The evidence base for the administration of intraoperative fluids in neonates is poor and extrapolated from adults and children. Differences from adults and children in physiology and anatomy of neonates inform our practice.

Explain the factors that are important in determining the type and amount of fluids given to neonates during surgery. Describe the indications and safeguards of blood and blood product administration in the neonate. Recognise the challenges of assessing whether a neonate requires fluids or is fluid replete. Management of fluids in the neonate undergoing major surgery is complex, and is influenced by the gestational age, postnatal age, physiological maturation of organ systems, type of surgery, concomitant illness, and blood loss. In addition, prematurity increases these challenges, as organ systems are immature and body fluid compositions are different to that of a healthy term baby. Much of the evidence is derived from the critically ill neonate; thus, caution must be exercised in extrapolating these data to the neonate undergoing surgery. Neonatal physiology and cardiorespiratory adaptation at birth Changes in body composition and cardiorespiratory adaptation The transition from fetal life to neonatal life involves significant changes in the body water composition, and depends on the gestational age at birth and the stage of cardiorespiratory adaptation (Fig 1). 1 The proportion of extracellular fluid (ECF) is higher in preterm infants and depends on the level of prematurity. Postnatal diuresis Soon after birth, pulmonary vascular resistance decreases dramatically with a consequent increase in blood flow to the lungs and left atrium. This stimulates the production of atrial natriuretic peptide, which in turn stimulates sodium (Na) and water diuresis from the kidneys, and results in a decrease in the ECF volume. This cardiorespiratory adaptation results in a physiological weight loss of 5e10% in term neonates and up to 15% in Anil Visram BSc FRCA is a consultant in paediatric anaesthesia at the Royal London Hospital. He has interests in neonatal fluids and point-of-care testing.

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