A study of the acid base balance of arterial blood in 92 premature infants, aged 1 to 65 days and 1.1 kg. to 2.3 kg. in weight, has been presented. The temporal artery blood was analyzed for pH, plasma CO2 content, chloride, total protein, total base. Alveolar carbon dioxide tension (pCO2) and "R" were calculated. Acid base analyses on the femoral artery blood of 16 adolescent well boys were used as controls. The study reveals the following salient facts:
There is a wide variation in the blood chemical findings between normal, well premature infants. In addition, repeat determinations upon the same infants revealed a more labile blood chemical picture than is found in older infants or adults.
No premature infant had all fractions of the acid base balance within the adult normal range.
The mean values for pH, CO2 content and protein were reduced in premature infants, while the mean values for total base, chloride, phosphate and "R" were elevated as compared to the values for the adult controls. The mean value for carbon dioxide tension was normal.
Sixty-seven per cent of the premature infants had the chemical findings of an uncompensated metabolic acidosis; 13% had a normal pH and CO2 content; 10% had a respiratory acidosis, 7% had a respiratory alkalosis and 3% were unclassified.
There was no statistical correlation of acid base values to birth weight or age or weight at the time of chemical sampling.
There was no difference of acid base values in infants who had been transfused by blood or plasma and those infants who had never been given blood or plasma transfusions.
By clinical examination alone, the nature of the acid base variations could not be anticipated in what we generally consider as well premature infants. There was no correlation between the variations of the acid base disturbance and the prognosis for life in these babies.
The fact that most premature infants have an increased hydrogen ion concentration and an unstable acid base balance may be additional reasons why premature babies so easily develop severe acidosis when any stress occurs, whether it is improper feeding, infection, etc.
The cause of the acidosis in premature infants has not been established. The theory that premature infants have a partial anaerobic metabolism with a decreased production of carbon dioxide is tenable but not established.
THE ACID-BASE BALANCE OF PREMATURE INFANTS 1