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Updated: Oct 18, 2025
The Hypoxic Ischemic Encephalopathy Model of Perinatal Ischemia
Published on: November 19, 2008
Management of perinatal HPP during critical illness/ECMO
Neetu Krishnan1, Nancy Dunbar2
1Department of Pediatric Endocrinology, University of Connecticut, Farmington, CT, USA.
Insights
Enzyme replacement therapy (ERT) for hypophosphatasia (HPP) must be interrupted during extracorporeal membrane oxygenation (ECMO). This interruption can cause dangerous calcium and phosphorus level increases, requiring careful monitoring.
Area of Science:
- Biochemistry
- Critical Care Medicine
- Pediatric Endocrinology
Background:
- Hypophosphatasia (HPP) is a rare metabolic bone disease.
- Asfotase alfa is an enzyme replacement therapy (ERT) for HPP.
- Management of ERT during critical illness requires careful consideration.
Observation:
- A pediatric patient with severe HPP on ERT experienced cardiorespiratory arrest due to influenza A.
- Life-saving extracorporeal membrane oxygenation (ECMO) necessitated a 2-week ERT interruption.
- This interruption led to persistent hypercalcemia and hyperphosphatemia.
Findings:
- Cessation of ERT during ECMO resulted in loss of functional tissue-nonspecific alkaline phosphatase (TNSALP).
- This loss caused decreased bone mineralization and elevated serum calcium and phosphorus levels.
- These metabolic derangements resolved gradually after ERT resumption.
Implications:
- ERT interruption during ECMO in HPP patients can lead to significant metabolic disturbances.
- Close monitoring of calcium and phosphorus levels is crucial when ERT must be temporarily ceased.
- This case highlights the need for tailored critical care protocols for HPP patients requiring advanced life support.
Objectives:
With the advent of asfotase alfa, the enzyme replacement therapy (ERT) approved for hypophosphatasia (HPP), health care providers need to navigate management of ERT during critical illness.
Case Presentation:
We present the case of a young girl, treated with ERT for severe perinatal HPP, who had cardiorespiratory arrest in the setting of influenza A. Her life-saving treatment involving extra corporeal membrane oxygenation (ECMO) required a two-week interruption of ERT leading to persistent hypercalcemia and hyperphosphatemia. A three year old female presented with respiratory distress and blood tinged secretions. She was influenza A positive with bilateral opacities on chest X-ray (CXR). Worsening respiratory distress and bradycardic arrest required intubation, CPR and venoarterial ECMO cannulation. She remained on ECMO for 10 days with anticoagulation restrictions requiring her thrice-weekly subcutaneous ERT to be held. Hypercalcemia (12.3 mg/dL) and hyperphosphatemia (7.6 mg/dL) developed two weeks after restarting ERT and resolved six weeks later.
Conclusions:
We highlight that the obligatory cessation of ERT while on ECMO led to the loss of functional TNSALP with a profound decrease in bone mineralization leading to excess circulating calcium and phosphorus. In cases where it is necessary to interrupt ERT, we advise close monitoring of calcium and phosphorous levels.
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