Fluid balance in burn patients

It is vital to ensure a burn patient’s fluids are balanced. After the first 24 hours, you will need to take a different approach due to changes in the burn patient’s pathophysiological response.

If the burn injury is new, conduct fluid resuscitation as part of the ABCDEF method.

Changes in the burn patient’s fluid balance after 24 hours

As the patient transitions from the ebb phase into the flow phase, you can no longer base fluid administration on restricted urine production.

This is because of pathophysiological changes: from 48 hours post-burn, cardiac output increases. This causes renal blood flow and glomerular filtration rate to become elevated, together with the solute load, resulting in an osmotic diuresis. This impairs the renal concentration mechanism, and urine production is elevated.

Burn patients also lose water by evaporation from wounds, increased respiration, and increased urine production.

Fluid requirements for adult burn patients after 24 hours

Formula for estimating hourly insensible fluid loss in burns

(15 + % TBSA burned) x total body surface area = ml per hour fluid loss

You can measure total body surface area (TBSA), based on height, weight and sex. Free TBSA calculators are available online:

For a bedside estimation, these are typical values for TBSA:

  • Neonate 0.25 m2
  • Two-year old 0.5 m2
  • Ten-year old 1.14 m2
  • Adult female 1.6 m²
  • Adult male 1.9 m2

How to estimate fluid requirements

Add at least 1 ml of fluids per kilogram body weight per hour for adequate urine output.

Example: A ten-year old boy, weight 35Kg, with 20% TBSA burned.

  • Insensible fluid loss of approximately (25+20) x 1.14 = 51.3 ml/hour.
  • Anticipated urine production = at least 35 ml/hour.
  • Minimal total fluid requirement = 51 + 35 = 86 ml/hour, or approx. 2,000 ml/day.

This formula serves as an initial guideline only. You can determine actual requirements by clinical observation, especially thirst, hemodynamic parameters and laboratory tests. Remember: urine production is an unreliable indicator of normovolemia at this stage.

Patients should be allowed to drink freely – preferably calorie-rich fluids, which contribute to nutritional requirements. Intravenous fluids (e.g. glucose/salt solutions) may be necessary for patients who are unable to drink.

Suspect dehydration if serum sodium concentration becomes elevated, especially if urine sodium is low.

Fluid resuscitation

Fluid balance in burn patients