A 34-year-old woman arrives at the regional burn center via ambulance after being rescued … — USMLE Step 2 CK

A 34-year-old woman arrives at the regional burn center via ambulance after being rescued from a residential house fire. She sustained deep partial-thickness and full-thickness thermal burns. Physical examination reveals that her entire right leg and her entire right arm are burned. Her uninjured skin is intact. The patient weighs $75 \text{ kg}$ . The incident occurred exactly $2 \text{ hours}$ prior to her arrival at the hospital. Two large-bore intravenous lines are established.

Using the traditional Parkland formula ( $4 \text{ mL/kg/}\% \text{TBSA}$ ), what should be the initial intravenous fluid infusion rate (in $\text{mL/hr}$ ) to administer the required volume over the remainder of the first 8 hours post-injury?

Answer: 675 mL/hr

Answer

675

The patient requires a total of

8100 \text{ mL}

of fluid over the first 24 hours based on the Parkland formula (

4 \text{ mL} \times 75 \text{ kg} \times 27\%

). Half of this volume (

4050 \text{ mL}

) must be given in the first 8 hours post-injury. Since 2 hours have already elapsed, the

4050 \text{ mL}

must be administered over the remaining 6 hours, requiring a rate of

675 \text{ mL/hr}

Step-by-Step Solution

Calculate the Total Body Surface Area (TBSA) burned.

27\%

According to the Rule of Nines for adults, the entire right leg accounts for

18\%

and the entire right arm accounts for

9\%

. Summing these yields

18\% + 9\% = 27\%

Calculate the total 24-hour fluid requirement using the Parkland formula.

8100 \text{ mL}

The traditional Parkland formula is

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

. Therefore,

4 \times 75 \times 27 = 8100 \text{ mL}

for the first 24 hours.

Determine the fluid volume required for the first 8 hours post-injury.

4050 \text{ mL}

Burn resuscitation protocols require half (

50\%

) of the total 24-hour fluid volume to be administered in the first 8 hours from the time of the burn.

Calculate the hourly infusion rate based on the time elapsed since the injury.

675 \text{ mL/hr}

Since

2 \text{ hours}

passed prior to arrival, there are only

6 \text{ hours}

remaining in the first 8-hour resuscitation window. The required rate is

4050 \text{ mL} / 6 \text{ hours} = 675 \text{ mL/hr}

Key Concept

Fluid resuscitation in burn patients using the Rule of Nines and the Parkland formula, adjusting for pre-hospital delays.

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