Reference values for strong ion difference--a novel tool for fetal metabolic assessment

Area of Science:

• Neonatal physiology
• Biochemistry
• Obstetrics

Background:

• Evaluating fetal acid-base status is crucial for neonatal well-being.
• Stewart's physiochemical theory offers a comprehensive approach to acid-base abnormalities.

Purpose of the Study:

• To establish reference values for strong ion difference (SID) in umbilical cord blood.
• To investigate the feasibility of using SID for evaluating fetal metabolism.
• To compare acid-base variables in umbilical cord blood between neonates born via spontaneous delivery and cesarean section.

Main Methods:

• Prospective observational study comparing 40 women with normal spontaneous delivery to 40 with elective cesarean section.
• Measurement of strong ion difference (SID) in umbilical cord vein blood.
• Comparison of acid-base variables including pH, pCO2, and weak acids.

Main Results:

• Established reference values for apparent SID (34.61+/-3.92 mequiv./L) and effective SID (37.43+/-1.93 mequiv./L) after normal delivery.
• Similar SID values were observed after elective cesarean section (apparent: 35.98+/-2.56; effective: 38.29+/-2.38 mequiv./L).
• Cesarean section was associated with higher pCO2 and lower plasma weak acids (albumin, phosphate) compared to normal delivery.

Conclusions:

• Strong ion difference (SID) provides a comprehensive method for assessing neonatal acid-base abnormalities.
• SID is a valuable potential tool for evaluating fetal acid-base status.
• Understanding SID in umbilical cord blood can offer insights into fetal metabolic state.