Dosages Based on Body Surface Area (BSA)

• BSA calculations

provide more accurate dosage calculations that are specific to the patient’s size and severity of his/her illness.

Dosages Based on BSA – CALCULATING BSA

Dosages Based on BSA (cont.)

Rule 17-5 Rule 17-5 Calculating the BSA using a formula:

1. If you know the height in cm and weight in kg, calculate

Dosages Based on BSA (cont.)

Rule 17-5 Rule 17-5 (cont.)

2. If you know the height in inches and weight in pounds, calculate

.

Dosages Based on BSA (cont.)

Find the body surface area for an adult who is 5’6” talland who weighs 168 lb.

BSA = 1.88 m2 = 1.9 m2

Example Example

Dosages Based on BSA (cont.)

Rule 17-6 Rule 17-6 Calculating BSA using a Nomogram:

Using a straight edge, align the straightedge so it intersects at the height and weight.

Creates an intersection in the BSA scale.

Dosages Based on BSA (cont.)

Find the body surface for a baby who is 24 in tall and weighs 14 lb and 8 oz.

Use the “Child’s Nomogram.”

BSA = 0.21 m2

Example Example

Calculating Dosage Based on BSA

Rule 17-7 Rule 17-7 Calculating dosage based on BSA:

Step A: Calculate the patient’s BSA in m2

Step B Calculate the desired dose:

dosage ordered per m2 x BSA = desired dose

Calculating Dosage Based on BSA

Rule 17-7 Rule 17-7 (cont.)

Step C Think! . . . Is It Reasonable?

Confirm whether the desired dose is safe.

If it is safe, calculate the amount to administer using preferred method.

Calculating Dosage Based on BSA (cont.)

Ordered: CeeNU (1st dose) 140 mg now for a child 38 in tall and weighing 47

lb

Per package insert: first dose is a single oral dose providing 130 mg/m2.

BSA = 0.76 m2

Desired dose should be 98.8 mg.

Ordered dose of 140 mg is too large for the patient.

Example Example

Practice

Patient: 34 cm tall, 5 kg

Ordered: Cerubidine 5.5 mg IV weekly

On hand: Cerubidine injection 5mg/mL

Recommended pediatric dose 25 mg/m2

If dose is safe, calculate amount to administer:

BSA = 0.23 m2 Desired dose = 5.8 mg

Dose ordered is a safe dose.

Amount to administer = 1.2 mL