We read with interest the report by Cataldi et al of the case‐control study on acute renal failure in preterm infants in seven Italian neonatal intensive care units.1 We have recently completed a one year study of acute renal failure (ARF) in 467 consecutive admissions to a tertiary neonatal referral unit. There were 5661 live births in the adjoining maternity unit over the year, and 47 admissions were from outborn patients (one surgical, 46 medical). We defined ARF as plasma creatinine >100 µmol/l at 48 hours of age based on published data of declining creatinine concentrations in infants of various gestational ages.2 Forty one infants (8.8% of NICU admissions) fulfilled this criterion, with renal impairment occurring in 23 of 63 (37%) admissions <28 weeks gestation, 10 of 123 (8%) at 28–32 weeks gestation, four of 93 (4%) at 33–36 weeks gestation, and four of 188 (2%) term infants. Cataldi et al noted that 79% of cases of ARF occurred in very low birthweight infants <1500 g, who were all <37 weeks gestation, compared with 63% in our series, which included infants of any gestation.
We also found the causes of ARF to be multifactorial, with sepsis the predominant insult in 16/41 (39%), perinatal asphyxia in 7/41 (17%), and hypotension not associated with sepsis in 4/41 (10%). A pH<7.3 was found in 59% of infants at the time of onset of the ARF, and 39% received inotropic support. In 13/41 (32%) infants, we found no specific cause other than prematurity. We agree that drug administration may be an important factor, with indomethacin being used prophylactically on our unit in all ventilated patients with a birth weight less than 1000 g or <28 weeks gestation.
The clinical management for ARF was conservative in all cases, with no infant requiring dialysis.3 Death was the outcome in 10/41 patients (24%), and in only one was renal failure felt to be a contributing cause. Cataldi et al reported an 11% mortality in their 71 patients, but these data were gathered over three years in seven different units, and our series represents a one year survey in one tertiary unit. Mortality depends on the proportion of external admissions to the unit and the treatment of extreme preterm infants. The patients who died in our series (table 1) were more premature with a lower birth weight and had a more profound acidosis. All but two of the survivors in our study had a plasma creatinine <100 µmol/l before discharge. One term infant with perinatal asphyxia had persistent renal impairment, and one child had surgical treatment for posterior urethral valves with associated renal dysplasia.
Table 1 Gestation (mean), weight (mean), peak creatinine (median), and pH (mean) in infants who died compared with all preterm infants and all patients in our study.
Died (n = 10) | All preterm (n = 37) | All patients (n = 41) | |
---|---|---|---|
Gestation (weeks) | 26 | 27 | 28 |
Weight (kg) | 0.805 | 1.13 | 1.335 |
Creatinine (µmol/l) | 143 | 138 | 149 |
pH | 7.131 | 7.249 | 7.248 |
We would concur with Cataldi et al that renal impairment is common in low birthweight infants, and careful attention to fluid and electrolyte management, along with drug dosing, is essential. However, there is still a paucity of information on the long term outcomes of neonates with ARF. Assessment of renal function should be part of the long term follow up of preterm cohorts, as acute renal impairment combined with potential oligonephronia could lead to hypertension and renal impairment in later life.2,4
Footnotes
Competing interests: none declared
References
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