[Measured quantities in perinatal medicine--the base excess]

Area of Science:

• Perinatal Medicine
• Neonatal Diagnostics
• Blood Gas Analysis

Background:

• Neonatal studies indicate base excess (BE) in cord blood has diagnostic and prognostic value for hypoxic newborns.
• Accurate BE computation requires hemoglobin (Hb) concentration, oxygen saturation, and fetal fluid compartment distribution, factors often overlooked by automated blood gas equipment.
• This study investigates optimal BE calculation methods for newborns.

Purpose of the Study:

• To analyze and verify which base excess (BE) calculation method best correlates with neonatal outcome conditions.
• To evaluate the impact of fetal hemoglobin (HbF) oxygen saturation curves and fetal fluid compartment distribution on BE values.
• To assess the prognostic potential of different BE values against APGAR scores and fetal heart frequency (FHF).

Main Methods:

• Computed three BE values: actual BE, BE corrected for oxygen saturation (BE,oxy), and BE in the extracellular fluid (BE,ecff) for 7701 newborns.
• Applied three fetal Hb oxygen saturation curves (Zander, Hellegers, Severinghaus).
• Correlated BE values with 1-min APGAR, 1- and 5-min APGAR sums, and ante-partum FHF in 342 fetuses.

Main Results:

• Correcting BE for oxygen saturation significantly increased correlation with APGAR indices (r and rho).
• BE,oxy median was -7.7 mmol/L, while BE,ecff median was -3.2 mmol/L, showing reduced numerical values.
• Fetal Hb saturation curves had minimal impact; BE,ecff calculations did not fit reality.

Conclusions:

• Computational correction of BE for real oxygen saturation is mandatory in perinatal medicine.
• Algorithms for fetal hemoglobin should be utilized; BE in the extracellular fluid compartment is not recommended.
• Accurate determination of umbilical cord Hb concentration is crucial due to its variability.