Intravenous fluid therapy for hospitalized and critically ill children: rationale, available drugs and possible side effects

Human beings are constituted mainly of water. In particular, children's total body water might reach 75-80% of their body weight, compared to 60-70% in adults. It is therefore not surprising, that children, especially hospitalized newborns and infants, are markedly prone to water and electrolyte imbalances. Parenteral fluid therapy is a cornerstone of medical treatment and is thus of exceptional relevance in this patient population. It is crucial to appreciate the fact that intravenous fluids are drugs with very different characteristics, different indications, contraindications and relevant side effects. In the present review, we will summarize the physiology and pathophysiology of water and electrolyte balance, underlining the importance and high prevalence of non-osmotic antidiuretic hormone release in hospitalized and critically ill children. Furthermore, we will discuss the characteristics and potential side effects of available crystalloids for the paediatric population, making a clear distinction between fluids that are hypotonic or isotonic as compared to normal plasma. Finally, we will review the current clinical practice regarding the use of different parenteral fluids in children, outlining both the current consensus on fluids employed for resuscitation and replacement and the ongoing debate concerning parenteral maintenance fluids.