The Modified Brooke formula estimates the intravenous fluid a burn patient needs in the first 24 hours after injury. It uses a lower volume than the classic Parkland formula, reflecting modern concern about the harms of over-resuscitation, while keeping the same two-phase timing.
Background: Parkland versus Modified Brooke
The Parkland formula (4 mL/kg/%TBSA), developed by Dr. Charles Baxter at Parkland Hospital in Dallas in the 1960s, became the dominant resuscitation guide for decades. The Modified Brooke formula (2 mL/kg/%TBSA) was developed as a lower-volume alternative, built on the observation that many patients were receiving far more fluid than the Parkland formula projected because staff were correcting for inadequate urine output by continually increasing infusion rates — a phenomenon known as “fluid creep.”
Excessive resuscitation carries real risks: abdominal compartment syndrome, pulmonary oedema, and extremity compartment syndrome are all associated with over-resuscitation. By targeting a lower initial volume, the Modified Brooke approach attempts to thread the needle between under-resuscitation (which causes hypovolaemia and organ failure) and over-resuscitation.
Neither formula is universally preferred; many burns units select based on local protocol and clinician experience.
How the formula works
The total crystalloid volume is proportional to body weight and the extent of the burn:
total 24h = 2 mL x weight(kg) x %TBSA
first 8h = total / 2
next 16h = total / 2The hourly rate for the first phase is the first-half volume divided by the hours remaining in the eight-hour window, which matters when resuscitation starts late because the clock runs from the time of the burn, not from hospital arrival. The second-phase rate is the second-half volume divided by sixteen hours. The Parkland total (4 mL/kg/%TBSA) is shown alongside for comparison.
Worked example
For a 70 kg adult with a 30% TBSA burn, presenting 2 hours after the injury:
total 24h = 2 × 70 × 30 = 4,200 mL
first 8h = 2,100 mL — to be given over the remaining 6 hours of the first phase
rate = 2,100 / 6 = 350 mL/hour
next 16h = 2,100 mL
rate = 2,100 / 16 = 131 mL/hour
Parkland equivalent: 4 × 70 × 30 = 8,400 mLThe 2-hour delay means the first-phase volume must be delivered more rapidly. This is why the time-since-injury input is critical to the calculation.
Estimating TBSA and clinical endpoints
Use the Rule of Nines for a rapid initial estimate: each arm is 9%, each leg is 18%, the front and back of the trunk are 18% each, the head is 9%, and the perineum is 1%. For a more accurate assessment, particularly in children (where head-to-body proportion differs with age), use a Lund-Browder chart.
Count only partial-thickness and full-thickness burns. Superficial (first-degree) burns are excluded from the TBSA used in resuscitation formulae.
The calculated volume is a starting point, not a prescription. Titrate the infusion rate to physiological endpoints:
- Urine output of 0.5–1.0 mL/kg/hour in adults (a useful and practical target)
- Mental status
- Blood pressure and heart rate trends
Reassess frequently and adjust. Major burns (typically defined as greater than 20–25% TBSA, or involving the face, hands, feet, genitalia, or major joints) warrant early referral to a specialist burns centre.
This is an educational calculator. It does not replace clinical judgement or specialist burns care.