Critical Care Scenarios Episode 96: Understanding ammonia, with Prem Kandiah
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Dec 24, 2025 Dr. Prem Kandiah, a neurointensivist and ammonia expert, dives deep into the complexities of ammonia physiology and its critical care implications. The discussion highlights the unique ways ammonia can affect the brain, including mechanisms of injury and the importance of timely measurement. Kandiah explores less-known causes of hyperammonemia, such as urease-producing infections and malnutrition, especially in post-bariatric patients. He also offers practical tips for accurate ammonia testing and discusses acute management strategies.
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Layered Ammonia Clearance Protects The Brain
- The liver, kidneys, muscle and gut form layered defenses that clear ammonia produced during digestion.
- When these fail (bypass, liver shutdown, sarcopenia), ammonia can spill to the brain and cause astrocyte injury and swelling.
Glutamine Drives Astrocyte Swelling
- Astrocytes convert ammonia to glutamine which increases intracellular osmotic load and causes cytotoxic swelling.
- Ammonia also contributes to mitochondrial injury and can produce both cytotoxic and vasogenic brain edema.
Use Serial Ammonia Trends In Cirrhosis
- In cirrhosis an isolated ammonia level often poorly correlates with encephalopathy and is most useful when sustained or extremely high.
- Use serial measurements to judge treatment response rather than a single admission value.