PEDIATRIC AND ADULT DOSAGE CALCULATION BASED ON WEIGHT

Transcription

1 PEDIATRIC AND ADULT DOSAGE CALCULATION BASED ON WEIGHT

2 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 2

3 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 3

4 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, SOUND- ALIKES IMPROPER EDUCATION OF PARENTS CALCULATION ERRORS ERRORS IN MEASURING DEVICES (HOUSEHOLD VS. METRIC) 4

5 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 5

6 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. 6

7 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 7

8 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 8

9 DIMENSIONAL ANALYSIS (DA) 9

10 CONVERTING POUNDS/OUNCES TO KG 1. CHILD WEIGHS 14 LB 6 OZ. CONVERT TO KG. 10

11 CONVERTING POUNDS/OUNCES TO KG (CONT.) 11 Mosby items and derived items 2014, 2010, 2006, 2002,. 1998, 1994 by Mosby, Inc., an imprint of Elsevier Inc.

12 DIMENSIONAL ANALYSIS (DA) 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. CONVERT 14.4 LB TO KG 12

13 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? 13

14 CASE STUDY 6 (CONT.) ANSWER: TARA WEIGHS 14.8 KG. 14

15 CONVERTING GRAMS TO KILOGRAMS NEONATES ARE WEIGHED IN GRAMS 1,000 G = 1 KG CALCULATE WEIGHT OF 3,000 G INFANT IN KG 15

16 DIMENSIONAL ANALYSIS (DA) 16

17 REVIEW OF CONCEPTS CONVERT THE CHILD S WEIGHT IN KG ROUND TO 10 TH 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 17

18 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 10 TH 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 18

19 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. 19

20 SINGLE-DOSE MEDICATIONS 20

21 SINGLE-DOSE MEDICATIONS (CONT.) 21

22 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 22

23 SINGLE-DOSE RANGE MEDICATIONS (CONT.) 23

24 SINGLE-DOSE RANGE MEDICATIONS (CONT.) 24

25 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 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: MG/KG/DOSE Q4-6HR AS NEEDED. IS THE DOSE SAFE? (TARA WEIGHS 14.8 KG) IF SO, HOW MUCH WILL YOU ADMINISTER? 25

26 CASE STUDY 6 (CONT.) ANSWER: THE DOSE IS SAFE, ADMINISTER 4.7 ML AFTER CHECKING CALCULATIONS AND DOSAGE WITH ANOTHER NURSE. 26

27 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 27

28 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? 28

29 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 29

30 ADULT DOSAGES BASED ON BODY WEIGHT INFORMATION USED TO CALCULATE DOSAGES FOR CHILDREN CAN ALSO BE USED FOR ADULTS EXAMPLE 3: ORDER: TICAR 4 G IV Q6H. CLIENT WEIGHS 175 LB. RECOMMENDED DOSE IS 200 TO 300 MG PER KG PER DAY GIVEN IN DIVIDED DOSES EVERY 4 TO 6 HOURS. IS THE DOSAGE SAFE? 30

31 ADULT DOSAGES BASED ON BODY WEIGHT (CONT.) 31

32 ADULT DOSAGES BASED ON BODY WEIGHT (CONT.) 3. Determine mg allowed per dose for dosing every 6 hr (4 doses in 24 hr) 15,900 mg 4 = 3,975 mg/dose 23,850 mg 4 = 5,962.5 mg/dose 4. Determine if dose is safe 4 g q6h = 4,000 mg q6h Dose is within safe dose range 32

33 CALCULATING DOSAGES USING BODY SURFACE AREA BSA USED FOR INFANTS, CHILDREN, BURN VICTIMS, ANTINEOPLASTIC AGENTS, RENAL PATIENTS WEST NOMOGRAM IS BEST KNOWN BSA CHART COMPARE TO CHART INDICATING NORMS FOR CHILDREN OF SAME HEIGHT AND WEIGHT BSA CAN ALSO BE DETERMINED BY A FORMULA CALCULATION USING HEIGHT AND WEIGHT 33

34 Figure 25-1 West nomogram for estimation of body surface area. (From Kliegman RM, Stanton BF, St. Geme JW, Schor NF, Behrman RE: Nelson textbook of pediatrics, ed 19, Philadelphia, 2011, Saunders.) 34

35 READING THE WEST NOMOGRAM INCREMENTS ARE INTENTIONALLY IRREGULAR NORMAL HEIGHT/WEIGHT (2 ND FROM LEFT) BSA CAN BE DETERMINED BY WEIGHT ALONE EXAMPLES: NORMAL HEIGHT AND WEIGHT IN CHILDREN AND SMALL ADULTS CHILD WEIGHING 70 LB HAS BSA OF 1.1 M 2 CHILD WEIGHING 10 LB HAS BSA OF 0.27 M 2 CHECK READINGS TWICE TO CONFIRM 35

36 70 lb child Normal ht/wt 10 lb child Normal ht/wt 36

37 READING THE WEST NOMOGRAM (CONT.) FOR ABNORMAL HEIGHT/WEIGHT, USE FAR LEFT AND FAR RIGHT ON NOMOGRAM USE RIGID STRAIGHT EDGE TO SPAN THE TWO MEASURE IN CENTIMETERS OR INCHES; MATCH TO KILOGRAMS AND POUNDS, RESPECTIVELY BSA IS AT INTERSECTION OF SA COLUMN (CENTER) 37

38 50 lb / 36 in child Abnormal ht/wt 38

39 READING THE WEST NOMOGRAM (CONT.) SAFETY ALERT IN ORDER TO USE THE NORMAL COLUMN ON THE WEST NOMOGRAM, YOU MUST BE FAMILIAR WITH THE NORMAL HEIGHT AND WEIGHT STANDARDS FOR CHILDREN. CHECK RELIABLE RESOURCES SUCH AS A PEDIATRIC GROWTH AND DEVELOPMENT CHART. DO NOT GUESS ON THE NORMAL HEIGHT AND WEIGHT. 39

40 CALCULATING BSA WITH FORMULA USED IN CRITICAL CARE DOSING AND CHEMOTHERAPY FOR CHILDREN AND ADULTS SAFEST WAY USE FORMULA AND CALCULATOR THAT PERFORMS SQUARE ROOT FUNCTION BASED ON MEASUREMENTS OBTAINED USE SEPARATE FORMULAS FOR METRIC AND U.S. (HOUSEHOLD) UNITS CANNOT MIX THE TWO! 40

41 FORMULA FOR CALCULATING BSA FROM KILOGRAMS AND CENTIMETERS 1. MULTIPLY WEIGHT IN KILOGRAMS BY HEIGHT IN CENTIMETERS 2. DIVIDE THE PRODUCT OBTAINED IN STEP 1 BY 3, ENTER THE SQUARE ROOT SIGN INTO THE CALCULATOR 4. ROUND THE FINAL BSA IN SQUARE METERS (M 2 ) TO NEAREST HUNDREDTH 41

42 FORMULA FOR CALCULATING BSA FROM KILOGRAMS AND CENTIMETERS (CONT.) CALCULATE THE BSA FOR A CHILD WHO WEIGHS 23 KG AND IS 128 CM TALL. 42

43 FORMULA FOR CALCULATING BSA FROM POUNDS AND INCHES 1. MULTIPLY WEIGHT IN POUNDS BY HEIGHT IN INCHES 2. DIVIDE THE PRODUCT OBTAINED IN STEP 1 BY 3, ENTER THE SQUARE ROOT SIGN INTO THE CALCULATOR 4. ROUND THE FINAL BSA IN SQUARE METERS (M 2 ) TO NEAREST HUNDREDTH 43

44 FORMULA FOR CALCULATING BSA FROM POUNDS AND INCHES (CONT.) CALCULATE THE BSA FOR AN ADULT WHO WEIGHS 170 LB AND IS 67 IN TALL 44

45 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 45

46 CALCULATING BSA FOR CHILD DOSING USING FORMULA (CONT.) 46

47 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? 47

48 CASE STUDY 6 (CONT.) ANSWER: TARA S BSA IS 0.61 M². 48

49 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 49

50 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.) 50

51 CALCULATING IV MEDICATIONS BY BURETTE DROP FACTOR IS 60 GTT/ML FORMULA: 51

52 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 52

53 CALCULATING IV MEDICATIONS BY BURETTE (CONT.) 53

54 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. 54

55 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? 55

56 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? 56

57 CASE STUDY 6 (CONT.) ANSWER: ML NS. DRAW UP 3 ML (2.96 ROUNDED) AND FURTHER DILUTE WITH 30 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. 57

58 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 HER MOTHER THANKS YOU FOR ALL YOUR HELP. 58

59 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 59