Serial Blood‐Gas Tensions and Acid‐Base Balance during the First Hour of Life in Human Infants1

Abstract

Summary 1. Serial determinations of oxygen and carbon dioxide tension, pH, CO 2 content, sodium, potassium, chloride, magnesium, total protein and hematocrit beginning within 5 minutes of birth and continuing through the first hour have been performed in newborn infants. 2. The data support the concept that the delivery process is invariably asphyxiating whether delivery is vaginal or by cesarian section. Furthermore, the major recovery occurs within 10 minutes of delivery in healthy infants. 3. Arterial oxygen tension was reduced throughout the entire period. Even though the mean arterial oxyhemoglobin satura tion was within normal limits at one hour of age the mean oxygen tension remained low. The interpretation of these findings is discussed. 4. The administration of high oxygen concentration to the mothers for periods up to 30 minutes failed to effect the infants' PaO 2 . 5. Evidence is presented for a right to left shunt through the ductus arteriosus when the newborn is quiet as well as crying. 6. Serum potassium concentration was found to be considerably elevated in all infants. The mechanisms for this are discussed. 7. Differences in acid‐base balance, serum protein concentration and packed cell volume between infants delivered vaginally and by cesarian section were noted. The explanation of these differences is not known.