BYPASSING THE UREA CYCLE IN THE ICU

Abstract

SESSION TITLE: Medical Student/Resident Critical Care Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Hyperammonemic encephalopathy is a rare, yet devastating complication of Rou-en-Y gastric bypass surgery. Though the mechanisms which underlie this complication are not completely understood, a partial underlying inborn error of metabolism has been proposed. In this case we describe a patient who presented with worsening altered mental status and ultimately improved after empiric treatment for a partial urea cycle disorder. CASE PRESENTATION: A 45 year-old female with a history of Roux-en-Y gastric bypass and recently diagnosed bilateral pulmonary emboli presented with altered mental status. One day prior to admission, she became lethargic and ultimately unresponsive, prompting her family to bring her to the hospital. She had 60 lbs of weight loss in the last 2 months, which her family attributed to poor oral intake. In the last 6 months, she had multiple episodes of dizziness, falls, and syncope as well as multiple admissions for nausea, intractable vomiting, and abdominal pain. On presentation, the patient was hemodynamically stable.Abdominal ultrasound revealed changes consistent with steatosis without evidence of cirrhosis. Laboratory results were significant for elevated ammonia (169 µmol/L) and INR (1.7). The patient was started on lactulose and rifaximin for suspected hepatic encephalopathy. After three days of therapy, the patient’s mental status declined and ammonia levels had increased to 192 µmol/L. She was intubated and started on continuous renal replacement therapy (CRRT) for ammonia clearance. Mental status improved. However, cessation of CRRT resulted in increased ammonia levels and worsening mental status. Further laboratory studies revealed deficiencies in zinc, selenium, and copper. Given the refractory hyperammonemia, encephalopathy, and history of gastric bypass surgery, the patient was started on treatment for a suspected partial urea cycle disorder, including arginine and sodium benzoate, as well as supplementation of zinc and copper, resulting in improvement of ammonia levels and mental status. Ultimately, the patient was discharged to an outside facility. DISCUSSION: Encephalopathy in the ICU patient is a frequent occurrence, and may be due to a myriad of metabolic derangements. Inborn errors of metabolism are not common in adult ICU patients, but should be considered in those with a history of gastric bypass surgery presenting with refractory hyperammonemia. As seen in our case, this deadly complication may be reversible with prompt initiation of empiric treatment. CONCLUSIONS: A rare complication of Rou-en Y gastric bypass surgery, hyperammonemic encephalopathy should be considered in patients with refractory hyperammonemia and a history of gastric bypass surgery. Reference #1: Fenves, A.Z., Shchelochkov, O.A. and Mehta, A. (2015), Hyperammonemic syndrome after Roux-en-Y gastric bypass. Obesity, 23: 746-749. doi:10.1002/oby.21037 Reference #2: Nagarur, A., & Fenves, A. Z. (2017). Late Presentation of Fatal Hyperammonemic Encephalopathy After Roux-En-Y Gastric Bypass. Baylor University Medical Center Proceedings, 30(1), 41–43. doi: 10.1080/08998280.2017.11929521 DISCLOSURES: No relevant relationships by Abigail Go, source=Web Response No relevant relationships by John Mwangi, source=Web Response No relevant relationships by Ara Vartanyan, source=Web Response