Fluid and electrolyte balance is important for the maintenance of normal function and wellbeing. The equilibrium of fluid balance between the body and its environment is maintained via the intake of fluids and electrolytes versus the loss of fluids through normal urine production, via the gastrointestinal tract and through insensible losses of the skin and respiratory tract.
Fluid and electrolyte balance also needs to be maintained within the different fluid compartments of the body. This includes the state of balance between the intracellular fluids (ICF) and extracellular fluids (ECF), comprising fluids in intravascular and extravascular spaces. The balance of electrolytes between the ICF and ECF is mediated via the sodium pump present in cell membranes, while the balance in the ECF (between intravascular and extravascular space) is mediated via the capillary membrane.
Infants and children are susceptible to disruptions in fluid balance and nutrition during periods of acute illness or exacerbations of existing, chronic conditions for two main reasons. First, infants and young children are physiologically immature in relation to fluid balance, and lack some of the mechanisms to protect them against disruptions to fluid balance, such as dehydration. Second, infants are dependent on parents or adult carers to provide them with fluids and food. Because of these vulnerabilities to fluid balance and nutrition, nurses working in paediatric settings need to be skilful in their assessment and monitoring of fluid balance in infants and children, and able to manage a range of therapies to correct fluid and nutritional deficits. In this chapter, you will expand your understanding and develop skills in the management of peripheral and central intravenous therapy and enteral feeding. An additional section on current insulin therapies is also included.
Differences in the fluid balance and nutrition of infants and children
There are several differences in the composition of fluids in the body of infants, particularly newborns and younger infants. These differences mean that infants and children are more susceptible to fluid losses than adults.
Newborn babies have higher total body water (75–80 per cent) than adults (60 per cent). Premature infants have higher total body water than even infants born at term. In newborn infants, there is a greater proportion of body water in the extracellular space.