Understanding the different types of intravenous fluids is a key area of perioperative practice. Whilst there is a choice of crystalloid and colloid solution, the majority of anaesthetists will administer balanced crystalloid solutions which contains electrolytes and pH close to that of plasma, such as Hartmann’s solution or Plasma-Lyte 148, avoiding the routine administration of 0.9% Sodium chloride 5% Glucose, and colloids such as starches an gelatins.

Fluids are given intraoperatively for three reasons: firstly, to replace existing deficits (which can be substantial in emergencies, bowel obstruction, prolonged starvation etc), secondly to maintain fluid balance and finally to replace surgical losses (both blood/fluid loss and insensible losses from evaporation).

In practice, most anaesthetists start with 1–2 l of crystalloid, although the volume of fluid administered can be guided by clinical assessment (arterial blood pressure and heart rate). In major cases a fluid challenge (e.g. 250 mls of crystalloid) is administered and the response of central venous pressure or stroke volume are assessed. This will help to minimise the risk of both hypervolaemia and hypovolaemia, both of which will impair tissue oxygenation.

Intravenous fluids are routinely given to children when the enteral route is not sufficient or it’s not an option, such as during surgery and anaesthesia. Lack of understanding of the composition of fluids and the appropriate rate to administer them has been associated with serious morbidity and mortality in children. Recent evidence has shown that giving children isotonic fluids with a sodium concentration similar to plasma decreases the risk of hyponatraemia without an increase in adverse effects. This has led to a change in guidelines, which now recommend that isotonic fluids are used in children along with regular monitoring of fluid balance and electrolytes. Current evidence supported by several anaesthesia societies across the world recommend that children are allowed and should be encouraged to drink clear fluids up to one hour before elective surgery. Evidence is starting to emerge from enhanced recovery programmes in children of improved outcomes from individualised perioperative fluid therapy and avoidance of prolonged preoperative fasting. Strategies to reduce blood transfusion in children having surgery include treatment of preoperative iron deficiency, acceptance of low transfusion thresholds, cell salvage and tranexamic acid administration.

The main aim of a perioperative fluid therapy is to maintain or normalize the patient’s homeostasis. Small children have higher fluid volumes, metabolic rates and fluid needs than adults. Therefore, short perioperative fasting periods (formula milk 4 hours, breast milk 3 hours, clear fluids 1 hour) are important to avoid iatrogenic dehydration, hypotension, ketoacidosis and uncooperative behavior. Balanced electrolyte solutions with 1–2.5% glucose are favored for intraoperative maintenance infusion. Glucose- free balanced electrolyte solutions should then be added as needed to replace intraoperative fluid deficits or minor blood loss. Gelatin solutions or hydroxyethyl starch are useful in hemodynamically unstable patients or those with major blood loss, especially when crystalloids alone are not effective and blood products are not indicated. The monitoring should focus on the maintenance or restoration of a stable tissue perfusion.In nonsurgical or postoperative children, balanced electrolyte solutions should be used instead of hypotonic solutions, both with 5% glucose, as recent clinical studies and reviews showed a lower incidence of hyponatremia.

Fluid administration is one of the basic components in the management of neurosurgical patients. However, there is still debate on the ideal fluid. Issues related to adequate volume replacement and effects on the intracranial pressure persist. Studies have demonstrated the harmful effects of colloids over crystalloids. Normal saline has remained a fluid of choice but there is now emerging evidence that it, too, is not free of its harmful effects. Hypertonic saline has also been accepted by many practitioners, but its use and administration require close monitoring. There is now growing evidence on the use of balanced solutions for neurosurgical patients. However, this evidence comes from a small number of studies. Hemodynamic monitoring for fluid therapy in these patients is prudent as these patients are prone to hypovolemia. Dynamic parameters like stroke volume variance and pulse pressure variance are considered more reliable to monitor fluid therapy in comparison to static parameters. This chapter briefly covers various clinical situations in neurosciences with respect to fluid therapy and use of hemodynamic monitoring while providing fluid therapy and its effect on patient outcome.