Background Little is known about normative ammonia concentrations in extremely low birthweight (ELBW) babies and whether these vary with birth characteristics. We aimed to determine ammonia concentrations in ELBW babies in the first week after birth and relationships with neonatal characteristics and protein intake. Methods Arterial blood samples for the measurement of plasma ammonia concentration were collected within 7 days of birth from ProVIDe trial participants in six New Zealand neonatal intensive care units. Results Three hundred and twenty-two babies were included. Median (range) gestational age was 25.7 (22.7–31.6) weeks. Median (interquartile range (IQR)) ammonia concentration was 102 (80–131) µg/dL. There were no statistically significant associations between ammonia concentrations and birthweight or sex. Ammonia concentrations were weakly correlated with mean total (Spearman’s r s = 0.11, P = 0.047) and intravenous ( r s = 0.13, P = 0.02) protein intake from birth, gestational age at birth ( r s = −0.13, P = 0.02) and postnatal age ( r s = −0.13, P = 0.02). Conclusions Plasma ammonia concentrations in ELBW babies are similar to those of larger and more mature babies and only weakly correlated with protein intake. Currently, recommended thresholds for investigation of hyperammonaemia are appropriate for ELBW babies. Protein intake should not be limited by concerns about potential hyperammonaemia.

中文翻译：

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出生后第一周极低出生体重婴儿的血浆氨浓度：ProVIDe 随机临床试验的二次分析

背景 对于极低出生体重 (ELBW) 婴儿的正常氨浓度以及这些浓度是否随出生特征而变化，人们知之甚少。我们的目的是确定 ELBW 婴儿出生后第一周的氨浓度及其与新生儿特征和蛋白质摄入量的关系。方法 从新西兰六个新生儿重症监护病房的 ProVIDe 试验参与者中采集出生 7 天内的动脉血样本，用于测量血浆氨浓度。结果 包括 322 名婴儿。中位（范围）孕龄为 25.7（22.7–31.6）周。氨浓度中位数（四分位距 (IQR)）为 102 (80–131) µg/dL。氨浓度与出生体重或性别之间没有统计学上的显着关联。氨浓度与出生时平均总蛋白摄入量（Spearman's rs = 0.11，P = 0.047）和静脉注射蛋白摄入量（rs = 0.13，P = 0.02）、出生时孕龄（rs = -0.13，P = 0.02）和产后的相关性较弱。年龄（rs = -0.13，P = 0.02）。结论 ELBW 婴儿的血浆氨浓度与较大且更成熟的婴儿相似，仅与蛋白质摄入量相关性较弱。目前，高氨血症调查的推荐阈值适用于 ELBW 婴儿。不应因担心潜在的高氨血症而限制蛋白质摄入量。