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Editor—Recently, Miallet al 1 have reported a rapid rise in serum creatinine in the first 48 hours of life in neonates. But we have noticed in our clinical day to day practice that this rise is transient and may not be clinically significant. To confirm this, we looked at the initial serum creatinine levels on a stable group of term neonates admitted to the neonatal intensive care of King Fahd Hospital of the University, Al-Khobar, Saudi Arabia.
Neonates with congenital anomalies, perinatal asphyxia, and those requiring ventilatory support were excluded. The serum creatinine levels were measured together with electrolytes by using an automatic analyser (Dimension, Delaware, USA), which were relayed by the reporting computer system (Ulti-view, Los Angeles, USA). Serum creatinine was available for the first 72 hours on a limited number of neonates, as most of the selected babies were stable within the first 48 hours of life and there was no need for extra serum electrolyte and creatinine measurements. Out of all the newborns admitted during the three month study period who fulfilled the inclusion criteria, 13 neonates had serum creatinine measurements available for the first 72 hours. These readings werenoted down and were analysed using the SPSS statistical package to calculate the mean, standard deviation and statistical significance.2
Out of thirteen neonates, seven (53.8%) had an increase in their plasma creatinine on the second day while four (30.7 %) had a reduction. The remaining two (15.3%) had no change in their creatinine. After 72 hours of life, 12 out of 13 (92%) of the cases had a reduction in the creatinine (fig 1). By the third day, the mean serum creatinine of the cohort had dropped to a significant level, 0.64 mg/dl to 0.44 mg/dl, p = 0.04 (table 1).
The study demonstrated a trend of fall in serum creatinine level by 72 hours. This reflected the improvement in the renal function and GFR. The improvement in the GFR has shown to be a function of postconceptional age, reflected by lower creatinine levels in term and near term infants as compared with preterm infants.3-5
We noted that the rise in creatinine in first 48 hours was transient and by the third day most of the creatinine levels (92%) had dropped down. One could argue about the sample size of our study. The sample size was restricted as no extra blood was extracted for the purpose of study. The results with 12 out of 13 cases (92%) suggest that there may not be wide variation in the results. However, a larger study will provide more reliability and validity to our preliminary results.
In conclusion, caution should be exercised in interpretation of serum creatinine levels in the first 72 hours of life. A raised serum creatinine level in early newborn period does not necessarily indicate renal failure or kidney disease.
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