CICM SAQ 2012.2 Q14


Critically evaluate the role of the following investigations in the critically ill patient:

1. Serum ammonia
2. B-type natriuretic peptide (BNP)


Answer and interpretation

1. Serum ammonia

  • Used as an indicator of hepatic encephalopathy
  • Normal values do not rule out encephalopathy – therefore of limited utility in patients with known chronic liver disease
  • Not useful as a monitor during therapy
  • Very high levels may indicate cerebral herniation
  • May be useful to indicate undiagnosed cirrhosis in patients presenting with altered mental status
  • May also be elevated in: TPN, GI Bleed and steroid use, portosytemic shunts and inborn errors of metabolism.

2. B-type natriuretic peptide (BNP)

  • Released from cardiac cells in response to ventricular wall distension
  • Elevated in heart failure
  • Can be used as a diagnostic marker in patients presenting with dyspnoea to emergency department, and can be useful prognostically and to guide therapy in heart failure
  • May be elevated in many other conditions in critical care, including sepsis, acute lung injury, PE and intracranial bleed
  • Interpretation of BNP in ICU patients is therefore complex and while it may have a role in prognosis and response to therapy in future its current place is unclear.
  • Pass rate: 42%
  • Highest mark: 9.0
Exams LITFL ACEM 700

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Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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