Module 14
Pediatric Dosage Calculations
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
Dosage Calculation Based on
Weight: Objectives
After reviewing this chapter, you should be able
to:
1.Convert body weight from pounds to kilograms
2.Convert body weight from kilograms to pounds
3.Calculate dosages based on milligrams per
kilogram
4.Determine whether a dosage is safe
5.Determine body surface area (BSA) using the
West Nomogram
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
2
Dosage Calculation Based on
Weight: Objectives (Cont’d)
6. Calculate BSA using formulas according to
units of measure
7. Determine dosages using the BSA
8. Calculate the flow rates for pediatric IV
therapy
9. Calculate the safe dosage ranges and
determine normal range for medications
administered IV in pediatrics
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
3
Background

From Cohen, M. (2010):








Error rate in children is 3 times higher than in
adults
Confusion between adult and pediatric formulations
Oral liquids available in multiple pediatric strengths
Incorrect dilution of medications
Look-alike packaging, look-alike names, soundalikes
Improper education of parents
Calculation errors
Errors in measuring devices (household vs. metric)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
4
Background (Cont’d)



Make sure dosage is safe.
Physiological capabilities are different in
infants and children than in adults
Two methods to calculate pediatric dosages:



Body weight (BW)
Body surface area (BSA) based on height and
weight
Nurse responsible for verifying before giving
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
5
Background (Cont’d):
SAFETY ALERT
As the nurse administering meds to children, you are
legally responsible for recognizing incorrect and unsafe
dosages and for alerting the prescriber.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
6
Principles Relating to
Basic Pediatric Calculations
1. Use same methods (R&P, DA, Formula)
2. Pediatric doses are smaller (in mcg)
3. IM dosages rarely exceed 1 mL; for small infants, 0.5
mL
4. Subcut dosages are not to exceed 0.5 mL
5. For dosages less than 1 mL, use TB syringe
6. Pediatric doses are rarely rounded to tenths; use TB so
hundredths can be given
7. All answers must be labeled
8. Know institution policy on rounding dosages
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
7
Calculation of Pediatric Dosages
Based on Body Weight


Compare ordered dosage to recommended
safe dose range
Pounds to kilograms (2.2 lb = 1 kg)


To convert pounds to kg, divide pounds by 2.2
To convert kg to pounds, multiply kg by 2.2
• Example 1: Convert child’s BW of 30 lb to kg
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
8
Dimensional Analysis (DA)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
9
Converting Pounds/Ounces to Kg
1. Child weighs 14 lb 6 oz. Convert to kg.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
10
Converting Pounds/Ounces to Kg
(Cont.)
Mosby items and derived items © 2014, 2010, 2006, 2002,
. 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
11
Dimensional Analysis (DA)

Convert 14.4 lb to kg
SAFETY ALERT
Use caution when
converting ounces to a
fraction of a pound.
Remember to add the
remaining whole
pounds to get the total
pounds before
converting to kilograms.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
12
Case Study 6
Tara Bates is your 4-year-old patient admitted
to the pediatric unit with MRSA infection to the
right inner thigh with plans for I and D tomorrow
morning. You weigh Tara and find she is 32 lb
and 9 oz. You must convert the weight to kg
when filling out the surgical checklist. What is
Tara’s weight in kg?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
13
Case Study 6 (Cont.)
Answer:
Tara weighs 14.8 kg.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
14
Converting Grams to Kilograms



Neonates are weighed in grams
1,000 g = 1 kg
Calculate weight of 3,000 g infant in kg
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
15
Dimensional Analysis (DA)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
16
Review of Concepts




Convert the child’s weight in kg—round to
10th
Recommended dosage—reputable source
Total daily dosage—amount allowed in a 24
hour period
Divided doses—amount of drug from total
daily dose divided into various increments
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
17
Review of Concepts (Cont.)



Safe dose—high and low ranges of
recommended versus what is ordered
Calculate safe dose by multiplying wt by
recommended dose—round to 10th
Compare the ordered dose to the
recommended dose and determine if the
dosage is safe

If safe, calculate the amount and administer
 If unsafe, notify the prescriber
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
18
Review of Concepts (Cont.)
SAFETY ALERT
Before administering any medication to a child, always
ask yourself if the dosage is safe. When in doubt,
contact the prescriber before administering. Pediatric
medications should always be checked by two nurses.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
19
Single-Dose Medications
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
20
Single-Dose Medications (Cont.)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
21
Single-Dose Range Medications

Some medications can indicate a minimum
and a maximum range

Example 2: Vistaril 15 mg IM q4h prn nausea
Child weighs 38 lb. Is the dosage safe?
Recommended dose: 0.5 to 1 mg/kg/dose q4h
2.2 lb: 1 kg = 38 lb: x kg
X = 17.3 kg
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
22
Single-Dose Range Medications
(Cont.)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
23
Single-Dose Range Medications
(Cont.)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
24
Case Study 6 (Cont.)
You continue with your assessment of Tara and
notice that she feels warm to the touch and her
cheeks are flushed. An oral temperature
reveals a fever of
101.5 ° F. You review the
chart and find the following order:
Tylenol Elixir (160 mg/5 mL) 150 mg PO q4h
prn fever > 99° F
The safe dose range reads:
10-15 mg/kg/dose q4-6hr as needed.
Is the dose safe? (Tara weighs 14.8 kg) If so,
how much will you administer?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
25
Case Study 6 (Cont.)
Answer:
The dose is safe, administer 4.7 mL AFTER checking
calculations and dosage with another nurse.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
26
Pediatric Daily Dosages
1. Calculate total daily dosage
2. Divide daily dosage by number of doses to
be administered
3. Use R&P, Formula Method, or DA to
calculate number of tabs or caps or mL to
administer the dose
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
27
Pediatric Daily Dosages (Cont.)
Order: Dilantin 30 mg p.o. q8h. Child weighs 18 kg.
Recommended dosage is 5 mg/kg/day in two or three
equally-divided doses. Is the dosage safe?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
28
Pediatric Daily Dosages (Cont.)
1. Calculate safe total daily dosage:
5 mg/kg/day x 18 kg = 90 mg per day
2. Determine amount for each dose (3):
30 mg q8h = 30 mg three times daily
30 mg × 3 = 90 mg daily; therefore it is safe
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
29
Calculating BSA for Child Dosing
Using Formula


A pediatric dosage may be calculated from a
recommended adult dosage using a formula
The formula uses the average adult dosage,
the average adult BSA (1.7 square meters),
and the child’s BSA
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
30
Calculating BSA for Child Dosing
Using Formula (Cont.)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
31
Case Study 6 (Cont.)
Two hours after administering the Tylenol,
Tara’s temperature has normalized. The
surgical team has been talking to Tara and her
mother regarding the procedure. The
anesthesiologist asks you to add Tara’s BSA to
the chart. You recall her height: 35.5 inches
and her weight: 32 lb 9 oz. What is her BSA?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
32
Case Study 6 (Cont.)
Answer:
Tara’s BSA is 0.61 m².
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
33
IV Therapy and Children





Very specific to level of development
Use microdrop sets and/or electronic devices
Secondary infusions may be delivered as
IVPB or in burette (calibrated chamber)
Flush tubing (usually with 15 mL or so) after
medication delivered, to get all of the
medication
Check protocol of institution
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
34
Figure 25-2 Volume-controlled device (burette). (From Potter PA, Perry AG, Stockert P,
Hall A: Fundamentals of nursing, ed 8, St Louis, 2013, Mosby.)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
35
Calculating IV Medications by
Burette


Drop factor is 60 gtt/mL
Formula:
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
36
Calculating IV Medications by
Burette (Cont.)
Example: Antibiotic of 100 mg in 2 mL—dilute in
20 mL of D5W to infuse over 30 minutes. A
15 mL flush follows. Administration set is
burette.
Step 1: Read label to determine volume of
medicine available (100 mg:2 mL)
Step 2: Allow 18 mL of D5W to run into
burette. Add 2 mL containing the
medication
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
37
Calculating IV Medications by
Burette (Cont.)
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
38
Calculating IV Medications by
Burette (Cont.)
SAFETY ALERT!
IV infusions should be monitored as frequently as every
hour. A solution to flush the IV tubing is administered
after the medication.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
39
Case Study 6 (Cont.)
You are to administer a preop antibiotic to Tara
(14.8 kg). The order reads:
Vancomycin 148 mg IV over 2 hours q6h
The safe dose range is :
40 mg/kg/day in 6-8 divided dosages.
Is the dose safe?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
40
Case Study 6 (Cont.)
Answer: The dose is within safe range.
You have available 500 mg vials that must be
reconstituted with 10 mL sterile water for a
concentration of 50 mg/mL. This must be
further diluted with NS to ≥ 5 mg/mL and
administered over at least 60 min.
How much of the reconstituted medication will
you draw up and how much will you further
dilute with?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
41
Case Study 6 (Cont.)
Answer:
Draw up 3 mL (2.96 rounded) and further dilute
with 30 mL NS.
You are to administer the medication over 2 hours.
Your facility policy requires you to use a Burette with
microdrip tubing and a pump.
Calculate the rate in gtt/min and mL/hr.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
42
Case Study 6 (Cont.)
Answer:
Run the infusion at 15 gtt/min and 15 mL/hr. You also
remember to flush the tubing at the same rate with an
additional 15 mL NS.
Tara tolerates the medication well and sleeps through
the night without pain or fever. She has been NPO after
midnight and she is dressed in a clean gown before she
is taken to surgery at 0700. Her mother thanks you for
all your help.
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
43
Reminders: Pediatric Oral and
Parenteral Medications
1.Dosages for children are smaller than those for
adults
2.Most medications for children are liquid
3.Oral route is preferred to parenteral
4.Not more than 1 mL IM for small children and
older infants; small infants should receive not
more than 0.5 mL IM
5.Parenteral doses are usually given with tuberculin
(TB) syringes
6.Calculate dosages to administer using a ratio and
proportion, formula, or dimensional analysis
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
44
Practice Problems
A child weighing 42 lb 5 oz is prescribed
Rocephin 800 mg IV B.I.D. The recommended
dosage is 50–75 mg/kg/day
1. Convert the weight to kg.
2. Determine the safe dose range for the child.
3. Is the ordered dose safe? If not, what is your
next step?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
45
Practice Problems (Cont.)
The prescriber changes the order to Rocephin
500 mg IV over one hour B.I.D. You have on
hand Rocephin 2 g per 50 mL.
4. How much will you administer?
5. What will be the rate mL/hr?
6. What is the rate in gtt/min with microdrip
tubing?
Mosby items and derived items © 2014, 2010, 2006, 2002, 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.
46