The Principle
The Stewart Light approach integrates Stewart’s physicochemical model with the time-proven bedside concept of standard base excess (SBE). Rather than abandoning SBE, it partitions the calculated SBE into physiologically meaningful components derived from Stewart’s framework, making complex acid–base disorders easier to understand at the bedside.
The Evolution
The concept originated from the work of Brian M. Gilfix (J Crit Care, 1993), who was inspired by the unpublished work of Vladimir Fencl. It was subsequently refined and popularized by several authors, including David A. Story (Br J Anaesth, 2004). Quite recently a pH-dependent reference for the strong ion difference (SID) was introduced to improve the partitioning of metabolic acid–base disorders, particularly in patients with marked acidaemia or alkalaemia (Br J Anaesth, 2026).
The Present State
A detailed description of the Stewart Light algorithm and its clinical application can be found in our educational article published in Intensive Care Medicine as part of the ICU Toolbox collection: A pragmatic approach to complex acid-base disturbances of critical illness.
The Stewart Light algorithm for bedside acid–base analysis. Reproduced from Duška et al., Intensive Care Medicine (2026) under CC BY-NC 4.0.