Renal functions were assessed during two 12-hour periods, before and after the administration of a single oral dose of caffeine (15 mg/kg) in 13 preterm infants. Each infant acted as his own control. Heart rate, mean blood pressure, hematocrit, blood pH, arterial PO₂ and PCO₂ remained stable throughout the two successive periods. Mean protein serum level slightly increased from period I to period II. Urine flow rate (+63 ± 57%), water output/input ratio (+49 ± 54%) and creatinine clearance (+79 ± 102%) increased significantly after the administration of caffeine.

The adverse effects of nonselective cyclo-oxygenase (COX) inhibitors on the immature kidney have been described in newborn rabbits, but it is much more laborious and difficult to study its relative impact on renal function in human neonates. Amikacin clearance was therefore used as surrogate marker to study the impact of nonselective COX-inhibitors on glomerular filtration rate. Clinical characteristics and amikacin clearance of infants on respiratory support were retrospectively collected. Results in neonates in whom either ibuprofen-lysine or acetylsalicylic acid was administered prophylactically to induce closure of a patent asymptomatic ductus arteriosus were compared to infants not cotreated with any COX-inhibitor (Mann-Whitney U-, chi-square tests). Amikacin clearance was calculated in 142 infants, of whom 50 were cotreated with ibuprofen and 33 with acetylsalicylic acid. There were no significant differences in clinical characteristics between the three groups. Compared to controls (0.52, range 0.09-2.33 ml/kg/min), a significant similar decrease in amikacin clearance in infants cotreated with ibuprofen (0.38, range 0.13-0.80 ml/kg/min, p<0.01) or acetylsalicylic acid (0.38, range 0.13-0.78 ml/kg/min, p<0.01) was demonstrated. Using amikacin clearance as marker, a significant and similar reduction in glomerular filtration rate was documented in preterm infants cotreated with ibuprofen or acetylsalicylic acid.

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of venous and capillary sampling, but it would have been interesting to have had two groups, one in which capillary sampling preceded arterial sampling and one in which it was done afterwards. Our data did not show a variation in the white cell count, and I wonder what mechanism Dr Shohat proposes for his observed rise during and after lumbar puncture. These points emphasise the difficulties in establishing a reference range of white blood count values for infants, particularly preterm infants, and in interpreting results by comparing them with published ranges. Application of the International Committee for Standardisation in Haematology guidelines for the standardisation of blood specimen collection procedures for reference values is obviously impractical. but it is clear that the method of sampling does