Strong ion gap, anion gap, and base excess in critically ill neonates and infants during ECMO
Article
Ali, S, Totapally, BR, Raszynski, A. (2008). Strong ion gap, anion gap, and base excess in critically ill neonates and infants during ECMO
. International pediatrics : the journal of the Miami Children's Hospital, 23(1), 34-40.
Ali, S, Totapally, BR, Raszynski, A. (2008). Strong ion gap, anion gap, and base excess in critically ill neonates and infants during ECMO
. International pediatrics : the journal of the Miami Children's Hospital, 23(1), 34-40.
Background: To identify and quantify true metabolic acidosis in neonates and infants during extracorporeal membrane oxygenation (ECMO) by using a physiochemical approach (strong ion gap) and to compare the ability of indirect measures such as base excess (BE), anion gap (AG), and corrected anion gap (AGcorr) to detect unmeasured anions. Methods: In this retrospective chart review study, the medical records of 34 neonates and infants treated with ECMO were reviewed for simultaneously obtained results of blood gas values, serum electrolytes, and albumin levels from a total of 97 arterial blood samples. Stewart's method was used to calculate strong ion difference (SIG). Indirect measures, such as BE, AG, AGcorr, and standard bicarbonate were compared to assess SIG. Results: Tissue acidosis, defined as SIG of >5, was present in 56 (58%) samples. Hyperchloremia (Clcorr >110 mEq/L) was present in 8 (8%) samples. AGcorr was better than AG in detecting true tissue acidosis (77% vs 50%). BE and standard bicarbonate showed a poor correlation (-0.21 and -0.36 respectively; P<0.05) and a poor discriminatory ability (area under the curve, 0.56 and 0.34). AG and AGcorr had the best correlation (0.78 and 0.82 respectively; P<0.05) and better discriminatory ability (AUC, 0.86 and 0.83 respectively). SIG levels were significantly higher in expired patients than in who survived (16.0 ± 3.9 vs 8.1 ± 5.8; P < 0.05). Conclusions: Metabolic acidosis due to unmeasured anions as measured by strong ion gap is common among critically ill newborns and infants treated with ECMO. The AGcorr is the best, and the BE and the standard bicarbonate are the worst measures of SIG.
