A 42-year-old woman is transported to the emergency department after a grease fire erupted… — USMLE Step 2 CK

A 42-year-old woman is transported to the emergency department after a grease fire erupted at the commercial kitchen where she works. The incident occurred exactly 3 hours before her arrival at the trauma center. She weighs $80 \text{ kg}$ . On primary survey, her airway is patent, breathing is spontaneous but tachypneic, and hemodynamics are stable. Physical examination reveals deep partial-thickness and full-thickness burns involving her entire anterior trunk, her entire right arm, and the anterior surface of her right lower extremity. The remainder of her skin is uninjured. Using the traditional Parkland formula ( $4 \text{ mL/kg/\%TBSA}$ ), at what rate (in $\text{mL/hour}$ ) should the initial intravenous crystalloid infusion be set to deliver the appropriate fluid volume over the remainder of the first 8-hour window?

Answer: 1152 mL/hour

Answer

The initial fluid resuscitation rate should be set to 1152 mL/hour.

The correct calculation identifies

36\%

TBSA using the Rule of Nines, computes the total 24-hour fluid requirement as

11,520 \text{ mL}

, allocates half (

5,760 \text{ mL}

) to the first 8 hours post-injury, and divides this volume by the remaining 5 hours to achieve the appropriate rate of

1,152 \text{ mL/hour}

Step-by-Step Solution

Calculate the Total Body Surface Area (TBSA) affected by the burns.

18\% + 9\% + 9\% = 36\%

TBSA

According to the adult Rule of Nines, the anterior trunk is

18\%

, the entire right arm is

9\%

, and the anterior surface of one leg is

9\%

Calculate the total fluid requirement for the first 24 hours using the traditional Parkland formula.

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

The Parkland formula dictates

4 \text{ mL}

of Lactated Ringer's per

\text{kg}

of body weight per percent of TBSA burned.

Calculate the fluid volume required for the first 8 hours.

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

Half of the total 24-hour calculated fluid volume must be administered in the first 8 hours following the burn injury.

Determine the time remaining in the initial 8-hour window.

8 \text{ hours} - 3 \text{ hours} = 5 \text{ hours}

The first 8-hour window begins at the time of the injury, not the time of hospital arrival. The patient arrived 3 hours post-injury.

Calculate the hourly infusion rate.

5,760 \text{ mL} \div 5 \text{ hours} = 1,152 \text{ mL/hour}

Dividing the required fluid volume by the remaining hours gives the constant rate for the infusion pump.

Key Concept

Burn fluid resuscitation calculations integrating the Rule of Nines, Parkland formula, and appropriate time adjustments.

Estimated Time:2m 0s

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