Acid Base Homeostasis: Stewart Approach at the Bedside

Despite its simplicity and wide availability, traditional approach fails to provide us with an insight into mechanisms of acid base abnormalities or accurately quantify individual components of it or provide clinician with an approach to decide probable ways to rectify the problem (if necessary). Sometimes, traditional approach fails to identify complex acid base disorders seen in critically ill patients. The approach to acid base disorders provided by Peter Stewart is based on robust physicochemical evidence. Stewart approach identified three independent variables that determine acid base homeostasis—total carbon di-oxide, strong ion difference (SID), and total nonvolatile acid anion (Atot). Fencl provided some simple calculations to measure these independent variables at the bedside. Stewart approach provides us with an insight into the acid base abnormalities and helps us in quantifying individual components producing any disturbance and measures to be taken to rectify them (if needed). Stewart’s approach is also useful in understanding effects of different intravenous fluids on acid base physiology of plasma.