S2532 Hyperammonemia Over 500 µmol/L as a Cause of the Seizure

Abstract

INTRODUCTION: Hyperammonemia is a dangerous metabolic disturbance characterized by an excess of ammonia in the blood that may lead to cerebral edema, brain injury, and death. It is commonly secondary to acute or chronic liver failure, inborn errors of metabolism, upper gastrointestinal bleeding, medication-induced, chemotherapy, and non-hepatic causes such as ureterosigmoidostomy, and infections. Hyperammonemia is a life-threatening condition that can affect patients of any age. Elevations of ammonia in plasma could be either from increased production or decreased detoxification. The hepatic urea cycle is the main pathway to detoxify ammonia. It can become defective due to an inherited enzyme deficiency or secondary to accumulated toxic metabolites. CASE DESCRIPTION/METHODS: An 83-Year-old female with history of chronic kidney disease presented with acute loss of motor function in the bilateral lower extremities and areflexia. The initial working diagnosis was cord infarct or cord related to lower motor neuron disease. Lumbar puncture and spinal cord MRI were unrevealing. Ammonia level was 595µmol/L. The patient was transferred to ICU where she started to have seizures. She was started on lactulose and Keppra. CTA of the abdomen showed extensive atherosclerotic changes in her mesenteric vessels. She was started on continuous dialysis, but became hypotensive requiring inotropes and later expired. DISCUSSION: There is a poor correlation between plasma ammonia levels and patients' mental status. However, studies have shown that sustained ammonia levels above 150 to 200 µmol/L greatly increase intraneuronal osmolality and increase the risk for intracranial hypertension leading to encephalopathy. An absolute ammonia level above which dialysis is recommended in adults is not well defined and relies heavily on clinical evaluation. Monitoring ammonia levels, neurologic status, arterial or venous pH, and hemodynamic parameters in hyperammonemia patients could prompt for acute dialysis. Dialysis can be discontinued once the mental status is restored to the baseline and ammonia levels have declined or stabilized. Hyperammonemia must be excluded in patients with an unexplained change in consciousness or encephalopathy. Early detection and treatment of hyperammonemia with medical and supportive management is crucial. Ammonia is a dialyzable agent and can be easily removed via renal replacement therapy.