1. 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.
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).
BSA is important for burn victims, chemotherapy patients, radiation therapy patients, and open-heart surgery patients.

2. Dosages Based on BSA – CALCULATING BSA
BSA is stated in square meters (m2).
Must know height and weight.
Use a formula or a special chart called a nomogram.
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).

3. Dosages Based on BSA (cont.)
Rule 17-5 Calculating the BSA using a formula:
If you know the height in cm and weight in kg, calculate
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).

4. Dosages Based on BSA (cont.)
Rule 17-5 (cont.)
If you know the height in inches and weight in pounds, calculate .
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).
If the result is less than one, round to the nearest hundredth.
If the result is greater than one, round to the nearest tenth.

5. Dosages Based on BSA (cont.)
Find the body surface area for an adult who is 5’6” tall and who weighs 168 lb. BSA = 1.88 m2 = 1.9 m2
Example
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).

6. Dosages Based on BSA (cont.)
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.
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).

7. Dosages Based on BSA (cont.)
Example
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
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).
Find the height and weight and place a straight edge on the appropriate lines for each.
Where the line intersects the center graph is the patient’s BSA.

8. Calculating Dosage Based on BSA
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
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).

9. Calculating Dosage Based on BSA
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.
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).

10. 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
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).

11. 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
Learning Outcome: 17.4 Calculate dosages based on body surface area (BSA).
Step A Convert height and weight to BSA m2.
Sq root of 34cm x 5 kg/3131
BSA = 0.23 m2
Step B Calculate desired dose.
25 mg/ m2 x 0.23 m2 = D [cancel units (m2)]
5.8 mg = D
Step C Desired dose is less than maximum recommended dose of mg / m2.
Calculate amount to administer.
Step A No conversion is needed.
Step B H = 5 mg Q = 1 mL D = 5.8 mg
5.8 mg/5 mg x 1 mL = A
1.2 mL = A