Pediatric Pharmacology

J A N B A Z N E R - C H A N D L E R R N , M S N , C N S , C P N P B O W D E N T E X T B O O K C H A P T E R 9

Developmental Considerations

• – – – – Pharmacokinetics Absorption Distribution Metabolism Elimination • Pharmacodynamics: how drug produces physiologic and biochemical changes

Absorption

 Gastrointestinal absorption  Gastric pH is high in neonate  Intestinal motility (transit time) is decreased in neonates and increased in older infant and children  Bile acid pool and biliary function is diminished in neonates

Absorption of Drugs

    Rectal Intramuscular- varies Topical / dermal – related to skin hydration Intraocular – thin membranes can cause systemic effects

Distribution

  Neonates have a higher proportion of total body water – related to water solubility of drug Lower portion of body fat – lower doses of lipophilic drugs  Digoxin: drug books with have different dosing for the neonates, infant and children

Digoxin Example

  IV children > 10 years (digitalizing dose): 8 to 12 mcg/kg given as 50% of the dose initially and ¼ of initial dose each of 2 subsequent doses at 6-12 hour intervals.

IV infants 1-24 months (digitalizing dose): 30 to 50 mcg/kg given as 50% of initial dose and ¼ of initial dose in each 2 subsequent doses at 6-12 hour intervals.

 Davis Drug Guide

Digitalizing Dose

 What does this mean?

Distribution Continued

   Protein concentration at birth is 80% of adult values Fetal albumin has limited drug binding ability  High potential for toxicity Immature blood-brain barrier  Drug to treat neonatal sepsis will penetrate the brain  Drugs can accumulate in the brain tissue

Metabolism

  Newborn enzymatic microsomal system is less effective Liver maturation varies

Elimination

  Glomerular filtration and tubular secretion are reduced at birth Gradual increase in renal function to adult level (about 1-2 years)

Nursing Responsibilities

      Right medication Right dose Right patient Right route Right time Right approach

Six Rights

Right Dose

• • • • Drug dose calculated on weight in kilograms or BSA Adult dosages used in children who weigh more than 50 kilograms Double-check math calculations on all medication given – – – BSA is the most accurate way to calculate dosages Used in calculating chemotherapy Neonates ICU

Dispensing Correct Dose

 Many drugs come in multi-dose containers  Keflex 250 mg / 5 mL   Amoxicillin 125 mg / 5 mL Acetaminophen comes in various concentration: 80 mg / 0.8 mL , 120 mg / 5 mL , 250 mg / 5 mL

Right Patient

 Identification by 2 sources  All children need identification wristband    Two person identification (parent / nurse) All mediation taken into room should be labeled with child’s name, name of drug, and dose MAR 

Is the mediation appropriate for the patient?

Right Route / Time

  Medications can be ordered po, sub-q, IM, IV Medications should be administered within ½ hour before or ½ hour after prescribed time.

 Problem if multiple intravenous medications ordered to be given at the same time

Developmental Considerations

 Infant  Administer medication before the infant feeds   Offer med in small amount of formula or cereal / fruit Give via spoon or syringe  Parent may give but nurse must be in the room and observe medication being given

Developmental Considerations

• – – – – – Toddler Simple explanation Small cup or spoon (syringe may be seen as a “shot”) Ask parent how child takes medication May need to restrain in lap and offer small amounts while holding the cheeks together until child swallows the med If giving injection – have parent or another nurse assist

Conversions you need to remember

      1 teaspoon = 5 mL 1 tablespoon = 15 mL 1 ounce = 30 mL 1 gram (g) = 1000 milligrams (mg) 1 milligram (mg) = 1000 micrograms (mcg) 1 liter (L) = 1000 milliliters (mL)

grains (gr) to milligrams (mg)

    gr 1 = 60 mg gr ¾ = 45 mg gr ½ = 30 mg gr ¼ = 15 mg

Measuring cup

How many mL in 4 teaspoons

?

Calculations

      Pounds to kilograms Safe Dosing How to calculate medication dose using ration / proportion IV medications 24 hour fluid calculations Naso-gastric drainage replacement

Pounds to Kilograms

• Pounds to kilograms = pounds 2.2

Nursing Alert: In pediatrics you need to carry out to the hundredths ( do not round )

Kilogram Example

  20 pounds 5 ounces First need to convert 5 ounces to a fraction of a pound 5 divided by 16 = 0.31

 20.31 pounds divided by 2.2 = 9.23 kilograms  Note medication would be calculated based on 9.23 kilograms. DO NOT ROUND

Pounds to kilograms

 If a child weights 6 lbs 6 ounces what is the weight in kg?

 6 ounces = 0.37 pounds 16 ounces  6.37 pounds divided by 2.2 kg = 2.89 kg

Medication dosage

 For a dosage of medication to be safe, it must fall within the safe range as listed in a Drug Handbook, PDR or other reliable drug reference.

Safe Medication Dose

   Calculate daily dose ordered (Physician orders) Calculate the low and high parameters of safe range (from drug book) Compare the patient’s daily dose to see if it falls within the safe range.

Calculation

  A child is 2 years and weighs 36 lbs Physician order: Amoxicillin 215 mg po tid for a bilateral otitis media (ear infection)  First you would need to change 36 lbs to kg  36 divided by 2.2

 Patient weight in kg = 16.36 kg

Calculating Safe Range

 Davis drug guide: PO (children) < 40 kg:

Amoxacillin 6.7 to 13.3 mg / kg q 8 hours.

 (low range)16.36 x 6.7 = 109.6 mg q 8hours  (high range)16.36 x 13.3 = 217.5 mg q 8 hours

Safe Range

 109.6 mg to 217.5 mg of Amoxicillin Q 8 hours.

 Is the 215 mg dose ordered by the MD safe? Yes (it falls within the safe range)

How much medication do you give?

Amoxicillin Suspension comes: 250 mg per 5 mL you want to give 215 mg  250 mg 215 mg 5 ml = x ml  1075 250x  Give 4.3 mL po every 8 hours

Nursing Alert

 Read the medication ranges carefully: dosing can be for:  dose range for 24 hours  dose range for q 8 hours  dose range for q 12 hours

Fluid Control

  Crucial in the pediatric population Units often have policies that children under a certain age are on a fluid control pump.

Fluid overload

    Know what the IV rate is.

Hourly recording of IV fluid intake.

Don’t try and catch up on fluids.

Calculate fluids used to administer IV medications into the hourly fluids amount

Daily Fluid Needs

  Fluid needs should be calculated on every patient to assure that the infant / child is receiving the correct amount of fluids.

Standard formula for pediatrics needs to be memorized.

Maintenance Fluid Requirement

   Up to 10 kg  100 mL / kg/ 24 hours 11 to 20 kg  1000 mL + 50 mL / kg / 24 hours Greater than 20 kg  1500 mL + 20 mL / kg / 24 hours

Bowden text page 740

Fluid Calculations

  Since children are in the hospital for various illnesses they will often have increased fluid needs: dehydration, fever, vomiting, diarrhea, inability to take po fluids.

24 hour fluid calculations may be 1 ½ to 2 times maintenance.

Fluid Calculation

 7.27 kilograms  100 mL x 7.27 kg = 727 mL

727 mL / 24 hours or 30 mL per hour

Fluid Calculation Problems

   9 pound infant 9 pounds = 4.09 kg (always calculate to 100 th ) 4.09 x 100 mL = 409 mL / 24 hours 0r 17 mL / hour  1 ½ times maintenance = 1.5 x 409 = 613 mL / 24 hour or 25 mL / hour

Fluid Calculation

• • • • • 36 pound child 36 pound = 16.36 kg 10 kg x 100 mL = 1000 mL 6.36 kg x 50 mL = 318 mL 1318 mL / 24 hours or 55 mL / hour • 1 ½ times maintenance = 1.5 x 1318 = 1977 mL / 24 hours or 82 mL / hour

Fluid Calculations

      52 pounds 52 pounds = 23.63 kg 100 mL x 10 = 1000 mL 50 mL x 10 = 500 mL 20 mL x 3.63 = 72 mL Total fluids = 1000 + 500 + 72 = 1572 mL / 24 hours or 65 mL / hour  1 ½ times maintenance = 1.5 x 1572 = 2358 mL / 24 hours or 98 mL / hour

Fluid Calculation

   64 pound child Convert pounds to kilograms = 29.09 kg Fluid calculations:   100 mL x 10 kg = 1000 mL 50 ml x 10 kg = 500 mL  20 ml x 9.09 kg = 181 mL

1681 mL / 24 hours or 70 mL / hour

IV Medications

Key concepts

   Time over which a medication should be administered is critical information Minimal dilution (end concentration of medication) is important for medications such as aminoglycosides).

Therapeutic blood levels

Buretrol or Volume Control Chamber

Total of medication in chamber + 20 ml IV fluid needed to flush the medication.

Page 316 Bowden text

IV Buretrol

   A buretrol or volutrol is an inline receptacle between the client’s IV catheter set and the bag of fluids.

Capacity is 120 to 150 mL Rationale: the nurse can fill the buretrol to a certain level and if the IV pump malfunctions, only the volume in the buretrol will flow to the client.

Nursing Alert

• – – – If the IV medication is not “flushed” with 15 to 20 mL of fluids the medication will still be in the line and could be a problem If IV rate is KO (5-10 mL per hour) the medication in the tubing would take 2 to 4 hours to get to the patient If you are giving two or more IV medications the drugs could be mixed in the tubing if the appropriate flush is not done

* THE MD ORDERS WILL NEVER INCLUDE THE FLUSH IN THE ORDER

Nursing Alert

 Include the extra fluid given to administer IV mediations and fluids used to “flush” the tubing in the calculation of the child’s total fluid intake.

Flushing buretrols / solusets

  http://www.iv-therapy.net/node/1319 Two great articles that explain the concept of “flushing” the line after giving an IV medication

Syringe Pump

Calculation of fluids needs to include the fluid in the syringe + the fluid in tubing.

• 4 mL of medication + 5 mL in tubing • 9 ml of fluid in total

Syringe pumps

 http://www.youtube.com/watch?v=clh6kPXhOlE

Parenteral Pediatric Medications

     Step 1: Convert lb to kg Step 2: Determine the safe range in mg/kg Step 3: Decide whether the dose is safe by comparing the order with safe dose range Step 4. Calculate the dose needed Step 5. Check reference for diluent and duration for administration.

Clinical Judgment 9-1

  Bowden Textbook page 217 2 nd Edition

Example #1

  Child: 5 years: weight 44 lbs Order: famotidine (Pepcid) 5 mg IV bid

Drug Guide Information

 Usual Dosage:

0.5 mg / kg / day divided twice daily (maximum 40 mg / day)



Administration: May be administered IV push over a period not less than 2 minutes or as an intermittent infusion over 15 to 30 minutes; final concentration not to exceed 4 mg/mL.

Example #1

  Convert pounds to kg: 44 lb = 20 kg Determine safe dose:   20 kg x 0.5 mg = 100 mg 100 mg divided by 2 (drug is given twice a day)  5 mg is safe it meets mg / kg rule and does not exceed 40 mg/day.

 5 mg bid = total of 10 mg/day

Example #1

   Calculate the dose Pepcid is provided as 10 mg/mL 10 mg = 5 mg 1 mL x mL 5 = 10x 0.5 mL of Pepcid

Example #1

   Calculate the dose Pepcid is provided as 10 mg/mL 10 mg = 5 mg 1 mL x mL 5 = 10x 0.5 mL of Pepcid

Example #2

  Child: 4 years: weight 17 kg Physician order: Fortaz (Ceftazidime) 280 mg IV q 8 hours

Drug Guide Information

   Dosing:  Safe dose 30 to 50 mg/kg/day Drug supplied as 1 gram powder. Directions: Dilute with 10 mL of sterile water to equal 95 mg/mL.

Administration: intravenous infusion over 15 to 30 minutes; may be given IV over 3-5 minutes at final concentration of 100 mg/mL

Example #2

Safe dose is 30 to 50 mg/kg/day • • Low range: 17 kg x 30 mg = 510 mg/day High range: 17 kg x 50 mg = 859 mg/day Safe range is 510 to 859 mg/day or 170 to 286 per dose. If the order is to give the drug q 8 hours you would need to divide the safe range by 3 or multiple the q 8 hour dose x 3.

Example #2

Drawing up the medication: 1 gram / 10 mL or 95 mg / 1 mL 95 mg = 280 mg 280 1 mL x mL 95x = 2.94 mL or 2.9 mL DO NOT ROUND UP TO 3 mL

Example # 2

  Adding medication to the volutrol Take the 2.9 mL of Ceftazidine – inject it into the port on the volutrol and add additional IV fluid to = 10 mL.

Replacing NG Fluid Loss

NG – cc/cc replacement

 If a child has a nasogastric tube that is draining fluid the physician will often write and order for:  NG drainage – cc/cc replacement q 4 hours What does this mean?

Nasogastric Output

  NG output is measures q 4 hours.

At the beginning of the shift the night nurse reports that the drainage was 150 mL for the last 4 hours and you need to replace this over the next four hours.  Note: this is in addition to the IV hourly rate ordered.

Sample problem

   IV hourly rate is 115 mL/hour NG output to be replaced over the next 4 hours is 150 cc’s or 37 mL/hour.

IV would be set at 115 mL + 37 mL = You would run the IV at 152 mL / hour for the next four hours.

Practice Problems

    Do the practice problems.

Can be done individually or in groups.

Testing will be on like problems.

You must achieve 90% or better to be able to safely administer medications in the clinical setting.