Acid-Base Disturbance Analysis: Comparison of the Traditional and Stewart Approaches

Introduction: The new approach to acid-base balance which initially proposed by Stewart in 1978 was success to provide a new insight which more easy to understand what is the cause, the mechanism and the degree of acid-base disturbance. The purpose of the present study was to compare two different methods of analysis acid-base disturbance in patients admitted to Pediatric Intensive Care Unit (PICU). Methods: The study was performed in 43 patients admitted to the pediatric intensive care unit of Cipto Mangunkusumo Hospital, Jakarta. Sodium, potassium, chloride, albumin, lactate and arterial blood gases were measured. All samples were taken from artery in every patient. The anion gap (AG) was calculated using the Narins method (1977), the corrected anion gap (AGcorr) using the Moviat method (2003), the strong ion gap (SIG) using Kellum method (1995) and the base excess unmeasured anions (BEUA) using the Fencl-Stewart method simplifi ed by Story (2003). Results: The presence of unmeasured ions identifi ed by signifi cantly abnormal BEUA was poorly identifi ed by SBE. Of the 43 patients included in the study, 18 (41.9%) had a different interpretation of acid-base balance when the Fencl-Stewart method was used compared to using SBE. There was good correlation between SIG and AG (r =0.831), and there was excellent correlation between SIG and AGcorr (r =0.991). Conclusions: In the condition of electrolyte unbalance and hypoalbuminemia the Stewart approach is better than the traditional approach. Nevertheless, the calculation of SIG is more timeconsuming, therefore the corrected anion gap (AGcorr) was suggested to use in clinical practice as a combination with SBE.