Tuesday, November 24, 2015

Q: All of the following are the risk factors for hyperammonemia in recent lung transplant patients except?

A)  use of total parenteral nutrition (TPN),

B) Persistent abdominal complaints
C) Pre-transplant diagnosis of idiopathic pulmonary arterial hypertension
D) History of seizure

Answer: D
 (seizure is the result, not the risk for hyperammonemia in post lung transplant patients)

Severe hyperammonemia is an unfortunate, unexpected and hard to manage complication after lung transplant. The cause of  hyperammonemia is due to urea cycle abnormalities but exact mechanism is still not very clear. Any unexplained central symptoms including lethargy, delirium, seizure or coma in post-lung transplant patients should quickly prompt the diagnosis of  hyperammonemia as morbidity and mortality is very high, if left untreated. Diagnosis can be confirmed by presence of  Ureaplasma in blood, plasma or BAL via PCR.

Treatment is 4 folds

1. Prevention: of exogenous nitrogen sources in feeding, 
2. Removal: Hemodialysis in severe cases to clear ammonia 
3. Replacement: Administration of intravenous sodium benzoate and sodium phenylacetate to serve as alternatives to urea for the excretion of nitrogenous wastes
4. Killing: of Ureaplasma organisms via antibiotics as macrolides, fluoroquinolones, and tetracyclines


1. Lichtenstein GR, Yang YX, Nunes FA, et al. Fatal hyperammonemia after orthotopic lung transplantation. Ann Intern Med 2000; 132:283. 

2. Bharat A, Cunningham SA, Scott Budinger GR, et al. Disseminated Ureaplasma infection as a cause of fatal hyperammonemia in humans. Sci Transl Med 2015; 7:284re3. 

3. Rueda JF, Caldwell C, Brennan DC. Successful treatment of hyperammonemia after lung transplantation. Ann Intern Med 1998; 128:956. 

4. Anwar S, Gupta D, Ashraf MA, et al. Symptomatic hyperammonemia after lung transplantation: lessons learnt. Hemodial Int 2014; 18:185.

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