POST-GASTRIC BYPASS HYPERAMMONEMIC ENCEPHALOPATHY: A RARE AND POTENTIALLY FATAL CAUSE OF ENCEPHALOPATHY IN THE ICU

Abstract

TOPIC: Critical Care TYPE: Fellow Case Reports INTRODUCTION: In the US the prevalence of obesity has risen to 39.8% and affected about 93.3 million of US adults in 2015. Morbidly obese patients are increasingly pursuing bariatric surgery. While the benefits of bariatric surgery are numerous, it is important to recognize and understand the short term and long term postoperative complications. Hyperammonemic syndrome is an uncommon but severe complication of gastric bypass surgery. CASE PRESENTATION: A 43 year old woman with history of non-alcoholic fatty liver disease and history of prior gastric sleeve which was followed by Roux-en-Y Gastric Bypass (RYGB) surgery was admitted for shortness of breath and altered mental status. On hospital day number 10 patient was transferred to ICU for altered mental status, worsening hypoxia, retroperitoneal bleed and septic shock. Patient was subsequently intubated, given transfusions, placed on vasopressors, and given broad-spectrum antibiotics. After 72 hours her overall shock resolved and her ventilator requirements were minimal, but she remained in a comatose state. Initial workup including CT head and brain MRI were unremarkable. Initial routine EEG was consistent with low voltage delta frequencies which could be seen in the setting of severe encephalopathy. Ammonia level had risen to 169 umol/L, which was significantly elevated from prior level of 81 umol/L on admission (Table 1). In addition to aggressive treatment with lactulose and rifaximin, multiple supplements were added, including: Zinc, multivitamin, and L-carnitine. Subsequent EEG on ICU revealed myoclonic status epilepticus for which antiepileptic drugs were given. Repeat MRI of the brain revealed increased diffusion-weighted signal intensity within the cortex and subcortical white matter of suggesting hypoxic and anoxic brain injury. DISCUSSION: Hyperammonemic syndrome related to bariatric surgery is characterized by hyperammonemia, elevated plasma glutamine, hypoalbuminemia, reactive hypoglycemia, nutritional deficiencies of essential amino acids, and low zinc levels, in the absence of overt liver fibrosis or evidence of significant hepatocellular injury (1). The mortality rate approaches 50% and it tends to occur at a high rate in women (1). Patients may present with irritability, vomiting, ataxia, mental retardation, lethargy, and eventually alteration in consciousness and coma (1). There are multiple genetic and nongenetic hypothesized mechanisms (Table 2). Treatment strategies for hyperammonemia include: lactulose, rifaximin, repletion of deficient amino acids, zinc, micro nutrients, and prevention of seizures and cerebral edema (2). CONCLUSIONS: It is important to consider hyperammonemia related to bypass as a potential etiology for neurologic changes in patients with prior bypass, especially in the ICU setting where multiple etiologies can cause encephalopathy and hyperammonemia. REFERENCE #1: Fenves, A. et al. "Hyperammonemic Syndrome After Roux-En-Y Gastric Bypass." Obesity Journal. Volume 23. Number 4. 2015. REFERENCE #2: Krishnan P, Ramdas P, Landsberg. "Bariatric Surgery causing hyperammonemia." Cureus 11 (7): e5098. DOI 10.7759/cureus.5098. July 8, 2019 DISCLOSURES: No relevant relationships by SOHAIB KHAN, source=Web Response No relevant relationships by Jessica Nash, source=Web Response No relevant relationships by Mehul Patel, source=Web Response No relevant relationships by Mena Tawfik, source=Web Response