Progression of renal function in preterm neonates with gestational age ≤32 weeks

Abstract

Serum creatinine (SeCr), creatinine clearance (CrCl), and fractional excretion of sodium (FeNa) were measured in 83 preterm neonates divided into four groups according to gestational age (GA). At birth, there were no differences in mean SeCr values in the four groups nor any significant correlation between initial values and GA. In all groups there was an initial SeCr increase; an inverse correlation between SeCr and GA was observed from the 3rd day of life to the 5th week (p<0.001). CrCl showed a positive correlation to GA from the first week onwards (p<0.001); in each group CrCl values correlated positively to days of life (p=0.0001). Rate of CrCl increase correlated positively to GA (p=0.0005). FeNa showed an inverse correlation to GA from the first week (p<0.001). In each group, the FeNa value correlated negatively to postnatal age (p<0.001) and the velocity of decrease was directly correlated to GA (p=0.0358). Our findings indicate that glomerular function shows a progression directly correlated to GA and postnatal age, while tubular function correlates inversely to the same parameters. The values reported could be useful for following renal function in very low birth weight infants.

Factors affecting postnatal changes in serum creatinine in preterm infants with gestational age <32 weeks

“…SeCr increased after birth of the preterm infant, reaching a peak that was at the second day for infants born at 29 to 31 weeks of GA and at the fifth day for those born at p28 weeks of GA. SeCr peak was found to be higher for lower GA. Our results are consistent with others: Bueva and Guignard 18 showed a negative correlation between plasma creatinine and GA in one study comparing preterm infants versus term infants between the first and the second day of life; Gallini et al 5 found that during the first week of life, the maximum value of SeCr was significantly higher for GA lower than 27 weeks than for 27 to 28, 29 to 30 and 31 to 32 weeks GA; recently Auron and Mhanna 6 showed that in VLBW infants younger than 29 weeks or smaller than 1000 g there was a delay in the decrease of their SeCr that extended beyond the first day of life. So, gestation and age-based reference charts have been proposed for the interpretation of creatinine values in extremely premature babies <28 weeks GA. 21 Our study also disclosed EOS, RDS and ibuprofen-treated hsPDA as other independent factors associated with high postnatal SeCr increase.…”

“…Moreover, a positive correlation between SeCr at admission in NICU and GA was not observed in previous investigations. 5,6,8,17,21 Therefore, the finding of a positive correlation between GA and baseline SeCr, though statistically significant, should be interpreted with caution.…”

“…In preterm infants born less than 32 weeks of gestational age (GA), previous reports showed that SeCr concentration had a postnatal increase with a peak between the second and the fourth day of life that was followed by a SeCr decrease. 5 Both the increased peak and the slow decrease of SeCr in smaller premies reflect decreased renal function associated with low GA. 6 Postnatal SeCr changes in preterm infants may result from tubular creatinine reabsorption in the immature kidney 7 and from a physiologically low GFR during the first days of life. 8 Moreover, in sick preterm infants, many clinical conditions inducing hypotension, hypovolemia and hypoxemia and the use of nephrotoxic drugs may lead to further reduction of GFR.…”

Serum creatinine in very low birth weight infants during their first days of life

“…In their study these authors assessed 66 term and preterm infants (1000 to 2500 g BW of which only 11 patients were 1001 to 1500 g), whereas in our study we evaluated 136 infants 25 to 32 weeks GA (<1500 g). In another study, Gallini et al 6 have shown a correlation between serum SCr and postnatal age in 83 preterm infants <32 weeks GA. In their study there was no difference in SCr among infants of different GA at birth, but these authors found an inverse correlation between SCr and GA from the third day of life to the fifth week.…”

“…[2][3][4] While in the immediate postnatal period the newborn SCr likely reflect maternal values, 2,4 further increase in the levels of SCr in premature infants have been attributed to increased tubular reabsorption of creatinine due to renal tubular immaturity and also to reduced creatinine clearance. 2,3 It has also been shown by several investigators that creatinine clearance and glomerular filtration rate (GFR) increase with postnatal age in premature infants, [5][6][7][8] and in the absence of urine creatinine measurements, SCr can be used to estimate GFR. [9][10][11][12] However, little is known about the relationship between gestational age/birth weight (GA/BW) and SCr in VLBW infants at birth following stabilization of their SCr.…”