Fluid balance in neonates Flashcards
Describe how GFR changes during the neonatal period.
In children, GFR is size dependent, and is proportional to body surface area.
In children under 2, the corrected GFR is not stable. Immediately after birth and in utero GFR is very low.
In the first 2 weeks after birth the GFR has doubled, and goes up by a factor of 6 by 3 months.
Over age 3, GFR becomes more proportional to surface area
Why are fluid requirements higher during infancy?
High metabolic rate
High surface area/ body weight ratio (water lost through the skin)
Less efficient renal urine concentration
How does the ability to concentrate urine change with development?
In the first 6 months, kidneys ability to concentrate urine is poor. The only matches adult lovels once over the age of 2.
Describe the changes in Na+ balance in neonates
In utero, the fractional excreteion of Na+ is very high. At 25 weeks over 5% of Na+ is excreted, however Na+ balance is maintained by maternal kidneys.
Fractional exertion falls rapidly to adult levels by week 40.
Problems in pre-term babies because their kidneys are unable to retain Na+. Positive Na+ balance is required for development. Therefore supplementation is required.
