Anaesthesia Coffee Break BONUS EPISODE: Professor David Story chats to us about Acid Base Physiology
Sep 15, 2021
Professor David Story, a leading anaesthetist and researcher from the University of Melbourne, dives deep into the complexities of acid-base physiology. He explains the importance of understanding the Stewart approach and simplifies the definitions of acids for clinical use. The conversation explores practical models for assessing acid-base disorders during surgery, including the impact of CO2 on mixed disorders. Additionally, Story highlights the clinical value of quantifying 'other ions' and introduces useful tools like the bedside Stewart app for quick assessments.
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Use A Fixed 'Magic Point' Framework
- Think of acid–base around a fixed 'magic point' (pH 7.40, PaCO2 40, HCO3- 24) and interpret disorders as movements from that point.
- Mixed disorders are common in perioperative snapshots because compensation takes time and the snapshot shows both primary and uncompensated changes.
Bicarbonate Is A Marker, Not The Mechanism
- Bicarbonate is a useful marker but not the mechanistic driver; the kidneys act via strong ion handling (mainly Na+ and Cl-).
- Framing acid–base in terms of strong ion difference (Stewart) unifies fluids, renal handling and plasma chemistry.
Use The Bedside Stewart App To Quantify
- Try the bedside Stewart app (bedside Stewart) to practise quantifying sodium–chloride, albumin, lactate and 'other ions' effects.
- Use quantification to prioritise fixes: correct the dominant component first rather than guessing from bicarbonate alone.