Wilkins B H
Department of Child Health, Bristol University.
Arch Dis Child. 1992 Oct;67(10 Spec No):1146-53. doi: 10.1136/adc.67.10_spec_no.1146.
Plasma urea and creatinine concentrations and urea and creatinine clearances and excretion were measured in a sample of 40 infants of 25.5-33 weeks' gestation, birth weight 720-2000 g, between the ages of 0.5 and 33 days. Creatinine excretion rate was between 60 and 120 mumol/kg/day in the first five postnatal weeks (mean 90.5) and was independent of sex or growth retardation. This can be used in clinical practice to estimate instantaneous urine flow rate V, if the creatinine concentration is measured in a randomly voided urine sample, from the formula V = 90.5/urine creatinine, with 95% confidence limits +/- 39%. There is a wide range of plasma creatinine at all gestations and ages decreasing from range 75-130 mumol/l in the first two days to 35-80 mumol/l at 3 weeks of age. Plasma urea is a poor indicator of glomerular filtration rate (GFR) in sick preterm infants. GFR (ml/min/kg) can be estimated from plasma creatinine from the formula GFR = 69.2/plasma creatinine but this estimate is imprecise with 95% confidence limits +/- 46%. Urea:creatinine clearance ratio was usually less than 1.0 (range 0.18 to 1.5) and was lower when the urine flow rate was low. Urea excretion was up to 17 mmol/kg/day in the first two weeks, higher in the more immature infants. These high levels were paralleled by a high plasma urea concentration, up to 18 mmol/l. A high plasma urea is not necessarily associated with renal failure or dehydration.
对40名孕龄25.5 - 33周、出生体重720 - 2000克、年龄在0.5至33天的婴儿进行了血浆尿素和肌酐浓度、尿素和肌酐清除率及排泄量的测量。出生后前5周肌酐排泄率在60至120μmol/kg/天之间（平均90.5），且与性别或生长迟缓无关。如果在随机采集的尿液样本中测量肌酐浓度，可根据公式V = 90.5/尿肌酐，利用该值在临床实践中估算即时尿流率V，其95%置信区间为±39%。在所有孕周和年龄段，血浆肌酐范围广泛，从出生前两天的75 - 130μmol/l降至3周龄时的35 - 80μmol/l。血浆尿素对患病早产儿的肾小球滤过率（GFR）而言并非良好指标。GFR（ml/min/kg）可根据血浆肌酐通过公式GFR = 69.2/血浆肌酐估算，但该估算并不精确，95%置信区间为±46%。尿素:肌酐清除率通常小于1.0（范围0.18至1.5），且尿流率低时更低。出生后前两周尿素排泄量高达17mmol/kg/天，在更不成熟的婴儿中更高。这些高水平与高达18mmol/l的高血浆尿素浓度相对应。高血浆尿素不一定与肾衰竭或脱水相关。
