Fluid replacement in peds
Perioperative fluid replacement for children and infants is a complex and somewhat controversial topic. Traditionally, the first step in determining the hourly fluid requirements for a child described by Holliday and Segar and coined as the “4/2/1” rule: For children < 10 kg their hourly fluid needs are body weight (kg) x 4. For children 10-20 kg, their hourly fluid needs are 40 ml + (BW – 10 kg) x 2 . Finally, for children > 20 kg, their needs are calculated by 60 mL + (BW – 20 kg) x 1. Thus, a 22 kg child would be thought to require 62 ml/hr of a hypotonic maintenance fluid (traditionally 5% dextrose in 0.45% sodium chloride).
According to Smith’s Anesthesia for Infants and Children:
- Determination of maintenance fluid needs per the 4/2/1 rule
- Estimation of volume deficit from preoperative fasting (hourly maintenance needs x number of fasting hours)
- This volume delivered 50% of the first hour of anesthesia and 50% over the next 2 hours
- Severity of surgical procedure and tissue trauma as it results in redistribution of fluids in the body compartments.
- Mild trauma 2-6 ml/kg/hr
- Moderate trauma 4-8 ml/kg/hr
- Severe trauma 6-10 ml/kg/hr
- Fluids needed to replete blood losses and to support blood pressure based on losses
Due to the large volume of fluids that can be administered perioperatively, it is recommended to use isotonic crystalloids form volume repletion during this setting. Tough dextrose-containing hypotonic fluids are most commonly used for maintenance fluids in pediatrics, they should not be used for boluses or volume beyond calculated hourly maintenance needs.