Chapter 10 Dosage Problems for Infants and Children
IS THE DOSE SAFE? GET IT RIGHT THE FIRST TIME.
Overdose: Toxic effects
Underdose: therapeutic failure
Children’s medication: by mouth in liquid form or intravenously
IV therapy: microdrip, buretrols, infusion pumps
Nurse MUST consult pediatric reference.
Adult guidelines – not safe for children
Use calculator and double/triple check answers
Common equivalents
1 g = 1000 mg
1 mg = 1000 mcg
1 kg = 2.2 lb
16 oz = 1 lb
1 tsp = 5 mL
1 oz = 30 mL
Microdrip = 60 gtt/mL
q4◦ = every four hours
Dosage based on mg/kg and body surface area
Convert ounces to pounds
Infant weights 20 lb 12 oz
12 oz x (1 lb/16 oz) = 0.75 lb
infant weights 20 + 0.75 = 20.75 lb
20.75 lb x 1 kg = 9.412 kg
2.2 lb
Convert pounds to kilograms
Infant weighs 33 lb. ? kg rounded to nearest hundredth
33 lb x 1 kg = 15 kg
2.2 lb
Steps and Rule – mg/kg/ body weight
Step 1. Convert lb to kg by dividing by 2.2
Step 2. Determine the safe dose range in milligrams per kg using a reference
Step 3. Decide whether the ordered dose is safe by comparing the order with the safe dose range listed in the reference
Step 4. Once you have determined the ordered dose is safe, calculate the dose needed.
Ex. 1: Child weighing 33 lb is ordered Augmentin 150 mg po q8h
Label: Augmentin is a dry powder
Info: children <= 40 kg receive 6.7 to 13.3 mg/kg q8h
Need to: a) convert to kg
b) calc low and high safe dose
c) see if dose safe
d) prepare the dose
1. 33 lb x 1 kg = 15 kg
2.2lb
2. Low Dose: 6.7 mg x 15 kg = 100.5 mg
High Dose: 13.3 mg x 15 kg = 200 mg
3. Is dose safe??:
safe range: 100 to 200 mg q8h
Dose is safe as it falls within 100 to 200 mg range
4. Dosage: label states that 90 mL of water should be added gradually to make a concentration of 125 mg/5mL
(why gradually? Make sure drug goes into solution)
(D/H) x S = 150 mg x 5 mL = 6 mL
125 mg
Dose can be measured using calibrated safety dropper or oral syringe
Ex 2: premature infant weighs 1500 g
Order: digoxin 37.5 mcg po x 1
Is dose safe? What amount should be given
1. 1500 g x 1 kg/1000g = 1.5 kg
2. safe dose range: Nursing guide states: loading dose: 20 to 30 mcg/kg
low dose mg = 20 mcg x 1mg = 0.02 mg
1000 mcg
high dose mg = 30 mcg x 1 mg = 0.03 mg
1000 mcg
Factor in child’s weight
Low range : 1.5 kg x 0.02 mg = 0.03 mg
High range: 1.5 kg x 0.03 mg = 0.045 mg
3. ordered dose: 37.5 mcg = 0.0375 mg
4. formula method to calculate Digoxin elixir (0.125 mg/2.5 mL)
0.0375 mg x 2.5 mL = 0.75 mL
0.125 mg
Use calibrated safety dropper
Determining BSA in m2
Use the nomogram
Height in column on left with weight in column on right
Middle column – where intersects = BSA
Different charts for infants and young children
If a child weighs more than 65 lb or is more than 3 ft tall, use adult nomogram
BSA: used mainly in calculating chemotherapy dosages.
www.halls.md/body-surface-area/bsa.htm
Step and Rule – m2 Medication Orders
Step 1 – Find BSA in m2
Step 2 – Determine the safe dose using a reference
Step 3 – Decide whether the ordered dose is safe
Step 4 – Calculate the dose needed
Ex. 2 yr old child weighs 27 lb 12 oz; height 35 in;
Order: leucovorin calcium 5.5 mg po q6h x 72 hr
Supply: 1 mg/mL reconstituted by pharmacy
1. BSA = 0.55 meters squared (nomogram) for 27.75 lb and height = 35 inch
2. Safe dose is 10 mg/m2/dose qh6
10 mg x 0.55 m2 = 5.5 mg = safe dose q6h
3. Order is 5.5 mg q6h. Dose is safe
4. Formula method
5.5 mg x 1 mL = 5.5 mL
1 mg
Give 5.5 mL po q6h
Administering Intravenous Medications
When administered: when child can’t take oral liquids, has fluid electrolyte imbalances or needs IV medication.
Calculate dosage in mg/kg
Drugs for IVPB must be initially diluted following manufacturer’s directions
Steps to Solving Parenteral Pediatric Medications IVP
Step 1 – Convert lb to kg
Step 2 – Determine the safe dose range in mg/kg using a reference
Step 3 – Decide whether the ordered dose is safe by comparing the order with the safe dose range listed in the reference
Step 4 – Check the reference for diluent and duration for administration
Step 5 – Check the reference for diluent and duration for administratin
Ex. Child 5 years; weight 44 lb
Order: famotidine 5 mg IV bid
Literature: 0.25 mg/kg q12h IV up to 40 mg/day
Dilute to 5 or 10 mL with 5% dextrose or 0.9% sodium chloride and injected over at least 2 minutes
Supply: See label
1. 44 lb x 1 kg/2.2 lb = 20 kg
2. safe dose
20 kg x 0.25 mg/kg = 5 mg
3. dose is safe; meets mg/kg rule and does not exceed 40 mg/day
5 mg bid = total 10 mg/day
4. Calculate dose
D/H x S = 5mg x 1 mL = 0. mL
10 mg
5. Dilute with 5 or 10 mL suggested diluent. Inject over 2 minutes
Steps to Solve Parenteral Pediatric Medications IVPB
1. Decide whether the dose is safe; check a pediatric reference.
2. Decide whether the dilution ordered meets the minimum pediatric safety standard.
3. Prepare the medication according to directions
4. Draw up the dose and dilute further as needed.
5. Set the pump in mL/hr. If the infusion time is 30 minutes, set the pump for double the amount because the pump delivers mL/hr.
Eg. The order is 10 mL over 30 minutes. Set the pump for 20 mL/ hr. It will deliver 10mL in 30 minutes.
6. When the IV is completed , add a flush of 20 mL to the Buretrol to clear the tubing of the medication. Be sure to chart the flush as fluid intake. Follow institutional requirements regarding the IV flush.
Ex. Child 4 years; weight 17 kg
Order: fortaz 280 mg IV q8h in 10 mL D51/3NS
Literature: Safe dose 30 to 50 mg/kg/day
Concentration for IV use: 50 mg/mL over 30 minutes
Supply: 1 g powder. Directions: Dilute with 10 mL sterile water for injection to make 95 mg/mL; stable for 7 days if refrigerated
1. Safe dose is 30 to 50 mg/kg/day
Low range 30 mg x 17 mg = 510 mg/day
High range 50 mg x 17 mg = 850 mg/day
Order is 280 mg q8h (three doses)
280 mg x 3 = 840 mg
Dose falls within safe range
2. minimum safe dilutin is 50 mg/mL. Dose is 280 mg
280 mg = 5.6 mL
50 mg/mL
Order is 10 mL – is safe as it is more that minimum
3. Dilute 1 g with 10 mL sterile water to make 95 mg/mL
D/H x S = 280 mg x 1 mL = 2.9 mL
95 mg
Withdraw 2.9 mL; label vial and store in refrigerator
4. run about 5 mL D51/3NS into Buretrol. Add 2.9 mL drug. Add more D51/3NS to make 10 mL
5. Set pump at 20. This is 20 ml/hr. The pump will deliver 10 mL in 30 minutes
6. When the IV is completed, add a 20-mL flush of D51/3NS to clear IV tubing of medication
General Guidelines for Continuous IV Medications
1. Continuous IV medications for children and infants are calculated with methods and formulas used in Chapter 9.
2. Continuous IV dosages are based on weight in kilograms.
3. An infusion pump and/or volume control sets are always used.
4. Small bags of fluid are used to prevent fluid overload.
5. Follow institutional requirements for continuous IV infusions.
6. Consult a pediatric text or drug reference to determine the safe dosage range.
Chapter 11 Dimensional Analysis
STEPS TO SETTING UP A DIMENSIONAL ANALYSIS PROBLEM
1. Identify desired dose. Place it in the numerator.
2. Identify the supply or available dose.
3. Identify what you are solving for. Circle this measurement system.
4. Identify any conversions needed. Add the conversion factors to the equation. Add these to the equation so that like measurement systems will cancel each other.
5. Combine steps 1 and 2. Set up the problem so that the measurement systems that you do not need for the answer will cancel. This should leave the measurement system desired on the top.
6. If possible, reduce the fraction. Cancel out any measurement systems.
7. Multiply the numbers in the numerator. Multiply the numbers in the denominator.
8. Divide the numerator by the denominator
e.g.: Order: D5W 1000 mL over 10 hr
Supply: Drop factor of 20 gtt/mL
1000 mL 20 gtt 1hr
___________________________ = 33.3 gtt/min
10 hr mL 60 min