Situation: A 40-year-old woman weighing 55 kg is rescued after being trapped for 20 minutes in a closed room of a burning house, where furniture and plastic items were burning. She has partial-thickness burns of the face, neck, anterior trunk, and both arms, estimated at 30% of total body surface area. She does not smoke. Burn shock resuscitation with lactated Ringer's solution is running at 280 mL/hour. The unit protocol for thermal burns reads: keep urine output at 0.5–1 mL/kg/hour; when output is outside this range for 2 consecutive hours, change the infusion rate by 20% in the direction that corrects it. Her urine is clear yellow, and no diuretic has been given. Hour 3 urine output: 62 mL Hour 4 urine output: 71 mL What rate should the nurse set now?

Her target range is 0.5–1 mL/kg/hour × 55 kg = 27.5–55 mL/hour. Both hours are above 55 mL, so she is being over-resuscitated, and the rate is decreased by 20%: 280 × 0.8 = 224 mL/hour. Excess fluid in burn shock causes edema, compartment syndromes, and respiratory compromise (fluid creep).

Target urine output calculation

The patient weighs 55 kg, and the protocol target is 0.5–1 mL/kg/hour. Multiplying gives a target range of 27.5–55 mL/hour. This range is the bedside surrogate used to judge whether the current infusion rate is matching the patient’s actual intravascular needs during the first 48 hours after a major burn.

Interpreting the two consecutive hourly outputs

Hour 3 output was 62 mL, and hour 4 output was 71 mL. Both values exceed the upper limit of 55 mL/hour. Because the protocol requires two consecutive hours outside the target range before changing the rate, the condition for adjustment is met. The direction of correction is to reduce the infusion rate, since urine output above the target indicates that more fluid is being given than the patient currently needs.

Applying the 20% adjustment

The current rate is 280 mL/hour. A 20% decrease is calculated as 280 × 0.8 = 224 mL/hour. The nurse should set the pump to 224 mL/hour and continue to monitor hourly urine output, vital signs, and respiratory status.

Urine output above the target range for two consecutive hours signals over-resuscitation, so the infusion rate is reduced by 20%.

Why over-resuscitation is dangerous in burn shock

Fluid creep, or giving more crystalloid than the patient actually requires, is a recognized complication of burn resuscitation. Excess lactated Ringer’s solution expands not only the intravascular space but also the interstitial compartment. In a patient with a 30% total body surface area burn involving the face, neck, and anterior trunk, excessive fluid can worsen facial and airway edema, increase the risk of compartment syndrome in burned extremities, and impair pulmonary gas exchange. The purpose of hourly urine output monitoring is not simply to keep the number high, but to keep it within a narrow range that reflects adequate organ perfusion without fluid overload.

Key point! A single high urine output does not automatically require a rate change. The protocol requires two consecutive hours outside the range, which prevents overcorrection from transient changes in urine flow.

Watch out! Do not increase the rate when urine output is high. High output in this context means the current fluid rate is excessive, not that the kidneys need more volume.

Clinical reasoning for the remaining options

Option	Rate	Reason it is incorrect
1	260 mL/hour	This is only a small reduction and does not follow the protocol’s required 20% change.
3	336 mL/hour	This is a 20% increase, which would worsen over-resuscitation and increase edema risk.
4	280 mL/hour	Keeping the same rate ignores two consecutive hours of urine output above the target range.

Pathophysiologic basis for using urine output as the target

During burn shock, massive capillary leakage shifts fluid from the intravascular space into the interstitium. Renal perfusion falls, and urine output drops unless volume is replaced. However, urine output is an indirect marker. It reflects renal blood flow and, by extension, overall organ perfusion, but it does not directly measure cardiac output or tissue oxygenation. This is why protocols set a range rather than a single number. A urine output below the lower limit suggests under-resuscitation and risk of acute kidney injury, while output above the upper limit suggests excessive volume administration and risk of edema-related complications.

The use of urine output as a resuscitation endpoint is supported by burn resuscitation research, which has used target urine output ranges to guide both manual and automated fluid titration. The rationale is that maintaining urine output within a defined range helps avoid both under-resuscitation and fluid creep.

Why the face and neck burns raise the stakes

This patient has partial-thickness burns of the face and neck. Even without an inhalation injury, edema from over-resuscitation can narrow the upper airway. Excess fluid worsens facial and laryngeal swelling, which may convert a stable airway into a difficult one. Reducing the infusion rate when urine output is high is therefore not only about fluid balance; it is also a protective measure for airway patency.

Key point! In burns involving the face and neck, the consequences of fluid creep are magnified because airway edema can progress rapidly. Hourly reassessment of voice, swallowing, and respiratory effort remains essential even after the rate is reduced.