3.1.4.11. Infants
General Factors affecting Acid-Base Balance in Infants
Low Bicarbonate depends on Gestational Age
- As compared to normal adults, the plasma [HCO3] in neonates is lower due to the lower renal threshold and lower capacity to reabsorb bicarbonate.
- The more immature the neonate, the lower the level.
- Very low birth weight babies have bicarbonate levels of 12-16 mmoles/l but term babies have levels of 20-22 mmol/l
Low Reserve to excrete an Acid Load
- At birth in term infants, acid excretion is working near maximum capacity and there is little reserve to deal with acidosis.
- The lower bicarbonate levels in preterm babies means they have even less capacity than a term neonate to buffer an acid load
- The ability to excrete an acid load improves over the first couple of months of life
Other Factors
- Growth results in deposition of base in new bone as the calcium salts in bone are alkaline salts
- On a weight basis, fixed acid production is higher than in adults (eg neonates and children < 12 months : fixed acid production is 2 to 3 mmol/kg/day).
NB:
- As opposed to 1-1.5mmol/kg/day