Fatal Encephalopathy Caused by a Urea Cycle Disorder

Ammonia and nutritional therapy in the critically ill: when to worry, when to test and how to treat?

PURPOSE OF REVIEW

Hyperammonaemia is almost always develops in patients with severe liver failure and this remains the commonest cause of elevated ammonia concentrations in the ICU. Nonhepatic hyperammonaemia in ICU presents diagnostic and management challenges for treating clinicians. Nutritional and metabolic factors play an important role in the cause and management of these complex disorders.

RECENT FINDINGS

Nonhepatic hyperammonaemia causes such as drugs, infection and inborn errors of metabolism may be unfamiliar to clinicians and risk being overlooked. Although cirrhotic patients may tolerate marked elevations in ammonia, other causes of acute severe hyperammonaemia may result in fatal cerebral oedema. Any coma of unclear cause should prompt urgent measurement of ammonia and severe elevations warrant immediate protective measures as well as treatments such as renal replacement therapy to avoid life-threatening neurological injury.

SUMMARY

The current review explores important clinical considerations, the approach to testing and key treatment principles that may prevent progressive neurological damage and improve outcomes for patients with hyperammonaemia, especially from nonhepatic causes.

Ornithine Transcarbamylase Deficiency Presenting as Acute Encephalopathy After Strabismus Surgery

Acute encephalopathy with an unclear etiology is a common presentation to the hospital. We describe the case of a 50-year-old male who presented with a one-day history of slurred speech, nausea, insomnia, and altered mental status. His surgical history was notable for a strabismus surgery two days ago. He presented with elevated ammonia levels that continued to increase. Metabolic studies were suggestive of hyperammonemia secondary to ornithine transcarbamylase (OTC) deficiency triggered due to fasting prior to the strabismus surgery. OTC gene sequencing confirmed the diagnosis of OTC deficiency. We summarize the current case reports in the literature and review the treatment options for OTC deficiency. Our case occurred after a low-risk outpatient strabismus surgery and is a good example of maintaining a broad differential and revising the suspected diagnosis constantly.