Anion gap in mechanically ventilated newborn infants within the first week of life

In 410 consecutively admitted mechanically ventilated neonates (gestational age, 34.8 +/- 4.0 weeks', birthweight, 1930 +/- 890 g) anion gap [(Na + K) - (HCO3 + Cl)] was calculated at admission to the neonatal intensive care unit. Within their first week of life, 47 neonates died and 113 neonates were extubated; in the remaining 250 neonates anion gap was also calculated at day 7. Despite a statistically significant lower anion gap in survivors than in nonsurvivors (P < 0.05), an elevated anion gap was clinically no predictor of mortality either at the day of admission (22.7 vs 25.3 mmol/L) or after the first week of life (20.3 vs 23.2 mmol/L). Mechanically ventilated neonates exhibited during their first week of life a much larger anion gap than critically ill adults in recent studies. The individual critically ill newborn might be too frequently subject to metabolic disturbances as detected by anion gap to allow any prognostic information.