Hyperammonemia Post Lung Transplant: A Rare and Fatal Complication

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Introduction Among the extra pulmonary complications associated with lung transplantation, severe hyperammonemia has been reported as a rare and fatal complication with an incidence of up to 4% and a fatality rate of 67% in some case series. We present a case report of a patient who underwent bilateral lung transplantation and developed severe hyperammonemia in his immediate post-operative course. Case Report A 66 year old male with past medical history of idiopathic pulmonary fibrosis was referred to our center for evaluation for bilateral lung transplantation. He underwent a technically uncomplicated successful procedure and his immediate post-operative course was complicated by metabolic acidosis and acute renal failure. On post op day 4 he developed mental status changes and was noted to have elevated plasma ammonia of 154 mcmol/L. Laboratory and imaging studies were negative for acute hepatic dysfunction. A head CT was negative for cerebral edema or acute findings. He was started on rifaximin, lactulose enemas and via nasogastric tube, in addition to empiric macrolide therapy. Despite these interventions his mental examination and ammonia level did not improve in the following 24 hours. He was initiated on L-arginine, sodium benzoate and levocarnitine for possible undiagnosed glutathione synthase deficiency. Continuous renal replacement therapy (CRRT) for more rapid ammonia clearance was also started. He required CRRT for 5 days with gradual improvement in mental status. CRRT was discontinued once plasma levels normalized. He was slowly weaned off the above pharmacological interventions in the ensuing 3 weeks. He was discharged to inpatient rehabilitation without the need of any medical therapies for hyperammoenmia on post op day 30. He remained well for a period of 4 years post-transplant and eventually succumbed to chronic lung allograft dysfunction. Summary The primary underlying mechanism for post transplant hyperammonemia remains unknown, but several risk factors have been linked to this condition. The most commonly reported are disseminated opportunistic infection with ureaplasma or mycoplasma, high nitrogen loads, pulmonary hypertension and hepatic glutamine synthetase deficiency. Treatment regimens are multimodal but overall aimed at reducing ammonia levels and providing neuroprotection. Early initiation of treatment is paramount for improving survival and outcomes. Among the extra pulmonary complications associated with lung transplantation, severe hyperammonemia has been reported as a rare and fatal complication with an incidence of up to 4% and a fatality rate of 67% in some case series. We present a case report of a patient who underwent bilateral lung transplantation and developed severe hyperammonemia in his immediate post-operative course. A 66 year old male with past medical history of idiopathic pulmonary fibrosis was referred to our center for evaluation for bilateral lung transplantation. He underwent a technically uncomplicated successful procedure and his immediate post-operative course was complicated by metabolic acidosis and acute renal failure. On post op day 4 he developed mental status changes and was noted to have elevated plasma ammonia of 154 mcmol/L. Laboratory and imaging studies were negative for acute hepatic dysfunction. A head CT was negative for cerebral edema or acute findings. He was started on rifaximin, lactulose enemas and via nasogastric tube, in addition to empiric macrolide therapy. Despite these interventions his mental examination and ammonia level did not improve in the following 24 hours. He was initiated on L-arginine, sodium benzoate and levocarnitine for possible undiagnosed glutathione synthase deficiency. Continuous renal replacement therapy (CRRT) for more rapid ammonia clearance was also started. He required CRRT for 5 days with gradual improvement in mental status. CRRT was discontinued once plasma levels normalized. He was slowly weaned off the above pharmacological interventions in the ensuing 3 weeks. He was discharged to inpatient rehabilitation without the need of any medical therapies for hyperammoenmia on post op day 30. He remained well for a period of 4 years post-transplant and eventually succumbed to chronic lung allograft dysfunction. The primary underlying mechanism for post transplant hyperammonemia remains unknown, but several risk factors have been linked to this condition. The most commonly reported are disseminated opportunistic infection with ureaplasma or mycoplasma, high nitrogen loads, pulmonary hypertension and hepatic glutamine synthetase deficiency. Treatment regimens are multimodal but overall aimed at reducing ammonia levels and providing neuroprotection. Early initiation of treatment is paramount for improving survival and outcomes.