Burn Resuscitation: Judging Adequacy When the Numbers Disagree
A 34-year-old woman is admitted 3 hours after a house fire with deep partial- and full-thickness burns over the anterior trunk, both arms, and the face - estimated at 45% total body surface area by the Lund-Browder chart. She weighs 70 kg. She was intubated in the field for stridor and soot in the oropharynx. Initial resuscitation used the Parkland formula (4 mL/kg/%TBSA), and she has received 6,300 mL of lactated Ringer's in the first 3 hours. Urine output over the last hour was 20 mL. She is on norepinephrine at 0.1 mcg/kg/min for a mean arterial pressure of 58 mmHg. Lactate is 4.6 mmol/L, hematocrit is 52%, and the urine is dark and concentrated. Carboxyhemoglobin was 18% on arrival and is now 6%.
1. Assess whether this resuscitation is adequate, and explain why the formula output and the clinical picture diverge.
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The numbers. Parkland predicts 4 × 70 × 45 = 12,600 mL over 24 hours, half in the first 8 hours from the time of injury. At 3 hours post-injury she has received 6,300 mL, which is roughly on pace for the formula. Urine output of 20 mL/h is below the usual target of 0.5–1 mL/kg/h (35–70 mL/h).
Why the picture diverges from the formula.
- Timing: formulas are indexed to the time of injury, not to the time of admission. If the burn occurred more than an hour before resuscitation began, she is behind, not on pace.
- Formulas are starting estimates, not targets. Actual needs vary widely; patients with inhalation injury, delayed resuscitation, or large burns frequently require substantially more than predicted.
- The endpoints that matter are perfusion endpoints, not the volume delivered: urine output, lactate clearance, base deficit, mental status, and hemodynamics. By these she is under-resuscitated - oliguric, acidotic, hypotensive on a vasopressor, with a rising hematocrit suggesting hemoconcentration from plasma loss into the interstitium.
- Dark concentrated urine raises concern for rhabdomyolysis (check creatine kinase) and for hemoglobinuria, both of which increase the risk of acute kidney injury and may warrant higher urine output targets.
- Vasopressor use at this stage suggests either inadequate volume or a non-volume cause (e.g., myocardial depression from burn-related inflammatory mediators, or sepsis).
Assessment. She is under-resuscitated despite appearing to follow the formula, and the formula should not be used to justify withholding fluid.
2. Outline your fluid and monitoring plan for the next 6 hours, including how you would avoid both under- and over-resuscitation.
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Fluids.
- Continue lactated Ringer's; avoid colloids and starches early. Titrate the rate to urine output of roughly 0.5–1 mL/kg/h (consider 1 mL/kg/h if rhabdomyolysis or hemoglobinuria is present, after confirming with CK and urinalysis).
- Increase the rate in increments (e.g., 20–30%) and reassess hourly, rather than making large jumps.
- Recognize that burn patients can become markedly edematous with over-resuscitation ("fluid creep"), which worsens airway edema, compartment pressures, and pulmonary function. The goal is the lowest rate that achieves adequate perfusion.
Monitoring.
- Hourly urine output via catheter; hourly titration.
- Trend lactate and base deficit every 2–4 hours; aim for clearance.
- Frequent reassessment of hemodynamics; consider dynamic measures of volume responsiveness once the acute phase is past, but recognize that these are less reliable in burns.
- Monitor for abdominal and extremity compartment syndromes - bladder pressure if the abdomen is involved, and serial assessment of burned extremities for escharotomy need.
- Check creatine kinase, urinalysis, and electrolytes (watch for hypocalcemia and hyperkalemia).
Vasopressor. Treat hypoperfusion with volume first; if hypotension persists after adequate filling, vasopressors are appropriate, but they should not substitute for volume in the early phase.
Reassess the estimate. Lund-Browder should be rechecked; over- or under-estimation of TBSA is common and directly distorts the formula.
3. At hour 8 she is oliguric again despite 1,200 mL/h of fluid, bladder pressure is 22 mmHg, and her peak airway pressures are rising. What is your differential and next step?
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Differential for oliguria despite high-volume fluid.
- Abdominal compartment syndrome - bladder pressure 22 mmHg with new organ dysfunction (oliguria, rising airway pressures) meets criteria. Burn resuscitation is a classic setting because of massive capillary leak and fluid creep.
- Over-resuscitation with edema - the high rate may be causing interstitial edema that impairs renal perfusion and chest wall compliance rather than improving it.
- Acute kidney injury from rhabdomyolysis, hemoglobinuria, or hypoperfusion.
- Cardiac dysfunction from burn-related myocardial depressants.
- Sepsis - burn wounds colonize early; consider wound inspection and cultures.
Next step. The rising airway pressures plus bladder pressure of 22 mmHg point to intra-abdominal hypertension with early ACS. Rather than continuing to escalate fluid - which will worsen the compartment pressure - I would:
- Reduce the fluid rate to the minimum consistent with perfusion, accepting a lower urine output temporarily if other perfusion markers are improving.
- Measure bladder pressure serially and treat IAH medically: sedation, neuromuscular blockade if needed, gastric and rectal decompression, drainage of any free fluid.
- Reassess for escharotomy need on the trunk - a circumferential full-thickness burn of the torso can act as a restrictive shell and contribute to elevated intra-abdominal and intrathoracic pressures.
- Check CK and urinalysis to guide renal protection.
- If organ dysfunction persists despite these measures, escalate to surgical decompression.
The key judgment is recognizing that more fluid is not the answer when the compartment pressure is the problem.