An overlooked aspect on metabolic acidosis at birth: blood gas analyzers calculate base deficit differently.

• Background: Metabolic acidosis (MA) at birth is commonly defined as umbilical cord arterial pH <7.0 plus base deficit (BD) ≥12.0 mmol/L. BD is not a measured entity but calculated from pH and pCO(2) values, with the hemoglobin (Hb) concentration included in the calculation algorithm as a fixed or actual value. Various blood gas analyzers use different algorithms, indicating variations in the MA diagnosis. Objective. To calculate the prevalence of MA in blood and extracellular fluid (ecf) with algorithms from three blood gas analyzer brands relative to the Clinical and Laboratory Standards Institute (CLSI) algorithm. Design: Comparative study. Setting. University hospital. Sample. Arterial cord blood from 15354 newborns. Main outcome measure. Prevalence of MA. Methods. Blood was analyzed in a Radiometer ABL 735 analyzer. BD was calculated post hoc with algorithms from CLSI and Corning and Roche blood gas analyzers, and with actual and fixed (9.3 mmol/L) Hb values. Results: The prevalence of BD ≥12.0 mmol/L in blood was with the CLSI algorithm 1.97%, Radiometer 5.18%, Corning 3.84%, and Roche 3.29% (CLSI vs other; McNemar test, P <0.000001). Similarly, MA prevalences were 0.58%, 0.66%, 0.64% and 0.64% (P≤0.02). BD ≥12.0 and MA rates were lower in ecf than in blood (P≤0.002). Algorithms with actual or fixed Hb concentration made no differences in MA rates (P≥0.1). Conclusion. The neonatal metabolic acidosis rate varied significantly with blood gas analyzer brand and fetal fluid compartment for calculation of BD.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Reproduktionsmedicin och gynekologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Obstetrics, Gynaecology and Reproductive Medicine (hsv//eng)

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