DRUG DOSAGE CALCULATION IN PEDIATRICS BY MANISHA THAKUR

DRUG DOSAGE CALCULATION IN PEDIATRICS:
PEDIATRIC DOSAGE DIFFERENT FROM ADULTS
FORMULAS: YOUNG, CLARK, DILLING, FRIED RULES
BASED ON AGE, BASED ON BODY SURFACE AREA, WEIGHT
EXAMPLES.
DRUG DOSAGE CALCULATION
DAILY FLUID REQUIREMENT
CALCULATION OF DRIP RATE
INFUSION PUMP FLOW RATE CALCULATION.

1. CRITERIA FOR DRUG DOSAGE CALCULATION IN PEDIATRICS Presented by: Ms. Manisha Thakur Child Health Nursing

2. INTRODUCTION It is important that you are able to do calculations confidently, as mistakes may result in the patient receiving the wrong dose which may lead to serious consequences for the patient. Patient safety depends on accurate I.V ., oral drug dosing; precise calculations are essential to this process. Nurses shouldn't be apprehensive when oral, parentral drug dosages are presented in practice.

3. Proper drug dosing of the pediatric patient Proper drug dosing of the pediatric patient depends on: Age and weight. Overall health status. The condition of such biologic functions as respiration and circulation. The stage of development of body systems for drug metabolism (e.g., liver enzymes) and drug elimination (e.g., renal system).

4. Cont … In the neonate, these biologic functions and systems are underdeveloped: Renal function, for example, develops over the span of the first 2 years of life. This fact is particularly important because the most commonly used drugs in neonates, infants, and young children are antimicrobial agents, which are eliminated primarily through the kidneys. If the rate of drug elimination is not properly considered, drug accumulation in the body could occur, leading to drug overdosage and toxicity.

5. How is Pediatric Dosage Calculation Different than Adults? There is no standard dose. All doses are based on a recommended dosage based on: Body weight in kilograms (for this dosage test) Body Surface Area.

6. conversions 1 teaspoon = 5 mL / cc 1 tablespoon = 15 mL / cc 1 ounce = 30 mL / cc 1 gram (g) = 1000 milligrams (mg ) 1 milligram (mg) = 1000 micrograms (mcg ) 1 liter (L) = 1000 milliliters (mL) 20 Drops per ml

7. Measuring cup How many mL in 4 teaspoons ? 20 ml

8. conversions How to convert kg into pounds????? weight × 2.2 = weight in pounds How to convert pound into kg????? weight in pounds 2.2 =weight in kg

9. DOSE CALCULATION Dose calculation related to: Young`s rule Dilling`s rule Fried`s rule Clarke`s rule

10. Cont … DOSE CALCULATION RELATED TO AGE Young`s rule = 𝐴𝑔𝑒 (𝑦𝑒𝑎𝑟) /𝐴𝑔𝑒 in 𝑦𝑒𝑎𝑟 + 12 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠e Example: if adult dose is 600 mg and child's age is 3 years, what is C? C = 600 mg (3 yr / 3 yr + 12) C = 1800 mg

11. Cont … Dilling`s rule = 𝐴𝑔𝑒 (𝑦𝑒𝑎𝑟) / 20 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠 e Example: What will be the dose for the child of 10 years old if adult dose is 600mg? =Dose of a child = 10/20 X 600 = 300 mg

12. Cont … Fried`s rule = 𝐴𝑔𝑒 (𝑚𝑜𝑛𝑡 hs ) / 150 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠 e

13. Cont … DOSE CALCULATION RELATED TO BOGY WEIGHT Clarke`s rule = 𝐵𝑜𝑑𝑦 𝑤𝑒𝑖𝑔h𝑡 𝑙𝑏 /150 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠𝑒

14. Cont … DOSE CALCULATION RELATED TO BODY SURFACE AREA 𝐶h𝑖𝑙𝑑 𝑑𝑜𝑠𝑒 = 𝐶h𝑖𝑙𝑑 `𝑠 𝑏𝑜𝑑𝑦 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎/𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑑𝑢𝑙𝑡`𝑠 𝑏𝑜𝑑𝑦 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 × 𝑎𝑑𝑢𝑙𝑡`𝑠 𝑑𝑜𝑠e

15. 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.

16. IV fluid calculations The maintenance dose for administration of IV fluids is based on the following formula 100 mL of fluid for the 1st 10 kg of weight 50 mL of fluid for the 2nd 10 kg of weight 20 mL of fluid for and additional kg

17. Cont … Example: Jose weighs 16 pounds Weight in kg = 7.27 kg Using the formula provided how many ml of fluid would he need in 24 hours . Fluid Calculation 7.27 kilograms 100 mL x 7.27 kg = 727 mL 727 mL / 24 hours or mL per hour 30 ml/hour

18. Cont … 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 = 500mL 20 ml x 9.09 kg = 181 mL 1681 mL / 24 hours or mL / hour 70ml/hour

19. Cont …. Fluid calculations can be rounded. You cannot administer a fraction of a mL . In child #1 the calculated hourly rate of 29.7 would be rounded to 30 mL / hour In child #2 the calculated hourly rate of would be rounded to 70 mL / hour.

20. Cont … Since children are in the hospital for various illnesses they will often have increased fluid needs: dehydration, fever, vomiting, diarrhea, inability to take fluids . 24 hour fluid calculations may be 1 ½ to 2 times maintenance.

21. Cont … In Child number #1 maintenance fluid needs are 713 mL / 24 hours.1 ½ time maintenance would be 713 x 1.5 = 1069 mL / 24 hours or 45 mL / hour. In child # 2 maintenance fluid needs are 1681 mL / 24 hours.1 ½ times maintenance would be 1681 x 1.5 = 2522 mL / 24 hours or 105 mL / hour.

22. CALCULATION OF DRUG DOSAGE & DROP RATE Hourly recording of IV fluid intake . Don’t try and catch up on fluids . Calculate fluids used to administer IV medications into the hourly fluid calculations.

23. Cont …. Drug dose – it is sum of the amount ordered divided by total amount an multiplied by volume. Amount ordered (mg) × volume (ml) Actual amount (mg ) Example: Inj . Cefotaxim 250 mg iv BD. Calculate drug dose…? 250 mg × 2.5 ml 250 mg Answer: 2.5ml.

24. On the basis of body surface area adult dose × surface area of child in m 2 1.8 = child dose Costeff,s formula 4 × weight + 7 Weight+ 90 = body surface area of child in m2

25. Approximate Body Surface Area

26. Cont … In case the calculated amount is less than 1ml, then…. Amount ordered (mg) × volume (ml) × 40 units Actual amount (mg)

27. Example…. Inj. Rantac 10 mg IV BD…. Calculate drug dose…? 10 × 2 × 40 50 16 units.

28. CONT…. Macrodrip tubing administers a larger drop and may be used for 10 gtts /mL, 15 gtts /mL or 20 gtts / mL. Microdrip tubing administers 60 gtts / mL. These are called drop factors. The drop factor is the number of drops contained in 1 milliliter.

29. CALCULATION OF DRIP RATE Amount of fluid in ml / total time of infusion in min. X drop factor ( gtts /ml) = I/V infusion rate Note: drops are always rounded to nearest whole no.

30. Cont … Example : The physician has ordered D5W 1200 milliliters in 12 hours using 15 drops per milliliter infusion rate. What is the IV infusion rate in drops per minute? Given : Amount of fluid: 1200 mL Total time of infusion: 12 hrs Administration set drop factor: 15 gtts /mL IV infusion rate: ? gtts /min Step 1: Convert 12 hours into minutes. 12 hrs x 60 min/ hr = 720 min Step 2: Use the formula above to calculate the IV infusion rate. IV infusion rate = 1200 /720 x 15 = 100/4 = 25  Therefore , the IV infusion rate is 25 drops per minute.

31. Drug dosage calculation Formula: Amount DESIRED (D)/ Amount on HAND (H) X QUANTITY (Q) = Y (Tablets Required) Note : When medication is given in tablets, the QUANTITY = 1 since the amount of medication available is specified per (one) tablet.

32. Infusion pump Infusion pumps do not have a calibrated drop factor. The flow rate depends on the volume of fluid ordered and the time of infusion. FORMULA : Volume (ml)/ time (h) = (Flow rate in ml/ hr )

33. cont : Step 1: Determine your givens. Volume : 1200 mL Time : 10 h Step 2: Since the volume is given in mL and the time is given in hours, the flow rate can be calculated in one step using the formula. Volume ( ml)/ time (h) = ( Flow rate in ml/ hr ) Step 3: Use the formula to calculate the IV flow rate ( gtts /min). 1200 (ml) = 120 ml/ hr 10 (h)

34. Preparing parenteral medication from drug supplied as a powder ( reconstituion ) On the drug label or the package insert will state the diluents to be used and the exact amount to be added. When adding a solution or diluents to the powder, you will notice that the directions will state the volume and dose after the solution has been added.