Related Experiment Videos
Metabolic acidosis, nitrogen balance and weight gain in preterm infants
Insights
Preterm infants show increasing nitrogen retention and acid excretion in early life. Weight gain aids acid elimination, suggesting growth influences acid-base balance in neonates.
Area of Science:
- Neonatal Physiology
- Pediatric Nephrology
- Biochemistry
Background:
- Acid-base homeostasis is critical for preterm infant development.
- Understanding nitrogen balance and acid excretion is key to managing neonatal metabolic health.
Purpose of the Study:
- To investigate the relationship between nitrogen balance, weight gain, and acid-base homeostasis in preterm infants.
- To analyze nitrogen excretion, acid retention, and their combined effect ('total acid') during the first six weeks of life.
Main Methods:
- Weekly monitoring of nitrogen balance, urinary nitrogen excretion (NAE), and blood acid-base parameters in 15 male preterm infants.
- Calculation of 'total acid' as the sum of NAE and acid retention.
- Correlation analysis between acid-base parameters, nitrogen metabolism, and weight gain.
Main Results:
- Nitrogen retention increased in the first three weeks, then slightly decreased.
- Urinary nitrogen excretion and acid retention peaked in the early weeks, with NAE becoming more significant over time.
- Total acid peaked at three weeks and correlated positively with nitrogen intake and retention, suggesting a role in acidosis.
Conclusions:
- Nitrogen retention contributes to acidosis in preterm infants.
- Increasing weight gain is associated with decreased 'total acid' per unit of nitrogen, indicating growth aids acid elimination.
- Growth plays a role in acid elimination independent of renal function development in neonates.
Abstract:
Nitrogen balance, urinary NAE and the acid base parameters in the blood of 15 male preterm infants with birth weights of 1000--2370 g (mean 1715 g) and gestational age of 29--37 weeks (mean 33.3 weeks) were determined weekly, in the first six weeks of life. The sum of NAE plus acid retention, as "total acid", was used to investigate the relationship between nitrogen balance, weight gain and acid-base homeostasis. During the first three postnatal weeks, nitrogen intake, urinary and faecal loss of nitrogen as well as the nitrogen retention were rapidly increasing. Later, urinary excretion continued to rise, the intake remained unchanged and as a result, the amount of retained nitrogen decreased slightly. Urinary NAE was steadily increasing to reach the maximum of 2.8 mEq/kg by the fourth week. Acid retention was the most pronounced in the second and third week, thereafter it fell until the end of the study. The importance of NAE relative to acid retention was continuously increasing throughout the observation period. The "total acid" increased gradually and reached its peak value in the third week of life. Subsequently a continuous fall was seen. During the first three weeks of life there was a significant positive correlation between "total acid" and nitrogen intake and urinary nitrogen extraction. Since the increase in "total acid" went parallel with the increasing nitrogen retention, the latter may be assumed to be an additional factor in producing acidosis. Calculated per 100 mg nitrogen ingested, retained or excreted with urine, "total acid" was decreasing with the increasing rate of weight gain. This indicates that the growth process -- irrespective of the postnatal development of renal H+ handling -- is also involved in the elimination of acids.