Fluid rate calculations

Fluids are administered for several purposes, including replacement of lost vascular volume (e.g. bleeding), replacement of total body water deficits and electrolyte losses or imbalances (e.g. hypernatremia or hyponatremia associated with diarrhoea or excessive sweating), correction of metabolic acid-base abnormalities (secondary to metabolic or respiratory disease or during prolonged general anaesthesia) and correction of low oncotic pressure (due to protein loss or deficit), provision of parenteral nutrition (glucose, proteins as amino acids, lipids, vitamins, trace minerals) and treatment for specific medical conditions.

Fluids can be administered intravenously (through an 18G or larger bore IV catheter) or orally (via a naso-gastric tube).

While there are a number of different types of fluids which can be administered, common resuscitation fluid protocols are 60 to 80 mL/kg isotonic polyionic crystalloids plus a one off hypertonic crystalloid as a bolus.

On average, these doses can be summarised as follows for resuscitation of a:

Foals (50 - 80 kgs) - 1 to 4 L isotonic polyionic crystalloids and 2 L 5% dextrose as a bolus.

Adults (450kg) - 20 to 30 L isotonic polyionic crystalloids and 2 L 7.5% hypertonic saline as a bolus.

Once this initial bolus has been administered, the isotonic polyionic crystalloids are dropped to maintenance rate at 2.5 mL/kg/h for adult horses and 3 to 5 mL/kg/h for neonatal foals.