Dear Editor

 

 

We read with interest the report by Cataldi et al of the case control study on acute renal failure in preterm infants in 7 Italian NICUs.¹We 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 out-born patients (1 surgical, 46 medical).We defined ARF as a plasma creatinine >100µmol/l at 48 hrs of age based on published data of declining creatinine levels in infants of various gestational ages.²41 infants (8.8% ofNICU admissions) fulfilled this criteria with renal impairment occurring in 23 of 63 (37%) admissions <28 weeks gestations, 10 of 123 (8.1%) 28 – 32 weeks gestation, 4 of 93 (4.3%) 33 – 36 weeks gestation and 4 of 188 (2.1%) of term infants.Cataldi et al noted that 79% of cases of ARF occurred in very low birth weight infants <1500g who were all <37 weeks gestation compared to 63% in our series, which included infants of any gestation.

 

We also found the causes of ARF to be multifactorial in origin 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%).59% of infants had a pH <7.3 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 1000g or <28 weeks gestation.

 

The clinical management for ARF was conservative in all cases with no infant requiring dialysis.³10/41 patients (24%) died 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 were gathered over 3 years in 7 different units and our series represents a one year survey in one tertiary unit. The mortality rate will depend upon the proportion of external admissions to the unit and the treatment of extreme pre-term 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 2 of the survivors in our study had a plasma creatinine < 100µmol prior to 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.

 

We would concur with Cataldi et al that renal impairment is common in low birth weight 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

 

References

1.Cataldi L, Leone R, Moretti U, et al.Potential risk factors for the development of acute renal failure in preterm newborn infants: a case-control study.Arch Dis Child Fetal Neonatal Ed 2005;90:F514-519

 

2.Drukker A, Guignard J-P.Renal Aspects of the Term and Preterm Infant: A Selective Update. Current Opinion in Pediatrics 2002, 14:175-182

 

3.Strazdins V, Watson AR, Harvey B on behalf of the European Pediatric Peritoneal Dialysis Working Group.Renal replacement therapy for acute renal failure in children: European guidelines.Pediatr Nephrol 2004;19:199-207

 

4.Rostand SG.Oligonephronia, primary hypertension and renal disease: ‘is the child father to the man?’.Nephrol Dial Transplant 2003;18(8):1434-1438

Table 1:The gestation (mean), weight (mean), peak creatinine (median) and pH (mean) in infants who died compared to all preterm infants and all patients in our study.

 

	Died (n=10)	All preterm (n=37)	All patients (n = 41)
Gestation (wks)	26	27	28
Weight (kgs)	0.805	1.13	1.335
Creatinine (µmol/l)	143	138	149
pH	7.131	7.249	7.248