Food Shall Be Thy Remedy: Hyperammonemic Coma Reversed by L-Carnitine Supplementation

Abstract

Gastric bypass related hyperammonemia (GaBHA) is a rare and potentially fatal complication following bariatric surgery. Proposed mechanisms include unmasking a genetic disorder involving the urea cycle, severe nutritional deficiencies, or stress induced from acute illness. We present a case of GaBHA that progressed to cerebral edema requiring three weeks of mechanical ventilation. A 57-year-old malnourished, Caucasian female with a distant history of Roux-En-Y gastric bypass was transferred for a diffuse ulcerated rash. She was evaluated one week prior and given cephalexin for presumed cellulitis of her lower extremities. On our initial evaluation the patient was hypothermic (33.7 C) and tachycardic (110 bpm). Physical exam revealed normal mentation, injected eyes with exudate and a desquamated rash on arms, legs, and feet (Figure 1). Shortly after admission the patient became progressively encephalopathic, hypoxemic, and hypotensive. She was intubated and placed on vasopressors as well as broad-spectrum antibiotics. Work-up of her encephalopathy included a brain MRI that showed diffuse cerebral edema and an ammonia of 136 MCMOL/L (11-32 MCMOL/L) that peaked at 251 after initiating tube feeds. A clear source of infection was not found, but she received treatment for cellulitis and aspiration pneumonia. Imaging of liver noted hepatic steatosis with normal liver and coagulation function. GaBHA was suspected and she was started on a low protein diet (less than 10 g/day), L-carnitine replacement, and multivitamins including zinc, niacin, and vitamin C. Continuous renal replacement therapy was started for ammonia clearance and weaned off after stabilization of ammonia. We observed slow improvement in her encephalopathy and myopathy allowing extubated twenty-two days later. Ultimately the exact mechanism causing GaBHA wasn't apparent. Likely multifactorial from both vitamin and mineral deficiencies (Zinc 14 ug/dL, Copper 41 ug/dL and Vitamin-C 16 umol/L) and septicemia. Our treatment was aimed at restricting protein and supplementing vitamins and co-factors like L-carnitine. Limiting protein and muscle breakdown by providing other macronutrients decreases the amount of amino acids getting hydrolyzed into ammonia. In addition, stimulating an anabolic state helps prevent fat oxidation. Carnitine is an essential co-factor in transportation of fatty acids into the mitochondria for βoxidation. Limiting fat oxidation, by higher levels of insulin for example, and supplementing co-factors will prevent another mechanism for hyperammonemia via metabolites of urea cycle. Case reports have also theorized medications, like antibiotics, altering the gut microbiome inducing GaBHA. We recommend increased vigilance for GaBHA in patients with a history of bariatric surgery.