A 35-year-old man is brought to the emergency department after a structural fire. He weigh… — USMLE Step 2 CK

A 35-year-old man is brought to the emergency department after a structural fire. He weighs $80 \text{ kg}$ . The burn injury occurred exactly 2 hours prior to his arrival at the emergency department. Physical examination reveals deep partial-thickness and full-thickness burns involving the entire anterior surface of his torso, his entire right arm, and the entire anterior surface of his right leg. No other burn injuries are identified. Using the traditional Parkland formula ( $4 \text{ mL/kg}$ per percentage of total body surface area), what should be the target intravenous fluid administration rate (in $\text{mL/hr}$ ) for this patient for the remainder of the first 8-hour post-injury period?

Answer: 960 mL/hr

Answer

960

The correct infusion rate is

960 \text{ mL/hr}

. The Rule of Nines assigns 18% to the anterior torso, 9% to an entire arm, and 9% to the anterior surface of a leg, totaling 36% TBSA. Using the Parkland formula (

4 \text{ mL} \times 80 \text{ kg} \times 36\%

), the 24-hour requirement is

11,520 \text{ mL}

. Half of this (

5,760 \text{ mL}

) must be given in the first 8 hours post-injury. Because the injury occurred 2 hours ago, the

5,760 \text{ mL}

must be infused over the remaining 6 hours (

5,760 / 6 = 960 \text{ mL/hr}

Step-by-Step Solution

Calculate the burned Total Body Surface Area (TBSA).

36%

Using the Rule of Nines: anterior torso (18%) + entire right arm (9%) + anterior right leg (9%) = 36%.

Calculate the total 24-hour resuscitation fluid volume.

11,520 mL

The traditional Parkland formula is

4 \text{ mL} \times \text{weight (kg)} \times \%\text{TBSA}

. For this patient:

4 \times 80 \times 36 = 11,520 \text{ mL}

Determine the fluid volume required for the first 8 hours.

5,760 mL

Half (50%) of the total 24-hour calculated volume must be given in the first 8 hours post-injury.

11,520 / 2 = 5,760 \text{ mL}

Calculate the hourly infusion rate for the remaining time.

960 mL/hr

The first 8-hour window begins at the time of injury, not time of arrival. Since 2 hours have elapsed, the 5,760 mL must be infused over the remaining 6 hours.

5,760 / 6 = 960 \text{ mL/hr}

Key Concept

Initial burn resuscitation requires accurately estimating TBSA using the Rule of Nines, calculating total fluid needs, and strictly administering the first half of the fluid over the first 8 hours measured from the TIME OF INJURY.

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