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Plasma creatinine rises dramatically in the first 48 hours of life in preterm infants
L S Miall1, M J Henderson, A J Turner
1Regional Neonatal Intensive Care Unit, St. James's University Hospital, The Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom. lawrence@drmiall.freeserve.co.uk
Insights
Plasma creatinine levels dramatically rise in preterm infants within the first 48 hours of life, particularly in those less than 30 weeks gestation. These elevations are expected and not indicative of renal failure when considered alone.
Area of Science:
- Neonatal physiology
- Pediatric nephrology
Background:
- Published data indicate plasma creatinine decreases in the first 28 days of life.
- Neonatal creatinine levels are higher in more premature infants.
- Existing reference data for creatinine begins on day 2 of life.
Purpose of the Study:
- To document plasma creatinine changes during the initial 48 hours of life.
- To investigate the reasons for elevated creatinine in preterm infants compared to maternal levels.
Main Methods:
- A prospective observational study was conducted in a regional neonatal intensive care unit.
- 42 preterm infants (gestational age 23-35 weeks) were included.
- Plasma creatinine and urea were measured in cord blood and serial arterial blood gas samples.
Main Results:
- Mean creatinine at birth was 73 micromol/L, rising significantly over 48 hours.
- Peak creatinine in the most preterm infants (23-26 weeks) reached 221 micromol/L.
- Peak creatinine showed a strong inverse relationship with gestational age and birth weight, and correlated with illness severity.
Conclusions:
- Contrary to previous assumptions, creatinine levels increase significantly in the first 48 hours of life, especially in infants under 30 weeks gestation.
- Dramatic creatinine rises within the first 48 hours are anticipated in preterm neonates.
- Elevated creatinine levels in the first 48 hours should not be solely relied upon for diagnosing renal failure.
Objective:
Published data show that plasma creatinine falls steadily during the first 28 days of life and that creatinine levels in the neonatal period are higher in more premature infants. However, the best reference data commence on day 2 of life. The objective of this study was to document how plasma creatinine changes in the first 48 hours of life and to examine the reason for the apparently high levels of creatinine in preterm infants, compared with maternal levels.
Design:
A prospective observational study on a regional neonatal intensive care unit.
Patients:
A total of 42 preterm infants, mean gestational age of 29.4 weeks (range: 23-35), mean birth weight of 1.42 kg (.55-2.77), divided into 4 gestation groups: 23 to 26 weeks (n = 9), 27 to 29 weeks (n = 13), 30 to 32 weeks (n = 12), and 33 to 35 weeks (n = 8).
Interventions:
Measurement of plasma creatinine and urea concentration in cord blood and in serial samples taken for routine arterial blood gas analysis.
Outcome Measurements:
Changes in creatinine concentration with time and relationship to gestational age, birth weight, and illness severity.
Results:
Mean creatinine at birth was 73 micromol/L (95% confidence interval [CI]: 68-79 micromol/L). Plasma creatinine rose significantly over the first 48 hours. Mean peak creatinine in the most preterm infants (23-26 weeks) was 221 micromol/L (CI: 195-247 micromol/L). Peak plasma creatinine was inversely related to gestation (Spearman's coefficient: -.73) and birth weight (Spearman's coefficient: -.76). Significant differences in creatinine concentration were seen among different gestational groups at 24 and 48 hours of life. Peak creatinine correlated with a high Clinical Risk Index for Babies score (Spearman's coefficient:. 64). The fall in creatinine began later in more premature infants. All 38 surviving infants had normal renal function; their mean plasma creatinine at discharge was 52 micromol/L (CI: 46-58 micromol/L).
Conclusions:
Rather than falling steadily from birth, creatinine rises dramatically in the first 48 hours of life, especially in infants of <30 weeks' gestation. Even large rises in creatinine in the first 48 hours may be expected and should not be used in isolation to diagnose renal failure.