![]() These changes are caused by considerable evaporative water loss via the immature skin as well as by continuing natriuresis (as present during foetal life) ( 11). hypernatraemic and hyperchloremic) contraction (duration hours to days). The immediate postnatal phase is characterised by a relative oliguria ( 10) followed by a diuretic phase, during which body fluid compartments are rearranged by isotonic or hypertonic (i.e. The time course of adaptation may be divided into three major phases: Subsequent adaptation includes the onset of autonomic renal regulation of fluids and electrolytes, and intake of fluids and other nutrients. Immediate adaptation processes after birth affect the metabolism of water and electrolytes as a result of discontinuation of placental exchange and the onset of considerable insensible water loss and thermoregulation. 1.0-1.5 mmol Na + per kg body weight per day. A daily weight gain of 15 g/kg in a neonate results in a net storage of about 12 ml of water and approx. Endogenous water production equals 0.6 ml H 2O per gram of carbohydrates, 1.0 ml H 2O per gram of fat and 0.4 ml H 2O per gram of protein oxidised ( 9). In the assessment of fluid balance, metabolic water production may be of particular importance in paediatric patients because of their high metabolic rates. Blood volume in neonates is 85-100 ml/kg body weight compared to 60-70 ml blood volume/kg body weight in adolescents and adults ( 8). ![]() ECF is subdivided into intravascular and extravascular components as well as a “third space” which characterises free fluid in preformed body compartments under physiological (like urine in the bladder, cerebral spinal fluid, etc) and pathological conditions (like ascites, or pleural effusions). The total volume of intracellular water increases with the number and size of body cells during body growth. Premature infants are vulnerable to imbalances between intra- and extracellular compartments. Potassium (K+) is the major ion of the ICF, and its intracellular concentration depends on the Na/K-ATPase activity which is impaired at insufficient supplies of oxygen and energy ( 7). Total body water is divided into two compartments: intracellular fluid (ICF) and extracellular fluid (ECF). Extremely low birth weight infants (ELBW) and very low birth weight (VLBW) infants have relatively low body fat contents and a higher percentage of LBM and of body water than older infants, which is related to high water turnover. Water turnover, like energy turnover, is related to lean body mass (LBM) but has no close relationship to body fat mass (FM). Water turnover is high in neonates and decreases with increasing age and the concomitant decreases of metabolic rate and growth velocity ( 4-6). During intrauterine life body water content decreases along with the relative increase of fat mass particularly during the third trimester of gestation ( 3). The amount of total body water (TBW) decreases markedly from intrauterine life to adulthood: water contributes to 90% of body weight in the 24 weeks old foetus, 75% in term infants, and 50% in adults ( 1,2). Therefore, recommendations for children are often based on extrapolations from data in neonates and adults. ![]() Most published studies on the adaptation processes of water and electrolyte metabolism relate to the preterm neonate, while studies on water and electrolyte metabolism in older paediatric patients are limited. Water and electrolyte requirements per unit body mass are very high after birth and decrease with age until adulthood. Water is an essential carrier for nutrients and metabolites, and it comprises the major part of human body mass at any age. ![]() Key Words: Neonate, Preterm infants, Infants, Children, Fluids, Sodium, Potassium, Chloride. Type of publications: original articles, case series, case-control studies, and overviews. Timeframe: publications from 1969 until 2004. Please note that ArticlePlus files may launch a viewer application outside of your web browser. Click on the links below to access all the ArticlePlus for this article.
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