, citrulline, sodium benzoate, and strict protein restriction. She was started on multiple anti-seizure medications (lacosamide, brivaracetam, midazolam, perampanel) and CRRT for ammonia clearance. Following resolution of her status epilepticus she was weaned off of all sedatives however did not return to neurologic baseline. Brain imaging was significant for sequelae of anoxic brain injury and progressive cerebral atrophy. She underwent tracheostomy placement and was discharged to a long-term care facility. Discussion This case illustrates neurologic complications resulting from acute metabolic decompensation ina patient with OTC deficiency. Management of OTC deficiency in adults focuses on rapid recognition and ammonia reduction to prevent cerebral edema and herniation. Renal replacement therapy provides the most efficient clearance, with intermittent hemodialysis preferred for rapid reduction and continuous kidney replacement therapy for stabilization. Pharmacologic therapy includes intravenous ammonia scavengers—sodium phenylacetate and sodium benzoate—which provide alternative nitrogen excretion pathways. These should be initiated promptly and continued until oral therapy resumes. Nutritional management aims to reverse catabolism and prevent further ammonia production. Total caloric intake should reach 100-120% of estimated needs, primarily from glucose and fat, with temporary protein restriction. Protein should be reintroduced within 24 hours once ammonia stabilizes, guided by amino acid profiles. Neuroprotective strategies include continuous EEG monitoring for seizure detection, as clinical signs may be absent in sedated patients. Liver transplantation may be considered in metabolically unstable or recurrent cases. Conclusion Adult ICU management of OTC deficiency requires rapid ammonia clearance, scavenger therapy, reversal of catabolism, individualized nutrition, and vigilant neurologic monitoring to prevent irreversible injury. This abstract is funded by: None