Acid-base calculations. The ones that make my head hurt. Every time I read up on it, I seem to almost grasp it and get a deeper understanding – which slips away slightly after a week or two. And a few weeks later, I read up on acid-base again to repeat the cycle… There are many ways to explain the acid-base balance in the body. To me, the Stewart approach has been the most helpful. Here are three steps, three links, to understanding Stewart.
First, a recent must-read: Facing acid–base disorders in the third millennium – the Stewart approach revisited, an easy to read/easy to grasp article that takes you through the history of acid-base approaches why they are useful but also their downsides – culminating in Stewart’s approach (as modified by Fencl and others). It sheds light on the history and development of understanding acid-base disorders, and also how scientists disagree on these approaches. And therefore it creates a framework where it’s easier to understand both the ‘traditional’ Henderson-Hasselbach equation with its different interpretations, as well as the Stewart approach.
Bringing Stewart to the bedside
Sencond, a great resource for the Stewart approach and acid-base disorders is the acidbase.org site, created and administered by a friend and collegue in Denmark. Great site with lots of good links and references. It also has a good Stewart approach acid-base analyser to input numbers from your patients, and play with what will theoretically happen if you add certain fluids, electrolyte or bicarbonate solutions. It also links to the definitive book on the Stewart approach – Stewart’s Textbook of Acid-Base.
Third is, of course, a regular trip over to emcrit.org to listen to his 4 lectures on acid-base using the Stewart approach is also on my schedule. It’s Stewart explained really well. I’m always amazed by how acid-base smart I feel after listening to Weingart in those podcasts – and equally amazed by how quickly the enlightenment slips through my fingers over the following weeks. One day I will get the acid-base conundrum to stick permanently in my brain. Until then, I’ll keep reading and practising.
The three references:
Facing acid–base disorders in the third millennium – the Stewart approach revisited, Int J Nephrol Renovasc Dis, Jun 2014. Free Full Text.
For additional information and acid-base analyser, head over to
Emcrit’s acid-base lectures – with shownotes containing additional articles.