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Published on: October 31, 2012
Universal screening for hyperammonemia after lung transplantation: A retrospective cohort study of incidence and
Katherine D Wick1, Jagadish Patil1, Jordan Dunitz1
1Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Minnesota, Minneapolis, MN.
Background:
Hyperammonemia after lung transplant (HALT) is a highly morbid condition with variation in approaches to detection and treatment across centers. Traditionally, HALT has been defined as a serum ammonia level greater than 200 μmol/L; however, patients may be at risk of adverse outcomes at lower levels. We studied outcomes associated with a universal screening protocol for elevated serum ammonia.
Methods:
This was a retrospective study of lung transplant recipients at the University of Minnesota between 2013 and 2024. Screening was implemented in October of 2021. We defined hyperammonemia as serum ammonia of 50 μg/dLμmol/L or greater and HALT as those patients in whom hyperammonemia prompted treatment based on clinician judgment. Our primary outcome was 90-day mortality. We compared the incidence of elevated serum ammonia, HALT, 90-day mortality, hospital and intensive care unit lengths of stay, and HALT-focused treatments before and after protocol implementation. The relationship between HALT and 90-day mortality was tested using a multivariable Cox proportional hazards model. The relationship between pre-selected risk factors and HALT was also tested using multivariable logistic regression.
Results:
There was a significantly higher number of patients with elevated serum ammonia (13.6% post-protocol vs 4.3% pre-protocol, p = 0.003). Incidence of hyperammonemia requiring treatment was non-significantly higher (8.2% vs 3.9%, p = 0.12). Receiving a transplant pre-protocol was associated with a significantly higher risk of 90-day mortality when adjusted for potential confounders (HR 6.86, 95% CI 1.81-26.1, p = 0.005). HALT was also independently associated with 90-day mortality with a hazard ratio of 5.50 (95% CI 1.17-25.8, p = 0.031).
Conclusion:
Universal screening for hyperammonemia was associated with a lower adjusted risk of death. Ammonia levels as low as 50 μmol/L were associated with an increased risk of adverse outcomes. Centers should consider protocolized screening and treatment for HALT, which may improve outcomes of lung transplant.
