Fluid and electrolyte pathophysiology in common febrile illness in children and the implications for clinical management

Achieving fluid homeostasis and the management of fluid and electrolyte complications are constants in the treatment of seriously ill children worldwide. Consensus on the most appropriate fluid strategy for unwell children has been difficult to achieve and has evolved over the last two decades, most notably in high-income countries where adverse events relating to poor fluid management were identified more readily, and official robust inquiries were possible. However, this has not been the situation in many low-income settings where fluids that are prohibited from use in high-income countries may be all that are available, local guidelines and processes to recognise adverse events are not developed, and there has been limited training on safe fluid management for front-line healthcare workers. This narrative review outlines the fluid and electrolyte pathophysiology of common febrile illnesses in children, describes the evolution of this field and concludes with implications and principles of a fluid management strategy for seriously ill children. This review was prepared as a physiological background paper to support evidence presented to the WHO Guideline Development Group for Fluid Guidelines in Children, Geneva, March 2024.